Federal Motor Vehicle Safety Standards; Seating Systems, 57998-58038 [2024-15390]
Download as PDF
<![CDATA[
57998
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety
Administration
49 CFR Part 571
[Docket No. NHTSA–2024–0001]
RIN 2127–AM53
Federal Motor Vehicle Safety
Standards; Seating Systems
National Highway Traffic
Safety Administration (NHTSA),
Department of Transportation (DOT).
ACTION: Advance notice of proposed
rulemaking.
AGENCY:
Through this document,
NHTSA fulfills the statutory mandate in
section 24204 of the Infrastructure
Investment and Jobs Act (IIJA), which
directed the Secretary of Transportation
to issue an advanced notice of proposed
rulemaking to update Federal Motor
Vehicle Safety Standard No. 207,
‘‘Seating systems.’’ NHTSA also
partially grants rulemaking petitions
submitted by Kenneth J. Saczalski of
Environmental Research and Safety
Technologists (ERST) and by Alan
Cantor of ARCCA, Inc. (ARCCA), which
sought changes to the Federal Motor
Vehicle Safety Standards (FMVSS)
petitioners stated would improve the
safety of children during rear-end
crashes. NHTSA denies a petition from
the Center for Auto Safety (CAS), which
sought to require additional warnings
instructing adults regarding which rear
seating position to place children.
DATES: Comments must be received no
later than September 16, 2024. The
Saczalski and Cantor petitions are
granted in part and the CAS petition is
denied as of July 16, 2024. See
ADDRESSES and Section VIII. Public
Participation for more information about
submitting written comments and
reviewing comments submitted by other
interested parties.
ADDRESSES: You may submit written
comments, identified by docket number
or RIN, by any of the following methods:
• Federal eRulemaking Portal: Go to
https://www.regulations.gov. Follow the
online instructions for submitting
comments.
• Mail: Docket Management Facility,
U.S. Department of Transportation, 1200
New Jersey Avenue SE, Room W12–140,
Washington, DC 20590–0001.
• Hand Delivery or Courier: 1200
New Jersey Avenue SE, West Building,
Ground Floor, Room W12–140,
Washington, DC, between 9 a.m. and 5
p.m. E.T., Monday through Friday,
except Federal holidays. To be sure
khammond on DSKJM1Z7X2PROD with PROPOSALS2
SUMMARY:
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
someone is there to help you, please call
202–366–9826 before coming.
Instructions: For detailed instructions
on submitting comments and additional
information on the rulemaking process,
see the Public Participation heading of
the SUPPLEMENTARY INFORMATION section
of this document. Note that all
comments received will be posted
without change to https://
www.regulations.gov, including any
personal information provided. Please
see the ‘‘Privacy Act’’ discussion in
Section IX. Regulatory Analyses and
Notices.
Confidential Business Information: If
you claim that any of the information or
documents provided to the agency
constitute confidential business
information within the meaning of 5
U.S.C. 552(b)(4), or are protected from
disclosure pursuant to 18 U.S.C. 1905,
you must submit supporting
information together with the materials
that are the subject of the confidentiality
request, in accordance with part 512, by
email or secure file transfer to the Office
of the Chief Counsel, Litigation and
Enforcement Division. Do not send a
hardcopy of a request for confidential
treatment to NHTSA’s headquarters.
Your request must include a request
letter that contains supporting
information, pursuant to § 512.8. Your
request must also include a certificate,
pursuant to § 512.4(b) and part 512,
appendix A.
You are required to submit one
unredacted ‘‘confidential version’’ of the
information for which you are seeking
confidential treatment. Pursuant to
§ 512.6, the words ‘‘ENTIRE PAGE
CONFIDENTIAL BUSINESS
INFORMATION’’ or ‘‘CONFIDENTIAL
BUSINESS INFORMATION
CONTAINED WITHIN BRACKETS’’ (as
applicable) must appear at the top of
each page containing information
claimed to be confidential. In the latter
situation, where not all information on
the page is claimed to be confidential,
identify each item of information for
which confidentiality is requested
within brackets: ‘‘[ ].’’
You are also required to submit to the
Office of the Chief Counsel one redacted
‘‘public version’’ of the information for
which you are seeking confidential
treatment. Pursuant to § 512.5(a)(2), the
redacted ‘‘public version’’ should
include redactions of any information
for which you are seeking confidential
treatment (i.e., the only information that
should be unredacted is information for
which you are not seeking confidential
treatment).
For questions about a request for
confidential treatment, please contact
Dan Rabinovitz in the Office of the Chief
PO 00000
Frm 00002
Fmt 4701
Sfmt 4702
Counsel at Daniel.Rabinovitz@dot.gov or
(202) 366–8534.
FOR FURTHER INFORMATION CONTACT: Mr.
Tyler Brosten, Office of Crashworthiness
Standards (Telephone: 202–366–1740;
Email: tyler.brosten@dot.gov, Facsimile:
202–493–2739), or Mr. Eli Wachtel,
Office of Chief Counsel (Telephone:
202–366–2992; Email: eli.wachtel@
dot.gov). You may mail these officials at:
National Highway Traffic Safety
Administration, 1200 New Jersey
Avenue SE, Washington, DC 20590.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Introduction
II. Occupant and Seat Back Dynamics and
Field Data on Rear Impact Crashes
A. FARS and CRSS Data Analysis
B. CISS Data Analysis
C. Field Data Analyses From Relevant
Literature
III. Statutory and Regulatory Background
A. The Safety Act and the Infrastructure,
Investment and Jobs Act
B. Regulatory History of FMVSS No. 207
and FMVSS No. 202, and Associated
Research/Analyses
1. 1963—SAE Recommended Practice for
Seats
2. 1967—Publication of FMVSS No. 207,
Seating Systems
3. 1968—Publication of FMVSS No. 202,
‘‘Head Restraints’’
4. 1969—Report on Seat Safety Studies at
ITTE
5. 1974—Notice of Proposed Rulemaking
(NPRM) To Revise FMVSS No. 207
6. 1978—NHTSA Publishes a Request for
Comment on Rulemaking Priorities
7. 1989—NHTSA Receives Petitions for
Rulemaking on Revisions to FMVSS No.
207
8. 1992—2000 NHTSA Publishes a Request
for Comment on Possible Revisions to
FMVSS No. 207, Grants Two Petitions
and Conducts Research
9. 2004—NHTSA Issues Final Rule
Upgrading FMVSS No. 202, Head
Restraints
10. 2004—NHTSA Terminates Rulemaking
on FMVSS No. 207, Seating Systems
11. Further Regulatory Changes Since 2004
IV. Review of Additional Literature
A. Occupant Dynamics
B. Rear Impact Protection Technology
C. Non-Contact Injuries
1. Neck Injuries
2. Thorax Injuries in High-Speed Rear
Impacts
D. Summary
V. Petitions for Rulemaking at Issue in This
Document
A. Statutory and Regulatory Background
B. Petition of Kenneth J. Saczalski
1. FMVSS No. 207, Seating Systems
2. Use of FMVSS No. 301, ‘‘Fuel System
Integrity,’’ To Test Seats
3. FMVSS No. 213, Child Restraint Seats
C. Petition of Alan Cantor
1. Use of FMVSS No. 301, ‘‘Fuel System
Integrity,’’ To Upgrade FMVSS No. 207
2. Rearward Rotation Limit and Structural
Symmetry Requirement
E:\FR\FM\16JYP2.SGM
16JYP2
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
3. Additional Dynamic Testing and NCAP
Implementation
4. FMVSS No. 209, Seat Belt Assemblies
D. NHTSA’s Analysis of Saczalski and
Cantor Petitions
1. Analysis of Data and Research Provided
by Cantor and Saczalski Regarding Safety
Need
2. Rear Structure Intrusion
3. Cost and Practicability
E. Assessment of the Specific
Recommendations by Cantor and
Saczalski
1. Matters on Which NHTSA Is Granting
the Petitions
2. Matters on Which NHTSA Is Denying
the Petitions
F. Conclusion of NHTSA Assessment of
Cantor and Saczalski Petitions
G. Center for Auto Safety (CAS) Petition
H. Analysis of CAS Petition
VI. Unified Approach to Rear Impact
Protection
A. Introduction
B. FMVSS No. 207
C. Analysis of Approaches To Updating
Standards for Occupant Protection in
Rear Impact
1. Seat Back Strength and Other
Mechanical Properties
2. Test Parameters
3. Quasi-Static Testing
4. Dynamic Testing
D. Crash Avoidance Technology
VII. NHTSA’s Forthcoming Research
A. Field Data Analysis and Market
Research
B. Test Procedure Assessment
1. High-Speed Test
2. Exploratory Testing
3. Low-Speed Test
C. Parametric Modeling
D. ATD and Injury Risk Function
Development
E. Cost Analysis
F. Summary
VIII. Public Participation
A. How can I inform NHTSA’s thinking on
this rulemaking?
B. How do I prepare and submit
comments?
C. How can I be sure that my comments
were received?
D. How do I submit confidential business
information?
E. Will the agency consider late comments?
F. How can I read the comments submitted
by other people?
IX. Regulatory Analyses and Notices
A. Executive Order (E.O.) 12866, E.O.
13563, and E.O. 14094 and DOT
Regulatory Policies and Procedures
B. Paperwork Reduction Act
C. Privacy Act
D. Plain Language
E. Regulation Identifier Number (RIN)
X. Conclusion
I. Introduction
As part of its safety mission, NHTSA
issues Federal Motor Vehicle Safety
Standards (FMVSSs) 1 and other
regulations for new motor vehicles and
motor vehicle equipment to save lives,
1 The
FMVSS are codified in 49 CFR part 571.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
prevent injuries, and reduce economic
costs due to road traffic crashes. All
FMVSSs must meet the requirements of
the National Traffic and Motor Vehicle
Safety Act of 1966 (the ‘‘Safety Act’’).2
That is, they must ‘‘be practicable, meet
the need for motor vehicle safety, and be
stated in objective terms.’’ 3 On
November 14, 2021, the Infrastructure,
Investment and Jobs Act (IIJA; Pub. L.
117–58 4) was passed. Section 24204 of
IIJA, ‘‘Motor Vehicle Seat Back Safety
Standards,’’ directs the Secretary of
Transportation to issue an advance
notice of proposed rulemaking
(ANPRM) within two years to update 49
CFR 571.207. The publication of this
ANPRM fulfills this statutory mandate.
FMVSS No. 207 establishes
requirements for seats, seat attachment
assemblies, and their installation in
passenger cars, multipurpose passenger
vehicles, trucks designed to carry at
least one person, and buses.5 The
standard, among other things, sets
minimum requirements for the strength
of the seat back and its associated
restraining devices and adjusters.6
While in its rearmost position, a seat
back must withstand a rearward
moment (torque) of 373 Newton-meters
(Nm) (3,300 Inch-pounds (in-lb)),
applied by a horizontal force measured
vertically from the seating reference
point.7 The standard also contains a test
procedure. The test specifies an
application of a rearward force on the
uppermost cross member of the seat
back structure, that results in a moment
applied to the attachment (often the
U.S.C. 30101.
U.S.C. 30111(a). The Secretary must also (1)
‘‘consider relevant available motor vehicle safety
information; (2) consult with the agency established
under the Act of August 20, 1958 (Pub. L. 85–684,
72 Stat. 635), and other appropriate State or
interstate authorities (including legislative
committees); (3) consider whether a proposed
standard is reasonable, practicable, and appropriate
for the particular type of motor vehicle or motor
vehicle equipment for which it is prescribed; and
(4) consider the extent to which the standard will
carry out’’ the purpose of the Safety Act. 49 U.S.C.
30111(b). The purpose of the Safety Act is to
‘‘reduce traffic accidents and deaths and injuries
resulting from traffic accidents.’’ 49 U.S.C. 30101.
4 Public Law 117–58.
5 49 CFR 571.207 S1 and S2.
6 FMVSS No. 207 also contains provisions
dictating the strength of seat attachments to the
vehicle in both the front and rear directions. For the
purposes of this ANPRM, ‘‘strength’’ with respect
to seat backs refers to the maximum rearward
moment or force a seat back is able to withstand.
‘‘Stiffness’’ refers to the resistance of the seat back
to any (or a specified) amount of deformation and
deflection. Stated another way, ‘‘stiffness’’ can be
thought of as the increase in resistive force or
moment per unit deformation or rotation. Rigidity
is the characteristic of a structure, such as a seat
back, exhibiting relatively limited deformation
when exposed to a force. Rigid and yielding seat
back structures are opposites.
7 49 CFR 571.207 S4.
PO 00000
2 49
3 49
Frm 00003
Fmt 4701
Sfmt 4702
57999
recliner mechanism) of the seat back
and the remainder of the seat structure.
Although FMVSS No. 207 sets the
minimum seat back strength
requirement, since 1968 the de facto
minimum requirement for seat back
strength has effectively been set by
FMVSS No. 202 (now 202a), ‘‘Head
restraints.’’ 8 This standard requires
head restraints and establishes
requirements for them to reduce the
severity of neck injuries in rear impact
crashes. Currently, FMVSS No. 202a
requires a fully extended head restraint
to withstand an 890 Newtons (N) (200
pound force (lb-f)) rearward load for 5
seconds applied 65 millimeters (mm)
(2.5 inches (in)) below its top when
adjusted to its highest position, which
must be at least 800 mm.9 This creates
an effective torque requirement on the
seat back of 654 Nm (5,790 in-lb), where
654 = 890*(0.8–0.065), significantly
higher than the 373 Nm (3,300 in-lb)
required by FMVSS No. 207.
In addition to the requirement in IIJA,
this ANPRM addresses three petitions
for rulemaking NHTSA received
requesting various amendments to the
FMVSS related to the deformation of
seat backs in rear impacts.10 Two of the
petitioners, Kenneth J. Saczalski of
ERST. and Alan Cantor of ARCCA
requested that the agency increase the
strength requirements for seat backs in
the front row. They argue that seats that
comply with the current standard may
yield excessively during a crash, which
can lead to spinal cord and brain
injuries due to contact between the
seated occupant’s head and vehicle
structures in the rear seat compartment.
In addition, they state that under the
current standard, in certain higher
speed rear end crashes, a seat could
yield to the point that the seat becomes
fully reclined (hereinafter described as
‘‘seat back failure’’). This may cause a
belted occupant in the front seat to slide
underneath the seat belt, leading to
ejection into the rear seat space or
outside the vehicle. (The petitioners
refer to this phenomenon as ‘‘ramping.’’)
Ramping poses injury risk to occupants
seated directly behind the occupied
front seat. In addition, the petitioners
have asked NHTSA to revise other
FMVSSs in ways that they stated would
mitigate the injurious effects of
excessively yielding seat backs. This
ANPRM seeks to further develop the
8 The head restraint and seat back are
interconnected parts of the seating system.
9 49 CFR 571.202(a) S4.2.7.
10 These petitions, dated October 28, 2014
(Environmental Research and Safety Technologists,
Inc.), and September 28, 2015 (ARCCA), are
available in the rulemaking docket at https://
www.regulations.gov/.
E:\FR\FM\16JYP2.SGM
16JYP2
58000
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2
record on occupant protection in rear
impacts to inform a potential future
rulemaking. As explained in section V.,
this document grants these petitions in
part.
The third petitioner, CAS, requested
the addition of warning language to
child restraint system labels and
owner’s manuals to warn parents
against placing a child behind an
occupied front seat.11 As explained in
section V.H., this document denies this
petition.
IIJA requires that NHTSA issue an
ANPRM to update FMVSS No. 207.
Congress stated, however, that an
update must be consistent with the
considerations described in 49 U.S.C.
30111(b) of the Safety Act and issued
pursuant to the Safety Act. Therefore, it
must be practicable, meet the need for
safety, and be stated in objective terms
as provided in 49 U.S.C. 30111(a). This
ANPRM discusses issues that have
historically contributed to the
complexities of regulatory action on
seating systems.
As outlined in the regulatory and
research review below, a major
challenge in NHTSA’s efforts to set
standards for rear impact protection
relates to the determination of whether
a seat should yield, thereby reducing
forces acting on the seat occupant, or be
stiffer, and thus prevent rare
occurrences like ramping or interaction
with other occupants. Finding the
appropriate balance inherent in rear
impact protection is a theme and central
debate in much of the research and
analysis conducted on this issue.
Complicating this question is the
dramatic difference in frequency
between relatively common and
generally minor cervical spine injuries
(such as whiplash) caused by forces
acting on a seat occupant that can occur
even in low-speed rear impacts and
severe injuries, which are rare. Studies
suggest that no more than 1% of rear
impacts cause any type of serious or
higher severity injury,12 which are
mostly associated with impacts with
vehicle structures, not other
occupants.13 14 In contrast, cervical
11 This petition, dated March 9, 2016, is also
available in the rulemaking docket at https://
www.regulations.gov/.
12 The severity of injury is ranked in accordance
with the Abbreviated Injury Scale (AIS). An AIS
level 3 injury is a serious injury, level 4 a severe
injury, and levels 5 and 6 are critical and fatal
injuries, respectively. www.aaam.org.
13 Prasad, Priya, et al. ‘‘Relationships between
passenger car seat back strength and occupant
injury severity in rear end collisions: Field and
laboratory studies.’’ SAE transactions (1997): 3935–
3967.
14 Parenteau, Chantal S., and David C. Viano.
‘‘Serious head, neck and spine injuries in rear
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
spine injuries, such as whiplash, are
highly common injuries in rear impacts
and occur at many different speeds,
including at low speed, with some
estimates of over 100,000 injuries
annually in the United States.
Additionally, despite decades of
industry and agency research into
whiplash, the understanding of the
biological mechanisms that cause these
injuries remain limited. This has
restricted NHTSA’s ability to develop
objective updated performance
standards for seat backs, such as
updated strength requirements or a
comprehensive dynamic test for rear
impact protection. In particular, factors
like test speed and what metrics of seat
back and head restraint performance to
test (i.e., strength only vs.
anthropomorphic test dummy injury
metrics) remain unclear. These and
other related issues present a challenge
to updating FMVSS No. 207 in a manner
that is objective, practicable, and meets
the need for safety.
This ANPRM is part of NHTSA’s
ongoing effort to meet this challenge.
Here, we detail a unified approach to
occupant protection in rear impacts.
Although IIJA mentions only FMVSS
No. 207, NHTSA is considering
integrating FMVSS Nos. 207 and 202a
because of the clear connection between
head rests and seat backs. An integrated
approach would enable NHTSA to
comprehensively evaluate the
performance of the seating system for
rear impact protection and better
balance considerations relevant to both
high speed (severe injuries) and lowspeed (whiplash injury prevention)
impacts. As part of this approach,
NHTSA is considering a quasi-static test
or a dynamic test requirement with at
least two (low and high) impact severity
ranges. This ANPRM discusses many
considerations associated with each
approach and seeks comment on them,
including choice of anthropomorphic
test device (ATD), performance criteria
(such as ATD metrics), test severities,
and crash pulse delivery methods.
This ANPRM has four main areas of
focus. In section II, NHTSA details the
safety problem in rear impact occupant
protection. In section III, NHTSA
describes the regulatory and research
history of seat backs, and in section IV,
NHTSA summarizes a literature review
in this area to provide context for the
ANPRM.15 In section V, NHTSA
discusses the Cantor, Saczalski, and
impacts: frequency and sources.’’ IRC–21–10,
IRCOBI Conference. 2021.
15 The research in the public domain on the area
of seat back strength is extensive, and this
document does not attempt to fully synthesize it.
PO 00000
Frm 00004
Fmt 4701
Sfmt 4702
CAS petitions. Finally, in section VI,
NHTSA describes the unified approach
with regard to FMVSS No. 207 and
FMVSS No. 202a, and in section VII,
NHTSA describes its research efforts in
this area and the knowledge gaps that
may need to be filled prior to
implementing this unified approach.
Throughout the document, we seek
comment on a variety of topics to
inform a determination about what
upgrade, if any, to FMVSS No. 207 (and
FMVSS No. 202a) can meet the
requirements of the Safety Act with the
aim of improving occupant protection in
rear impact collisions.
II. Occupant and Seat Back Dynamics
and Field Data on Rear Impact Crashes
Controlled interaction of the occupant
with the seat back is the primary
countermeasure to injury in motor
vehicle rear collisions. In these crashes,
the seat back supports the occupant
during sudden forward acceleration,
when a range of injury risks may be
generated. Because it is necessary to
provide a broad range of injury
protections, the rear impact protection
issue has been framed as both a balance
and competition between high and lowseverity protection measures. To
introduce the issue, this section begins
with a brief discussion of rear impact
seat back dynamics and follows with a
survey of field data regarding rear
impacts.
In front row seats, the seat back frame
is typically connected to the lower seat
structure, or pan, by a mechanical joint.
When a seat back is subjected to an
inertial load from the occupant during
a rear collision, the seat back frame
rotates and bends rearward around this
joint. When asymmetric loading on the
seat back occurs, this dynamic can
result in twisting of the seat back
around its longitudinal axis. The force
acting on the seat back is proportional
to the occupant’s mass and forward
acceleration. As the seat back rotates
rearward, the force applied to the seat
back becomes less perpendicular to the
seat back plane as the applied force is
further defined by transverse forces
made up of seat back-occupant friction
and pocketing,16 seat belt restraints, and
other factors that maintain occupant
seat retention.17 These actions have long
been understood to absorb energy,
reduce forces acting on the seat
occupant, and disperse acceleration of
16 Pocketing refers to displacement of the
occupant’s torso into the relatively pliable interior
of a seat back.
17 Seat retention refers to the occupant restraint
system’s ability to keep the occupant coupled to the
seat.
E:\FR\FM\16JYP2.SGM
16JYP2
58001
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
the occupant over time.18 19 When the
force applied to the seat back exceeds
the material’s elastic limit, it begins to
deform in a way that permanently bends
the seat (plastic deformation). For some
rear impacts, this deformation may
exceed the seat structure’s ability to
substantially oppose the applied force,
resulting in seat back failure due to
significant material bending or fracture,
at which point the seat back is said to
fail. At the point of seat back failure or
significant seat back deformation, seat
occupants in rearward seat rows may be
exposed to injury risk due to contact
with the front seat back or front
occupants. Paradoxically, the
restraining force applied by the front
seat on its occupant can lead to injury,
just as a seat belt can injure an occupant
in a frontal crash. The following subsection examines field data to further
lay out the current understanding of the
risks to vehicle occupants in rear
impacts. Later sections will provide
additional discussion on the literature
regarding rear impact injuries and
protection. The literature outlines a
continued debate around how best to
protect occupants, the uncertain
understanding of how certain injuries
occur in rear impacts, and varied
approaches and developments in
technology for rear impact protection.
A. FARS and CRSS Data Analysis
In general, rear collisions result in
fewer fatalities and serious injuries
when compared to other impact
directions. Table II.1 shows overall
crash statistics for the sum of light
vehicles (passenger cars and light
trucks) in year 2020 organized by
impact directions and injury severities.
NHTSA compiled this data set in the
2020 Traffic Safety Facts from FARS
(Fatality Analysis Reporting System)
and CRSS (Crash Report Sampling
System).20 We note that the data include
all vehicle rows. The data show that rear
impacted light vehicles accounted for
24.1% of crashed light vehicles and
21.8% of vehicles with injured
occupants, but only 7.2% of vehicles
with fatalities in 2020.
TABLE II.1—PASSENGER CARS AND LIGHT TRUCKS INVOLVED IN CRASHES, BY INITIAL POINT OF IMPACT, CRASH
SEVERITY, AND CRASH TYPE FOR YEAR 2020
Crash severity
Crash type by initial point of impact
Fatal
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Number
Injury
Percent
Number
Property damage only
Percent
Number
Percent
Total
Number
Percent
Single-Vehicle Crashes:
Front ...........................................................
Left Side .....................................................
Right Side ..................................................
Rear ...........................................................
Noncollision ................................................
Other/Unknown ..........................................
10,883
890
886
222
1,714
1,430
67.9
5.6
5.5
1.4
10.7
8.9
358,800
21,960
33,795
16,334
27,237
7,157
77.1
4.7
7.3
3.5
5.9
1.5
791,913
54,317
85,283
84,915
40,898
25,991
73.1
5.0
7.9
7.8
3.8
2.4
1,161,597
77,167
119,965
101,473
69,849
34,580
74.2
4.9
7.7
6.5
4.5
2.2
Total ....................................................
16,025
100.0
465,285
100.0
1,083,319
100.0
1,564,629
100.0
Multiple-Vehicle Crashes:
Front ...........................................................
Left Side .....................................................
Right Side ..................................................
Rear ...........................................................
Noncollision ................................................
Other/Unknown ..........................................
15,987
3,221
2,649
2,772
76
704
62.9
12.7
10.4
10.9
0.3
2.8
1,183,348
224,185
206,256
561,310
702
2,787
54.3
10.3
9.5
25.8
0.0
0.1
2,354,919
522,635
486,970
1,395,634
2,474
17,515
49.3
10.9
10.2
29.2
0.1
0.4
3,554,254
750,041
695,875
1,959,717
3,253
21,007
50.9
10.7
10.0
28.1
0.0
0.3
Total ....................................................
25,409
100.0
2,178,589
100.0
4,780,149
100.0
6,984,146
100.0
All Crashes:
Front ...........................................................
Left Side .....................................................
Right Side ..................................................
Rear ...........................................................
Noncollision ................................................
Other/Unknown ..........................................
26,870
4,111
3,535
2,994
1,790
2,134
64.9
9.9
8.5
7.2
4.3
5.2
1,542,149
246,145
240,051
577,646
27,939
9,945
58.3
9.3
9.1
21.8
1.1
0.4
3,146,832
576,953
572,254
1,480,551
43,372
43,507
53.7
9.8
9.8
25.3
0.7
0.7
4,715,850
827,209
815,839
2,061,189
73,101
55,586
55.2
9.7
9.5
24.1
0.9
0.7
Total ....................................................
41,434
100.0
2,643,874
100.0
5,863,467
100.0
8,548,775
100.0
Of the over 2 million rear impacted
light vehicles in 2020, only 0.15%
(2994/2,061,189) involved fatalities, as
compared with 0.57% (26,870/
4,715,850) of the 4.7 million front
impacted light vehicles and 0.47%
(7646/1,643,048) of the 1.6 million side
impacted light vehicles involved
fatalities; a fatal rear collision is
typically associated with a high DV 21
collision.22 However, the injury rate in
light vehicles that underwent a rear
collision in 2020 is comparable to other
crash directions, as 30% of rear
impacted light vehicles involved injury,
while 33% of frontal and 30% of side
impacted light vehicles involved injury.
The count of occupant injury and
fatality for different collision directions
is classified by vehicle type for year
2020 in table II.2 Traffic Safety Facts
from FARS and CRSS. Restricting the
discussion to light vehicles (passenger
cars and light trucks), 6.1% of passenger
car occupants and 4.6% of light truck
occupants killed were due to rear
18 Anderson JO. Dynamics of Occupants in
Automotive Accidents Involving Rear Impacts.
Warren, MI: Research Laboratories General Motors
Corporation; 1961. Report No. R–34–1295.
19 Severy DM, Mathewson J, Bechtol O.
Controlled automobile rear-end collisions and
investigation of related engineering and medical
phenomena. Can Serv Med J. 1955;11:727–759.
20 National Center for Statistics and Analysis.
(2022, October). Traffic Safety Facts 2020: A
compilation of motor vehicle crash data (Report No.
DOT HS 813 375). National Highway Traffic Safety
Administration.
21 DV is defined as the maximum change in
velocity of the struck vehicle after impact.
22 Wang, J.-S. (2022, May). MAIS(05/08) injury
probability curves as functions of DV (Report No.
DOT HS 813 219) National Highway Traffic Safety
Administration.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
PO 00000
Frm 00005
Fmt 4701
Sfmt 4702
E:\FR\FM\16JYP2.SGM
16JYP2
58002
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
impact DV for large trucks would be on
average smaller than for light vehicles.23
fatalities in rear impacted large trucks
was only 2.9%. This would be
consistent with the expectation that rear
impacts. The combined light vehicle
total was 5.4%. In contrast to the light
vehicle fatality rate, the percentage of
TABLE II.2—VEHICLE OCCUPANTS KILLED AND INJURED, BY INITIAL POINT OF IMPACT AND VEHICLE TYPE FOR YEAR 2020
Vehicle type
Injury severity/initial point of impact
Passenger
cars
Large
trucks
Other/
unknown
Buses
Subtotal
Motorcycles
Total
Occupants Killed:
Front .........................................................
Left Side ...................................................
Right Side ................................................
Rear .........................................................
Other ........................................................
Noncollision ..............................................
Unknown ..................................................
7,724
1,849
1,633
822
160
581
703
5,997
1,129
840
474
106
1,309
497
523
35
50
24
16
146
37
6
1
0
1
2
2
4
273
53
52
70
12
280
125
14,523
3,067
2,575
1,391
296
2,318
1,366
3,444
300
259
242
32
858
444
17,967
3,367
2,834
1,633
328
3,176
1,810
Total ..................................................
13,472
10,352
831
16
865
25,536
5,579
31,115
Occupants Injured:
Front .........................................................
Left Side ...................................................
Right Side ................................................
Rear .........................................................
Other ........................................................
Noncollision ..............................................
Unknown ..................................................
696,221
121,449
109,313
273,123
5,600
15,248
381
440,711
74,875
77,510
194,857
3,584
21,698
274
21,175
4,058
4,429
9,136
1,228
4,895
13
1,958
2,623
920
1,096
0
1
23
3,023
596
447
698
38
2,012
34
1,163,087
203,600
192,620
478,909
10,451
43,854
725
41,952
6,623
5,863
4,765
289
23,010
26
1,205,039
210,222
198,483
483,675
10,740
66,864
751
Total ..................................................
1,221,335
813,509
44,934
6,620
6,849
2,093,246
82,528
2,175,774
Further, according to the 2020 Traffic
Safety Facts, 22.3% of passenger vehicle
injuries occurred in rear impacts (light
trucks = 24.0%, heavy trucks = 20.3%).
For each vehicle type, the proportion of
fatalities for rear impacts is significantly
lower than the corresponding
proportion of injuries for rear impacts,
compared to other initial impact
directions. The rear impact proportion
of fatalities in light trucks and heavy
trucks is lower than in passenger cars,
but the rear impact proportion of
injuries in light trucks is slightly greater
than in passenger cars and heavy trucks.
The disparity in rear collision
proportion of injuries for different
vehicle types is discussed in the
literature review below.
B. CISS Data Analysis
NHTSA also examined the Crash
Investigation Sampling System (CISS)
data files for the years 2017–2020 to
determine the number of rear impacts
compared to other crash modes and
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Light
trucks
23 DV is inversely proportional to the struck
vehicle weight. Large trucks (including single-unit
trucks and truck tractors) have a gross vehicle
weight rating (GVWR) greater than 10,000 pounds.
Passenger cars and light trucks (including pickups,
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
determine the injury risk (number of
injured occupants divided by the
number of exposed occupants) of
vehicle occupants in rear impacts.
These data are limited because CISS
currently reports only police reported,
tow-away crashes, and, as will be
explained later, most rear impacts are
not tow-aways. The data were divided
into different crash types: rollover,
frontal, side, rear, other, and unknown.
In addition, for rear impacts, the data
were segmented by the change in
velocity of the impacted vehicle (DV).
All data presented here are weighted to
represent national estimates. The
maximum abbreviated injury scale 24
(MAIS) for each injured occupant is
presented so that an occupant with
multiple injuries is counted only once
in the analysis. An occupant was
counted as having a whiplash injury
(MAIS 1 neck injury) even if they had
other AIS 1 injuries. Crashes with fire
have been excluded from the sample. If
an occupant had a whiplash injury but
also had a MAIS 2+ injury, they were
not added to the whiplash injury count.
As was the case for the FARS and CRSS
data above, we have not restricted the
data by seating row.
The total annualized number of
involved individuals was estimated to
be 4.5 million, including crash types
categorized as ‘‘unknown’’ and ‘‘other.’’
Rear impact crashes accounted for only
373,237 or 8.3% of all tow-away crash
involving individuals in the CISS
database (Figure II.1). Only rollover
crashes yield fewer occupants involved
in tow-away crashes. Looking at the
proportion of occupants with serious
and higher severity injuries (MAIS 3–6)
by crash type, we see that MAIS 3–6 are
underrepresented in rear impacts (4.3%
= 3,814/88,437) and overrepresented in
rollover (19.7% = 17,415/88,437). By
contrast whiplash injury is
overrepresented in rear impacts (15.8%
= 31,206/197,060) as compared to the
number of towed rear impacts.
vans, and utility vehicles) have a GVWR not greater
than 10,000 pounds.
24 The severity of injury is reported in CISS 2017–
2020 using the 2015 Abbreviated Injury Scale,
where AIS 1 are minor injuries, and the 2–6
categories are moderate, serious, severe, critical,
and fatal injuries, respectively.
PO 00000
Frm 00006
Fmt 4701
Sfmt 4702
E:\FR\FM\16JYP2.SGM
16JYP2
58003
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
70% - - . - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ,
60%
50%
□ MAIS
40%
3-6
II Whiplash
■ All
Occupants
30%
20%
10%
0%
-+-------"..__
Rollover
Frontal
Side
Rear
Figure 11.1: Proportion of Injured and All Occupants (including uninjured) by Impact
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
PO 00000
Frm 00007
Fmt 4701
Sfmt 4725
E:\FR\FM\16JYP2.SGM
16JYP2
EP16JY24.006</GPH>
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Type (2017 - 2020 CISS)
58004
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
Figure II.2 and Figure II.3 show the
risk of MAIS 3–6 and whiplash injury 25
for each towed crash mode. The risk of
MAIS 3–6 injury in rear impacts is 1.0%
(= 3,814/373,237), which is about 60%
of the next highest risk (1.7% for side).
The whiplash injury risk in rear impacts
is approximately 8.4% (= 31,206/
373,237), which is about 1.5 times the
next highest risk (5.7% for rollover).
These whiplash injury rates do not
consider non-towed crashes, where the
majority of whiplash injuries are known
to occur.26
6%
5%
4%
3%
2%
1%
Rollover
Frontal
Rear
Side
25 Risk of MAIS 3–6 injuries in a crash mode is
equal to the number of occupants with MAIS 3–6
injuries in that crash mode divided the total
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
number of occupants (injured and uninjured) in
that crash mode. Similar computation is done to
determine risk of whiplash injuries.
PO 00000
Frm 00008
Fmt 4701
Sfmt 4725
26 Final Regulatory Impact Analysis for FMVSS
No. 202 Head Restraints for Passenger Vehicles,
Docket NHTSA–2004–19807.
E:\FR\FM\16JYP2.SGM
16JYP2
EP16JY24.007</GPH>
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Figure II.2: Risk of MAIS 3 - 6 Injury by Impact Type (2017 - 2020 CISS)
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
58005
10%--.----------------------------------,
9%
8%
7%
6%
5%
4%
3%
2%
1%
0%
-+---
Rollover
Frontal
Side
Rear
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
PO 00000
Frm 00009
Fmt 4701
Sfmt 4725
E:\FR\FM\16JYP2.SGM
16JYP2
EP16JY24.008</GPH>
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Figure 11.3: Risk of Whiplash Injury by Impact Type (2017 -2020 CISS)
58006
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
Figure II.4 shows the distribution of
towed rear impacts by the change in
velocity of the rear impacted vehicle.
Most of the crashes are in the 11–20
kilometers per hour (km/h) (6.8–12.4
miles per hour (mph)) DV range. Table
II.3 provides tabulated annual occupant
injuries in rear collisions according to
injury severity and DV. For occupants in
a known DV rear impact crash, the
majority of injuries are estimated to be
no injury (MAIS 0) in all DV ranges. The
most probable known DV range for
injury of any type is the 11–20 km/h
(6.8–12.4 mph) category, which is
consistent with this being the most
common impact speed range. More than
three-quarters of MAIS 3+ rear impact
injuries occur above 31 km/h (19.3
mph). Figure II.5 gives the risk of MAIS
2 and MAIS 3+ injuries as a function of
impact DV in towed rear crashes. The
highest risk for MAIS 2 injuries is 8.4%
(= 891/10,630) for 51+ km/h (31.7+
mph) DV crashes. The highest risk for
MAIS 3+ is 7.0% (= 1,572/22,425) for
the 31–40 km/h (19.3–24.9 mph) DV
range. Figure II.6 shows that for
whiplash, the highest risk is 11.7% (=
2,624/22,425) for injury in towed
crashes occurring in the 26–35 km/h
(16.2–21.8 mph) range. The risk at 51+
km/h is similar at 11.1% (= 1,183/
10,630) and at other speeds is between
2.8% and 9.7%.
50%
40%
30%
20%
10%
0%
0 - 10
11 - 20
21 - 30
31 - 40
JiV (km/h)
41 - 50
51+
Figure 11.4: Distribution of Towed Rear Impacts by 8V (2017 - 2020 CISS)
TABLE II.4—ANNUAL REAR IMPACT INJURY BY DV
[2017–2020 CISS]
MAIS
0
Whiplash
MAIS 1 no
whiplash
MAIS
2
MAIS
3–6
Total
Unknown ..........................................................................
0–10 .................................................................................
11–20 ...............................................................................
21–30 ...............................................................................
31–40 ...............................................................................
41–50 ...............................................................................
51+ ...................................................................................
101,022
22,057
88,352
46,618
13,085
1,811
5,173
12,637
675
7,680
6,302
2,624
107
1,183
13,950
913
15,469
10,429
4,157
1,661
2,746
4,495
59
2,793
1,455
988
94
891
789
0
474
249
1,572
92
638
132,893
23,704
114,769
65,052
22,425
3,764
10,630
Total Known DV ........................................................
Total ..........................................................................
177,095
278,117
18,569
31,206
35,375
49,325
6,279
10,775
3,025
3,813
240,345
373,237
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
PO 00000
Frm 00010
Fmt 4701
Sfmt 4725
E:\FR\FM\16JYP2.SGM
16JYP2
EP16JY24.009</GPH>
khammond on DSKJM1Z7X2PROD with PROPOSALS2
DV
(km/h)
58007
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
9% ~ - - - - - - - - - - - - - - - - - - - - - - ~
8%
7%
6%
5%
□ MAIS
4%
3-6
IIMAIS 2
3%
2%
1%
11 - 20
0 - 10
21 - 30
31 - 40
t:,,.V (km/h)
41 - 50
51+
Figure 11.5: Risk of MAIS 2 and 3 - 6 injuries by Rear Impact /1V (2017 - 2021 CISS)
12%
10%
8%
6%
4%
2%
11 - 20
21 - 30
31 - 40
t:,,.V (km/h)
41 - 50
51+
Figure 11.6: Whiplash Injury Risk by Rear Impact /1 V (2017 - 2020 CISS)
Figure II.6 provides the whiplash
injury rates for towed crashes. CISS
does not collect injury data for non-
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
towed crashes. In 2004, using State data,
the Final Regulatory Impact Analysis for
the upgrade of FMVSS No. 202 found
PO 00000
Frm 00011
Fmt 4701
Sfmt 4702
four times as many whiplash injuries in
all crashes compared to those in towaway crashes. NHTSA plans to update
E:\FR\FM\16JYP2.SGM
16JYP2
EP16JY24.011</GPH>
0 - 10
EP16JY24.010</GPH>
khammond on DSKJM1Z7X2PROD with PROPOSALS2
0%
58008
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
this analysis to accurately represent the
current whiplash injury risk. Older field
data, however, are still useful to provide
a sense of the very large proportion of
whiplash injuries that occur at low
speed.
With historical data, we can attempt
to generate estimates that include nontowed whiplash. Between 1982 and
1986, non-towed crash data were
collected. Table II.5 shows the
distribution of an approximation of
whiplash injuries occurring in towed
and non-towed impacts for the 1982–86
National Automotive Sampling System
(NASS) data. The greatest ratio of nontowed to towed whiplashes was 20
times for the 0–10 km/h (0–6.2 mph) DV
range. The next highest ratio was for the
11–20 km/h (6.8–12.4 mph) range at 8
times.27 As expected, this ratio drops
significantly at higher speeds because
there are fewer non-towed crashes at
these speeds. If we use the ratio of
NASS data for non-towed to towed
crashes as a multiplier for the CISS
towed whiplash injury estimates in each
speed range to attempt to account for
the non-towed whiplash injuries in the
newer data set, the result is column four
in table II.5. If we distribute
proportionally the cases of whiplash
injuries where the impact speed was
unknown to the known cases, the result
is given in the fifth column. In this
column we see that more than threequarters (125,221/161,623) of all
whiplash injuries occur at impact DV
less than 20 km/h (12.4 mph). For only
towaway rear impacts (not shown
graphically) this DV limit captures 45%
(8,355/18,570) of whiplash injuries. The
whiplash injury distribution is shown
graphically in Figure II.7. This estimate
is provided to give a general sense of
how considering whiplash injury only
in tow-away crashes significantly
underestimates overall whiplash injury
distribution, particularly for lower
speed crashes. This estimate comes with
a large degree of uncertainty because it
is based on historical NASS data.
TABLE II.5—ADJUSTMENTS TO WHIPLASH INJURIES TO ACCOUNT FOR NON-TOWED CRASHES
Ratio total
to towed
(82–86 NASS)
DV
(km/h)
Towed whiplash
injury
(2017–2020 CISS)
Compensated
whiplash
injury
Unknown DV
distributed
Unknown ...............................................................................................................................
0–10 ......................................................................................................................................
11–20 ....................................................................................................................................
21–30 ....................................................................................................................................
31–40 ....................................................................................................................................
41–50 ....................................................................................................................................
51+ ........................................................................................................................................
5.1
19.8
8.1
2.8
1.1
1.0
1.0
12,637
675
7,680
6,302
2,624
107
1,183
64,553
13,339
61,868
17,550
2,768
110
1,183
........................
22,210
103,011
29,220
4,609
184
1,972
Total Known DV .............................................................................................................
Total ...............................................................................................................................
..........................
..........................
18,570
31,207
96,819
161,372
........................
161,372
70%
60%
50%
40%
30%
20%
10%
11 - 20
0 - 10
21 - 30
31 - 40
41 - 50
51+
/l.V (km/h)
Figure II.7: Distribution of Whiplash Injury by Impact t-..V for Rear Impacts
(2017 - 2020 CISS) with Compensation for Whiplash Injury in Non-Towed Vehicles
27 We note that these ratios are approximations
from a slightly different DV segmentation.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
PO 00000
Frm 00012
Fmt 4701
Sfmt 4725
E:\FR\FM\16JYP2.SGM
16JYP2
EP16JY24.012</GPH>
khammond on DSKJM1Z7X2PROD with PROPOSALS2
0%
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
58009
C. Field Data Analyses From Relevant
Literature
III. Statutory and Regulatory
Background
must also consider all of the factors set
forth in 49 U.S.C. 30111(b).
In an earlier 1997 study of the
National Automotive Sampling SystemCrashworthiness Data System (NASS–
CDS) across years 1980–1994, Prasad 28
found that rear impact collisions
accounted for 11% of all possible struck
vehicle scenarios. The distribution of
crashes indicated that 50% of all rear
impacts occur at DVs of 21 km/h (13
mph) or less, 86% occur at DVs less than
32 km/h (20 mph) and 94% occur at DVs
of 40 km/h (25 mph) or less.
Furthermore, when examining the
distribution of injuries, it was found
that less than 1% of rear end collisions
resulted in severe injury of AIS 3 or
more.
In another study, Parenteau 29
examined 1999 to 2015 NASS–CDS
crash data to investigate the risk for
MAIS 3+ outcomes including fatalities
in crashes involving vehicles from
model year (MY) 2000 and later. The
risk for severe injury was lowest in rear
crashes. The authors found head trauma
to be the most likely severe injury for
frontal passengers in rear collisions,
followed by thorax and spinal injuries.
The severe injuries were mostly the
result of contact with the windshield,
head restraint, and B-pillar. Many of
these severe injuries develop from a seat
retention issue (such as not wearing a
seat belt) in which the occupant
decouples from the seating system. It is
unclear to what extent seat strength and
retention issues overlap. The most
severe injuries were attributed to
forward intrusion of rear components.
Most rear collisions lead to a
relatively low DV of the struck vehicle
and this contributes to moderating
injury of the vehicle occupants. The
characteristics of the struck vehicle
affect the injury severity and fatality risk
of the occupants. As discussed in the
next section, the majority of reported
rear collision injuries are cervical
injuries with or without clear pathology,
while a small percentage of rear
collisions are associated with high DV
and severe injuries.
A. The Safety Act and the
Infrastructure, Investment and Jobs Act
B. Regulatory History of FMVSS No. 207
and FMVSS No. 202, and Associated
Research/Analyses
28 Prasad, Priya, et al. ‘‘Relationships between
passenger car seat back strength and occupant
injury severity in rear end collisions: Field and
laboratory studies.’’ SAE transactions (1997): 3935–
3967.
29 Parenteau, Chantal S., and David C. Viano.
‘‘Serious head, neck and spine injuries in rear
impacts: frequency and sources.’’ IRC–21–10,
IRCOBI Conference. 2021.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
Congress enacted the Safety Act for
the purpose of ‘‘reduc[ing] traffic
accidents and deaths and injuries
resulting from traffic accidents.’’ 30 To
accomplish this, the Safety Act
authorizes the Secretary of
Transportation to promulgate FMVSSs
as well as to engage in other activities
such as research and development. The
Secretary has delegated the authority for
implementing the Safety Act to
NHTSA.31 The Safety Act requires that
FMVSSs ‘‘be practicable, meet the need
for motor vehicle safety, and be stated
in objective terms.’’ 32 To meet the
Safety Act’s requirement that standards
be ‘‘practicable,’’ NHTSA must consider
several factors, including technological
and economic feasibility.33
In IIJA, Congress required NHTSA to
issue this ANPRM to update FMVSS No.
207. The statute further states that if the
Secretary determines a final rule
complies with the Safety Act, a rule
shall be issued with a compliance date
not later than 2 motor vehicle model
years after the model year the rule goes
into effect.34 Under this requirement,
NHTSA is required to issue a final rule
only if it meets the requirements of the
Safety Act, namely that it is practicable,
meets the need for safety, and is
objective. In determining whether to
proceed with the rulemaking, NHTSA
U.S.C. 30101.
CFR 1.94.
32 49 U.S.C. 30111(a). The Secretary must also (1)
consider relevant available motor vehicle safety
information; (2) consult with the agency established
under the Act of August 20, 1958 (Pub. L. 85–684,
72 Stat. 635), and other appropriate State or
interstate authorities (including legislative
committees); (3) consider whether a proposed
standard is reasonable, practicable, and appropriate
for the particular type of motor vehicle or motor
vehicle equipment for which it is prescribed; and
(4) consider the extent to which the standard will
carry out the purpose of the Safety Act to reduce
traffic accidents and deaths and injuries resulting
from traffic accidents. 49 U.S.C. 30111(b).
33 See, e.g., Paccar, Inc. v. Nat’l Highway Traffic
Safety Admin., 573 F.2d 632, 634 n.5 (‘‘ ‘Practicable’
is defined to require consideration of all relevant
factors, including technological ability to achieve
the goal of a particular standard as well as
consideration of economic factors.’’) (citations and
quotations omitted). Technological feasibility
considerations counsel against standards for which
‘‘many technical problems have been identified and
no consensus exists for their resolution . . .’’ while
economic feasibility considerations focus on
whether the cost on industry to comply with the
standard would be prohibitive. Simms v. Nat’l
Highway Traffic Safety Admin., 45 F.3d 999, 1011
(6th Cir. 1995); See, e.g., Nat’l Truck Equip. Ass’n
v. Nat’l Highway Traffic Safety Admin., 919 F.2d
1148, 1153–54 (6th Cir. 1990).
34 IIJA, section 24204 (2021).
PO 00000
30 49
31 49
Frm 00013
Fmt 4701
Sfmt 4702
1. 1963—SAE Recommended Practice
for Seats
The basis of the current FMVSS No.
207 standard is a recommended practice
established by SAE International on
November 1, 1963: SAE J879—Passenger
Car Front Seat and Seat Adjuster. SAE
J879 established uniform test
procedures and minimum performance
requirements for motor vehicle seats
and seat adjusters.
J879 defined two test procedures. The
first procedure, ‘‘Simulated Occupant
Loading,’’ tested rearward seat back
strength. It required a seat back to
withstand a rearward moment of 480
Nm (4,250 in-lb) that was generated via
a static load applied to the uppermost
cross member of the seat back frame.
However, this moment was calculated
‘‘about the rear attachments of the seat
frame to the seat adjusters.’’ The July 1,
1968, revision to J879, J879B—Motor
Vehicle Seating Systems, modified the
moment to 373 Nm (3,300 in-lb)
measured about the H-point, and the
direction of the force was specified to be
perpendicular to the seat back frame
angle. The other procedure, ‘‘Simulated
Inertial Loading,’’ established a 20 g
minimum strength requirement for
horizontal inertial seat loadings, applied
in both the forward and rearward
direction. This specification was
designed to ensure that seat anchorages
were strengthened to the point where
the seats would remain attached to the
vehicle body structure (typically the
floor), preventing their inertia from
releasing them and creating a ram-like
action within the passenger
compartment. During these tests, the
seat back is braced to the seat base to
isolate the seat attachment to the
vehicle.
2. 1967—Publication of FMVSS No. 207,
Seating Systems
In February 1967, FMVSS No. 207
was enacted, and it went into force
beginning with MY 1969 passenger
cars.35 It was later extended to
multipurpose vehicles, trucks, and
buses in 1972.36
FMVSS No. 207 mostly mirrored the
1963 version of SAE J879. However, the
minimum rearward moment
requirement was set at 373 Nm (3,300
35 32
36 36
E:\FR\FM\16JYP2.SGM
FR 2415 (Feb. 3, 1967).
FR 22945 (Dec. 2, 1971).
16JYP2
58010
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
in-lb) as measured about the H-point.37
Additionally, provisions were added for
seats that folded forward to allow access
to rear seats and to assure that seats had
a positive restraining device (latch) to
prevent them from swinging forward
during a frontal crash. This prevented
adverse inertial forces by a flailing seat
back to the back of an occupant as they
pitched forward during a frontal
collision. The additional requirement
also helped protect unrestrained rear
seat occupants during frontal crashes or
a hard breaking event who might
otherwise get thrown over a pitchedforward seat back and could suffer
injuries due to head impacts with the
windshield or dash panel.
The new provision required the latch
(and, hence, the seat back itself) to
withstand a forward load of 20 times the
weight of the seat back. The load was
applied to the seat back at its center of
gravity. There was a concurrent revision
to SAE J879 in July 1968. SAE also
changed the moment value and its
reference point in J879 to be consistent
with FMVSS No. 207. However, the SAE
requirement applied the force
generating the moment in a direction
perpendicular to the seat back instead of
horizontally (see Figure III.1). The result
of this change was that a slightly higher
force must be applied in FMVSS No.
207 to achieve the same moment level.38
Since then, the requirements of FMVSS
No. 207 and SAE J879B have not
changed.
LOAD (P) -MAL TO Hlf I.ICk
AT IPPiR - E M I H
/
I
I
I
I
I
"II" PCllll-._
(SH S.A.E.~826)
,,-----
'I
f
I
U J J /D
-- --..._r
__ ,
\
I
MMm (PI D) IDMfUiD HOIT IHI
S. &. E. IU■JIIN "Jt• POINT
requirements for seat back strength were
set forth through static loads.
3. 1968—Publication of FMVSS No. 202,
‘‘Head Restraints’’
In 1968, NHTSA issued FMVSS No.
202, ‘‘Head restraints,’’ requiring head
restraints on cars manufactured after
January 1, 1969.39 The standard
specified that the head restraint must
sustain an 890 N (200 lb-f) rearward
load applied 65 mm (2.5 in) below the
top of the head restraint, while
deflecting less than four inches (102
mm) and without a seat back failure.
The standard also specified that the top
of the head restraint must be at least 700
mm (27.5 in) above the H-point as
measured along the torso reference line
of the J826 manikin.40 This effectively
placed a 565 Nm (5,000 in-lb) moment
minimum strength requirement on the
seat back while also placing a lower
bound on seat back stiffness because
this moment must be achieved within a
specified amount of deflection. Thus,
between FMVSS Nos. 202 and 207, all
Following the issuance of FMVSS No.
207, Derwyn Severy, a principal
investigator at the Institute of
Transportation and Traffic Engineering
(ITTE) at UCLA, published a paper 41 at
the 13th Stapp Car Crash Conference
advocating safer seat designs (‘‘Stapp
paper’’). The ITTE had been conducting
field investigations and crash tests
throughout the 1960s as they worked to
develop design concepts for vehicle
seats.
The 1969 Stapp paper provided the
basis for several seat design
recommendations. Included were
recommendations to increase the seat
back strength requirement to 11,300 Nm
(100,000 in-lb) and limit the seat back
rotation to 10 degrees in a quasi-static
37 The rulemaking that established FMVSS No.
207 did not discuss why it set a rearward moment
with a different reference point and value than
recommended by the 1963 version of SAE J879. See
32 FR 2415.
38 The magnitude of the force increase is equal to
the inverse of the cosine of the angle of the seat
back from the vertical. So a seat back with a 25 deg
angle would have a 1.1 (1/cos(25)) times greater
load applied in FMVSS No. 207 than in SAE J879.
39 33 FR 2945 (Feb. 12, 1968).
40 SAE J826–1995: Devices for Use in Defining
and Measuring Vehicle Seating Accommodation; 49
CFR 571.10; 73 FR 58896 (Oct. 8, 2008).
41 Severy, Derwyn M.; Brink, Harrison M.; Baird,
Jack D; Blaisdell, David M.; ‘‘Safer Seat Designs,’’
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
4. 1969—Report on Seat Safety Studies
at ITTE
PO 00000
Frm 00014
Fmt 4701
Sfmt 4702
test. According to Severy, this load level
was consistent with collision-induced
forces caused by the seat inertial forces
augmented by a 50th percentile male
occupant in a 30 g rear-end crash.
In 1976, Severy published a follow-on
paper on seat design.42 In it, he offered
his observations on safety
improvements in production seats
brought about by the 1968 standard:
‘‘that laboratory tests established that
production seats from cars large and
small, foreign and domestic, and from
vehicles 30 years old to new, have seat
back strengths remarkably alike and that
substantially exceed the required
FMVSS No. 207 criteria.’’ Severy
additionally stated that production seats
were incapable of effectively resisting
motorist inertial forces for any but light
impact exposures without experiencing
excessive yield and/or component
separation.
Proceedings of the 13th Stapp Car Crash Conference
Society of Automotive Engineers; Warrendale, PA
December 2–4, 1969; Boston, MA.
42 Severy, D.M., Blaisdell, D.M., and Kerkoff, J. F.;
‘‘Automotive Seat Design and Collision
Performance,’’ 1976 SAE Transactions, Sec. 4, Vol.
85.
E:\FR\FM\16JYP2.SGM
16JYP2
EP16JY24.013</GPH>
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Figure III.1 - FMVSS No. 207 moment schematic (left). SAE J879 moment schematic (right).
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
5. 1974—Notice of Proposed
Rulemaking (NPRM) To Revise FMVSS
No. 207
In February 1974, Carl Nash of the
Public Interest Research Group
petitioned NHTSA to implement a
dynamic requirement for seat backs. He
asked NHTSA to add a rear impact test
into FMVSS No. 208, ‘‘Occupant crash
protection,’’ with acceptance criteria
based on head rotation of a seated crash
test dummy. Nash also called on
NHTSA to consolidate FMVSS No. 202
with FMVSS No. 207 because of the
close relationship between head
restraints and seats in mitigating
injuries in rear impacts.
In March 1974, NHTSA published an
NPRM that included proposed seat back
requirements that essentially mirrored
Nash’s request.43 However, instead of
amending FMVSS No. 208, NHTSA
proposed to add the dynamic barrier test
to a new, revised version of FMVSS No.
207. The test was to be conducted using
the same moving barrier apparatus as
that of the FMVSS No. 301 rear impact
test for fuel system integrity, which had
been proposed a year earlier.44
Although a seated dummy was
specified, NHTSA did not propose any
requirements based on dummy head
rotation as requested by Nash. Instead,
NHTSA proposed a maximum seat back
rotation of 45 degrees. The proposal also
integrated the requirements of FMVSS
No. 202 into a single, consolidated
standard.
To support a decision for a final rule,
NHTSA contracted with the University
of New Mexico to conduct rear impact
tests. Sled tests were run on yielding vs.
rigid seat backs using post-mortem
human subjects (PMHS).45 At the time,
NHTSA was concurrently investigating
whether to revise FMVSS No. 202 to
better mitigate the effects of whiplash.
In consideration of this, rigid and
yielding seats were tested with and
without a head restraint. Sled tests were
run by simulating a crash in which a
stationary vehicle is struck from the rear
by another vehicle having the same
mass and travelling at a speed of 51 km/
h (32 mph). The investigators observed
that with no head restraint, rigid seats
produced higher whiplash effects than
yielding seats in low-speed rear
impacts. Also, ramping was exacerbated
in rigid seats with no head restraint.
Thus, the results were deemed to be
inconclusive as to whether yielding
43 See,
39 FR 10268 (Mar. 19, 1974).
38 FR 22417 (Aug. 20, 1973).
45 Hu, Anthony S., Stewart P. Bean, and Roger M.
Zimmerman. Response of belted dummy and
cadaver to rear impact. No. 770929. SAE Technical
Paper, 1977.
44 See
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
seats or rigid seats reduced the risk of
injury. In addition to the work at the
University of New Mexico, other basic
research was being conducted on the
more general topic of human injury
tolerance to rearward forces and the
biofidelity of the neck response of test
dummies in rear impacts.46 47 It is
noteworthy that NHTSA commissions
another study in 1974 on the safety of
occupants of large school buses (school
buses with gross vehicle weight rating
(GVWR) greater than 4,536 kilogram (kg)
(10,000 pounds (lb))) prior to issuance
of FMVSS No. 222.48 Following this
study, NHTSA developed the concept of
seating compartmentalization for school
buses, which led to the following
conclusion regarding the seating system:
‘‘The seats and restraining barriers must
be strong enough to maintain their
integrity in a crash yet flexible enough
to be capable of deflecting in a manner
which absorbs the energy of the
occupant.’’ 49 At least in the context of
larger school buses, NHTSA found there
was a benefit to yielding seats that
maintain structural integrity in order to
maintain occupant
compartmentalization when occupants
were not protected by seat belts. Based
on this conclusion, NHTSA developed a
force-deflection requirement for the
forward and rearward directions for
large school bus seat backs.50 The
rearward requirement protects
occupants in a rear collision, analogous
to the rear impact issue discussed in
this document.51
6. 1978—NHTSA Publishes a Request
for Comment on Rulemaking Priorities
On March 16, 1978, NHTSA
published a Request for Comments on
the agency’s plan to prioritize ongoing
rulemaking efforts.52 In establishing
priorities for the plan, NHTSA stated
that limited resources needed to be
focused on rules with the largest safety
benefits. It identified the 1974 proposal
to require stiffer seats as one of several
46 Ewing, Channing L., et al. ‘‘Effect of duration,
rate of onset and peak sled acceleration on the
dynamic response of the human head and neck.’’
Proceedings: Stapp Car Crash Conference. Vol. 20.
Society of Automotive Engineers SAE, 1976.
47 Muzzy, W. H. I., and Leonard Lustick.
‘‘Comparison of kinematic parameters between
hybrid II head and neck system with human
volunteers for minus-Gx acceleration profiles.’’
Proceedings: Stapp Car Crash Conference. Vol. 20.
Society of Automotive Engineers SAE, 1976.
48 39 FR 27584 (July 30, 1974).
49 72 FR 65509 (Nov. 21, 2007).
50 49 CFR 571.222—Standard No. 222; School bus
passenger seating and crash protection.
51 A rear impact into a large school bus is a much
less severe impact environment for the occupants
of the bus than that of occupants of a light vehicle
experiencing an equivalent rear impact.
52 43 FR 11100 (June 7, 1978).
PO 00000
Frm 00015
Fmt 4701
Sfmt 4702
58011
open rulemakings with low priority and
proposed to terminate it. In 1979, when
the plan was issued, the 1974 proposal
was terminated.53 No public comments
were received in response to the request
for comments.
Over the next several years, NHTSA
continued to investigate the safety of
occupants in rear impacts. Beginning in
1979, NHTSA conducted over 30 fullscale rear-impact crash tests on vehicles
with instrumented dummies seated in
the front seats. The FMVSS No. 301
barrier was driven into the stationary
vehicles at speeds ranging from 48–56
km/h (30 to 35 mph). These rear impact
crash tests are catalogued online.54
7. 1989—NHTSA Receives Petitions for
Rulemaking on Revisions to FMVSS No.
207
In 1989, Kenneth J. Saczalski and
Alan Cantor submitted their first
petitions for rulemaking on this subject
to NHTSA.55 56 Saczalski sought an
increase in the seat back moment
requirement in FMVSS No. 207 from
373 Nm (3,300 in-lb) to 6,330 Nm
(56,000 in-lb),a factor of 17 increase.
The aim was to reduce the incidence of
injuries due to ramping and ejection in
rear-end crashes. On July 24, 1989,
NHTSA notified Saczalski that his
petition was granted.
Cantor’s 1989 petition asked NHTSA
to amend FMVSS No. 207 to eliminate
occupant ramping during a rear impact.
Cantor did not provide a standardized
test procedure to measure and assess
ramping, nor did he describe a
practicable countermeasure that could
prevent ramping. Nonetheless, on
February 28, 1990, NHTSA notified
Cantor that his petition was granted.
After granting these petitions, NHTSA
published another request for comments
(1989 RFC) on the need for amending
the seat back performance requirement
in FMVSS No. 207 and opened a docket
to receive comments on the petitions
and pertinent issues.57 In his comments
submitted to this docket, Saczalski
provided additional
recommendations.58 He asked NHTSA
53 44 FR 24591 (Apr. 26, 1979), ‘‘Five Year Plan
for Motor Vehicle and Fuel Economy Rulemaking’’.
54 https://www.nhtsa.gov/research-data/researchtesting-databases#/vehicle/.
55 Docket 89–20-No.1–001 or Docket NHTSA–
1996–1817–0002. Both petitions have significant
overlap to the 2014 Saczalski and 2015 Cantor
petitions discussed in this document.
56 The previous NHTSA Seat Dockets, 89–20
Notices 1–3, are now available on the Docket
Management System (DMS) at NHTSA–1998–1817,
–4047 and –4064, respectively.
57 54 FR 40897 (Oct. 4, 1989). Originally NHTSA
Docket 89–20–No. 1, and later transferred to Docket
NHTSA–1996–1817.
58 Docket NHTSA–1996–1817–0002.
E:\FR\FM\16JYP2.SGM
16JYP2
58012
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
to also include a dynamic rear impact
crash test using the FMVSS No. 301
barrier and a 95th percentile male
dummy in the seat.
Most comments from the automotive
industry on the 1989 Saczalski and
Cantor petitions opposed any new seat
back stiffness requirements. They
argued that real-world crash data did
not indicate that a safety-related
problem existed. General Motors, for
example, cited its own field data to
conclude that any benefits associated
with seat standard changes for rear
impact protection were very limited.59
Ford cited a study of real-world crashes
to conclude that a safety need did not
exist.60 The authors of that analysis had
also reviewed test data from prior
studies (including those of Severy, et
al). They concluded that rigid seat backs
would probably exacerbate injuries
because yielding seats absorb energy
safely as they deform, thus reducing
injurious forces borne by the occupant,
including whiplash-causing forces.
Occupant rebound from a rear impact
and a subsequent hard thrust forward
was also cited as a negative effect of
rigid seats. Furthermore, a follow-up
study by two of the same authors
concluded that ramping is more likely
to occur in a rigid seat regardless of
whether a seat belt is used or a head
restraint is in place.61 On the other
hand, Mercedes-Benz supported an
upgrade to FMVSS No. 207.62 It noted
that seats in Mercedes vehicles were
specifically designed to reduce the
danger to front and rear occupants
during rear impacts as a result of
excessive rearward seat back
deformation and the resultant
interaction between occupants.
At the time, NHTSA commissioned a
study on injury incidence to support a
rulemaking decision.63 This analyzed
the problem using NASS real-world
crash data. The study confirmed that
seat back yield in severe rear crashes
does occur.64 Severe crashes were found
to be infrequent, however, amounting to
approximately 5% of all rear impacts.
59 Docket
NHTSA–1996–1817–0010.
NHTSA–1996–1817–0004.
61 James, M.B., Strother, C.E., Warner, C.Y.,
Decker, R.L., & Perl, T.R. (1991). Occupant
protection in rear-end collisions: I. Safety priorities
and seat belt effectiveness. SAE transactions, 2019–
2027.
62 Docket NHTSA–1996–1817–0015.
63 ‘‘Current Issues of Occupant Protection in Car
Rear Impacts,’’ February 1990, Data Link, Inc.,
NHTSA Docket 89–20–No. 1–21 or Docket
Management System NHTSA–1996–1817–22.
64 This study considered severe crashes as those
with a vehicle change in velocity greater than 15
mph, CDC extent of damage (exterior vehicle
damage) greater than 3, and at least one occupant
with a maximum AIS of 3 or greater or with
hospitalization or fatality.
khammond on DSKJM1Z7X2PROD with PROPOSALS2
60 Docket
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
The study also showed that impacts
with components in the rear seat
compartment and ejections are a
relatively small portion of the injuries.
Injuries due to occupant impacts to
components in the rear seat
compartment accounted for 2.8%
(unrestrained occupant) and 0.1%
(restrained occupant) of the most severe
injury to front seated occupants in rear
impacts, and only 3.2% of all harm to
unrestrained occupants in rear impacts
involved occupant ejection.
The study also concluded that current
seat designs provided reasonable safety
in rear-end crashes, and that seat belts
are effective in reducing injuries. The
report suggested that new head restraint
designs offered the best possibility to
mitigate the largest portion of injuries in
rear-end crashes.
Additionally, Transport Canada
submitted a report to the docket of 23
case studies of real-world rear impacts,
all of which involved vehicles that
experienced seat back failures, and 11 of
which resulted in occupant ejections.65
Of the cases involving a rear seat
passenger, four of the five rear
passengers sustained injuries attributed
to seat back failure of the front seat.
NHTSA provided a summation of the
comments and reports in a 1992
summary report.66 This document was
placed in the docket for the safety plan
discussed below. The report concluded
that improving seating system
performance may be more complex than
simply increasing the strength of the
seat back, and that a proper balance in
seat back strength and compatible
interaction with head restraints and seat
belts must be obtained to optimize
injury mitigation.
8. 1992–2000 NHTSA Publishes a
Request for Comment on Possible
Revisions to FMVSS No. 207, Grants
Two Petitions and Conducts Research
In November 1992, the agency
published another Request for Comment
on more recent research findings and a
proposed plan to address seat back
performance.67 At that time, the agency
had refrained from upgrading FMVSS
No. 207 until significant results from
research were obtained, though the
rulemaking action resulting from the
1989 petition grants was still open. The
first document the agency placed in the
docket was a report summarizing agency
findings up to that point. The 1992
report stated that four categories of
65 NHTSA Docket 89–20–No. 1–018 or Docket
Management System NHTSA–1996–1817–019.
66 NHTSA Docket 89–20–No. 3–001 or Docket
Management System NHTSA–1998–4064–001.
67 57 FR 54958 (Nov. 23, 1992).
PO 00000
Frm 00016
Fmt 4701
Sfmt 4702
performance issues need to be
addressed as part of potential future
changes to FMVSS No. 207.68 These
four categories are:
(1) Seating system integrity: the ability of
the seat and its anchorage to the vehicle to
withstand crash forces without failure.
(2) Energy absorbing capability: the extent
to which the seat and its attachment
components absorb energy and the manner in
which the seat and its attachment
components release energy during rebound.
(3) Compatibility of a seat and its head
restraint: The concern in this category is that
any change in seat back energy absorbing
capability could exacerbate head or neck
injuries if the geometry and energy absorbing
capability of the head restraint is not also
changed.
(4) Seat belt restraint system: a seating
system and its seat belt restraint system must
complement each other to prevent injury.
Over the ensuing 10-year period, the
agency conducted extensive physical
testing of seat backs, performed
computer modeling of seated occupants
in rear impacts, and conducted dynamic
testing of instrumented test dummies in
vehicle seats. At the same time, NHTSA
also assessed how new requirements for
head restraints could mitigate whiplash
injury in lower-speed rear-end crashes.
The details of those efforts are outlined
in several NHTSA reports provided in
docket folder NHTSA–1998–4064
(document numbers 24–27, 31).
NHTSA also granted two more
petitions related to seat back strength:
King (March 1998) 69 and Hogan
(December 1998).70 King petitioned for
a dynamic test using the FMVSS No.
301 rear impact test procedure. Hogan
stated that conformance to the current
regulation was being used in litigation
as a defense for the performance of
contemporary seat designs, and
therefore asked NHTSA to ‘‘suspend’’
FMVSS No. 207 until such time that the
standard could be improved.
In comments posted in dockets
NHTSA–1996–1817 71 and NHTSA–
1998–4064,72 most in the automobile
industry argued that seat back
deformation was protective to the
occupant by absorbing some crash
energy. However, there was recognition
that better seat back performance
requirements could improve occupant
safety in rear impacts greater than 40
km/h (25 mph). Greater control of
68 ‘‘Summary of Safety Issues Related to FMVSS
No. 207,’’ (1992), NHTSA–1998–4046–001.
69 NHTSA–1998–4377–0001.
70 NHTSA–1999–5482–0008.
71 These were originally posted to NHTSA Docket
89–20-No 1, and subsequently transferred to Docket
NHTSA–1996–1817.
72 These were originally posted to NHTSA Docket
89–20-No 3, and subsequently transferred to Docket
NHTSA–1998–4064.
E:\FR\FM\16JYP2.SGM
16JYP2
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
occupant kinematics in severe rear
crashes was thought to enhance
occupant safety, even for belted
occupants, by controlling rearward
deflection of the seat back. Further
comments presented by the Advocates
for Highway and Auto Safety expressed
concern about the harm caused by
bodily impact with vehicle structures
and noted the importance of negating
excessive seat back rotation, ramping,
and occupant rebound. One individual
consultant described the consultant’s
opinion regarding the deficiency of
FMVSS No. 207 and the impact that the
standard may have had on automotive
seat designs from that time. Another
consulting firm expressed concern about
the level of deformation that occurs due
to the force applied to seat backs of that
time in rear impacts and its effect on the
effectiveness of the restraint systems in
higher severity rear impacts.
The comments and research at the
time affirmed that the issues of seat
back, head restraint, and belt retention
were inextricably linked to overall
occupant safety. For example, in studies
such as the 1997 Prasad,73 1977
University of New Mexico study, and
1976 Severy study, the disbenefits of a
rigid seat were particularly evident in
seats with baseline head restraints.74 In
the 1997 Prasad study for example, the
authors found that stiffer seats led to
higher neck and lumbar spine loads in
rear impact tests. One complicating
factor from this period is that most of
the laboratory tests were performed with
Hybrid II or Hybrid III 50th percentile
male (HIII–50M) dummies, which are
seated dummies designed based on
human indices measured in frontal
crashes. The torso and pelvis of these
dummies do not articulate well in rear
impacts, and such articulation is needed
to faithfully exhibit ramping. While a
larger size ATD would more fully
exercise a seat back in a rear impact, the
additional use of a smaller ATD with
female-specific characteristics may have
provided a more comprehensive
assessment of occupant kinematics and
injury risk for different seat designs in
these earlier studies. Comments posted
in the docket also emphasized the rear
impact protection points NHTSA made
in the 1992 study, in particular the need
for energy absorption of the seat back,
while also recognizing that performance
73 See below in Review of Additional Literature,
Occupant Dynamics, for an in-depth discussion of
the findings.
74 The term ‘‘baseline’’ indicates head restraints
manufactured prior to the 2004 update of the head
restraint standard. These provided much less
protection than those mandated by today’s Federal
standard. 69 FR 74848 (Dec. 14, 2004).
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
requirements may enhance rear impact
protection.
9. 2004—NHTSA Issues Final Rule
Upgrading FMVSS No. 202, Head
Restraints
NHTSA’s research on rear impact
crashes and head restraints led the
agency in January 2001, to address the
problem of whiplash injuries by
proposing to upgrade the head restraint
standard, FMVSS No. 202.75 At the
time, the agency estimated that
approximately 800,000 whiplash
injuries occurred annually in all crash
types, resulting in a total annual cost of
$5.2 billion. Whiplashes in rear impacts
were estimated to be about 270,000
annually.
After considering public comments on
the proposal, NHTSA published the
final rule on December 14, 2004.76 It
was estimated to reduce the number of
whiplash injuries by about 17,000 per
year. The revised standard imposed an
increased head restraint height
requirement such that all outboard front
seat head restraints must be capable of
adjusting to at least 800 mm (31.5 in)
and not have an adjustment position
below 750 mm (29.5 in). It also imposed
a minimum backset 77 measurement that
required the head restraint to be closer
to the back of a seated occupant’s head.
The updated standard maintained the
requirement for the head restraint to
withstand a 200 lb-f or 890 N rearward
force applied 65 mm (2.5 in) below its
top, when adjusted to its highest
position, which must be at least 800
mm. Thus, this imposes an effective
rearward strength requirement on seat
backs of 654 Nm (5,790 in-lb), where
654 = 890*(0.8–0.065). This is a factor
of 1.75 greater than the rearward
strength requirement of FMVSS No. 207.
10. 2004—NHTSA Terminates
Rulemaking on FMVSS No. 207, Seating
Systems
By the time NHTSA finalized the
head restraint regulation in 2004, it was
clear to the agency that additional
research and data analyses were needed
to allow a fully informed decision on
any change to the seat back strength
requirement in FMVSS No. 207. A year
earlier, researchers at Johns Hopkins
University Applied Physics Laboratory
completed a study commissioned by
NHTSA, which strongly suggested that
seat back stiffness plays a role in
FR 968 (Jan. 4, 2001).
FR 74848 (Dec. 14, 2004).
77 Backset is defined as minimum horizontal
distance between the rear of a representation of the
head of a seated 50th percentile male occupant and
the head restraint, as measured by the head restraint
measurement device. 49 CFR 571.202(a).
PO 00000
75 66
76 69
Frm 00017
Fmt 4701
Sfmt 4702
58013
whiplash injury risk in low-speed rear
impacts.78 The main finding was that
the risk of whiplash injury cannot be
related to a single design factor, such as
head restraint height. The study
concluded that altering the seat back
design could have an effect on the
occurrence of whiplash. Additional
analyses were needed to assure that a
NHTSA-imposed seat back requirement
would not create a greater risk of
whiplash. Since it was not clear when
such analyses would be complete, on
November 16, 2004, NHTSA terminated
the FMVSS No. 207 rulemaking
proceeding that had been open since
1989.79 NHTSA was unable to fully
establish that a need for a stronger seat
back existed, establish a definitive link
between injury reductions and potential
new regulatory seat back requirements,
or show that new requirements under
consideration would not exacerbate risk
of neck injuries due to whiplash, roof
contacts, or rebound. However, NHTSA
did not make a finding that an FMVSS
No. 207 amendment was not warranted.
Instead, NHTSA stated that further
study is needed to make a definitive
determination of the relative merits of
different potential rulemaking
approaches and that research on seat
back issues would continue.
11. Further Regulatory Changes Since
2004
There have been two prominent
regulatory changes regarding occupant
safety in rear-end crashes that have been
fully implemented since NHTSA
terminated the rulemaking on FMVSS
No. 207: a revision to FMVSS No. 202,
and a revision to FMVSS No. 301, the
fuel system integrity standard. FMVSS
No. 202 is the standard focused on neck
injury protection in rear impacts.
Regarding FMVSS No. 301, while the
stated purpose of the standard is to
reduce incidence of fire and fuel
ingestion incidents, it utilizes a test
procedure that represents a relatively
severe rear impact in the field and has
been recommended by petitioners as a
viable basis for an upgrade to FMVSS
No. 207. Additionally, some researchers
have reported that vehicles compliant
with the updated FMVSS No. 301 have
shown significant reduction in fatality
risk in rear impact. 80 Therefore, as part
78 Kleinberger M, Voo LM, Merkle A, Bevan M,
Chang S: The Role of Seatback and Head Restraint
Design Parameters on Rear Impact Occupant
Dynamics. Proceedings of 18th International
Technical Conference on the Enhanced Safety of
Vehicles, Paper #18ESV–000229, Nagoya, Japan,
May 19–22, 2003.
79 69 FR 67068 (Nov. 16, 2004).
80 Viano, David C., and Chantal S. Parenteau.
‘‘Effectiveness of the revision to FMVSS 301: FARS
E:\FR\FM\16JYP2.SGM
Continued
16JYP2
58014
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
of our analysis of the need for new seat
back strength requirements, NHTSA
considers the effects that these changes
have had on seat performance and
occupant injury risk in moderate-tosevere rear-end crashes.
(a) FMVSS No. 202a, ‘‘Head Restraints’’
khammond on DSKJM1Z7X2PROD with PROPOSALS2
FMVSS No. 202a was issued in 2004
and applied an updated set of safety
requirements for head restraints
beginning with model year 2010.81
Although the new requirements were
not specifically intended to strengthen
seat backs, the head restraint upgrade
resulted in an increase in the minimum
acceptable seat back strength.
FMVSS No. 202a requires a fully
extended head restraint to withstand an
890 N (200 lb-f) rearward load.
Although this load was not changed in
FMVSS No. 202a, the minimum height
of the head restraint was raised from
700 mm to 800 mm. Thus, the effective
torque requirement on the seat back
increased from about 565 Nm (5,000 inlb) to 654 Nm (5,790 in-lb).82
FMVSS No. 202a also introduced a
new optional dynamic test for head
restraints. In the dynamic test, the entire
vehicle is tested on a sled with a seated
HIII–50M dummy and subjected to a
17.3 km/h (10.75 mph) rear impulse.
The dummy’s rearward head rotation
with respect to its torso must be limited
to 12 degrees for the dummy in all
outboard designated seating positions.
Though inertial forces of the occupant
acting on the seat back in FMVSS No.
202a testing are much lower compared
to those associated with an FMVSS No.
301 test pulse, FMVSS No. 202a’s
dynamic test may have potentially
resulted in stronger seat back designs for
those seats certified to this option
because a stiffer seat back with an
adequately positioned head restraint
would capture the head motion before
the limits are exceeded. Neither NHTSA
nor, to our knowledge, the petitioners,
however, have studied whether the
upgrade to FMVSS No. 202a has
resulted in injury reductions other than
whiplash.
and NASS–CDS analysis of fatalities and severe
injuries in rear impacts.’’ Accident Analysis &
Prevention 89 (2016): 1–8.
81 49 CFR 571.202a. See also 69 FR 74848 (Dec.
14, 2004). Many requirements became effective on
September 1, 2009, while others, in particular those
regarding rear head restraints, came into effect the
following year. Please review S2 of the standard for
further details.
82 Agency testing of pre-FMVSS No. 202a seats
showed seat back strength well in excess of 654
Nm, so there was no need for manufacturers to
increase seat back strength to meet the new head
restraint requirements of FMVSS No. 202a, see
Docket document no. NHTSA–1998–4064–0026.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
(b) Upgrade to FMVSS No. 301, Fuel
System Integrity
On November 13, 2000, NHTSA
proposed a more stringent rear impact
offset test using a lighter deformable
barrier.83 A final rule was published on
December 1, 2003, and the new
requirements for the fuel systems were
phased in during MYs 2007–2009.84
Although the fuel containment
requirements remained the same as the
previous version of FMVSS No. 301, the
crash test was generally more rigorous
for most passenger cars. Vehicles that
passed the new rear impact
requirements were found to provide
protection against crashes in which the
impact produced a 33 to 50 percent
higher DV (which corresponds to 110
percent more energy being dissipated in
the crash) compared to the previous
test.85
In a post-regulatory assessment,
NHTSA compared the structure of preand post-standard vehicles. NHTSA
observed substantial structure upgrades
in the newer vehicles, which may
mitigate intrusion of vehicle structures
into the rear seat occupant
compartment. For example, in the 2016
study, Viano and Parenteau found MY
2008 and onward FMVSS No. 301
compliant vehicles to have a 27.1–
32.8% reduction in fatality risk in rear
impacts compared to 1996–2001 MY
vehicles. Two considerations limit the
conclusions that can be drawn from this
data. First, injury risk was estimated
irrespective of post-crash fire. Thus,
some of the injury risk reduction could
be a reduction in the incidence of fire.
Second, the authors noted that the
changes in rear structures occurred
while front seats were transitioning to
higher retention designs, which may
contribute to the reduction in fatality
risk.
(c) NCAP
In 2007 NHTSA published a notice
requesting comments on an agency
report titled ‘‘The New Car Assessment
Program (NCAP) Suggested Approaches
for Future Program Enhancements.’’ 86
With regard to rear impact protection,
NHTSA proposed that it could provide
consumers with basic information on
rear crashes such as safe driving
behavior, proper adjustment of head
restraints, real-world safety data by
vehicle classes, and links to the
FR 67693 (Nov. 13, 2000).
FR 67068 (Dec. 1, 2003).
85 Pai, Jia-Ern. ‘‘Evaluation of FMVSS NO. 301,
‘Fuel System Integrity,’ as upgraded in 2005 TO
2009.’’ National Center for Statistics and Analysis,
National Highway Traffic Safety Administration.
Washington, DC (2014).
86 72 FR 3473 (Jan. 25, 2007).
PO 00000
83 65
84 68
Frm 00018
Fmt 4701
Sfmt 4702
Insurance Institute of Highway Safety
(IIHS) rear impact test results. The
agency further proposed that a dynamic
rear impact test, which addresses those
injuries not covered by the agency’s
current standards, could be investigated
and incorporated into the ratings
program. Several organizations and
manufacturers recommended that
NHTSA evaluate the effectiveness, cost,
and safety benefits of a rear impact test
before incorporating such a test into
NCAP. Industry comments suggested
that NHTSA should also evaluate the
effectiveness of the FMVSS No. 202a
update and that incorporating rear
impact safety into NCAP would be
better directed toward areas not fully
addressed by the current regulation.
Commentors suggested that NHTSA
should study whiplash-type injuries and
countermeasures and encourage public
education on the proper adjustment of
the head restraint. NHTSA concluded
that a dynamic test would not be
premature at that time since such an
option existed in FMVSS No. 202a.
However, NHTSA noted that the test
dummy used by IIHS is not used for
testing FMVSS compliance, and some of
the injury criteria used for the
assessment had not been correlated with
real-world injury. Ultimately, the
agency did not incorporate rear impact
protection information into the NCAP
program.
IV. Review of Additional Literature
NHTSA, industrial, academic, and
non-profit researchers have conducted
significant research into the rear impact
protection of seat backs and head
restraints, and research is ongoing.
Researchers have investigated occupant
dynamics in rear impacts, development
of safer seats for the occupant in rear
impacts, and occupant injury
mechanisms in rear impacts.
A. Occupant Dynamics
Occupant dynamics and protection in
rear collisions is a complex
multivariable problem. The ideal safe
seat for one occupant in a certain rear
collision scenario may not be the ideal
safe seat for another occupant or for a
different scenario. For example,
research suggests that females have a
higher risk of whiplash injury compared
to males and respond differently to a
rear impact.87 88 89 90 Additionally, other
87 Berglund A, Alfredsson L, Jensen I, et al.
Occupant- and crash-related factors associated with
the risk of whiplash injury. Ann Epidemiol
2003;13:66–72.
88 Carlsson, Anna. Addressing female whiplash
injury protection-a step towards 50th percentile
female rear impact occupant models. Chalmers
Tekniska Hogskola (Sweden), 2012.
E:\FR\FM\16JYP2.SGM
16JYP2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2
occupant characteristics, such as
weight, can play a significant role in
rear impact injury risk, as shown in the
NASS–CDS case number 2011–49–57
noted by Viano and Parenteau.91 This
case outlines a rear collision with an
estimated DV between 35 and 39 km/h
(21.7 and 24.2 mph). The 141 kg (311 lb)
driver of the rear impacted 2008 model
passenger vehicle suffered critical head
and neck injuries after decoupling from
the rotated driver seat back and
colliding with the rear seat back. The 68
kg (150 lb) right front passenger of the
same struck vehicle, however, had no
documented injury.92 The injury
severity suffered by the driver in this
case is rare in rear impacts. Viano and
Parenteau found passengers with
injuries of MAIS 4 or greater severity,
including fatalities, represented 0.08%
of passengers with injury in rear
collisions in MY 2008 and newer
vehicles. A quantitative description of
seat back response is complicated by the
potential sensitivity of response to a
range of initial conditions and external
factors including head posture,93
awareness,94 seat belt use and seat
geometry including initial seat back
recline angle,95 details of the crash
pulse,96 97 and specific occupant
characteristics such as weight
distribution. The initial posture and
location of the occupant is also thought
89 Viano, David C. ‘‘Seat influences on female
neck responses in rear crashes: a reason why
women have higher whiplash rates.’’ Traffic injury
prevention 4.3 (2003): 228–239.
90 Linder, Astrid, and Mats Y. Svensson. ‘‘Road
safety: the average male as a norm in vehicle
occupant crash safety assessment.’’
Interdisciplinary Science Reviews 44.2 (2019): 140–
153.
91 Viano, David C., and Chantal S. Parenteau.
‘‘Effectiveness of the revision to FMVSS 301: FARS
and NASS–CDS analysis of fatalities and severe
injuries in rear impacts.’’ Accident Analysis &
Prevention 89 (2016): 1–8.
92 Comparisons such as these should be made
with care because the driver and passenger seat may
not be structurally identical, with the driver seat
sometimes having more and powered adjustments
compared to the passenger seat.
93 Lenard, James, Karthikeyan Ekambaram, and
Andrew Morris. ‘‘Position and rotation of driver’s
head as risk factor for whiplash in rear impacts.’’
J Ergonomics S 3.2 (2015).
94 Siegmund, Gunter P., et al. ‘‘Awareness affects
the response of human subjects exposed to a single
whiplash-like perturbation.’’ Spine 28.7 (2003):
671–679.
95 Kang, Yun-Seok, et al. ‘‘Effects of seatback
recline and belt restraint type on PMHS responses
and injuries in rear-facing frontal impacts.’’ SAE
International journal of transportation safety 10.2
(2022): 09–10.
96 Hynes, Loriann M., and James P. Dickey. ‘‘The
rate of change of acceleration: Implications to head
kinematics during rear-end impacts.’’ Accident
Analysis & Prevention 40.3 (2008): 1063–1068.
97 Siegmund, Gunter P., et al. ‘‘The effect of
collision pulse properties on seven proposed
whiplash injury criteria.’’ Accident Analysis &
Prevention 37.2 (2005): 275–285.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
58015
protection and the characteristic of
rearward rotation of the seat back.
Other research suggests that
optimizing seat back design, including
stiffness, can reduce injury risks in rear
impact. In a 1996 study, Svensson, et
al.101 analyzed the influence of seat
back properties on neck injury using the
HIII ATD with a Rear Impact Dummy
(RID)-neck in low-speed rear collision
sled testing. The study found that it was
possible to significantly reduce harmful
head-neck motion of the ATD by
optimizing the head-to-head restraint
gap, seat back frame stiffness, and
characteristics of the seat-back cushion.
A separate statistical analysis
involving 20 years of the NASS database
by Burnett 102 found that front seat
occupants are significantly more
protected in rear collisions compared to
other crash directions, even for the most
severe rear impacts where major seat
yielding and occupant decoupling from
the seat can occur. The study also
conducted quasi-static mechanical
testing and rear impact sled tests of
seven production seats to investigate the
correlation between mechanical
parameters and ATD kinematics. The
study found no significant correlation
between the seat strength and any of the
recorded ATD metrics, while seat
stiffness and an energy absorption
parameter were nonlinearly correlated
with ATD metrics.
to influence injury risk. Many occupants
in rear collisions are believed to be outof-position (e.g., seated off-center), and
out-of-position occupants are thought to
have a higher probability of injury in
rear impacts than symmetrically or
normal-positioned occupants.98 99 100
Some research suggests that limiting
seat back rotation can have detrimental
effects, particularly regarding neck
injuries. In the 1997 Prasad study of
real-world rear impacts, the authors
concluded that a revision to severely
limit seat back rotation would have
detrimental effects. The study analyzed
the 1980–94 NASS database to compare
injury rates in pickup trucks with
passenger vehicles in rear impacts. This
allowed for comparison between
yielding seat performance with the
rotationally stiff seats of pickup trucks
(stiffness is due to the small gap
between seat and cab). A higher rate of
occupant injury in rear collisions across
all DVs was observed in pickup trucks.
The authors inferred that rotationally
rigid seats could have an increased rate
of injury in rear impacts. The 1997
Prasad study further analyzed a series of
sled tests to investigate the relationship
between seat stiffness and
anthropomorphic test device (ATD)
kinematics for rear impact DV of 16, 24,
and 40 km/h (9.9, 14.9, and 24.9 mph).
After assessing the range of sampled
speeds and ATD measurements, Prasad
hypothesized that (all else being equal)
stiffening of the baseline 1996
production seats can result in an overall
increase in whiplash type injuries at
low-to-moderate speeds and a greater
potential for serious neck injury at
higher speeds, in addition to other
conclusions. This study, however, has
limitations. Many of the pickups in the
crash data analyzed may not have had
head restraints because trucks were not
required to have head restraints until
MY 1993. Moreover, a rotationally rigid
seat represents the extreme end of the
debate around the seat strength set by
FMVSS No. 207. While modern
production seats are characterized by a
seat strength many times the value set
by FMVSS No. 207, these seats also
display a degree of balance between
high and low-speed rear impact
B. Rear Impact Protection Technology
This section discusses some seat
designs intended to improve rear impact
protection that have been incorporated
over the years.
In 1998, a set of design guidelines was
published by Volvo Cars and Autoliv,
Inc. for seats that emphasized the
importance of controlling an occupants’
absolute and relative head and torso
kinematics throughout the rear impact
process, to protect against neck and
other injuries.103 The Volvo Cars’
Whiplash Protection System (WHIPS)
was introduced in 1998 and is built
around these guidelines. In a significant
rear collision, the first generation
WHIPS seat back rotation point moves
rearward and later transitions to
rearward rotation. During seat back
rotation, a mechanical linkage
98 Strother, Charles E., Michael B. James, and John
Jay Gordon. ‘‘Response of out-of-position dummies
in rear impact.’’ SAE transactions (1994): 1501–
1529.
99 Benson, Brent R., et al. ‘‘Effect of seat stiffness
in out-of-position occupant response in rear-end
collisions.’’ SAE transactions (1996): 1958–1971.
100 Burnett, Roger A., Chantal S. Parenteau, and
Samuel D. White. ‘‘The effect of seatback
deformation on out-of-position front-seat occupants
in severe rear impacts.’’ Traffic Injury Prevention
(2022): 1–5.
101 Svensson, Mats Y., et al. ‘‘The influence of
seat-back and head-restraint properties on the headneck motion during rear-impact.’’ Accident
Analysis & Prevention 28.2 (1996): 221–227.
102 Burnett, Roger, et al. ‘‘The influence of
seatback characteristics on cervical injury risk in
severe rear impacts.’’ Accident Analysis &
Prevention 36.4 (2004): 591–601.
103 Lundell, Bjorn, et al. ‘‘The WHIPS seat-a car
seat for improved protection against neck injuries
in rear-end impacts.’’ Proc. 16th ESV Conference,
Paper. Vol. 98. 1998.
PO 00000
Frm 00019
Fmt 4701
Sfmt 4702
E:\FR\FM\16JYP2.SGM
16JYP2
58016
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2
irreversibly absorbs rotational energy, so
there is less energy directed into the
occupant and rebound is reduced. The
seat back will then continue to rotate
and deflect rearward as a typical
production seat. According to data
reported by Volvo, the first generation
WHIPS seat reduced soft tissue neck
injury risk by 21% to 47% as compared
to prior seats.104
Another technology for whiplash
injury protection is active head
restraints that was introduced by Saab
in the late 1990s.105 These systems aim
to reduce the head restraint contact time
by actively shifting the head restraint
forward in a rear impact through a
mechanical linkage in the seat structure
activated when the seat occupant moves
rearward into the seat. Data acquired by
the NCAP program for MY2023 show
that 21 vehicle models representing 4
percent of vehicle sales are reported as
having active head restraints or provide
the option. At least one automotive
supplier is working on an
electromechanical system that moves
the head restraint up to 40 mm forward
when a rear sensor in the vehicle
anticipates a rear impact.106
In the early 1990s, General Motors
(GM) Research and Development Center
undertook an in-depth study of seat
characteristics to improve occupant
safety in rear impacts. In general, the
GM seat design fostered movement of
the pelvis rearward and into the lower
portion of the seat back frame in a way
that would preclude ramping and
reduce the moment arm on the seat
back. A key design component was to
balance the stiffness of the seat resisting
the rearward movement of the pelvis
against the ability of the seat back frame
to resist backward rotation. GM
established their own quasi-static test
for the purposes of assuring that a given
seat met the design parameters. It was
a destructive test that made use of a
50th percentile male dummy loaded
rearward into the seat back through the
lumbar joint. The dummy was free to
move up, down, and sideways during
rear loading. The test also allowed the
seat back to rotate rearward and twist in
a manner similar to what was observed
in sled testing. Eventually, GM’s seat
104 Jakobsson, Lotta, Irene Isaksson-Hellman, and
Magdalena Lindman. ‘‘WHIPS (Volvo cars’
Whiplash Protection System)—the development
and real-world performance.’’ Traffic injury
prevention 9.6 (2008): 600–605.
105 Wiklund, Kristina; Larsson, Håkan (1 February
1998). ‘‘Saab Active Head Restraint (SAHR)—Seat
Design to Reduce the Risk of Neck Injuries in Rear
Impacts.’’ Journal of Passenger Cars.
106 ‘‘Can a high-tech headrest reduce whiplash
injuries,’’ Automotive News, August 14, 2022,
https://www.autonews.com/suppliers/high-techheadrest-designed-reduce-whiplash-injuries.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
design targets were published by SAE
International.107 The targets were
derived from various measurements
taken during their quasi-static test. The
targets contained many more parameters
than FMVSS No. 207’s single
requirement to withstand a 373 Nm
(3,300 in-lb) moment (see table 1 for a
list of the parameters). Notably, the GM
parameters included a criterion that
limited the seat stiffness to no more
than 25 kN/m, while attempting to
assure that the seat had sufficient energy
absorbing properties. GM stressed that
simply raising the FMVSS No. 207
moment beyond 373 Nm would not
achieve a desirable seat design.
According to GM, increasing only the
seat back’s stiffness would reduce the
beneficial effects of yielding.
A seat design feature that was rare 25
years ago, but appears to be much more
common in modern seats is a dual
recliner system.108 109 A dual recliner
system places gear mechanisms
controlling the static recline angle on
both sides of the seat. This improvement
significantly strengthened production
seats and reduced longitudinal axis
twisting.110 The agency does not have
an estimate of the current level of
implementation of dual recliners and
requests that commenters provide these
data.
An IIHS study of contemporary
production seats claims that a wide
range of seating systems have achieved
a balance between low-speed protection
while maintaining structural integrity at
higher speeds and occupant
retention.111 This study conducted rear
impact sled testing on 26 modern
production seats at a DV of 36.5 km/h
(22.7 mph) using a 78 kg (172 lb) Hybrid
III 50th percentile male dummy. The
maximum dynamic seat back rotation
ranged from 15° to 47° from the initial
1. Neck Injuries
The term whiplash has been used
since the 1920s to describe various
symptoms or signs of cervical spine
injury in motor vehicle accidents. The
first case series studies on motor vehicle
whiplash injury were published in the
early 1950s.112 Later in the 1960s,
studies were conducted on the
mechanisms of whiplash injury.113
These and related efforts developed the
notion that the whiplash injury rate
could be reduced by preventing
hyperextension of the neck. The initial
version of FMVSS No. 202 mandated
head restraints as a countermeasure to
this type of neck injury.114 After the
mandate was introduced, a statistical
analysis of crash data sets found modest
improvements in the whiplash injury
rates.115 A 1982 NHTSA report of rear
impacts in passenger cars, for example,
found that integral head restraints
reduced whiplash injury risk by 17%
while adjustable restraints reduced the
risk by 10%.116 A Swedish study found
107 Viano, David C. ‘‘Role of the seat in rear crash
safety.’’ Warrendale, PA: Society of Automotive
Engineers, 2002. 514 (2002).
108 About one third of the seats tested by the
agency in 1998 were dual recliners. This was a
convenience sample not intended to be
representative of the fleet. Molino L (1998),
Determination of Moment-Deflection Characteristics
of Automobile Seat Backs, NHTSA, November 25,
1998. See Regulations.gov, Docket document no.
NHTSA–1998–4064–0026.
109 Viano, David C., et al. ‘‘Occupant responses in
conventional and ABTS seats in high-speed rear
sled tests.’’ Traffic injury prevention 19.1 (2018):
54–59.
110 Herbst, B.R., Meyer, SE, Oliver, A.A., and
Forrest, S.M. Rear impact test methodologies:
quasistatic and dynamic. Proceedings of 21st
International Technical Conference on the
Enhanced Safety of Vehicles, 2009. Stuttgart,
Germany.
111 Edwards, Marcy A., et al. ‘‘Seat design
characteristics affecting occupant safety in low-and
high-severity rear-impact collisions.’’ IRCOBI
Conference, Florence, Italy, IRC–19–11. 2019.
112 Gay, James R., and Kenneth H. Abbott.
‘‘Common whiplash injuries of the neck.’’ Journal
of the American Medical Association 152.18 (1953):
1698–1704.
113 MacNab, Ian. ‘‘Whiplash injuries of the neck.’’
Proceedings: American Association for Automotive
Medicine Annual Conference. Vol. 9. Association
for the Advancement of Automotive Medicine,
1965.
114 NHTSA, FMVSS No. 202 Head Restraints for
Passenger Vehicles Final Rule, Final Regulatory
Impact Analysis, Nov. 2004, Docket No. NHTSA–
2004–19807.
115 O’Neill, Brian, et al. ‘‘Automobile head
restraints—frequency of neck injury claims in
relation to the presence of head restraints.
American journal of public health 62.3 (1972): 399–
406. Nygren, Ake, Hans Gustafsson, and Claes
Tingvall. Effects of different types of headrests in
rear-end collisions. No. 856023. SAE Technical
Paper, 1985.
116 Kahane, Charles J. An Evaluation of Head
Restraints, NHTSA Publication No. DOT HS 806
108, Washington, DC, 1982, pp. 154–160 and 181–
197.
PO 00000
Frm 00020
Fmt 4701
Sfmt 4702
angle and the dummy was retained by
all seat backs. During testing, the
vertical displacements of the dummies
was between 41 mm to 144 mm. The
authors concluded that a majority of
tested production seats provided
adequate occupant retention at a DV of
36.5 km/h (22.7 mph), but with a range
of performance metrics. Moreover, all 26
seats tested by IIHS had ‘‘Good’’ ratings
for low-speed rear impact protection as
determined by a separate IIHS test using
the BioRID dummy at a DV of 16 km/
h (10 mph).
C. Non-Contact Injuries
This section outlines a segment of the
literature concerning non-contact neck
and thorax injuries resulting from rear
collisions.
E:\FR\FM\16JYP2.SGM
16JYP2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2
a similar 20% decrease in neck injuries
as a result of the head restraint.117
However, the persistence of frequent
whiplash injury motivated later studies
of cervical spine dynamics in rear
collisions.
In 1995, the Quebec Task Force on
Whiplash Associated Disorders
categorized whiplash injuries into five
grades, 0 to IV, in order of increasing
severity. For convenience, we will
continue to refer to whiplash associated
disorders as whiplash injuries. The
Quebec study determined that 90% of
insurance claims fell within grades 0
and I where there was no clear
pathology based on existing technology,
but symptoms may include neck pain,
headache, memory loss, jaw pain,
hearing disturbance, and dizziness.
Grades II and III include
musculoskeletal and neurological signs;
grade IV contains cervical fractures and
dislocations. The most severe soft tissue
whiplash type injury occurring in grade
IV is typically characterized by disc
herniation and is often accompanied by
facet-joint hematoma, peripheral spinal
nerve and spinal cord contusion or
articular process fracture.118 The
findings of a study on very low velocity
rear collisions 119 led the authors to
conclude that a biomechanical ‘‘limit of
harmlessness’’ for whiplash exists for
rear collision DV between 10 to 15 km/
h. The author goes on to explain that
this is the speed range below which
there were no anatomical signs of
injury, but did not rule out
‘‘psychological injury.’’
Basic research of rear collision neck
kinematics indicate that neck and head
dynamics occur through a complex
process. The neck may experience
compression, tension, shear, torsion,
retraction, protraction, flexion, and
extension to varying degrees and at
different points in time. Studies on
cervical spine kinematics in rear
collisions by Svensson, et al.120 and
McConnell, et al.121 in 1993, Geigl, et
117 Nygren, Ake, Hans Gustafsson, and Claes
Tingvall. Effects of different types of headrests in
rear-end collisions. No. 856023. SAE Technical
Paper, 1985.
118 Davis, Charles G. ‘‘Mechanisms of chronic
pain from whiplash injury.’’ Journal of forensic and
legal medicine 20.2 (2013): 74–85.
119 Castro, W.H., et al. Do whiplash injuries occur
in low-speed rear impacts? European spine journal:
official publication of the European Spine Society,
the European Spinal Deformity Society, and the
European Section of the Cervical Spine Research
Society 6.6 (1997): 366–375.
120 Svensson, Mats Y., et al. Rear-end collisionsa study of the influence of backrest properties on
head-neck motion using a new dummy neck. No.
930343. SAE Technical Paper, 1993
121 McConnell, Whitman E., et al. Analysis of
human test subject kinematic responses to low
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
al.122 in 1994 and Panjabi, et al.123 in
1998 noted that the neck displayed an
unnatural S-shaped curve in the early
stages of the kinematics due to
retraction, and Panjabi hypothesized
that neck injury may occur before head
contact with the head restraint. In a
study by Feng, et al.,124 the authors
described early rear impact neck
dynamics through a series of kinematic
spinal processes. The authors noted that
rear impact forces are at first distributed
across the occupant’s torso through the
seat back and then are transmitted to the
neck and head. These initial forces
impose torso straightening and likely
movement of the occupant’s torso up
the seat back. The authors hypothesize
that axial compression is generated in
the spinal column, which travels up the
neck to the head. As the head moves
upwards axial tension is then proposed
to develop in the neck through
disproportionate movement of the head
and neck due to a constrained torso. As
these first actions evolve the head lag
phenomenon (also described in an
earlier 1976 study 125) or retraction
develops through a delay between the
forward motion of an occupant’s torso
and head. Retraction leads to shear in
the cervical column and curvature of the
neck is reduced. These theorized actions
occur before the head contacts the head
restraint.
2. Thorax Injuries in High-Speed Rear
Impacts
A recent NHTSA research study was
conducted with 14 PMHS tests in rear
facing seats in frontal collisions at a DV
of 56 km/h for different recline angles
and seat types to investigate thorax
injuries.126 The structure supporting the
seat back was rigidized to avoid
unpredictable permanent deformations
velocity rear end impacts. No. 930889. SAE
Technical Paper, 1993.
122 Geigl, B.C., et al. ‘‘The movement of head and
cervical spine during rear end impact.’’ Proceedings
of the International Research Council on the
Biomechanics of Injury conference. Vol. 22.
International Research Council on Biomechanics of
Injury, 1994.
123 Panjabi, Manohar M., et al. ‘‘Mechanism of
whiplash injury.’’ Clinical Biomechanics 13.4–5
(1998): 239–249.
124 Luan, Feng, et al., ‘‘Qualitative analysis of
neck kinematics during low-speed rear-end
impact.’’ Clinical Biomechanics 15.9 (2000): 649–
657.
125 Ewing CL., Thomas D., Lustick L., Muzzy
W.H., et al. The Effect of Duration, Rate of Onset
and Peak Sled Acceleration on the Dynamic
Response of the Human Head and Neck.
Proceedings of the 20th Stapp Car Crash
Conference, Dearborn, MI, Society of Automotive
Engineers, Inc., 1976.
126 Kang YS, et al. ‘‘Thoracic responses and
injuries to post-mortem human subjects (PMHS) in
rear-facing seat configurations in high-speed frontal
impacts,’’ Twenty-Seventh Enhanced Safety of
Vehicles Conference (2023).
PO 00000
Frm 00021
Fmt 4701
Sfmt 4702
58017
of the seat during the event. The goal of
the study was to examine non-standard
seating configuration for vehicles with
automated driving systems (ADS) with
reclined rear-facing seats in a frontal
collision. It may also, however, provide
some insight into rear impact dynamics
because the loading is rearward with
respect to the seat back orientation.
Additionally, the 56 km/h DV test is
very severe for a rear impact. The CISS
data reported in section II.B indicates
this speed represents more than 95% of
all towaway rear impacts. The authors
found that rib fractures occurred in the
PMHSs due to a complex combination
of chest compression and expansion
with upward shear loading. The
majority of rib fractures occurred after
peak chest compression when the
abdominal contents shifted rearward
and upward into the thorax due to the
ramping motion of the PMHS, which
created a combined loading
(compression/tension and shear) to the
thorax. Similar magnitudes of rib strains
were observed regardless of seat types,
while strain modes varied according to
recline angle and seat type. Fewer
injuries were seen with a more upright
25-degree seat back, compared to a more
typical initial seat angle of 45-degree
seat back.
D. Summary
While progress has been made in
understanding rear impact injuries, the
literature continues to point toward the
need for a greater understanding before
conclusions can be drawn about the
exact mechanisms of injury and the risk
factors involved, particularly in regards
to whiplash.127 Likewise, important
safety improvements have been made in
production seats over the last 50 years
and a greater understanding of the
relationship between seat back
characteristics and injury has been
achieved, but questions remain with
respect to precisely quantifying
protective characteristics. The
continued uncertainty around how best
to protect occupants as well as the
varied approaches and developments in
rear impact technology suggests that, as
NHTSA considers amendments to
FMVSS Nos. 207 and 202a, there is
value in preserving industry flexibility
in seat back and head restraint design
and strength parameters to allow further
127 Holm, Lena W., et al. ‘‘The burden and
determinants of neck pain in whiplash-associated
disorders after traffic collisions: results of the Bone
and Joint Decade 2000–2010 Task Force on Neck
Pain and Its Associated Disorders.’’ Journal of
manipulative and physiological therapeutics 32.2
(2009): S61–S69.
E:\FR\FM\16JYP2.SGM
16JYP2
58018
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
research into and development of these
systems.
V. Petitions for Rulemaking at Issue in
This Document
A. Statutory and Regulatory Background
Under 5 U.S.C. 553(e), 49 U.S.C.
30162(a)(1) and 49 CFR part 552,
interested persons can petition NHTSA
to initiate a rulemaking proceeding.
Upon receipt of a properly filed
petition, the agency conducts a
technical review of the petition,
material submitted with the petition,
and any additional information.128 After
conducting the technical review,
NHTSA determines whether to grant or
deny the petition.129 The Safety Act
states that all FMVSS requirements
must be practicable, meet the need for
motor vehicle safety, and be stated in
objective terms.130 Accordingly, NHTSA
will initiate a rulemaking only if the
agency believes that the proposed rule
would meet these criteria. If a petition
is granted, a rulemaking proceeding is
promptly initiated in accordance with
statute and NHTSA procedures. A grant
of a petition and a commencement of a
rulemaking proceeding do not, however,
signify that the rule in question will be
issued. That decision is made on the
basis of all available information
developed in the course of the
rulemaking proceeding, in accordance
with statutory criteria.131 If a petition
under this section is denied, the reasons
for the denial are published in the
Federal Register.132
khammond on DSKJM1Z7X2PROD with PROPOSALS2
B. Petition of Kenneth J. Saczalski
On October 28, 2014, Kenneth J.
Saczalski of ERST petitioned NHTSA to
amend FMVSS Nos. 207 (Seating
systems), 213 (child restraint systems),
and 301 (Fuel system integrity).
Saczalski requested that NHTSA
increase the static strength requirement
for seat backs by a factor of six and
implement a new dynamic requirement.
The dynamic requirement would assess
the seat back of a vehicle by performing
a rear impact crash test with a 50th
percentile male ATD positioned in the
seat. The petition also suggested adding
a rear impact requirement to FMVSS
No. 213, ‘‘Child restraint systems,’’ and
implementing a new requirement for
rear seats that would resist the forces of
loose cargo that may be stowed behind
the rear seats.
128 49
U.S.C. 30162(a)(1); 49 CFR 552.6.
CFR 552.8; see also 49 U.S.C. 30162(c).
130 49 U.S.C. 30111(a).
131 49 CFR 552.9; see also 49 U.S.C. 30162(c).
132 49 CFR 552.10.
129 49
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
2. Use of FMVSS No. 301, ‘‘Fuel System
Integrity,’’ To Test Seats
Saczalski petitioned NHTSA to
implement a new seat back requirement
using the dynamic rear-end crash test
prescribed in the latest revision of the
fuel system integrity test described in
FMVSS No. 301. In this test, a stationary
vehicle is struck in the rear by a 1,368
kg (3,015 lb) deformable barrier
travelling at 80 km/h (50 mph). The
barrier overlaps the rear end of the
vehicle by 70%.
Saczalski asserted that a dynamic, full
vehicle test is needed in addition to the
static requirements discussed above.
The main purpose of such a test would
be to fully assess the safety of children
in rear seats who may be exposed to
collapsing front seat backs. Saczalski
cites in his petition a 2008 study by
Children’s Hospital of Philadelphia
(CHoP).135 The study examined risk
levels through an epidemiological study
of real-world crashes, and found that in
a rear-end crash, children seated
directly behind a seat back that yielded
exhibited about twice the risk of injury
as children seated behind a seat back
that did not yield. Saczalski has asked
for a dynamic test to be run with Hybrid
III 95th percentile male dummies (HIII–
95M) in the front seats with 12-monthold dummies seated directly behind in
forward-facing child restraints.136 He
recommends a pass/fail limit on front
seat back rotation of no more than 25
degrees rearward from its initial seat
back orientation. He also recommends
that NHTSA impose pass/fail
requirements based on dummy
measurements within the head, neck,
chest, and extremities. This would
apply to the HIII–95M and the 12month-old dummies. Saczalski
recommends pass/fail requirements for
both dummies equivalent to ‘‘their
respective NHTSA injury reference
levels for the head, neck, chest, and
extremities.’’ 137
Saczalski also suggested that the test
be run with 20 kg (44 lb) simulated
luggage cases in the trunk area, which
he stated could push the rear seat
forward. According to Saczalski, such a
requirement will guard against injuries
due to the intrusion of a rear seat
occupied by a child into a yielding front
seat back.
133 ‘‘Rearward force’’ means the force against the
rear side of an occupant seat, regardless of
orientation. For a forward-facing seat, this would
mean a force applied in the rearward longitudinal
direction, whereas with a rear-facing seat, this
would mean a force applied in the forward
longitudinal direction.
134 Selecting the seat pivot point as the location
for the moment measurement reduces the force
needed to produce a given moment. Assuming a
vertical distance of 535 mm from the H-point to the
location of force application and a vertical distance
of 595 mm from the seat pivot to the force location
results in a 10% reduction in force for the same
moment measure about the pivot compared to the
H-point.
135 Jermakian JS, Arbogast KB, Durban DR, Kallan
NJ (2008), Injury risk for children in rear impacts:
role of the front seat occupant, 52nd AAAM Annual
Conference, Annals of Advances in Automotive
Medicine, October 2008.
136 The 12-month-old dummy, known as the
(CRABI) dummy, is already integrated into subpart
P of part 572.
137 Injury reference values recommended by
NHTSA for the CRABI and HIII–95M, when used
to assess air bags, are contained within: Eppinger
R, Sun E, Kuppa S, Saul R (2000), Supplement:
development of improved injury criteria for the
assessment of advanced automotive restraint
systems-II, National Highway Traffic Safety
Administration, March 2000.
1. FMVSS No. 207, Seating Systems
Saczalski seeks an amendment to
FMVSS No. 207, S4.2(d) to increase the
rearward force that occupant seats must
withstand from a 373 Nm (3,300 in-lb)
moment measured about the H-point to
a 2,260 Nm (20,000 in-lb) moment
measured from the pivot intersection of
the seat back structure and the seat
cushion frame.133 While this ostensibly
represents an increase by a factor of six,
because FMVSS No. 202a effectively
requires seat backs to withstand a 654
Nm (5,790 in-lb) moment, this would
only increase the performance
requirement by a factor of 3.5 above
current requirements, if measured about
the H-point. The actual factors would be
closer to a factor of 5.4 above the
required FMVSS No. 207 moment and
3.1 above the FMVSS No. 202a
requirement, depending on the relative
position of the seat pivot with respect to
the H-point.134
Saczalski also made a more general
request that FMVSS No. 207 seat
strength testing be conducted ‘‘to
ultimate strength levels’’ that establish a
seat’s capacity to withstand crash forces.
According to Saczalski, testing must be
repeated to examine strength variations
relating to adjustable seat components,
such as height adjusters. Saczalski does
not, however, provide a specific set of
performance requirements or tests that
he asserts should be conducted.
Saczalski also requested that NHTSA
add a requirement that seats not
experience a ‘‘sudden load collapse’’
(i.e., a failure of structural components
that causes the occupant support
loading to suddenly drop off) of 400
pounds force or greater within a short
span of rearward deformation.
According to Saczalski, this testing
should be done using a ‘‘torso bodyblock’’ device that replicates the upper
body weight of a 95th percentile male.
PO 00000
Frm 00022
Fmt 4701
Sfmt 4702
E:\FR\FM\16JYP2.SGM
16JYP2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
3. FMVSS No. 213, Child Restraint Seats
Saczalski asked NHTSA to include a
rear impact requirement for child
restraint systems within FMVSS No.
213, which does not contain such
requirements. He suggested using the
same test and performance criteria as
the European standard for child
restraint systems, United Nations
Economic Commission for Europe
Regulation 44 (ECE R.44),138 but run at
a higher test speed of 40 km/h.139 The
ECE standard contains requirements for
various sized child dummies subjected
to a 30 km/h rear impact. Like FMVSS
No. 213, the European standard also
includes requirements for a frontal
impact, but those are not discussed in
Saczalski’s petition.
khammond on DSKJM1Z7X2PROD with PROPOSALS2
C. Petition of Alan Cantor
In a letter dated September 28, 2015,
Alan Cantor of ARCCA petitioned
NHTSA to revise FMVSS No. 207 by
implementing new requirements for seat
back strength involving a crash test with
an ATD. He also requested that NHTSA
reinstate a provision to FMVSS No. 209,
‘‘Seat belt assemblies,’’ that he states
would prevent occupant injuries in rear
impacts.
1. Use of FMVSS No. 301, ‘‘Fuel System
Integrity,’’ To Upgrade FMVSS No. 207
Cantor requested a dynamic test to
assess seat back loading by occupants of
different sizes. He envisioned the use of
the current FMVSS No. 301 procedure
with Hybrid III 50th Percentile male
dummies (HIII–50M). Additionally,
Cantor requested that a test be
performed at oblique impact angles to
assess the potential of excessive seat
back twisting that Cantor stated could
facilitate rearward ramping and an outof-position orientation of the occupant
in the seat during subsequent impacts.
A full vehicle test was also envisioned,
but alternatively Cantor suggested that a
sled test could be run using an impulse
equivalent to that produced by the
dynamic procedure. Cantor did not
request a change to the static
requirements of FMVSS No. 207, nor
did he call for the use of rear seated
child dummies in the dynamic, full
vehicle test. Under Cantor’s rationale,
the test with the HIII–50M dummies
would serve as the basis for a new set
of FMVSS requirements. The
requirements would apply to front seats
138 Uniform Provisions Concerning the Approval
of Restraining Devices for Child Occupants of
Power-Driver Vehicles, (Child Restraint Systems),
ECE R.44, E/ECE/324/Rev (unece.org).
139 UNECE Regulation No. 44, Uniform provisions
concerning the approval of restraining devices for
child occupants of power-driven vehicles (‘‘Child
Restraint System’’).
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
as well as rear ‘‘bucket’’ seats, such as
those within minivans, that he suggests
may also have a propensity to collapse.
2. Rearward Rotation Limit and
Structural Symmetry Requirement
Cantor recommended a pass/fail limit
for rearward seat back rotation of no
more than 15 degrees from its initial
seat back orientation (measured in realtime during the test). For the oblique
impacts, there would be a requirement
that the differential rearward deflection
of the seat back is no more than 10
degrees between the left and right sides.
According to Cantor, this will assure
structural symmetry of the seat to
prevent excess twisting of the seat under
load, which can lead to ramping or outof-position orientation of an occupant if
subsequent impacts occur.
3. Additional Dynamic Testing and
NCAP Implementation
Cantor also requested another
dynamic test to assess seat back loading
to be performed with a Hybrid III 95th
male dummy (HIII–95M) and to
incorporate results into the NCAP star
rating for the vehicle. This test would be
performed in a manner similar to the
current FMVSS No. 301 procedure, but
at an impact speed of the barrier that is
8 km/h (5 mph) faster than the current
FMVSS No. 301 speed. He argues that
it would serve to inform consumers on
whether a given vehicle seat back has
the propensity to collapse. Cantor states
it would also provide incentive to
manufacturers to develop enhancements
to rear impact crash protection.
Cantor recommended the same pass/
fail limit for rearward seat back rotation
for the NCAP tests as he recommended
for the FMVSS No. 301 impacts. Cantor
did not specify how the results would
be factored into the NCAP rating.
4. FMVSS No. 209, Seat Belt Assemblies
Cantor requested that NHTSA restore
S4.1(b), which NHTSA deleted in a final
rule published in 1999.140 This
provision required the lap belt portion
of the seat belt be designed to remain on
the pelvis under all crash conditions.
Cantor states that restoring S4.1(b)
would assure that vehicles will be
equipped with seat belt technologies
that prevent ramping in rear impact
crashes.
D. NHTSA’s Analysis of Saczalski and
Cantor Petitions
NHTSA is denying in part the
Saczalski and Cantor petitions as they
pertain to the following
recommendations: Cantor’s requested
PO 00000
140 64
FR 27203 (May 19, 1999).
Frm 00023
Fmt 4701
Sfmt 4702
58019
amendments to NCAP and request to
restore anti-ramping language to FMVSS
No. 209, and Saczalski’s requests to add
a rear impact test to FMVSS No. 213 and
a cargo test requirement to FMVSS No.
207. As part of this rulemaking effort to
update FMVSS No. 207 and to facilitate
informed comment, NHTSA is granting
the petitions in part with regard to
updating the strength requirement in
FMVSS No. 207, the structural
symmetry requirement requested by
Cantor, and the possible development of
new test procedures for seat back
strength under FMVSS No. 207. NHTSA
notes that, at this time, insufficient
information has been provided to
support the petitioners’ suggested
specific strength levels or test designs,
but NHTSA seeks comment on this
issue. The remainder of this section
provides NHTSA’s opinions on the
recommendations in the petitions to
provide context and information to
support informed comment on an
update to FMVSS No. 207. Later in this
document, we discuss NHTSA’s current
thinking on an integrated and unified
approach to rear impact protection and
seeks comment on that approach.
1. Analysis of Data and Research
Provided by Cantor and Saczalski
Regarding Safety Need
In the past, NHTSA and petitioners on
this topic have not been able to
demonstrate that a safety need exists
regarding the seat back strength
requirement in FMVSS No. 207.141 In
their petitions, Saczalski and Cantor
both implied that factors related to child
safety have given rise to a new safety
need for stronger seat backs. NHTSA
acknowledges that there is evidence
that, in some crash scenarios, seat back
deformation or rearward movement due
to component failure can lead to injury,
but NHTSA believes that the petitioners
have not provided sufficient supporting
data to demonstrate a worsening safety
need related to seat back strength
compared to NHTSA’s past
determination. NHTSA discusses the
materials provided by petitioners below
and seeks comment on this question.
In support of his petition, Saczalski
references the CHoP study. NHTSA
agrees with Saczalski that the 2008
CHoP study is useful for understanding
the levels of risk to which children in
rear seats are exposed, but the CHoP
study did not determine that this risk
was associated with front seat back
strength. The information submitted by
petitioners did not provide new or
pertinent information to build upon the
141 See discussion in section III.B.10 of this
document and 69 FR 67068 (Nov. 16, 2004).
E:\FR\FM\16JYP2.SGM
16JYP2
58020
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
CHoP study or further demonstrate a
safety need.
Saczalski provided NHTSA with his
own publications, including one from
the 2014 annual meeting of the
International Federation of Automotive
Engineering Societies (FISITA).142 This
paper described 13 cases of infant
fatalities in rear-end crashes in which
the infant was seated behind an
occupied front seat. However, as with
the CHoP study, Saczalski’s paper did
not provide additional insight on
whether the fatalities were associated
with front seat back strength. Moreover,
because most of the fatalities occurred
in vehicles that were built prior to MY
2000, the cases he cites may not reflect
the lower level of risk associated with
new vehicles. Since then, improvements
have been made to FMVSS Nos. 202a,
301, and other standards that may
impact the conclusions reached in the
CHoP study and Saczalski’s paper. In
addition, changes in manufacturer’s
design targets and the more frequent use
of dual recliners may have resulted in
seat designs that are generally stronger.
Saczalski also provided the results of
several sled tests with crash test
dummies, which he argues demonstrate
that the seat back of a front-seated adult
can collapse on a child sitting in the
rear in a 48 km/h rear-end impact.
While these tests may illustrate the
potential consequences of seat back
deformation or failure, they simply
reinforce a finding of which NHTSA is
already aware: that it is possible for
some seat backs to yield in a severe rearend impact in a way that could
potentially injure occupants.
Finally, according to Saczalski,
fatality counts within the Fatal Accident
Reporting System (FARS) from 2001–
2011 show that fatalities in infants (0–
12 months) have doubled since 1990–
2000, from which he infers a worsening
safety need.
NHTSA believes that the conclusion
Saczalski draws from this data is
inaccurate. NHTSA has queried FARS
for infant and adolescent fatalities
where the child was known to be
restrained in a rear seat, non-ejected, in
a non-rollover, rear impact. Over the last
15 years captured in the study, the
average fatality rate is 7.7 per year,
ranging from 1 to 15 per year (See
Figure V.1). There is a great deal of
scatter and no clear fatality trend over
time. If the data are expanded to all
children up to an age of 5, the average
fatality rate is 31.9 per year, ranging
from 22 to 60 (See Figure V.2). Again,
there is no clear trend in the data. The
data for the 0–5-year-olds have less
scatter than that for the 0–12-montholds. This latest data is not supportive
of a claim that there is a fatality risk that
continues to increase. NHTSA notes that
these data provide an estimate of allcause mortality and therefore provide
no insights into whether front row seat
performance contributed to the child’s
death.
BILLING CODE 4910–59–P
FARS - Rear Impact, 0-12 Mo, Rear Seats
16
14
.,, 12
....
(I)
75
.....
10
LI..
8
ro
ro::::I
i:::
i:::
<t
6
4
2
0
2004
2006
2008
2010
2012
2014
2016
2018
2020
Crash Year
142 Saczalski K, Pozzi M, Burton J, Saczalski T
(2014), Experimental and field accident analysis
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
study of factors effecting child occupant injury risk
PO 00000
Frm 00024
Fmt 4701
Sfmt 4725
and safety in rear impacts, 2014 Annual FISITA
Meeting, Paper No. F2014–AST–013, 2014.
E:\FR\FM\16JYP2.SGM
16JYP2
EP16JY24.014</GPH>
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Figure V .1: NHTSAs finding of FARS reported infant annual fatalities in a rear seat, nonejected, in a non-rollover, rear impact
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
58021
FARS - Rear Impact, 0-SYO, Rear Seats
70
60
~
50
;!=
]j
40
n:,
LL.
~ 30
C
~ 20
10
0
2004
2006
2008
2010
2012
2014
2016
2018
2020
Crash Year
Figure V.2: NHTSAs finding of FARS reported adolescent annual fatalities in a rear seat,
non-ejected, in a non-rollover, rear impact
khammond on DSKJM1Z7X2PROD with PROPOSALS2
2. Rear Structure Intrusion
Saczalski states in his petition that
there are phenomena other than front
seat back failure and ramping that create
risk to children in rear seats. He notes
that rear-seated children in rear-end
collisions are often injured by poorly
designed rear structures that push
children forward into the front seat
back. He supports this claim using a
2008 study of NASS–CDS data, which
looked at the risk to children seriously
injured in rear impacts and indicated
that injury caused by intrusion from the
rear seating area is a larger problem than
deforming front seat.143 NHTSA
appreciates the analysis done by
Saczalski and agrees that there is
evidence to support a finding that there
is a safety risk to children in the rear
seat in a rear impact crash. NHTSA also
agrees that this risk involves more
factors than just front seat back collapse,
such as rear structure intrusion. NHTSA
seeks comment on the significance of
the intrusion issue in the overall context
of rear impacts and whether a
practicable solution to this issue exists.
NHTSA notes that the 2006 revision to
FMVSS No. 301, Fuel system integrity,
which would not have been in place for
the model years of the vehicles
Saczalski studied, may have induced
changes to rear vehicle structures that
mitigated the intrusion problem.
143 Viano D, Parenteau C (2008), Field Accident
Data Analysis of 2nd Row Children and Individual
Case Reviews, SAE Technical Paper 2008–01–1851.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
NHTSA wishes to emphasize that
Saczalski and Cantor do not appear to
have considered whether increasing the
requirement for seat strength would
have any unintended negative safety
impacts. This document discusses at
length the literature, such as the 1997
Prasad study, which suggest a possible
association between significantly stiffer
seats and increased incidence of
whiplash and other non-contact
injuries. NHTSA seeks comment on
these potential negative safety impacts,
which the agency believes is critical to
understanding the overall safety
problem in occupant protection in rear
impact and whether changes to FMVSS
No. 207 will meet a need for safety.
3. Cost and Practicability
Cantor argues in his petition that
upgrading seat back strength would not
impose a major cost on manufacturers,
claiming that many modern vehicles
have stronger seats compared to those in
1989 even in absence of a change to
FMVSS No. 207. To support this claim,
he cites his own testing, in which he
claims to have studied newer vehicles
using the FMVSS No. 207 procedure
and found that they ‘‘tested out’’
somewhere between 2.5 to 10 times the
current compliance level (373 Nm).
Based on his own testing, he concludes
that it would not be cost prohibitive for
original equipment manufacturers that
use less strong seats to increase seat
back strength, and he argues that an
upgrade to the standard is needed to
assure all seat backs have a minimum
strength.
PO 00000
Frm 00025
Fmt 4701
Sfmt 4702
NHTSA does not believe that Cantor’s
examples of actual seat back strength in
the modern vehicles provide new or
better data over what was known to
NHTSA in 2004, when NHTSA
terminated a rulemaking to increase seat
back strength. The variance seen in
Cantor’s test results is consistent with
that seen in the Severy data from the
1960s. It was also seen in data in a 1998
report prepared by NHTSA.144
NHTSA agrees that increasing seat
back strength is technically feasible.
Any rulemaking action to change the
seat back strength requirement,
however, must be practicable, meet the
need for motor vehicle safety, and be
stated in objective terms. As part of this
analysis, a rulemaking action would
assess whether this would be a costeffective way to increase overall motor
vehicle safety.
E. Assessment of the Specific
Recommendations by Cantor and
Saczalski
In this section, NHTSA presents its
assessment of specific matters
petitioned for by Cantor and Saczalski.
The first section discusses the matters
on which NHTSA is granting the
petitions and initiating rulemaking and
provides NHTSA’s opinions on those
specific petitioned-for issues to facilitate
informed comment. The second section
covers the issues on which NHTSA is
144 Molino L (1998), Determination of MomentDeflection Characteristics of Automobile Seat
Backs, NHTSA, November 25, 1998. See
Regulations.gov, Docket document no. NHTSA–
1998–4064–0026.
E:\FR\FM\16JYP2.SGM
16JYP2
EP16JY24.015</GPH>
BILLING CODE 4910–59–C
58022
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
denying in part and provides the
reasons for denial as required in 49 CFR
part 552.
1. Matters on Which NHTSA Is Granting
the Petitions
(a) Amend FMVSS No. 207 To Increase
Seat Back Moment Requirement and
Alter Load Application Method
Saczalski asked NHTSA to raise the
torque requirement about the seat back
pivot to 2,260 Nm (20,000 in-lb). This
would raise the current FMVSS No. 207
requirement of 373 Nm (3,300 in-lb) by
a factor of about 5.4 and by a factor of
about 3.1 above the FMVSS No. 202a
requirement of 654 Nm (5,788 in-lb). In
addition, Saczalski recommended that
the load be applied through a ‘‘body
block’’ representing a 95th percentile
male, rather than to the upper member
of the seat frame. NHTSA is granting the
petition on the torque requirement and
static test design issues in part, is
initiating rulemaking to consider
whether to upgrade FMVSS No. 207 on
these topics and seeks comment on the
analysis below.
Saczalski did not explain why a
torque limit of 2,260 Nm was preferable
to other limits that NHTSA has
considered previously (See table V.1)
and would not result in the potential
safety harms discussed above.
Furthermore, Saczalski does not provide
a compelling reason why a body block
test would be the most effective way to
test rearward moment strength
statically. NHTSA notes that Saczalski
is also requesting a dynamic
requirement, and he did not explain
why amending the FMVSS to use a body
block for the static test would be
necessary if NHTSA were to accept his
recommendation to incorporate a
dynamic test with a more biofidelic
dummy.
TABLE V.1—PAST RECOMMENDATIONS FOR REVISING THE QUASI-STATIC SEAT BACK TORQUE REQUIREMENT IN FMVSS
NO. 207
Current standard
Recommendations
Viano 1
(2003)
Saczalski
(2014
petition)
6327 Nm (56,000
in-lb).
‘‘withstand’’ torque
1700 Nm (15,000
in-lb).
specifics given
below.
2260 Nm (20,000
in-lb).
‘‘withstand’’ torque.
................................
2000 N over 10°
rot.
thru HIII–50M
lower torso.
25 kN/m.
2.0 deg/kN.
7.7 kN.
15 deg.
50 mm.
1780 N ‘‘sudden’’.
Test reference
FMVSS No. 207
(since 1968)
Severy
(1969)
NHTSA
(1974 NPRM)
H-point moment, min .........................
Seat back requirement ......................
373 Nm (3,300 inlb).
‘‘withstand’’ torque
11,300 Nm
(100,000 in-lb).
..............................
373 Nm (3,300 inlb).
..............................
Seat back rotation, max ....................
Load drop limit, max ..........................
..............................
..............................
10 deg .................
..............................
40 deg.
..............................
Load application ................................
upper member of
seat back frame.
..............................
..............................
..............................
..............................
..............................
upper member of
seat back frame.
..............................
..............................
..............................
..............................
..............................
upper member of
upper member of
seat back frame.
seat back frame.
.............................. ................................
.............................. ................................
.............................. ................................
.............................. ................................
.............................. ................................
Seat stiffness, max ............................
Frame compliance, max ....................
Load limit, min ...................................
Seat twist, max ..................................
Dummy H-point upward displ., max
(design target only).
Saczalski
(1989
petition)
thru HIII–95M body
block.
khammond on DSKJM1Z7X2PROD with PROPOSALS2
1 Viano’s quasi-static test equipment and procedure represents more of an alternate test method than a simple revision to FMVSS No. 207. Details are described in
Viano (2003), ‘‘Resolving the debate between rigid (stiff) and yielding seats: seat performance criteria for rear crash safety,’’ cited earlier.
Saczalski also suggested that NHTSA
impose a requirement so that, when
tested to failure, there is no sudden drop
in load of 1,780 N (400 lb-f) or greater
within a short span. NHTSA is also
granting the petition on this issue in
part. NHTSA is aware of others who
have recommended similar changes in
the past to assure a gradual deformation
of seat back components. NHTSA notes
that Saczalski did not suggest an
objective and practicable test procedure.
Depending on how a test is carried out,
a sudden load drop in a quasi-static test
may not necessarily indicate an unsafe
design. Even a drop to zero is not
necessarily problematic if a slight
perturbation in backward movement
brings the load back up. NHTSA seeks
comment on this requirement. What
safety benefits could be obtained from
such a requirement? Is there a
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
practicable and objective test procedure
that can be developed?
proposed pass/fail limit or deflection
amounts proposed.
(b) Structural Symmetry
(c) Dynamic Rear Impact Test Design
To assure structural symmetry of the
seat, Cantor petitioned for a pass/fail
limit for rearward seat back rotation of
no more than 15 degrees from its initial
seat back orientation (measured in realtime during the test) and 10 degrees of
differential rearward deflection between
the left and right sides for oblique
impacts. NHTSA is granting in part on
this issue and seeks comment. In
particular, does the increased
prevalence of dual recliners in the fleet
remove any safety benefits that may be
gained from a structural symmetry
requirement? If not, what test
procedures and anti-twisting standards
should NHTSA consider and why?
NHTSA notes that Cantor does not
provide data or evidence supporting his
Both Saczalski and Cantor petitioned
NHTSA to add a new dynamic crash test
to FMVSS No. 207, which would test
seat back performance using a 1,368 kg
(3,015 lb) deformable barrier that strikes
the rear of the vehicle at 80 km/h.145
NHTSA is granting the petitions in part
on this issue and seeks comment on the
analysis below. NHTSA has previously
considered, in the 1974 NPRM, adding
a new dynamic requirement of the type
recommended by Saczalski and Cantor.
Table V.2 shows the various dynamic
rear impact tests that have been
proposed and considered in the past.
PO 00000
Frm 00026
Fmt 4701
Sfmt 4702
145 This barrier test would be similar to the barrier
test that NHTSA included in its latest revision of
the FMVSS No. 301; see 68 FR 67068 (Dec. 1, 2003).
E:\FR\FM\16JYP2.SGM
16JYP2
58023
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
TABLE V.2—PAST RECOMMENDATIONS FOR A DYNAMIC SEAT BACK STRENGTH REQUIREMENT
Nash 1974
NPRM 1974
Saczalski 1989 1
Cantor 1999 2
Viano 2002
Saczalski 2015 4
FMVSS No. 301
(1974).
48 km/h ...............
1814 kg rigid .......
FMVSS No. 301
(1974).
48 km/h ...............
1814 kg rigid .......
FMVSS No. 301
(1974).
48 km/h ...............
1814 kg rigid .......
Sled test ..............
Impactor speed 3 ..
Barrier specs ........
FMVSS No. 301
(1974).
48 km/h ...............
1814 kg rigid .......
30–36 km/h3 ........
..............................
Impact angle ........
Impact overlap .....
Dummy size .........
Rear seat dummy
+/¥ 30 deg .........
100% ...................
HII–50M ...............
..............................
0 deg ...................
100% ...................
HII–50M ...............
..............................
0 deg ...................
100% ...................
HIII–95M ..............
..............................
0 deg ...................
100% ...................
50M2 ...................
..............................
0 deg ...................
100% ...................
HIII–50M ..............
..............................
FMVSS No. 301
(2003).
80 km/h.
1368 kg deformable.
+/¥ 30 deg.
70%.
HIII–50M.
Seat back rotation,
max.
Seat back twist,
max.
Head, HIC ............
No fail ..................
40 deg .................
40 deg .................
15 deg .................
35 deg .................
FMVSS No. 301
(2003).
80 km/h ...............
1368 kg deformable.
0 deg ...................
70% .....................
HIII–95M ..............
CRABI–12M in
FFCS.
25 deg .................
..............................
..............................
..............................
..............................
8 deg ...................
..............................
10 deg.
..............................
..............................
..............................
unspecified value
..............................
Head/neck extension.
Neck moment .......
45 deg .................
..............................
..............................
..............................
45 deg .................
CRABI 390 | HIII
700.
n/a .......................
10 deg.
45 deg .................
..............................
..............................
unspecified value
20 Nm ..................
Neck x-displacement.
Neck y-displacement.
Chest deflection ...
..............................
..............................
..............................
..............................
60 mm .................
CRABI 17 Nm |
HIII 179 Nm.
n/a .......................
..............................
..............................
..............................
..............................
30 mm .................
n/a .......................
..............................
..............................
..............................
..............................
..............................
Femur load ...........
..............................
..............................
..............................
..............................
..............................
CRABI 30 mm |
HIII 70 mm.
CRABI n/a | HIII
12.7 kN.
Test type ..............
Cantor 2015
15 deg.
1 Contained
within Saczalski’s comments to NHTSA’s 1989 Request for Comments. See Regulations.gov, Docket Document No. NHTSA–1996–1817–0024.
2 Contained within Cantor’s presentation to NHTSA on November 18, 1999. Cantor recommended the use of a dummy designed with an articulated pelvis. See
Regulations.gov, Docket Document No. NHTSA–1998–4064–0030 for a copy of the presentation.
3 Except for the Viano (2003) recommendation, the impactor speed for each recommendation represents the speed of the moving barrier when it strikes the stationary test vehicle. The Delta-V experienced by the test vehicle is about half of the impactor speed, depending on the mass of the vehicle. For the Viano recommendation, the 30–36 km/h impulse for the sled test corresponds to the Delta-V range observed in FMVSS No. 301 rigid barrier tests run at 54.2 km/h (33.2 mph).
4 Saczalski’s 2015 petition recommended use of ‘‘NHTSA injury reference values for the head, neck, chest, and extremities’’ for the HIII–95 seated in the front and
the CRABI seated in the rear. For convenience, we have entered IARVs for the CRABI ‘‘C’’ and the HIII–95M ‘‘H’’ in the table above that correspond to those that
NHTSA recommended in Eppinger, 2000 (cited earlier)
khammond on DSKJM1Z7X2PROD with PROPOSALS2
(1) The Saczalski Petition
In his petition, Saczalski states that a
dynamic test is needed, but he does not
explain the reason that he recommends
using a deformable barrier travelling at
80 km/h, a HIII–95M in the front seat,
and a rear seated CRABI in a forwardfacing child restraint.
NHTSA believes that his
recommendations are intended to
represent the crash Saczalski studied in
his 2014 FISITA paper, a real-world
crash that involved an infant fatality in
the rear seat.146 For the paper, Saczalski
reconstructed the crash by staging a
crash test on the same vehicle model (a
2004 Chrysler minivan) with a CRABI
dummy in the child restraint and an
HIII–95M in the front seat. A crash
pulse generating a DV of 40 km/h was
applied. The test resulted in seat back
yielding and head-to-head contact
between the two dummies. This
produced a head injury criteria (HIC) of
3192 in the CRABI dummy, which is
well above the reference value of HIC =
390.
146 The crash Saczalski describes in a forwardfacing child restraint, and a rearward DV of 40 km/
h. (Note: DV is the change in velocity of a vehicle
due to a crash or impulse. In this instance, the 80
km/h barrier impact with a stationary vehicle
resulted in a DV of 40 km/h.)
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
Saczalski then re-ran the test but
replaced the minivan’s standard front
seat with a stronger seat removed from
a 2004 Chrysler convertible. This was a
belt integrated seat design, where the
torso belt anchorage was attached to the
seat back. For such a seat design, the
seat back attachment to the seat base
must be much stronger than a typical
design because it must be capable of
sustaining the seat belt loading from
frontal crashes. According to Saczalski,
the replacement seat did not yield
significantly in the crash, resulting in no
head-to-head contact and a very low
(HIC=36) HIC value of the CRABI
dummy. In addition, Saczalski
presented a process by which he was
able to develop a predictive equation for
determining HIC in the CRABI dummy
as a function of the front seat occupant
mass and the impulse of the crash (DV),
which involved running slight
variations of the above-described
scenario multiple times using the same
model of 2004 Chrysler minivan. Based
on Saczalski’s findings, to avoid
occupant to occupant interaction in the
particular crash he studied, the seat
back of the front seat would need to be
strong enough to not excessively yield
in a crash that involves a DV of 40 km/
h when the seat is occupied by a HIII–
95M dummy.
PO 00000
Frm 00027
Fmt 4701
Sfmt 4702
Saczalski’s analysis in his FISITA
paper is informative, but insufficient to
support a final rule implementing the
test parameters utilized and suggested
in his petition. First, it is based on tests
of only a single vehicle model (a 2004
Chrysler minivan), two seat designs, and
a single child restraint system (CRS)
model. Additional data from a wider
variety of vehicles, seats, and CRS
models would be needed to determine
whether Saczalski’s findings in his
FISITA paper are consistent across the
U.S. fleet of passenger cars. Of
particular concern is the fact that the
belt integrated seat design used as an
acceptably performing seat is relatively
rare in the fleet (primarily used in
convertibles) and designed for seat belt
loading in the frontal direction.147
Second, the tests use a front seat test
dummy, the HIII–95M, which is not a
regulated test tool and may not have the
full scope of necessary traits for rear
impact testing at high speed. In
particular, the HIC response generated
by the dummy may be of limited value
for analyzing the situation in question
because the rear part of the dummy’s
147 2016–2016 estimates put convertible sales at
approximately 1.9% in the U.S. Source: https://
www.iseecars.com/most-convertibles-by-state-2017study.
E:\FR\FM\16JYP2.SGM
16JYP2
58024
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
head, which contacts the child dummy,
is not designed to provide an internal or
external biofidelic impact.
Third, the predictive HIC equation on
which Saczalski based his
recommended test setup does not use
adequate statistical methods. It is
generated using only five data points,
potentially making it insufficiently
robust. Moreover, it bases the prediction
through two of the more extreme data
points, while ignoring the other three.
As a result, the predictive function fits
the two selected points perfectly, but
very poorly fits the others. Finally,
because standard regression techniques
were not applied, there were no
statistical computations of standard
errors or other measures of fit, such as
R-squared. Given these shortcomings,
NHTSA does not believe it could base
its selection of test parameters in a new
dynamic seat back strength test on
Saczalski’s data. NHTSA seeks comment
on this analysis and whether there is
additional supporting data for
Saczalski’s proposed test design.
khammond on DSKJM1Z7X2PROD with PROPOSALS2
(2) The Cantor Petition
Cantor similarly does not provide
support for the test parameters he chose
in his recommendation for a dynamic
rear-impact seat back strength test. He
argues that because the impulse created
by the 80 km/h barrier is appropriate for
the FMVSS No. 301 fuel system
integrity standard, it would also be
appropriate for setting a minimum seat
back requirement. This is a
generalization that requires further
justification. Because the minimum
requirements for seat back strength and
fuel system integrity do not address the
same safety concerns, NHTSA believes
this is insufficient basis, on its own, to
implement this test parameters.
Finally, NHTSA would need to show
that any dummy used in a new dynamic
test is chosen appropriately. The
petitioners suggested the use of a Hybrid
III dummy (HIII–95M by Saczalski; HIII–
50M by Cantor). As stated, in regard to
Saczalski’s 2014 FISITA paper, the
Hybrid III dummies have significant
biofidelity limitations when used for
rear impact analysis. NHTSA seeks
comment on whether there is evidence
showing these limitations are acceptable
and would lead to appropriate seat
designs if these dummies are chosen for
a new dynamic test in FMVSS No. 207.
2. Matters on Which NHTSA Is Denying
the Petitions
(a) Incorporate a Cargo Stipulation Into
FMVSS No. 207
Saczalski requested that NHTSA
amend FMVSS No. 207 to include a
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
cargo stipulation in a dynamic vehicle
test. Saczalski argued that deformation
of the rear of the vehicle caused by
crash forces could cause loose cargo
stored in the rear (or trunk) to be pushed
forward into the back of the second row
of seats, causing those seats and their
occupants to in turn be pushed forward
into the back of the front row seats.
NHTSA previously denied a similar
request from Cantor in 2004, and
Saczalski did not provide additional
field data or analysis to support adding
specifications for cargo placement.148
Without further analysis, NHTSA is not
considering incorporating a cargo
stipulation in FMVSS No. 207 at this
time. This decision will allow NHTSA
to focus its resources more fully on the
aspects of the petitions related to
rearward seat back strength.
(b) Amend FMVSS No. 209 To Require
That Seat Belts Remain on Pelvis Under
All Conditions
Cantor requested NHTSA restore
language, previously deleted in 1999, in
FMVSS No. 209 requiring that the
pelvic restraint portion of both Type-1
and Type-2 seat belts remain on the
pelvis under all conditions.149 NHTSA
is denying this request.
Cantor states that restoration of this
paragraph will prevent ramping by
assuring that manufacturers install a
device that keeps the lap belt portion of
the seat belt on the pelvis under all
crash conditions. According to Cantor,
technology that would prevent ramping
is already available on the market,
including the following: a sliding/
cinching latch plate to prevent excess
shoulder belt webbing from
transitioning to the lap belt portion and
causing the lap belt to go slack; an
integrated seat in which both lap and
shoulder belt anchors are mounted to
the seat; and seat belt pretensioners
sensitive to rear impacts and designed
to work with an integrated seat with a
belt configuration as described above.
The agency removed this stipulation
from the standard in 1999 because it
148 Cantor sought inclusion of an unrestrained
cargo test for the safety of occupants in the rear seat.
71 FR 70477 (Dec. 5, 2006). 71 FR 70478. NHTSA
denied that petition because the incidence of
injuries caused by loose luggage was very low and
did not warrant an amendment to a Federal safety
standard, and Cantor did not provide any field data
demonstrating a correlation between cargo intrusion
and occupant safety.
149 The paragraph in question, S4.1(b), read as
follows: ‘‘4.1(b) Pelvic restraint. A seat belt
assembly shall provide pelvic restraint whether or
not upper torso restraint is provided, and the pelvic
restraint shall be designed to remain on the pelvis
under all conditions, including collision or rollover of the motor vehicle. Pelvic restraint of a Type
2 seat belt assembly that can be used without upper
torso restraint shall comply with requirement for
Type 1 seat belt assembly in S4.1 to S4.4.’’
PO 00000
Frm 00028
Fmt 4701
Sfmt 4702
was deemed redundant and
unnecessary.150 FMVSS No. 208, other
provisions in FMVSS No. 209, and
FMVSS No. 210 contained more specific
requirements that collectively have the
effect of requiring pelvic restraint and
thereby reducing the likelihood of
occupants submarining 151 during a
crash. It was also deemed unenforceable
because the regulation did not provide
an objective means to determine that a
lap belt complied with the requirement
and was in fact ‘‘designed’’ to remain on
the pelvis. In addition, NHTSA noted
that the meaning of the words, ‘‘remain
on the pelvis,’’ was unclear. Because
these conditions and reasons have not
changed since that action was taken,
NHTSA will not reinstate the requested
language.
(c) Add a Rear Impact Test to FMVSS
No. 213, Child Restraint Systems
Saczalski requested that NHTSA
revise FMVSS No. 213 by including a
rear impact requirement for child
restraint systems like the one described
in ECE Reg. No. 44. Saczalski’s only
change from Reg. No. 44 is performing
the rear impact test at a 40 km/h
velocity instead of 30 km/h. Saczalski
stated that such a revision is necessary
to prevent rear facing child restraint
systems (CRSs) from folding rearward
when they become trapped between a
rear seat and a yielding front seat back
during a rear impact crash.152
NHTSA is denying this request for
change. NHTSA considered adopting
ECE Reg. No. 44’s rear impact test into
FMVSS No. 213 in the past.153 In a 2002
ANPRM, NHTSA discussed agency tests
evaluating ECE Reg. No. 44’s rear impact
test conducted at 30 km/h (18.6 miles
per hour), with peak deceleration
between 14 g and 21 g over a 70millisecond time period. The tests were
dynamic sled testing performed by
NHTSA in research on FMVSS No. 202
and FMVSS No. 207, where NHTSA
added a rear-facing child restraint with
a 12-month-old test dummy to a 1999
Dodge Intrepid vehicle seat. One test,
simulating a dynamic FMVSS No. 202
150 64
FR 27203 (May 19, 1999).
refers to the tendency for a
restrained occupant to slide forward feet first under
the lap belt during a vehicle crash, which could
result in serious abdominal, pelvic, and spinal
injuries.
152 This condition was highlighted in Saczalski’s
2014 FISITA paper.
153 NHTSA analyzed this issue in a rulemaking
amending FMVSS No. 213 pursuant to the
Transportation Recall Enhancement, Accountability
and Document Act (TREAD Act), November 1,
2000, Public Law 106–414, 114 Stat. 1800. The
agency requested comments on the merits of
incorporating the rear impact test of ECE Reg. No.
44 into FMVSS No. 213 (ANPRM; 67 FR 21836,
21851 (May 1, 2002)).
151 ‘‘Submarining’’
E:\FR\FM\16JYP2.SGM
16JYP2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2
condition, was conducted at
approximately 17.5 km/h (11 mph). The
other two tests were conducted at
approximately 30.5 km/h (19 mph). In
all of the tests the 12-month-old dummy
in the rear-facing child restraint was
able to easily meet the injury criteria of
FMVSS No. 208, i.e. was below the
threshold for injury. After examining
these data, comments to the ANPRM,
and data showing that fatalities for
children in rear impact crashes
constitute a much smaller percentage of
the total than other crash modes,
NHTSA decided to focus its resources
on developing a side impact test and not
a rear impact test.154
NHTSA disagrees with Saczalski that
there is a need to adopt a 40 km/h
rearward impact test based on ECE Reg.
No. 44. NHTSA does not believe
adopting such a rear impact test is
warranted for a number of reasons. First,
rear impact fatalities among children
restrained in CRSs are generally in very
severe crashes that result in significant
passenger compartment intrusion into
the rear seating area. However, the ECE
Reg. No. 44 sled test requested by the
petitioner does not simulate such
intrusion into the seating area. Second,
the ECE test protocol does not evaluate
the circumstance about which Saczalski
is concerned. The rear impact test in
ECE Reg. No. 44 does not have a
simulated front seat and therefore does
not replicate the crash scenario the
petitioner seeks to evaluate. The
standard seat assembly in FMVSS No.
213 also does not include a simulated
front seat, and it is yet to be determined
if a representative front seat could be
designed and whether it could be made
to collapse in a compliance test in a
repeatable and reproducible manner.
Finally, the petitioner provides no
information about a practicable
countermeasure that CRSs can provide
that would prevent injuries and
fatalities if there is a front seat collapse
and/or intrusion into the rear seating
area. NHTSA undertakes rulemakings
on FMVSS No. 213 weighing various
principles and considerations, in
addition to the considerations and
requirements for FMVSS specified by
the Safety Act, statutory mandates,
Executive Order (E.O.) 12866,155 and
other requirements for agency
154 NHTSA withdrew the rulemaking in a final
rule, 68 FR 37620, 37624 (June 24, 2003). See also
Report to Congress, ‘‘Child Restraint Systems,
Transportation Recall Enhancement, Accountability
and Document Act,’’ February 2004. chromeextension://efaidnbmnnnibpcajpcglclefindmkaj/
https://www.nhtsa.gov/sites/nhtsa.gov/files/
documents/tread.pdf.
155 E.O. 12866, ‘‘Regulatory Planning and
Review,’’ September 30, 1993, as amended by E.O.
14094.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
rulemaking. In making regulatory
decisions on possible enhancements to
FMVSS No. 213, NHTSA considers the
consumer acceptance of cost increases
to an already highly effective item of
safety equipment and whether an
amendment could potentially have an
adverse effect on the sales of this
product. The net effect on safety could
be negative if CRSs are not used as
much because of cost increases. NHTSA
also weighs the effects of an amendment
on the ease of correctly using child
restraints. We consider whether an
amendment may cause child restraints
to become overly complex or frustrating
for caregivers, resulting in increased
misuse or nonuse of the restraints. The
petitioner did not provide information
that would enable NHTSA to assess
these practicability issues.
Based on the forgoing, NHTSA is
denying Saczalski’s request to amend
FMVSS No. 213.
(d) NCAP Implementation
Cantor requested that NHTSA
implement a rear-impact crash test into
the 5-star rating as part of his dual
FMVSS/NCAP approach. NHTSA’s
regulations at 49 CFR 552.3 state that a
petition for rulemaking may be filed
respecting the issuance, amendment or
revocation of a motor vehicle safety
standard. NCAP is not a motor vehicle
safety standard. Therefore, a petition for
rulemaking is not the appropriate
mechanism for requests to amend the
NCAP program. NHTSA therefore
denies Cantor’s petition for rulemaking.
After NHTSA’s planned research is
completed, however, we will be in a
better position to consider how best to
implement any necessary changes both
in our standards and/or NCAP.
F. Conclusion of NHTSA Assessment of
Cantor and Saczalski Petitions
In accordance with 49 CFR part 552
and after careful consideration, Cantor’s
request to restore pelvic restraint
language to FMVSS No. 209, and
Saczalski’s request to add a rear impact
test to FMVSS No. 213 and to add a
cargo test and requirement to FMVSS
No. 207 are denied based on the
information presented above. This
ANPRM provides the required
notification of the denial. As part of our
effort to facilitate further research and
data development to support a potential
rulemaking to updated FMVSS No. 207,
NHTSA grants in part both petitions
regarding updating the moment strength
requirement in FMVSS No. 207 and the
development of updated static and
dynamic test procedures for seat back
strength, and Cantor’s petitioned-for
request on structural symmetry. NHTSA
PO 00000
Frm 00029
Fmt 4701
Sfmt 4702
58025
seeks comment on the issues discussed
above.
G. Center for Auto Safety (CAS) Petition
On March 9, 2016, CAS petitioned
NHTSA to amend FMVSS No. 208 and
FMVSS No. 213 to require additional
warnings instructing parents to place
children in rear seating positions behind
unoccupied front seats, if possible, or
behind the lightest front seat occupant.
CAS requested that FMVSS No. 208,
S4.5.1(f), be amended so that the vehicle
owner’s manuals be required to include
the following language (or similar):
‘‘If possible, Children Should Be
Placed in Rear Seating Positions Behind
Unoccupied Front Seats. In Rear-End
Crashes, the Backs of Occupied Front
Seats Are Prone to Collapse Under the
Weight of Their Occupants. If This
Occurs, the Seat Backs and Their
Occupants Can Strike Children in Rear
Seats and Cause Severe or Fatal
Injuries.’’
CAS also requested that the label
found at FMVSS No. 213, Figure 10, be
amended to include the statement
‘‘Place behind an unoccupied front seat
where possible.’’
H. Analysis of CAS Petition
CAS requested that NHTSA add
warning statements in the owner’s
manual and on CRS labels to warn
parents to ‘‘Place behind an unoccupied
front seat where possible.’’ Currently,
the CRS label warns of the potential
injury that could result from placing a
CRS in front of an air bag but does not
make any statement relating to where
else in the vehicle the CRS should not
be placed. Moreover, the CRS label
instructs that ‘‘The back seat is the
safest place for children 12 and
under.’’ 156
CAS does not provide analysis
demonstrating a net benefit to placing
the child in a specific rear seat. Long
established data show that the rear seat
is the safest place for children under the
age of 13.157 Published NHTSA data
shows that rear seats are 25–75 percent
more effective in reducing fatalities
(compared to front seats) for children 0–
12 years old.158 However, the overall
risk to CRS-seated children in each rear
position depends on many factors other
than front seat occupancy. These factors
may include which side of the vehicle
156 FMVSS
No. 213, Figure 10.
ER et al. Seating positions and
children’s risk of dying in motor vehicle crashes. Inj
Prev. 1998;4:181–187. Durbin, DR et al. Effects of
seating position and appropriate restraint use on the
risk of injury to children in motor vehicle crashes.
Pediatrics. 2005;115:e305–e309.
158 Kuppa, S et al. Rear Seat Occupant Protection
in Frontal Crashes. 2005 Enhanced Safety of
Vehicles Conference, Paper No. 05–0212.
157 Braver,
E:\FR\FM\16JYP2.SGM
16JYP2
khammond on DSKJM1Z7X2PROD with PROPOSALS2
58026
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
is struck in a side impact (and where the
CRS is placed in relation to that impact)
and the risks involved in more common
frontal impacts. CAS fails to provide
sufficient data or other information to
conclude that the warning
recommended in its petition would
have any net benefit.
By contrast, there may be unintended
safety harms that such a label could
generate. The suggested label could
dilute the message about the importance
of placing children in the rear seat. It
could be read by some consumers as
inconsistent with the label required by
Figure 10 of FMVSS No. 213 that the
rear seat is the safest place for children
aged 12 and under. Such inconsistency
may confuse them and reduce the
efficacy of the current CRS label. The
label could lead some caregivers to
install the child restraint system in a
front seating position rather than a rear
seating position to avoid rear proximity
to an occupied front seat. This outcome
could have severe consequences if the
rear-facing CRS were positioned in front
of a deploying air bag. Another unsafe
outcome of such confusion could be
some caregivers deciding not to use a
CRS at all with their child when the
CRS cannot be placed behind an
unoccupied front seat. CAS did not
provide any assessment of the risk of
unintended consequences related to the
petition for a label. The guidance
recommended by CAS may result in the
continual removal and reinstallation of
a CRS by parents, depending on front
seat occupancy, as they decide which
seating position is safer. Such actions
could lead to fatigue, with some
caregivers eventually ignoring the
instruction. Not only would that
undermine the label’s purpose, but
NHTSA is also concerned that
caregivers may start to ignore other
instructions and warnings on the label,
such as the warning on the label
required by Figure 10 not to place the
CRS on the front seat with an air bag.
Such a warning is crucial to the safety
of the child and must be always
followed.
Finally, NHTSA rejects CAS’s request
to add language to FMVSS No. 208,
S4.5.1(f) and therefore required in
owner’s manuals, stating ‘‘If possible,
Children Should Be Placed in Rear
Seating Positions Behind Unoccupied
Front Seats. In Rear-End Crashes, the
Backs of Occupied Front Seats Are
Prone to Collapse Under the Weight of
Their Occupants. If This Occurs, the
Seat Backs and Their Occupants Can
Strike Children in Rear Seats and Cause
Severe or Fatal Injuries.’’ We are
denying this request for the same
reasons discussed above, namely that
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
CAS has not provided supporting
information demonstrating the benefit of
the change and has not provided
analysis of unintended consequences
that the amendment may cause. We also
emphasize that this language proposed
for the owner’s manual, by focusing
even more on the risk of seat back
collapse than the language proposed for
the label, has added potential to cause
confusion beyond the language
petitioned for the label. Therefore,
NHTSA will not incorporate the
requested amendment.
For these reasons, NHTSA does not
believe adopting CAS’s
recommendation to change the CRS
label or amend FMVSS No. 208,
S4.5.1(f) would be appropriate. The
agency continues to promote the
message that the rear seat is the safest
place for children. In accordance with
49 CFR part 552 and after careful
consideration, the CAS petition for a
labeling requirement to be added to
FMVSS No. 213 and to amend FMVSS
No. 208 is denied based on the
information presented above. This
ANPRM provides the required
notification of the denial.
VI. Unified Approach to Rear Impact
Protection
A. Introduction
As NHTSA undertakes this process,
our main considerations, as always, are
safety and the obligations the agency
has under the Vehicle Safety Act. IIJA
requires that we publish this ANPRM to
update FMVSS No. 207. Throughout
this rulemaking effort, we need to take
into account the Safety Act’s imperative
that FMVSS be practicable, meet the
need for motor vehicle safety, and be
stated in objective terms. The long-term
and ongoing challenge to meeting these
goals has been to develop an update to
FMVSS No. 207 and rear impact
protection in general that effectively
balances the tradeoffs to improve overall
safety with a reasoned consideration of
all factors involved. As far back as 1974,
NHTSA understood that there would be
advantages in taking a more unified
approach to rear impact protection. The
1974 NPRM preamble stated that
consolidation of Standards 202 and 207
logically reflects the relationship of the
seat and its head restraint and would
improve the possibilities of eventually
testing the whole seating system with a
dynamic test procedure.
In 1992, the agency again signaled
that it continued to believe that a
unified approach was likely the best
approach to rear impact protection. In
that report, the agency stated that there
are four categories of performance issues
PO 00000
Frm 00030
Fmt 4701
Sfmt 4702
that need to be addressed as part of
future changes to FMVSS No. 207.
These four categories are: (1) Seating
system integrity; (2) Seat energy
absorbing capability; (3) Compatibility
of a seat and its head restraint; and (4)
Seat and seat belt working together. In
the 2004 final rule to update FMVSS
No. 202, NHTSA again reiterated the
ultimate goal of adopting a method of
comprehensively evaluating the seating
system.
The four rear impact protection
categories outlined in 1992 indicate the
need to maintain a balance between
energy absorbing and stiffness
characteristics and the fact that the
severity and type of occupant injuries
varies with impact velocity in rear
collisions. Low-to-moderate velocity
crashes represent the majority of rear
collisions, and these crashes are
responsible for the majority of reported
injuries, mainly whiplash. At higher
impact velocities the injury risks for the
occupant of a seat include bodily impact
with vehicular structures, severe thorax,
pelvis, and neck injuries, and other
risks.159 Additionally, at higher impact
velocities deformation of the seat
sufficient to allow interaction between
front and rear occupant rows and
associated injuries can occur. The
debate around FMVSS Nos. 202a and
207 concerns how effective these
standards are in mitigating these risks
and the inevitable tradeoffs.
NHTSA seeks comment broadly on an
update to the FMVSS regarding
occupant protection in rear impacts.
Even if it has been clear for many years
that the ideal approach to rear impact
safety would incorporate consideration
of both moderate and severe rear
impacts, is there a sound scientific basis
for a reasonable update to the standards
for rear impact protection and are the
necessary technical tools available for a
sound rulemaking proposal? Can we
have a high degree of confidence that
any such proposal will be generally
beneficial? In the following section, we
further analyze, discuss, and seek
comment on potential paths forward for
an update to rear impact protection
required by the FMVSSs, with emphasis
on a unified approach.
B. FMVSS No. 207
Generally, the discussion around
FMVSS No. 207 has been a narrow focus
on seat back strength. However,
occupant protection in rear impact
involves many other issues. Some, such
as Prasad in 1997 and Burnett in 2004,
159 We note that 2017–2020 CISS data indicates
that at all rear impact crash speeds whiplash
remains more frequent than any MAIS 2+ injury.
E:\FR\FM\16JYP2.SGM
16JYP2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
suggested that seat back strength has
limited correlation with occupant
dynamics prior to seat back failure.
Such conclusions, however, were drawn
from older designs whose seat strength
is much lower than some have proposed
for a FMVSS No. 207 upgrade.160
Nonetheless, in its present form, the
standard provides limited guarantees on
how an occupant will respond to a rear
collision prior to the seat back failing.
In fact, the FMVSS No. 202a
requirements likely have a greater
influence on occupant protection
because the majority of rear collisions
yield minor or no injuries and occur at
relatively low DVs. For example, table
II.3 shows NHTSA’s estimate that in
rear collisions, 96% of injuries were
MAIS 1–2 and, if DV was known, 76%
of MAIS 1–2 injuries occurred at DV of
30 km/h or less. Therefore, the present
scope of FMVSS No. 207 is limited in
the sense that it focuses only on the first
category of the four seat performance
categories for rear impact protection,
i.e., seating system integrity.
Furthermore, a very high seat back
strength requirement in FMVSS No. 207
would likely result in a seat back with
very high stiffness due to the necessary
structural reinforcements. Such seats
may impose high occupant loading due
to rapid acceleration in higher speed
rear impacts.161 However, whether such
loading is necessarily injurious, the
speeds at which such loading may be
injurious, and whether the trade-offs
between stiffness and injury are
inherent or can be compensated for in
other design elements, are all matters to
be considered. On the other hand, a seat
back with very low strength may
quickly reach a rotation limit, or fail, at
lower rear impact speeds.
In striking this balance, manufacturers
have, in general, settled on seat back
strength that has increased on average
over the decades to many times the
value set by FMVSS No. 207.162 Viano,
et al., for example, noted that MY 1990s
dual recliner seats had an average peak
moment strength of 1,970 Nm while MY
2000s era dual recliner seats had an
average peak moment strength of 2,360
160 See
table VI.1, above.
reader is referred to the increased risks as
noted in the 1997 Prasad study and concerns drawn
out from the 1989 Request for Comments. We note,
however, that these conclusions are based on seats
that are now decades old. A more recent
examination of this can be found in 2023 Kang, for
a very severe rear impact condition and a rigid seat
structure.
162 Saunders, J., Molino, L.N., Kuppa, S., and
McKoy, F.L. Performance of seating systems in a
FMVSS No. 301 rear impact crash test. Proceedings
of 18th International Technical Conference on the
Enhanced Safety of Vehicles, 2003. Nagoya, Japan.
khammond on DSKJM1Z7X2PROD with PROPOSALS2
161 The
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
Nm.163 As noted in the 2019 Edwards
study,164 it appears as if some
manufacturers have strived to achieve
balance in modern seating systems
between low-speed whiplash protection
and structural integrity at higher speeds.
Currently, FMVSS No. 207 addresses
a segment of the overall rear impact
protection issue. In addition, the
regulated seat strength set by FMVSS
No. 207 is considerably lower than the
average seat strength of modern
production seats. The following section
outlines different approaches for
updating the standard to enhance or
broaden the scope of rear impact
protection, thereby further addressing
the rear impact protection points set by
NHTSA.
C. Analysis of Approaches To Updating
Standards for Occupant Protection in
Rear Impact
1. Seat Back Strength and Other
Mechanical Properties
A foundational consideration for
updating standards related to rear
impact protection is the strength of
cantilevered seat backs in the rearward
direction, regardless of how the seat
back strength is tested or measured. The
current strength level set by FMVSS No.
207 is far below the average design
strength of production seats. As a result,
manufacturers have great flexibility in
seat back design. This flexibility allows
manufacturers to readily adopt new
technology such as active head
restraints, and to allow their seat
designs to quickly evolve as the
understanding of rear impact protection
changes. Any increase in the seat back
strength requirement will reduce
manufacturer flexibility. Furthermore,
any new strength requirement should
reduce injuries and adequately balance
tradeoffs. As with any other regulatory
change, due consideration must be
given to overall cost effectiveness of
proposed changes to the regulatory
regime.
As a starting point, the required level
of seat back strength should limit the
interaction between the occupants of
different rows of seats in a rear impact.
It is not clear, however, what level of
crash severity is sufficient to protect
against and for what size of occupant.
No seat strength requirement can protect
all occupants in all possible rear impact
severities, but the selected strength
163 Viano, David C., et al. ‘‘Occupant responses in
conventional and ABTS seats in high-speed rear
sled tests.’’ Traffic injury prevention 19.1 (2018):
54–59.
164 Edwards, Marcy A., et al. ‘‘Seat design
characteristics affecting occupant safety in low-and
high-severity rear-impact collisions.’’ IRCOBI
Conference, Florence, Italy, IRC–19–11. 2019.
PO 00000
Frm 00031
Fmt 4701
Sfmt 4702
58027
should attempt to be protective of as
many occupants as possible within the
constraints of practicality and cost.
Therefore, we seek comment on the
correct minimum seat back strength
requirement. We further seek comment
on ways this parameter can be tested
and measured. We also seek comment
on the benefits or harm generated by the
manufacturer flexibility allowed by a
low minimum seat back strength
requirement, and how NHTSA should
understand those benefits or harms as
well as the cost to manufacturers to
comply with alternative elevated lower
bound seat back strength options.
Another issue is energy absorption.
The energy absorption or forcedeflection characteristics of seat backs
are currently not regulated by FMVSS
No. 207. Controlled deformation of the
seat back allows the occupant of a seat
to ride-down a crash in a manner that
may minimize injury. However, if the
seat back absorbs the crash energy
elastically rather than irreversibly,165
there may potentially be injurious
rebound of the occupant. Thus,
remaining residual energy after
occupant ride-down may be an
important consideration. We note that
FMVSS No. 222 incorporates a rearward
energy absorption and force deflection
requirement for school bus seat backs.
We seek comment on whether a similar
requirement should be incorporated into
FMVSS No. 207 and what the
performance level should be.
Older seat designs have typically used
a single recliner mechanism to control
seat back rotation. Because of the nature
of such a design, rearward seat back
load is not uniformly restricted, leading
to one side of the seat back rotating
more than the other; this lack of
structural symmetry may lead to a
subsequent twisting of the seat back. It
has been theorized that such twisting
reduces the ability of the seat back to
prevent occupant ramping. Both of the
current petitions discussed earlier in
this ANPRM desired some limit to be
placed on seat twist. We seek comment
on whether a similar requirement is
needed, what the performance level
should be and how it should be
measured.
We also seek comment on whether an
updated FMVSS should regulate other
seat characteristics that may be related
165 When the seat back deforms elastically it
absorbs energy like a spring and will return to its
original position and shape after the applied force
is removed. When the applied force is sufficient to
cause yielding in the seat back there is irreversible,
also termed inelastic or plastic, deformation in the
seat back which permanently absorbs some energy;
in which case the seat back will not return to its
original position and shape after the applied force
is removed.
E:\FR\FM\16JYP2.SGM
16JYP2
58028
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
to occupant ramping, such as pocketing
and the coefficient of friction of the
upholstery. We also seek comment on
any other seat characteristics that
should be regulated for rear impact
protection.
2. Test Parameters
This section discusses and requests
comment on means of testing or
measuring seat parameters. We first
discuss the benefits and limitations of a
quasi-static approach. Afterward, we
discuss and seek comment on a
dynamic testing regime that utilizes two
testing speeds to cover the variety of
rear impact occupant protection
scenarios.
khammond on DSKJM1Z7X2PROD with PROPOSALS2
3. Quasi-Static Testing
One approach to update FMVSS No.
207 is to increase the required seat back
moment while retaining the current test
procedure of loading the upper frame
member or some other part of the seat
back. This is appealing in its simplicity
but has some potential shortcomings.
First, the required moment is specified
to be applied through a horizontal force
and a distance from the seating
reference point. This works well as an
initial condition and within the
required moment value, which typically
results in a relatively small amount of
seat back rotation. Depending on the
increase in moment value, however,
significant seat back deformation could
occur during testing. In this
circumstance, maintaining a horizontal
load throughout the test becomes a
serious challenge.
In addition, it is not clear that loading
the seat back at the upper crossmember
is the best way to quasi-statically load
the seat back. Over the years, several
different methods of loading the seat
back have been developed that may
better achieve the goals of the test.166
For example, NHTSA has tested seat
backs to failure by modifying the
FMVSS No. 207 procedure such that the
loading arm rotates with the seat back
and the initial direction of loading
perpendicular to the seat back as
specified by SAE J879.167 Some
methods involve the use of body-blocks
or counter balanced ATDs, pushed or
pulled into the seat back, which loads
the seat back in a manner more closely
related to how a human may load the
seat back. Such methods can also
166 Burnett, R; Viano, D; Parenteau, C; (2022)
‘‘Quasi-Static Methods to Evaluate Seat Strength in
Rear Impacts.’’ Traffic Injury Prevention.
167 Molino, L (1998): Determination of MomentDeflection Characteristics of Automobile Seat
Backs. NHTSA Technical Report, DOT Docket
Management System NHTSA–1998–4064.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
measure force-deflection in addition to
strength.
However, existing quasi-static test
procedures are also limited because they
can tell us how the seat reacts when it
is loaded, but they cannot tell us
whether the seat’s characteristics are
potentially injurious to or protective of
the occupant in certain rear impacts.
Thus, the value of the quasi-static
method may be limited if the
relationship between mechanical seat
properties and occupant response in a
rear impact is not well understood. This
may lead to a lack of optimization and
the potential introduction of harmful
seat behavior.
We seek comment on the use of quasistatic testing in an updated rear impact
occupant protection regime. Could
changes be made to quasi-static
procedures or loading devices that
would help discern the effect of the seat
design on the seat’s occupant? Is this
important to fully understand how
changes to seat strength or other seat
design parameters will affect the
occupant prior to determining what
level of increase in minimum seat back
strength is sufficient? Is this information
necessary to develop objective
measures, tests, and strength
requirements for seat backs?
The above discussion is primarily
related to determining seat back
performance at higher severity levels.
Any unified approach, however, must
also consider the frequent lower speed
rear impacts correlated to whiplash
injury. Currently, FMVSS No. 202a
requires the head restraint to have a
minimum height and maximum backset
or optionally limit the head to torso
rotation of a Hybrid III dummy in a sled
test. What changes can be made to the
test method and standard for head
restraints from a quasi-static
requirement perspective that may
improve the protection against whiplash
in moderate severity rear impacts and/
or create more synergistic total rear
impact protection?
4. Dynamic Testing
Considering the limitations of quasistatic testing in an environment with
significant uncertainty regarding injury
dynamics, a dynamic assessment of seat
behavior at multiple impact severities
may be a more effective method for
achieving a unified and synergistic
approach to rear impact protection. As
noted above, this approach has been a
feature of past efforts to update standard
FMVSS No. 207 and is also consistent
with the four rear impact protection
points. In this section, we discuss and
seek comment on various dynamic
testing approaches to achieve the goal of
PO 00000
Frm 00032
Fmt 4701
Sfmt 4702
improved rear impact protection. Topics
of discussion include test speeds, seat
performance measures, ATD selection,
and ATD performance measures.
To fully assess the four rear impact
protection points, NHTSA is
considering a dynamic approach that
contains both a low and high-speed test.
Each of these regimes place distinct
requirements on the seating system, and
a dual speed regime can help ensure
balance in rear impact protection.
NHTSA believes a two-tiered approach
will preserve seat design flexibility
while improving protection for the
occupant across a range of rear impact
severities.
NHTSA is considering which ATDs
are best suited to use in rear-impact
dynamic testing, at both low and highspeed. A low-speed test would assess
the seating system’s ability to protect
against injuries to the cervical spine. As
mentioned previously, FMVSS No. 202a
currently includes a low-speed sled test
option using the HIII–50M test dummy.
NHTSA is considering a similar test
utilizing the BioRID 50th percentile
male dummy and believes this dummy
provides significant improvements over
other ATD options. A high-speed test
would assess the rear impact regime
where significant rearward rotation of
the seat back may occur, and occupant
retention becomes a concern as well as
contact with rear seat occupants. An
ATD used for this type of test should
have characteristics that replicate the
interaction of the occupant with the seat
back. NHTSA is also considering BioRID
for use in the higher speed test but
acknowledges that the two test
severities require different ATD
capabilities. NHTSA is aware of a
female rear impact dummy finite
element model, EvaRID FE, which is a
scaled down version of the BioRID, with
mass and geometrical dimension
representing a 50th percentile female.
The agency is also aware of the
development of a prototype 50th
percentile female rear impact dummy
known as the BioRID–P50F,168 and is
also interested in, and seeks comment
on, the potential for its use and to what
extent its state of readiness is consistent
with a potential rulemaking proposal.
The agency seeks comment on which
ATDs would be most appropriate to use
in both low and high-speed rear impact
testing of seats, and whether using two
different sized ATDs (for example,
BioRID and BioRID–P50F) in one or
both of these test configurations would
168 The physical BioRID–P50F dummy is
currently in prototype stage and not available for
evaluation by the agency.
E:\FR\FM\16JYP2.SGM
16JYP2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2
offer a more comprehensive assessment
of seat performance.
(a) Low-Speed Test
An upgraded low-speed test would
assess the energy absorption
characteristics and compatibility of the
seat and head restraint with respect to
occupant protection in low severity rear
impacts. The primary concern in lowspeed rear impacts are cervical spine
injuries associated with whiplash.
Therefore, a low-speed test should
promote best practices that mitigate
whiplash beyond what is currently
achieved by FMVSS No. 202a by
ensuring compliance with a standard
that establishes a minimum level of
injury prevention. During the
rulemaking establishing FMVSS No.
202a, the agency acknowledged
commenters’ criticism of the biofidelity
sufficiency of the HIII–50M used in
202a, particularly its neck, in the
rearward direction.169 Thus, it is
appropriate for the agency to explore the
use of alternative ATDs such as BioRID,
which may more accurately replicates
spinal, torso and head motion. As
discussed below, this comes with
challenges in determining an acceptable
and repeatable biomechanical
measurement. Below, we discuss and
seek comment on certain considerations
relevant to a low-speed test: test pulse
and injury criteria and test repeatability.
First, we consider the appropriate test
pulse. The low-speed regime is typically
associated with rear impact DV between
16 and 24 km/h. The dynamic sled test
option in FMVSS No. 202 has a DV
target of 17.3 ± 0.6 km/h. The Euro
NCAP whiplash assessment uses low,
medium and high severity sled
acceleration corridors with target DVs of
16.10, 15.65 and 24.45 km/h. The IIHS
dynamic whiplash rating uses a
simulated rear impact conducted on a
sled using a DV of 10 mph. In addition
to the issues outlined below, NHTSA
seeks comment on the test pulse for a
low-speed rear impact test, such as DV
and acceleration profile.
Next, we consider injury criteria and
test repeatability. Current low-speed
testing practices present challenges with
well-defined injury criteria and
repeatability of the tests. The
understanding of whiplash injury
mechanisms continues to evolve, and
169 69 FR 74873 (Dec. 14, 2004); The agency
concluded at that time that the HIII–50M was
sufficient to discern between acceptably safe head
restraint systems and those that allow unacceptable
levels of head-to-torso rotation. Nonetheless, the
agency stated it was likely ‘‘to revisit the decisions
made in [the] final rule about dynamic performance
values and the test device as more advanced
dummies are developed and the injury criteria
achieve broader consensus.’’
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
contemporary ATD injury criteria are
therefore derived from nonlinear
statistical correlations with
biomechanical data. Because of this
evolving understanding, existing
dynamic whiplash assessments use a
range of ATD measures. For example,
the 2009 EuroNCAP dynamic whiplash
ratings system 170 calculates a rear
impact seat performance rating using a
combination of seven measures from
rear impact sled testing using the
BioRID ATD. These measures are:
• NIC (neck injury criteria),
• Nkm (shear force and bending
moment),
• Head rebound velocity,
• Fx upper neck shear,
• Fz upper neck axial force,
• T1 acceleration up to head contact,
and
• Head restraint contact time
Any assessment based on a threshold
value of these parameters should
accurately assess the injury risk. To be
objective, the ATD metrics of a lowspeed test should also be based on a
fundamental understanding of the
biomechanical injury mechanisms. For
example, NIC is based on the principle
of neck retraction prior to the head
contacting the head restraint, described
earlier in the Neck injuries subsection,
leading to injurious pressure waves in
the spinal canal.171 An injury threshold
of 15 m2/s2 for the NIC was
suggested 172 after analyzing human
volunteer results 173 to find a lower
bound of injury tolerance. However, the
predictive basis of ATD metrics for lowspeed injury are usually based on a
statistical nonlinear analysis of
biomechanical data and shows varying
degrees of success in predicting real
world outcomes. In the 2019 Edwards
study,174 the authors compared lowspeed BioRID measurements with
insurance claim data. The standard
170 van Ratingen, Michiel, et al. ‘‘The Euro NCAP
whiplash test.’’ 21st international technical
conference on the enhanced safety of vehicles.
2009.
171 Aldman, B.: An analytical approach to the
impact biomechanics of head and neck injury.’’
Proceedings of the 39th American Association for
Automotive Medicine Conference; October 6–8,
1986, Montreal, QC. 1986.
172 Boström, Ola, et al. ‘‘A new neck injury
criterion candidate-based on injury findings in the
cervical spinal ganglia after experimental neck
extension trauma.’’ Proceedings of The 1996
International Ircobi Conference On The
Biomechanics Of Impact, September 11–13, Dublin,
Ireland. 1996.
173 Eichberger, Arno, et al. ‘‘Comparison of
different car seats regarding head-neck kinematics
of volunteers during rear end impact.’’ Proc. IRCOBI
Conf. 1996.
174 Edwards, Marcy A., et al. ‘‘Seat design
characteristics affecting occupant safety in low-and
high-severity rear-impact collisions.’’ IRCOBI
Conference, Florence, Italy, IRC–19–11. 2019.
PO 00000
Frm 00033
Fmt 4701
Sfmt 4702
58029
whiplash metrics, such as those listed
above, did not have a significant
correlation with the insurance claim
data for all the seats analyzed. The
longitudinal pelvis displacement of the
BioRID dummy into the seats, an
atypical metric in whiplash
assessments, had the most significant
correlation with insurance data. NHTSA
has also studied intervertebral rotations
in low-speed rear impacts using PMHS
and ATD occupants.175 176 177 NHTSA
found the intervertebral rotations of the
PMHS subjects to be comparable with
BioRID rotations 178 and the PMHS
intervertebral rotations were found to
correlate with PMHS subluxation
injuries (an incomplete or partial
dislocation of a joint or organ).179 The
use of ATD injury metrics in assessing
low-speed rear impact injury risk is still
developing, and further investigation is
needed to develop metrics or ratings
systems with a direct relationship to
real world whiplash injury. NHTSA’s
forthcoming research discussed later
will explore various ATD whiplash
criteria.
Multiple studies have shown lack of
reproducibility in low-speed impacts. In
2007, a study compared the
measurements of a BioRID–IIg dummy
in rear impact sled tests run across 18
identical production seats.180 The
authors were concerned that because the
loads in a low-speed rear impact test are
very low, there could be high variability
in results due to small changes in the
test setup. The study ran tests at 3
175 Moorhouse K, Kang Y, Donnelly B, Herriott R,
Bolte JH. (2012, Nov). Evaluation of The Internal
and External Biofidelity of Current Rear Impact
ATDs to Response Targets Developed from
Moderate-speed Rear Impacts of PMHS. STAPP Car
Crash Journal, 56, 12S–21.
176 Kang Y, Moorhouse K, Donnelly B, Herriott R,
Bolte JH. (2012, Nov). Biomechanical Responses of
PMHS in Moderate-speed Rear Impacts and
Development of Response Targets for Evaluating the
Internal and External Biofidelity of ATDs. STAPP
Car Crash Journal, 56, 12S–20.
177 Kang Y, Moorhouse K, Herriott R, Bolte JH.
(2013, May). Comparison of Cervical Vertebrae
Rotations for PMHS and BioRID II in Rear Impacts.
Traffic Injury Prevention, 14 (Supplement 1), S136–
S147.
178 Kang Y, Moorhouse K, Icke, K., Stricklin, J.,
Herriott R, Bolte J.H. Rear Impact Head and Cervical
Spine Kinematics of BioRID II and PMHS in
Production Seats (2015, Sept). International
Research Council on Biomechanics of Injury
(IRCOBI), IRC–15–38, 246–260.
179 Kang Y, Moorhouse K, Icke K, Herriott R, Bolte
JH. (2014, Sept). Head and Cervical Spine
Responses of Post Mortem Human Subjects in
Moderate Speed Rear Impacts. International
Research Council on Biomechanics of Injury
(IRCOBI), Berlin, Germany. IRC–14–33, 268–285.
180 Bortenschlager, Klaus, et al. ‘‘Review of
existing injury criteria and their tolerance limits for
whiplash injuries with respect to testing experience
and rating systems.’’ Proceedings of the 20th
International Technical Conference on Enhanced
safety of vehicles, Lyon, France. 2007.
E:\FR\FM\16JYP2.SGM
16JYP2
58030
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2
different severities with 6 equivalent
repetitions at each severity. The authors
found that the ATD metrics displayed
high variability across the equivalent
tests. The dummy rebound velocity
showed the least variability with 2.76%,
1.83% and 1.23% coefficient of
variation in the low, medium, and high
severity tests. The NIC had greater
variability with a 9.18%, 10.5%, and
13.83% coefficient of variation. The
neck shear Fx, however, had very high
variability with a 21.04%, 27.86%, and
32.57% coefficient of variation across
like tests. After computing the ranking
score for each of the 6-test series, the
authors found the scores to vary by 26%
from lowest to highest. Because of
variability in the measurements and
ranking scores the authors called into
question the discriminatory power of
the scoring system and noted the lack of
robustness in the scoring system. This
study underlines the challenge in
developing a low-speed rear impact
testing approach with high
reproducibility. Note that the values of
a characteristic for a rating system or
standard might be set in such a way as
to account for the variability associated
with the test.
The precise understanding of how
whiplash injuries occur is evolving, but
not complete. We seek comment on this
approach. Are the ATD measurements
described above sufficiently objective
and correlated with whiplash injury? If
so, can a low-speed test be conducted in
a repeatable and reproducible manner
that would ensure objective results and
positive safety outcomes that are
equitably distributed across all occupant
types? Do practicable countermeasures
for whiplash injuries exist to meet such
a regulatory requirement? Would the
requirement work synergistically with a
high-speed dynamic requirement?
(b) High-Speed Test
A high-speed test would assess rear
impact protection at a severity where
significant rearward deflection of the
seat back may occur, and occupant
retention becomes a concern. This test
would assess all four of the rear impact
protection points. The high inertial
forces placed on a seat back would test
seating system integrity and energy
absorption capabilities of the seat back
through rearward rotation and
deflection, as well as the ability of the
seat belt restraint system to maintain
retention and support an occupant in
rebound. Finally, compatibility of the
seat and head restraint would be
assessed through appropriate ATD
injury limits. The assessment would
likely include neck (whiplash or higherlevel injury), thorax, spine, and pelvis
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
results, but could include other body
regions as well.
Occupant injuries in a high-speed rear
impact are primarily severe head, neck,
and thorax injuries and have clear
pathology. Research conducted by
NHTSA has shown that severe thorax
injuries, i.e., rib fracture, may also occur
in a retained seat occupant through
inertia and interaction with the seat
back in very high-speed rear collisions
and rigid seat supporting structures.181
Seat retention provides continual
support to the occupant and is
important to avoid severe contact
injuries and injurious occupant
kinematics. A lack of occupant retention
may also lead to severe injuries to
passengers other than the forward row
occupants through occupant-tooccupant interaction. A high-speed test
would assess seating protection against
injury through data from an ATD and
related seating retention metrics. The
occupant retention metrics of concern
may include the maximum dynamic
seat back rotation angle and ATD
displacement measures. NHTSA seeks
comment on the appropriate occupant
retention metrics and ATD injury
criteria at high-speed. We request
comment on how the availability of
specific ATDs might limit or inform the
selected measurements.
The forces applied to seat backs in
rear impacts range over a continuum of
severities. The applied inertial forces
are proportional to the seat base
acceleration induced by the crash pulse,
the occupant’s mass, and acceleration.
The distribution of occupant mass along
the seat back influences the torque
generated at the seat back recliner
mechanism, and the torque is
proportional to the occupant’s mass. A
high-speed test would need to set a test
severity within the range of potential
real-world severities for which
practicable countermeasures may be
available. Extreme forces on the seat
back due a rear impact are a relatively
rare occurrence in the real-world, with
the highest forces requiring both a
relatively high DV and occupant mass.
As noted in our analysis of 2017—2020
CISS data reported in Figure II.4, 94%
of rear towaway collisions occur at DV
of 40 km/h (24.9 mph) or less. Table II.2
indicated that the most probable DV
range for MAIS 3+ injuries in rear
impacts was the 31–40 km/h (19.3–24.9
mph) range. For some seat designs, a
dynamic test in the DV range of 35 to 40
km/h (21.7 to 24.9 mph) that is
181 Kang, Yun-Seok, et al. ‘‘Biomechanical
responses and injury assessment of post mortem
human subjects in various rear-facing seating
configurations.’’ Stapp car crash journal 64 (2020):
155–212.
PO 00000
Frm 00034
Fmt 4701
Sfmt 4702
conducted with a 50th percentile male
ATD would likely lead to significant
rotation of the seat back and occupant
movement along the seat back, as
described in the 2019 Edwards study.182
The authors also noted that within the
context of a 50th percentile male ATD
and 37.5 km/h (23.3 mph) DV rear
impact sled test, a degree of balance was
achieved between low and high-speed
rear impact protection in a range of
production seats, as measured by the
low-speed ratings system, seat back
rotation, and occupant displacement in
the high-speed test. Such a dynamic test
conducted with a 95th percentile male
ATD or at higher DV, however, would
lead to greater forces on the seat back
with a greater potential for plastic
deformation of the seat structure, a more
extreme test of retention, and potential
interaction with rear seats. The highspeed test DV would ideally be high
enough to be sufficiently representative
of real-world crashes to generate
practicable and, ideally, cost effective
countermeasures for protection against
higher level injuries. NHTSA seeks
comment on the appropriate test
severities for a possible high-speed test
and the appropriate ATD to utilize.
Positioning of the ATD in the seat
may be an important factor in a highspeed test. Studies such as the 1994
Strother and James cited above, have
shown occupant posture to influence
injury outcome in rear impacts. In
addition, the sensitivity of an ATD itself
to positioning may be a factor to
explore. For example, how sensitive are
results to atypical positions like leaning
on the arm rest, creating an off-center
midsagittal plane for the ATD? NHTSA
seeks public comment on the
appropriate positioning of the ATD in a
high-speed rear impact test and whether
and/or what type of out-of-position
testing should be performed.
A well-designed high-speed rear
impact test would account for all four of
NHTSA’s rear impact protection points
in the context of high inertial forces
leading to significant rearward
deflection of the seat back. The
performance measures of concern may
include retention measures such as
maximum dynamic seat back rotation
angle, but also ATD injury metrics
relating to thorax and neck injury. In
addition to these concerns, NHTSA
seeks comment regarding what objective
rear impact protection metrics are of
most concern in a high-speed rear
impact test. Does existing ATD
182 Edwards, Marcy A., et al. ‘‘Seat design
characteristics affecting occupant safety in low-and
high-severity rear-impact collisions.’’ IRCOBI
Conference, Florence, Italy, IRC–19–11. 2019.
E:\FR\FM\16JYP2.SGM
16JYP2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2
technology adequately replicate
occupant kinematics at high-speeds?
What ATD injury metrics would be most
objective and relevant?
(c) Rear Impact Delivery Methods
Another factor to consider for a
dynamic testing approach is how the
crash pulse should be delivered to the
seat base. There are two basic
approaches to consider: a sled (with the
seat mounted to either the vehicle floor
plan or a rigid platform) or moving
barrier to vehicle approach. This section
explores the advantages and
disadvantages of each approach.
In experimental study of rear impacts,
the most common method for crash
pulse delivery is a sled-based method.
In this approach, a moveable sled is
accelerated with a high degree of
accuracy on a linear track. Mounted on
the sled may be a rigid platform to
which the vehicle seat is attached. With
appropriate mounting hardware, many
types of seats can be accommodated
without significant modification to the
setup. However, the mounting of the
seat to a rigid platform may not transmit
loading to the seat identically to how it
would be transmitted if the seat were
mounted to the vehicle floor pan. Thus,
a more realistic approach would be to
mount a floor pan to the sled and mount
the seat to the floor pan. Such an
approach can be expanded to mount all
or portions of the vehicle body and
interior to the sled, potentially allowing
for multiple ATDs in multiple rows of
seats. The agency uses a vehicle body
mounted sled test approach currently
for the optional dynamic testing in
FMVSS No. 202a.
Sled-based methods are relatively low
cost and deliver a highly repeatable
pulse that can be readily applied to all
seats. This removes a degree of
uncertainty about test repeatability.
However, a sled pulse only
approximates a real-world crash pulse.
A sled offers one-dimensional
translational motion, while actual rear
impact crash test may contain threedimensional translational motion and
rotation of the vehicle, albeit likely
relatively small accelerations in the
vertical and lateral direction. While a
sled-based approach is advantageous
from a cost and repeatability standpoint,
it may discount case-specific design
considerations. In addition, for higher
speed impacts, if seats were designed
around a universal rear impact sled
pulse, some seats may in turn be overdesigned and others under-designed
relative to their actual need for rear
impact protection. This is because the
design of rear impact protection in seats
could consider vehicle factors, e.g.,
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
vehicle weight and/or stiffness of the
vehicle.
A vehicle approach would deliver a
rear impact to a motor vehicle using a
moving barrier, similar to tests
conducted under FMVSS No. 301. In
fact, while conducting FMVSS No. 301
tests outlined in the 2003 Saunders
study, the agency has added
instrumentation to seat backs and
placed HIII–50M ATDs in the front seats
to assess the performance of seat backs.
As is the case with the vehicle body
being mounted to a sled, this approach
would test rear impact protection in the
context of the entire vehicle. However,
it differs in that the acceleration pulse
delivered to the seat will be a function
of the vehicle’s structural deformation.
In a real collision, the seat base
acceleration depends on vehicular
factors, e.g., vehicle mass and structural
characteristics, and therefore the
moving barrier to vehicle approach
would be closer to reality compared to
a typical sled-based approach. A moving
barrier to vehicle approach is more of a
consideration for higher speed impacts,
where the vehicle characteristics would
have a greater influence on the crash
pulse. A sled-based approach could
tune the sled pulse to the actual vehicle
crash pulse, if it were known, or use
some adjustment to the pulse that
considers vehicle-based factors.
Nonetheless, a barrier impact approach
would place a greater load on seats of
lighter and stiffer vehicles because DV
has positive correlation with these
features if all else is equal.
The barrier impact approach places
the seat in the full vehicle environment.
However, a sled-based approach allows
the possibility of the seat mounted on a
platform in isolation. Whether a full
vehicle or isolated seat is tested is less
likely to influence testing outcomes in
low-speed testing. However, high-speed
testing will cause much more seat back
deformation. In certain vehicle
environments, such as convertibles,
two-door cars, standard cab pickup
trucks, and vehicles with rigid second
row seating, there may be structures
near the seat back which could restrict
its rearward movement. Such
restrictions could be advantageous with
respect to meeting seat back rotation
limits. How such restrictions would
influence risk of injury, however, is not
obvious.
In summary, a sled-based method
using a rigid platform and a generic sled
pulse is the most cost effective and
simplest method for inertial loading of
a seat. Sled testing using the vehicle
floor and even more of the actual
vehicle would likely increase cost and
perhaps complexity. The use of generic
PO 00000
Frm 00035
Fmt 4701
Sfmt 4702
58031
sled pulses, whether for lower or higher
speed impact simulation may also
potentially allow for greater
repeatability, while sacrificing closeness
to reality. Sled testing using a vehicle
specific crash pulse would add some
complexity and the need for knowledge
of the crash pulse. A moving barrier to
vehicle test would be the option but
would deliver the best approximation to
the real-world impact while simplifying
crash pulse generation. It would have
instrumentation measurement
complexity similar to sled testing.
Additionally, a moving barrier to
vehicle test may also introduce more
avenues for test-to-test variability, part
of which can be attributed to vehicle
build variability. NHTSA seeks
comment on the different approaches
for delivering a rear impact crash pulse.
(d) Characteristics and Performance
Measures Needed for a Rear Dummy
As discussed above, fostering the
synergistic performance of seats
suggests dynamic testing should sample
at least two different DV regimes:
including a low-speed and high-speed
test. A different ATD could be used for
each test to adequately assess the range
of occupant kinematics that occur as DV
is varied. The primary ATD
performance measures of concern for a
low-speed test relate to whiplash
injuries and as noted earlier, important
characteristics include the ability to
replicate torso straightening and neck
kinematics. These factors are also
important for biofidelity in a high-speed
test along with thoracic compression,
spine flexibility, and pelvic rotation.183
The HIII–50M has long been widely
used for rear impact protection research,
even though this dummy was developed
and validated for frontal crash testing.
Nonetheless, the HIII–50M has provided
an effective means of ballasting the seat
and measurements of dummy
kinematics and loading. Over time,
significant progress has been made on
the development of the BioRID ATD,
which is designed specifically for rear
impacts. BioRID performance has thus
far been focused on low-speed testing to
assess neck injury risk but has more
recently been evaluated in higher speed
rear impact conditions. Additionally,
dynamic sled tests are used by ratings
groups, academic researchers and
industrial researchers to assess the
performance of seating systems in a rear
impact, and results are compared with
adult volunteers in low-speed tests and
183 Hagedorn, A., Stammen, J., Ramachandra, R.,
Rhule, H. et al., ‘‘Biofidelity Evaluation of THOR–
50M in Rear-Facing Seating Configurations Using
an Updated Biofidelity Ranking System,’’ SAE Int.
J. Trans. Safety 10(2):291–375, 2022.
E:\FR\FM\16JYP2.SGM
16JYP2
58032
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2
PMHS at higher speeds to validate
modern ATD measurements.184 185 These
efforts have built a better technological
basis for a dynamic test compared to the
past.
The BioRID 50th percentile male
dummy was developed by a Swedish
team in the 1990s.186 The development
was in response to low-speed rear
impact testing using human volunteers
indicating that torso straightening, and
angling of the lower spine were
essential for accurate cervical spine
dynamics,187 188 and the determination
that existing ATDs of that era did not
properly simulate the cervical vertebrae
motions. Therefore, development
focused on an ATD with more realistic
spinal motion, particularly in the neck,
and one that would simulate torso
straightening.189 The BioRID dummy
has an articulated mechanical spine and
is primarily intended to replicate spinal
motion in low-speed rear impacts.
BioRID vertebrae are connected by
linear pin joints and a tension cable.
This mechanical system shows
comparatively high torsional, shear,
compression, and tension inter-vertebral
forces in rear impacts.190 NHTSA has
evaluated the BioRID and believes it is
the best available 50th percentile male
ATD for the low-speed rear impact test
discussed in this ANPRM, but seeks
comment on this topic. NHTSA also
seeks comment on the potential use of
appropriate female crash test dummies
designed specifically for rear impact to
184 Willis, Claire, Jolyon Carroll, and Adrian
Roberts. ‘‘An evaluation of a current rear impact
dummy against human response corridors in both
pure and oblique rear impact.’’ Proceedings of the
19th International Technical Conference of the
Enhanced Safety of Vehicles, Paper. No. 05–0061.
2005.
185 Croft, Arthur C., and Mathieu MGM
Philippens. ‘‘The RID2 biofidelic rear impact
dummy: A pilot study using human subjects in lowspeed rear impact full scale crash tests.’’ Accident
Analysis & Prevention 39.2 (2007): 340–346.
186 Davidsson, Johan, et al. ‘‘BioRID I: a new
biofidelic rear impact dummy. ’’ Proceedings of the
International Research Council on the
Biomechanics of Injury conference. Vol. 26.
International Research Council on Biomechanics of
Injury, 1998.
187 McConnell, Whitman E., et al. Analysis of
human test subject kinematic responses to low
velocity rear end impacts. No. 930889. SAE
Technical Paper, 1993.
188 Ono, Koshiro, and Munekazu Kanno.
‘‘Influences of the physical parameters on the risk
to neck injuries in low impact speed rear-end
collisions.’’ Accident Analysis & Prevention 28.4
(1996): 493–499.
189 Lövsund, Per, and Mats Y. Svensson.
‘‘Suitability of the available mechanical neck
models in low velocity rear end impacts.’’ CNR–
PFT2 ELASIS International Conference on Active
and Passive Automobile Safety in Capri, Italy. 1996.
190 Viano, David C., et al. ‘‘Neck biomechanical
responses with active head restraints: Rear barrier
tests with BioRID and sled tests with Hybrid III.’’
SAE Transactions (2002): 219–237.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
offer a more comprehensive assessment
of seat performance.
For the higher speed rear impact test,
NHTSA is examining the use of BioRID
as well as the HIII–50M and Test device
for Human Occupant Restraint 50th
percentile male (THOR–50M) ATD.191
The BioRID has the advantages
articulated above, but there may be
limits to the speed of the crash
environment that it can be used in and
BioRID replicates only two-dimensional
motion of the spine with injury
assessment being limited to the cervical
spine.
The HIII–50M and THOR–50M have
limitations due to being designed for
frontal impacts. Nevertheless, these
dummies are typically used in studies of
high-speed rear impact dynamics and
have been used as seat occupants in rear
impact tests. In the case of high-speed
tests these ATDs enable the
measurement of seat back rotation and
retention by acting as ballasts that
impose a biofidelic inertial load on the
seat back. The 2019 Edwards study, for
example, used the HIII–50M dummy for
the high-speed test. The HIII–50M is
limited because it has a rigid thoracic
spine so its interaction with a seat back
is significantly different than a real
occupant whose bendable spine
conforms with the seat cushion profile
and structural cross members. The
THOR–50M ATD, a refinement of the
TAD–50M thorax, integrated a new
multi-directional neck and
instrumented pelvis, abdomen, and
lower extremity concepts. Both the HIII–
50M and THOR–50M allow for the
measurement of chest injury risk. While
a high-speed test that uses one of the
male ATDs discussed above is necessary
to assess seating system integrity, a
comprehensive test of seat retention
may also require a test using a female
ATD. NHTSA seeks comment on the
ATDs to use for high-speed rear impact
tests.
NHTSA is exploring a low and high
severity test as components of a unified
approach to updating FMVSS No. 207
and the ATD requirements of these tests
overlap with capabilities of the HIII–
50M, THOR–50M, and BioRID
dummies. NHTSA seeks comment on
the benefits and costs, in particular the
practicability and objectivity concerns,
of using different ATDs for different rear
impact test severities versus the use of
191 Hagedorn A, Stammen J, Ramachandra R,
Rhule H, Thomas C, Suntay B, Kang YS, Kwon HJ,
Moorhouse K, Bolte IV JH. Biofidelity Evaluation of
THOR–50M in Rear-Facing Seating Configurations
Using an Updated Biofidelity Ranking System. SAE
Int. J. Trans. Safety 10(2):2022, https://doi.org/
10.4271/09-10-02-0013.
PO 00000
Frm 00036
Fmt 4701
Sfmt 4702
a single ATD for both low and highspeed testing.
D. Crash Avoidance Technology
Over the last several years, automatic
emergency braking (AEB) and forward
collision warning (FCW) have become
more prevalent in the light vehicle fleet.
An AEB system uses various sensor
technologies and sub-systems that work
together to detect when the vehicle is in
a crash imminent situation, to
automatically apply the vehicle brakes if
the driver has not done so, or to apply
more braking force to supplement the
driver’s braking. A FCW system uses
sensors that detect objects in front of
vehicles and provides an alert to the
driver. FCW systems may detect
impending collisions with any number
of roadway obstacles, including
vehicles. NHTSA has recently published
a final rule requiring that all new light
vehicles be equipped with AEB and
FCW systems.192 NHTSA anticipates
that over time, AEB and FCW
prevalence in the fleet will increase and
the technology will improve. Therefore,
any future rulemaking action related to
the upgrade of rear impact protection
through modification of seat related
standards will need to fully consider the
effects of crash avoidance technology
such as AEB and FCW. AEB and FCW
are expected to reduce the incidence of
high-speed rear impact collisions, either
through avoiding a collision entirely or
mitigating impact speeds into lowerspeed collisions. If AEB and FCW have
this impact, their availability may in
turn affect crash frequencies and injury
types relevant to this ANPRM, such as
the incidence of seat back failure in
vehicles struck from the rear. AEB and
FCW may also reduce the incidence of
low-speed rear impacts that cause
injuries such as whiplash in occupants
of the struck vehicle. However, it is
possible that AEB and FCW, by
mitigating some high-speed impacts into
lower-speed collisions, may increase the
number of lower-speed rear impacts. It
is not clear what the net impact would
be. NHTSA seeks comment on how best
to consider the effects of this technology
on the issues discussed in the ANPRM.
In particular, how might a change in
frequency of rear impacts of different
velocities impact the benefit-cost
considerations for regulatory changes
discussed in this ANPRM, such as the
seat back strength requirement?
192 89 FR 39686 (July 8, 2024). This final rule
builds on a voluntary commitment, announced by
NHTSA in March 2016, by 20 vehicle
manufacturers to make AEB a standard feature on
nearly all new light vehicles.
E:\FR\FM\16JYP2.SGM
16JYP2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
VII. NHTSA’s Forthcoming Research
NHTSA is pursuing research to build
a greater understanding of the issues
presented in this document. Based upon
the current understanding of these
issues, the goals are to better define the
scope of the current rear impact safety
problem, validate seated ATD
measurements in rear impacts, quantify
rear impact injury risks, attempt to
develop injury risk curves, and analyze
rear impact dynamics and testing
procedures. Because the understanding
of the rear impact problem continues to
evolve, the priorities and objectives are
subject to change and likely to evolve as
research progresses. Currently, the aim
is to identify sled test DVs, test types
(e.g., static versus dynamic), test tools
(e.g., loading fixture, ATDs) and
performance limits (e.g., strength
requirements, displacement limits,
injury assessment reference values). It is
anticipated that the research outcomes
will contribute to the determination of
whether to propose an update to FMVSS
No. 202a and FMVSS No. 207 and, if the
determination is made to do so, provide
the basis for such a proposal. The
following discussion outlines NHTSA’s
path forward for research activities
related to this ANPRM.
A. Field Data Analysis and Market
Research
khammond on DSKJM1Z7X2PROD with PROPOSALS2
A study of rear impact field data will
investigate the scope of the rear impact
safety problem. NHTSA intends to
examine the incidence of injuries to the
seated front occupant, the types of
injuries, the degree to which modern
occupied seat backs fail or become
deformed (by row), and which parts of
the seat incur yielding (i.e., just the seat
back, the anchors and seat track, the
vehicle floor, etc.). For higher speed rear
impacts, this is needed to identify the
level of crash severity that may
represent a reasonable dynamic testing
level. Overall trends will be examined
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
by analyzing aggregate field data and
occupant injury and multiple seat row
interaction. An attempt will be made to
attribute vehicle occupant injury to seat
performance. It is expected that manual
reviews of case file material will be
necessary to discern seat performance
and failure mechanisms. NHTSA also
intends to examine how seat designs
may have improved across the fleet or
how second row seats differ in
performance from front row seats.
B. Test Procedure Assessment
NHTSA plans to conduct a sled-based
study of rear impact seat back and
occupant dynamics to develop a greater
knowledge base in the performance of
modern seats in both low and highspeed regimes and to investigate the
feasibility of a dynamic approach for
updating FMVSS No. 207 and rear
impact protection in general.
1. High-Speed Test
The agency expects to perform highspeed sled tests across a range of DVs
including the high-speed rear impact
fuel integrity test performed in FMVSS
No. 301 and at speeds identified in the
field data analysis mention above that
result in relatively high risks to vehicle
occupants. Through this testing, NHTSA
will attempt to determine what physical
characteristics govern occupant
protection and what severities lead to
substantial deformation of seat backs in
high-speed rear impacts. This testing
will take a variety of configurations and
serve a variety of functions. One
important question to be answered is
what deceleration pulse and/or DV will
achieve the agency’s regulatory goals,
particularly with respect to a front seat
occupant intruding into the rear seat
occupant space. Another important
research question is whether the
deceleration pulse and/or DV should be
vehicle specific or generic. It is expected
that sled testing will be performed with
partial vehicles as well as platform
PO 00000
Frm 00037
Fmt 4701
Sfmt 4702
58033
mounted seats to decern the effect of
these two configurations of seat
performance as well as to assess the
challenges related to testing a seat
within a vehicle. This testing will also
help identify the important seat
performance characteristics and the best
way to measure them. We expect to use
multiple ATDs and PMHS occupants in
the seats for a variety of tasks discussed
below.
2. Exploratory Testing
NHTSA recently conducted
exploratory high-speed rear impact sled
testing on a series of production seats to
gain insight into instrumentation and
measurement needs for such tests. The
test closely resembled the 2019 highspeed rear impact tests from the IIHS
study,193 except that NHTSA used the
THOR–50M as a normally positioned
occupant. NHTSA’s crash pulse
achieved a maximum sled acceleration
of 15.1 g after approximately 80 ms
resulting in a DV of 36 km/h (22.4 mph).
The test series consisted of 6 total sled
tests involving the front driver seat of
three different major auto manufacturers
in 2013 and 2018 MY used passenger
vehicles. The three models were tested
with and without seat belt
pretensioners. The seats were
instrumented with accelerometers, load
cells, strain gages and camera target
standoffs and fixed to the sled buck
with an initial seat back recline angle of
25°. The time-dependent seat back
rotation angle was determined by
postprocessing film data and 6DX
(Diversified Technical Systems) sensor
package measurements and are shown
in Figure VII.1 in the case of no
pretensioners.
BILLING CODE 4910–59–P
193 Edwards, Marcy A., et al. ‘‘Seat design
characteristics affecting occupant safety in low-and
high-severity rear impact collisions.’’ IRCOBI
Conference, Florence, Italy, IRC–19–11. 2019.
E:\FR\FM\16JYP2.SGM
16JYP2
khammond on DSKJM1Z7X2PROD with PROPOSALS2
58034
VerDate Sep<11>2014
Jkt 262001
PO 00000
Frm 00038
• 6DX (upperrigbt)
6DX (lower left)
'5il
<l)
::2, 40
--6DX(upperleft)
rn
Fmt 4701
Sfmt 4725
0
~
s::
~
§
0
·~20
~
~
E:\FR\FM\16JYP2.SGM
~
0
..:4
<.)
el
,£i
3
--Filin(rightside)
;;,-.'
::i 30
I
·.g 20
-6DX (lower left)
•• ···6DX(lower right)
·x«I
--Filin(rigbt side)
r/J
·xel
····-· 6DX(upperright)
'5il
<U
::2, 40
~· 6DX (lower right)
~0 30
16JYP2
EP16JY24.016</GPH>
Seat Back Rotation - Seat II
50
--6DX (upper left)
«l
to
~10
<U
r/"J
lfJ
0 4
-0.2
l
··f--+
-0.1
,
0
~
0.1
0.2
Time (s)
0.3
0.4
0.5
0
-0.2
-0.1
0
0.1
0.2
Time (s)
0.3
0.4
0.5
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
17:15 Jul 15, 2024
···-······•············------------------------------,
Seat Back Rotation - Seat I
J
50 I
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
58035
--6DX(upperleft)
......_,,_ 6DX (upper~!)
'bl)
~
~
6DX (lower left)
!40 .•. ,. ..........................,...... .
-~"'
'?
~ 30 -t'-•·•.......................... ,...... _. .................., ...............................,_,.,...... ._.............. ,.................: ? " " " ' - - - -.......==-..!
~
8
'j 20
~
1
i
<,I
10
+············· ... · .. ·····•······.. ··•··· .. ·· ............................................ Jf.·•·•........................... , .......................,.......................... ,.............................. ..
~
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
Time (s)
Figure VII.1: Seat back rotation angles measured by NHTSA in the current high-speed
rear impact test series, tiV = 36 km/h, seat I is MY 2018, seat II is MY 2018-2019 and seat III is
MY2013.
The seat backs reached their
maximum rearward rotation at
approximately twice the point of peak
sled acceleration and then, upon
reversing, decayed to a final recline
angle that is greater than the initial
recline angle. Seat I had the least
rearward rotation and its final recline
angle was the least among the three
models. Seat III had the most rearward
rotation and its final recline angle was
the greatest among the three models.
The difference between the initial and
final recline angles are a product of
irreversible deformation in the seat
frame and an indication of energy
absorbed by the seat. In seat I and to a
lesser extent seat II, as the rotation angle
decayed to the final angle there was
oscillation of the seat back about the
final angle; this is a characteristic of
spring-mass-damper systems. Seat III
had significant twisting about the
longitudinal axis as seen in the large
differences between the left and right
seat back rotations. A post-test visual
tear down analysis found that in all
seats the side bolsters bent inward
toward the occupant and deformation
was also seen in the lower seat frames
and pans. This initial series of tests
demonstrates that rearward excursion
and rotation are high-speed seat
performance metrics that can be reliably
obtained in different seat models.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
3. Low-Speed Test
C. Parametric Modeling
To broadly assess the rear impact
protection measures of a seat, the
performance should be compared in a
low- and high-speed test to analyze
whether improvements in seat
performance at high-speed impacts
sacrifice whiplash injury mitigation at
low-speeds. Thus, it is expected that
seats will be tested in both a low- and
a high-speed test, to see how the
performance compares in both rear
impact conditions. This study may
determine if the design requirements for
low- and high-speed performance align
or contradict one another.
As stated above, one important factor
in test procedure development will be
exploring the appropriate low- and
high-speed deceleration for rear impact
tests. A reasonable starting point for the
lower speed test is the head restraint
optional dynamic test in FMVSS No.
202a. We are aware of other sled pulses
used for whiplash assessment by IIHS
and EuroNCAP, however, and will
explore these as well. We will also
explore the need or acceptability of
platform mounted seats versus invehicle testing. Finally, a key factor for
low-speed testing will be the ATD.
NHTSA expects to focus on the use of
the BioRID for these tests.194 We also
expect to assess various whiplash injury
criteria.
A computational model of seat
occupant dynamics in a rear impact that
is validated against experimental data
could provide insight into a range of
safety issues. It is expected that both
ATDs and human body models will be
used as seat occupants and the impact
of various occupant characteristics on
injury risk can be determined, such as
the occupant size and gender. NHTSA
may also study the extent to which seat
design specifications have a positive
influence on injury risk. A
computational model can be run over a
range of deceleration pulses and seat
characteristics to determine at which
point significant seat deformation and
the onset of serious injuries to seat
occupant occurs.
194 See discussion at section IV.4., above, for
additional information related to use of the BioRID.
PO 00000
Frm 00039
Fmt 4701
Sfmt 4702
D. ATD and Injury Risk Function
Development
Rear impact testing with PMHS seat
occupants provides biomechanical data
for ATD evaluation as noted in the
NHTSA citations above. By comparing
equivalent pairs of ATD and PMHS
tests, more realistic injury risk functions
can be developed for the ATD seat
occupant in a rear impact. NHTSA has,
for example, performed extensive work
on low-speed whiplash injury risk
functions for the BioRID. NHTSA
expects the BioRID to be the focus of
low-speed testing in this research;
however, various whiplash injury
criteria will be explored.
E:\FR\FM\16JYP2.SGM
16JYP2
EP16JY24.017</GPH>
khammond on DSKJM1Z7X2PROD with PROPOSALS2
BILLING CODE 4910–59–C
58036
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
For high severity research, further
PMHS testing will provide the injury
information to correlate with ATD
measurements in an injury risk
function. This information will also be
correlated to seat performance
parameters to assist in identification of
factors that influence injury risk.
Additionally, both BioRID and THOR–
50M will be evaluated for high-speed
testing. The BioRID has a fully
articulated spine but was designed
specifically for lower speed rear
impacts. Thus, durability and biofidelity
in higher speed rear impacts will need
to be evaluated. The THOR–50M was
not designed for rear impacts, but has
thoracic measurements not available in
BioRID. However, its acceptability for
overall rear impact injury risk will need
further consideration. Once injury risk
functions are developed, the ATD(s)
will be used in a broader evaluation of
seats on the market against identified
performance metrics.
khammond on DSKJM1Z7X2PROD with PROPOSALS2
E. Cost Analysis
The purpose of a cost analysis is to
determine the financial implications of
improving rear impact protection. A
broad understanding will be gained by
performing a cost analysis in each
aspect of NHTSA’s research initiative. A
tear down analysis of tested seats
provides an indication of failure
mechanisms and protective design
measures. The cost differential between
good and poor performing seats could
be estimated by quantifying the
difference in design measures
determined through tear down. The
computational study could assess the
overall impact and cost of design
changes within a seat; for example, if
design changes are made to a poorly
performing seat for a high-speed test
with a specific occupant, would these
changes in fact have a detrimental
impact in other scenarios? After the cost
differential between good and poor
performing seats is well defined, then
market research and assessment of the
fleet will determine the overall costs of
improving rear impact protection.
F. Summary
NHTSA is pursuing research to gain a
greater understanding of the modern
rear impact protection issue that the
agency regulates under FMVSS Nos. 207
and 202a. An examination of recent rear
impact field data is helpful to define the
overall safety issue and determine
whether any countermeasure to a
problem is cost effective. This document
discusses a two-tiered dynamic testing
approach. NHTSA is pursuing sled
testing of rear impacts to explore this
dynamic approach and has conducted
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
an initial exploratory series of highspeed rear impact tests described above.
NHTSA has ongoing research in rear
impact sled testing using PMHS
occupants that in turn supports an ATD
based assessment of rear impact injuries
and dynamics. A computational
parametric study has also been
proposed to broadly investigate rear
impact dynamics and various protection
measures. If a rulemaking is pursued,
NHTSA will also perform research tasks
to develop the necessary cost and
benefit estimates for upgraded rear
impact protection estimates. NHTSA
would like this research to make
decisive contributions and therefore
seeks comment on the research
proposed here. Would a greater impact
be achieved if the agency’s resources
were directed in another area of rear
impact protection or more focused in a
critical area?
VIII. Public Participation
A. How can I inform NHTSA’s thinking
on this rulemaking?
Your comments will help us improve
this rulemaking. NHTSA invites you to
provide different views on options
NHTSA discusses above, new
approaches the agency has not
considered, new data, descriptions of
how this ANPRM may affect you, or
other relevant information.
NHTSA welcomes public review of all
aspects of this ANPRM, but requests
comments on specific issues throughout
this document. NHTSA will consider
the comments and information received
in developing a potential proposal for
how to proceed with updating
requirements for motor vehicles. Your
comments will be most effective if you
follow the suggestions below:
• Explain your views and reasoning
as clearly as possible.
• Provide solid technical and cost
data to support your views.
• If you estimate potential costs,
explain how you arrived at the estimate.
• Tell NHTSA which parts of the
ANPRM you support, as well as those
with which you disagree.
• Provide specific examples to
illustrate your concerns.
• Offer specific alternatives.
• Refer your comments to specific
sections of the ANPRM, such as the
units or page numbers of the preamble.
B. How do I prepare and submit
comments?
Your comments must be in writing.
To ensure that your comments are filed
correctly in the Docket, please include
the docket number of this document
located at the beginning of this notice in
your comments.
PO 00000
Frm 00040
Fmt 4701
Sfmt 4702
Your primary comments should not
be more than 15 pages long.195 You may
attach additional documents to your
primary comments, such as supporting
data or research. There is no limit on the
length of the attachments.
Please submit one copy of your
comments (two if submitting by mail or
hand delivery), including the
attachments, to the docket via one of the
methods identified under the
ADDRESSES section at the beginning of
this document. If you are submitting
comments electronically as a PDF
(Adobe) file, we ask that the documents
submitted be scanned using an Optical
Character Recognition (OCR) process,
thus allowing NHTSA to search and
copy certain portions of your
submission.
Please note that pursuant to the Data
Quality Act, for substantive data to be
relied upon and used by the agency, it
must meet the information quality
standards set forth in the OMB and DOT
Data Quality Act guidelines.
Accordingly, NHTSA encourages you to
consult the guidelines in preparing your
comments. DOT’s guidelines may be
accessed at www.transportation.gov/
regulations/dot-informationdissemination-quality-guidelines.
C. How can I be sure that my comments
were received?
If you submit comments by hard copy
and wish Docket Management to notify
you upon its receipt of your comments,
enclose a self-addressed, stamped
postcard in the envelope containing
your comments. Upon receiving your
comments, Docket Management will
return the postcard by mail. If you
submit comments electronically, your
comments should appear automatically
in the docket number at the beginning
of this notice on https://
www.regulations.gov. If they do not
appear within two weeks of posting, we
suggest that you call the Docket
Management Facility at 202–366–9826.
D. How do I submit confidential
business information?
NHTSA is currently treating
electronic submission as an acceptable
method for submitting confidential
business information to the agency
under part 512. If you claim that any of
the information or documents provided
in your response constitutes
confidential business information
within the meaning of 5 U.S.C.
552(b)(4), or are protected from
disclosure pursuant to 18 U.S.C. 1905,
you may either submit your request via
email or request a secure file transfer
195 49
E:\FR\FM\16JYP2.SGM
CFR 553.21.
16JYP2
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
link from the Office of the Chief Counsel
contact listed below. You must submit
supporting information together with
the materials that are the subject of the
confidentiality request, in accordance
with part 512, to the Office of the Chief
Counsel. Do not send a hardcopy of a
request for confidential treatment to
NHTSA’s headquarters.
Your request must include a request
letter that contains supporting
information, pursuant to § 512.8. Your
request must also include a certificate,
pursuant to § 512.4(b) and part 512,
appendix A.
You are required to submit one
unredacted ‘‘confidential version’’ of the
information for which you are seeking
confidential treatment. Pursuant to
§ 512.6, the words ‘‘ENTIRE PAGE
CONFIDENTIAL BUSINESS
INFORMATION’’ or ‘‘CONFIDENTIAL
BUSINESS INFORMATION
CONTAINED WITHIN BRACKETS’’ (as
applicable) must appear at the top of
each page containing information
claimed to be confidential. In the latter
situation, where not all information on
the page is claimed to be confidential,
identify each item of information for
which confidentiality is requested
within brackets: ‘‘[ ].’’
You are also required to submit one
redacted ‘‘public version’’ of the
information for which you are seeking
confidential treatment. Pursuant to
§ 512.5(a)(2), the redacted ‘‘public
version’’ should include redactions of
any information for which you are
seeking confidential treatment (i.e., the
only information that should be
unredacted is information for which you
are not seeking confidential treatment).
For questions about a request for
confidential treatment, please contact
Dan Rabinovitz in the Office of the Chief
Counsel at Daniel.Rabinovitz@dot.gov.
E. Will the agency consider late
comments?
NHTSA will consider all comments
received to the docket before the close
of business on the comment closing date
indicated above under the DATES
section. NHTSA will consider any latefiled comments to the extent possible.
khammond on DSKJM1Z7X2PROD with PROPOSALS2
F. How can I read the comments
submitted by other people?
You may read the comments received
by Docket Management in hard copy at
the address given above under the
ADDRESSES section. The hours of the
Docket Management office are indicated
above in the same location. You may
also read the comments on the internet
by doing the following:
(1) Go to https://www.regulations.gov.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
(2) Regulations.gov provides two basic
methods of searching to retrieve dockets
and docket materials that are available
in the system:
a. The search box on the home page
which conducts a simple full-text search
of the website, into which you can type
the docket number of this notice and
b. ‘‘Advanced Search,’’ which is
linked on the regulations.gov home
page, and which displays various
indexed fields such as the docket name,
docket identification number, phase of
the action, initiating office, date of
issuance, document title, document
identification number, type of
document, Federal Register reference,
CFR citation, etc. Each data field in the
advanced search function may be
searched independently or in
combination with other fields, as
desired. Each search yields a
simultaneous display of all available
information found in regulations.gov
that is relevant to the requested subject
or topic.
(3) Once you locate the docket at
httsp://www.regulations.gov, you can
download the comments you wish to
read. We note that because comments
are often imaged documents rather than
word processing documents (e.g., PDF
rather than Microsoft Word), some
comments may not be word searchable.
Please note that, even after the
comment closing date, NHTSA will
continue to file relevant information in
the Docket as it becomes available.
Further, some people may submit late
comments. Accordingly, NHTSA
recommends that you periodically
check the Docket for new material.
IX. Regulatory Analyses and Notices
A. Executive Order (E.O.) 12866, E.O.
13563, and E.O. 14094 and DOT
Regulatory Policies and Procedures
The agency has considered the impact
of this rulemaking action under
Executive Order (E.O.) 12866, E.O.
13563, E.O. 14094, and the Department
of Transportation’s regulatory
procedures DOT Order 2100.6A. This
ANPRM was determined to be
significant under E.O. 12866 and was
reviewed by the Office of Management
and Budget.
This ANPRM presents possible
avenues for updating regulations
regarding occupant protection in rear
impact and seeks public comment to
develop information that may inform a
future proposal. NHTSA is using this
ANPRM to solicit public feedback
before potentially proceeding with a
proposed rule.
We have asked commenters to answer
a variety of questions to elicit practical
PO 00000
Frm 00041
Fmt 4701
Sfmt 4702
58037
information about alternative
approaches and relevant technical data,
which will enable analysis of the costs
and benefits of a possible future
proposal.
B. Paperwork Reduction Act
Under the Paperwork Reduction Act
of 1995 (PRA), a person is not required
to respond to a collection of information
by a Federal agency unless the
collection displays a valid OMB control
number. This ANPRM would not
establish any new information
collection requirements.
C. Privacy Act
DOT solicits comments from the
public to better inform its rulemaking
process. DOT posts these comments,
without edit, including any personal
information the commenter provides, to
www.regulations.gov, as described in
the system of records notice (DOT/ALL–
14 FDMS), which can be reviewed at
www.dot.gov/privacy. Please note that
anyone is able to search the electronic
form of all comments received into any
of our dockets by the name of the
individual submitting the comment (or
signing the comment, if submitted on
behalf of an association, business, labor
union, etc.). For information on DOT’s
compliance with the Privacy Act, please
visit https://www.transportation.gov/
privacy.
D. Plain Language
Executive Order 12866 requires each
agency to write all rules in plain
language. Application of the principles
of plain language includes consideration
of the following questions:
• Have we organized the material to
suit the public’s needs?
• Are the requirements in the
document clearly stated?
• Does the document contain
technical language or jargon that isn’t
clear?
• Would a different format (grouping
and order of sections, use of headings,
paragraphing) make the document easier
to understand?
• Would more (but shorter) sections
be better?
• Could we improve clarity by adding
tables, lists, or diagrams?
• What else could we do to make the
document easier to understand?
If you have any responses to these
questions, please include them in your
comments.
E. Regulation Identifier Number (RIN)
The Department of Transportation
assigns a regulation identifier number
(RIN) to each regulatory action listed in
the Unified Agenda of Federal
E:\FR\FM\16JYP2.SGM
16JYP2
58038
Federal Register / Vol. 89, No. 136 / Tuesday, July 16, 2024 / Proposed Rules
khammond on DSKJM1Z7X2PROD with PROPOSALS2
Regulations. The Regulatory Information
Service Center publishes the Unified
Agenda in April and October of each
year. You may use the RIN contained in
the heading at the beginning of this
document to find this action in the
Unified Agenda.
VerDate Sep<11>2014
17:15 Jul 15, 2024
Jkt 262001
X. Conclusion
In accordance with 49 CFR part 552,
NHTSA grants in part and denies in part
the petitions by Mr. Saczalski and Mr.
Cantor and denies the CAS petition.
PO 00000
Frm 00042
Fmt 4701
Sfmt 9990
Issued in Washington DC, under authority
delegated in 49 CFR 1.95, 501.5, and 501.8.
Jack Danielson,
Executive Director.
[FR Doc. 2024–15390 Filed 7–15–24; 8:45 am]
BILLING CODE 4910–59–P
E:\FR\FM\16JYP2.SGM
16JYP2
]]>Agencies
[Federal Register Volume 89, Number 136 (Tuesday, July 16, 2024)]
[Proposed Rules]
[Pages 57998-58038]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-15390]
[[Page 57997]]
Vol. 89
Tuesday,
No. 136
July 16, 2024
Part II
Department of Transportation
-----------------------------------------------------------------------
National Highway Traffic Safety Administration
-----------------------------------------------------------------------
49 CFR Part 571
Federal Motor Vehicle Safety Standards; Seating Systems; Proposed Rule
Federal Register / Vol. 89 , No. 136 / Tuesday, July 16, 2024 /
Proposed Rules
[[Page 57998]]
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. NHTSA-2024-0001]
RIN 2127-AM53
Federal Motor Vehicle Safety Standards; Seating Systems
AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).
ACTION: Advance notice of proposed rulemaking.
-----------------------------------------------------------------------
SUMMARY: Through this document, NHTSA fulfills the statutory mandate in
section 24204 of the Infrastructure Investment and Jobs Act (IIJA),
which directed the Secretary of Transportation to issue an advanced
notice of proposed rulemaking to update Federal Motor Vehicle Safety
Standard No. 207, ``Seating systems.'' NHTSA also partially grants
rulemaking petitions submitted by Kenneth J. Saczalski of Environmental
Research and Safety Technologists (ERST) and by Alan Cantor of ARCCA,
Inc. (ARCCA), which sought changes to the Federal Motor Vehicle Safety
Standards (FMVSS) petitioners stated would improve the safety of
children during rear-end crashes. NHTSA denies a petition from the
Center for Auto Safety (CAS), which sought to require additional
warnings instructing adults regarding which rear seating position to
place children.
DATES: Comments must be received no later than September 16, 2024. The
Saczalski and Cantor petitions are granted in part and the CAS petition
is denied as of July 16, 2024. See ADDRESSES and Section VIII. Public
Participation for more information about submitting written comments
and reviewing comments submitted by other interested parties.
ADDRESSES: You may submit written comments, identified by docket number
or RIN, by any of the following methods:
Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow the online instructions for submitting
comments.
Mail: Docket Management Facility, U.S. Department of
Transportation, 1200 New Jersey Avenue SE, Room W12-140, Washington, DC
20590-0001.
Hand Delivery or Courier: 1200 New Jersey Avenue SE, West
Building, Ground Floor, Room W12-140, Washington, DC, between 9 a.m.
and 5 p.m. E.T., Monday through Friday, except Federal holidays. To be
sure someone is there to help you, please call 202-366-9826 before
coming.
Instructions: For detailed instructions on submitting comments and
additional information on the rulemaking process, see the Public
Participation heading of the SUPPLEMENTARY INFORMATION section of this
document. Note that all comments received will be posted without change
to https://www.regulations.gov, including any personal information
provided. Please see the ``Privacy Act'' discussion in Section IX.
Regulatory Analyses and Notices.
Confidential Business Information: If you claim that any of the
information or documents provided to the agency constitute confidential
business information within the meaning of 5 U.S.C. 552(b)(4), or are
protected from disclosure pursuant to 18 U.S.C. 1905, you must submit
supporting information together with the materials that are the subject
of the confidentiality request, in accordance with part 512, by email
or secure file transfer to the Office of the Chief Counsel, Litigation
and Enforcement Division. Do not send a hardcopy of a request for
confidential treatment to NHTSA's headquarters.
Your request must include a request letter that contains supporting
information, pursuant to Sec. 512.8. Your request must also include a
certificate, pursuant to Sec. 512.4(b) and part 512, appendix A.
You are required to submit one unredacted ``confidential version''
of the information for which you are seeking confidential treatment.
Pursuant to Sec. 512.6, the words ``ENTIRE PAGE CONFIDENTIAL BUSINESS
INFORMATION'' or ``CONFIDENTIAL BUSINESS INFORMATION CONTAINED WITHIN
BRACKETS'' (as applicable) must appear at the top of each page
containing information claimed to be confidential. In the latter
situation, where not all information on the page is claimed to be
confidential, identify each item of information for which
confidentiality is requested within brackets: ``[ ].''
You are also required to submit to the Office of the Chief Counsel
one redacted ``public version'' of the information for which you are
seeking confidential treatment. Pursuant to Sec. 512.5(a)(2), the
redacted ``public version'' should include redactions of any
information for which you are seeking confidential treatment (i.e., the
only information that should be unredacted is information for which you
are not seeking confidential treatment).
For questions about a request for confidential treatment, please
contact Dan Rabinovitz in the Office of the Chief Counsel at
[email protected] or (202) 366-8534.
FOR FURTHER INFORMATION CONTACT: Mr. Tyler Brosten, Office of
Crashworthiness Standards (Telephone: 202-366-1740; Email:
[email protected], Facsimile: 202-493-2739), or Mr. Eli Wachtel,
Office of Chief Counsel (Telephone: 202-366-2992; Email:
[email protected]). You may mail these officials at: National Highway
Traffic Safety Administration, 1200 New Jersey Avenue SE, Washington,
DC 20590.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Introduction
II. Occupant and Seat Back Dynamics and Field Data on Rear Impact
Crashes
A. FARS and CRSS Data Analysis
B. CISS Data Analysis
C. Field Data Analyses From Relevant Literature
III. Statutory and Regulatory Background
A. The Safety Act and the Infrastructure, Investment and Jobs
Act
B. Regulatory History of FMVSS No. 207 and FMVSS No. 202, and
Associated Research/Analyses
1. 1963--SAE Recommended Practice for Seats
2. 1967--Publication of FMVSS No. 207, Seating Systems
3. 1968--Publication of FMVSS No. 202, ``Head Restraints''
4. 1969--Report on Seat Safety Studies at ITTE
5. 1974--Notice of Proposed Rulemaking (NPRM) To Revise FMVSS
No. 207
6. 1978--NHTSA Publishes a Request for Comment on Rulemaking
Priorities
7. 1989--NHTSA Receives Petitions for Rulemaking on Revisions to
FMVSS No. 207
8. 1992--2000 NHTSA Publishes a Request for Comment on Possible
Revisions to FMVSS No. 207, Grants Two Petitions and Conducts
Research
9. 2004--NHTSA Issues Final Rule Upgrading FMVSS No. 202, Head
Restraints
10. 2004--NHTSA Terminates Rulemaking on FMVSS No. 207, Seating
Systems
11. Further Regulatory Changes Since 2004
IV. Review of Additional Literature
A. Occupant Dynamics
B. Rear Impact Protection Technology
C. Non-Contact Injuries
1. Neck Injuries
2. Thorax Injuries in High-Speed Rear Impacts
D. Summary
V. Petitions for Rulemaking at Issue in This Document
A. Statutory and Regulatory Background
B. Petition of Kenneth J. Saczalski
1. FMVSS No. 207, Seating Systems
2. Use of FMVSS No. 301, ``Fuel System Integrity,'' To Test
Seats
3. FMVSS No. 213, Child Restraint Seats
C. Petition of Alan Cantor
1. Use of FMVSS No. 301, ``Fuel System Integrity,'' To Upgrade
FMVSS No. 207
2. Rearward Rotation Limit and Structural Symmetry Requirement
[[Page 57999]]
3. Additional Dynamic Testing and NCAP Implementation
4. FMVSS No. 209, Seat Belt Assemblies
D. NHTSA's Analysis of Saczalski and Cantor Petitions
1. Analysis of Data and Research Provided by Cantor and
Saczalski Regarding Safety Need
2. Rear Structure Intrusion
3. Cost and Practicability
E. Assessment of the Specific Recommendations by Cantor and
Saczalski
1. Matters on Which NHTSA Is Granting the Petitions
2. Matters on Which NHTSA Is Denying the Petitions
F. Conclusion of NHTSA Assessment of Cantor and Saczalski
Petitions
G. Center for Auto Safety (CAS) Petition
H. Analysis of CAS Petition
VI. Unified Approach to Rear Impact Protection
A. Introduction
B. FMVSS No. 207
C. Analysis of Approaches To Updating Standards for Occupant
Protection in Rear Impact
1. Seat Back Strength and Other Mechanical Properties
2. Test Parameters
3. Quasi-Static Testing
4. Dynamic Testing
D. Crash Avoidance Technology
VII. NHTSA's Forthcoming Research
A. Field Data Analysis and Market Research
B. Test Procedure Assessment
1. High-Speed Test
2. Exploratory Testing
3. Low-Speed Test
C. Parametric Modeling
D. ATD and Injury Risk Function Development
E. Cost Analysis
F. Summary
VIII. Public Participation
A. How can I inform NHTSA's thinking on this rulemaking?
B. How do I prepare and submit comments?
C. How can I be sure that my comments were received?
D. How do I submit confidential business information?
E. Will the agency consider late comments?
F. How can I read the comments submitted by other people?
IX. Regulatory Analyses and Notices
A. Executive Order (E.O.) 12866, E.O. 13563, and E.O. 14094 and
DOT Regulatory Policies and Procedures
B. Paperwork Reduction Act
C. Privacy Act
D. Plain Language
E. Regulation Identifier Number (RIN)
X. Conclusion
I. Introduction
As part of its safety mission, NHTSA issues Federal Motor Vehicle
Safety Standards (FMVSSs) \1\ and other regulations for new motor
vehicles and motor vehicle equipment to save lives, prevent injuries,
and reduce economic costs due to road traffic crashes. All FMVSSs must
meet the requirements of the National Traffic and Motor Vehicle Safety
Act of 1966 (the ``Safety Act'').\2\ That is, they must ``be
practicable, meet the need for motor vehicle safety, and be stated in
objective terms.'' \3\ On November 14, 2021, the Infrastructure,
Investment and Jobs Act (IIJA; Pub. L. 117-58 \4\) was passed. Section
24204 of IIJA, ``Motor Vehicle Seat Back Safety Standards,'' directs
the Secretary of Transportation to issue an advance notice of proposed
rulemaking (ANPRM) within two years to update 49 CFR 571.207. The
publication of this ANPRM fulfills this statutory mandate.
---------------------------------------------------------------------------
\1\ The FMVSS are codified in 49 CFR part 571.
\2\ 49 U.S.C. 30101.
\3\ 49 U.S.C. 30111(a). The Secretary must also (1) ``consider
relevant available motor vehicle safety information; (2) consult
with the agency established under the Act of August 20, 1958 (Pub.
L. 85-684, 72 Stat. 635), and other appropriate State or interstate
authorities (including legislative committees); (3) consider whether
a proposed standard is reasonable, practicable, and appropriate for
the particular type of motor vehicle or motor vehicle equipment for
which it is prescribed; and (4) consider the extent to which the
standard will carry out'' the purpose of the Safety Act. 49 U.S.C.
30111(b). The purpose of the Safety Act is to ``reduce traffic
accidents and deaths and injuries resulting from traffic
accidents.'' 49 U.S.C. 30101.
\4\ Public Law 117-58.
---------------------------------------------------------------------------
FMVSS No. 207 establishes requirements for seats, seat attachment
assemblies, and their installation in passenger cars, multipurpose
passenger vehicles, trucks designed to carry at least one person, and
buses.\5\ The standard, among other things, sets minimum requirements
for the strength of the seat back and its associated restraining
devices and adjusters.\6\ While in its rearmost position, a seat back
must withstand a rearward moment (torque) of 373 Newton-meters (Nm)
(3,300 Inch-pounds (in-lb)), applied by a horizontal force measured
vertically from the seating reference point.\7\ The standard also
contains a test procedure. The test specifies an application of a
rearward force on the uppermost cross member of the seat back
structure, that results in a moment applied to the attachment (often
the recliner mechanism) of the seat back and the remainder of the seat
structure.
---------------------------------------------------------------------------
\5\ 49 CFR 571.207 S1 and S2.
\6\ FMVSS No. 207 also contains provisions dictating the
strength of seat attachments to the vehicle in both the front and
rear directions. For the purposes of this ANPRM, ``strength'' with
respect to seat backs refers to the maximum rearward moment or force
a seat back is able to withstand. ``Stiffness'' refers to the
resistance of the seat back to any (or a specified) amount of
deformation and deflection. Stated another way, ``stiffness'' can be
thought of as the increase in resistive force or moment per unit
deformation or rotation. Rigidity is the characteristic of a
structure, such as a seat back, exhibiting relatively limited
deformation when exposed to a force. Rigid and yielding seat back
structures are opposites.
\7\ 49 CFR 571.207 S4.
---------------------------------------------------------------------------
Although FMVSS No. 207 sets the minimum seat back strength
requirement, since 1968 the de facto minimum requirement for seat back
strength has effectively been set by FMVSS No. 202 (now 202a), ``Head
restraints.'' \8\ This standard requires head restraints and
establishes requirements for them to reduce the severity of neck
injuries in rear impact crashes. Currently, FMVSS No. 202a requires a
fully extended head restraint to withstand an 890 Newtons (N) (200
pound force (lb-f)) rearward load for 5 seconds applied 65 millimeters
(mm) (2.5 inches (in)) below its top when adjusted to its highest
position, which must be at least 800 mm.\9\ This creates an effective
torque requirement on the seat back of 654 Nm (5,790 in-lb), where 654
= 890*(0.8-0.065), significantly higher than the 373 Nm (3,300 in-lb)
required by FMVSS No. 207.
---------------------------------------------------------------------------
\8\ The head restraint and seat back are interconnected parts of
the seating system.
\9\ 49 CFR 571.202(a) S4.2.7.
---------------------------------------------------------------------------
In addition to the requirement in IIJA, this ANPRM addresses three
petitions for rulemaking NHTSA received requesting various amendments
to the FMVSS related to the deformation of seat backs in rear
impacts.\10\ Two of the petitioners, Kenneth J. Saczalski of ERST. and
Alan Cantor of ARCCA requested that the agency increase the strength
requirements for seat backs in the front row. They argue that seats
that comply with the current standard may yield excessively during a
crash, which can lead to spinal cord and brain injuries due to contact
between the seated occupant's head and vehicle structures in the rear
seat compartment. In addition, they state that under the current
standard, in certain higher speed rear end crashes, a seat could yield
to the point that the seat becomes fully reclined (hereinafter
described as ``seat back failure''). This may cause a belted occupant
in the front seat to slide underneath the seat belt, leading to
ejection into the rear seat space or outside the vehicle. (The
petitioners refer to this phenomenon as ``ramping.'') Ramping poses
injury risk to occupants seated directly behind the occupied front
seat. In addition, the petitioners have asked NHTSA to revise other
FMVSSs in ways that they stated would mitigate the injurious effects of
excessively yielding seat backs. This ANPRM seeks to further develop
the
[[Page 58000]]
record on occupant protection in rear impacts to inform a potential
future rulemaking. As explained in section V., this document grants
these petitions in part.
---------------------------------------------------------------------------
\10\ These petitions, dated October 28, 2014 (Environmental
Research and Safety Technologists, Inc.), and September 28, 2015
(ARCCA), are available in the rulemaking docket at https://www.regulations.gov/.
---------------------------------------------------------------------------
The third petitioner, CAS, requested the addition of warning
language to child restraint system labels and owner's manuals to warn
parents against placing a child behind an occupied front seat.\11\ As
explained in section V.H., this document denies this petition.
---------------------------------------------------------------------------
\11\ This petition, dated March 9, 2016, is also available in
the rulemaking docket at https://www.regulations.gov/.
---------------------------------------------------------------------------
IIJA requires that NHTSA issue an ANPRM to update FMVSS No. 207.
Congress stated, however, that an update must be consistent with the
considerations described in 49 U.S.C. 30111(b) of the Safety Act and
issued pursuant to the Safety Act. Therefore, it must be practicable,
meet the need for safety, and be stated in objective terms as provided
in 49 U.S.C. 30111(a). This ANPRM discusses issues that have
historically contributed to the complexities of regulatory action on
seating systems.
As outlined in the regulatory and research review below, a major
challenge in NHTSA's efforts to set standards for rear impact
protection relates to the determination of whether a seat should yield,
thereby reducing forces acting on the seat occupant, or be stiffer, and
thus prevent rare occurrences like ramping or interaction with other
occupants. Finding the appropriate balance inherent in rear impact
protection is a theme and central debate in much of the research and
analysis conducted on this issue.
Complicating this question is the dramatic difference in frequency
between relatively common and generally minor cervical spine injuries
(such as whiplash) caused by forces acting on a seat occupant that can
occur even in low-speed rear impacts and severe injuries, which are
rare. Studies suggest that no more than 1% of rear impacts cause any
type of serious or higher severity injury,\12\ which are mostly
associated with impacts with vehicle structures, not other
occupants.13 14 In contrast, cervical spine injuries, such
as whiplash, are highly common injuries in rear impacts and occur at
many different speeds, including at low speed, with some estimates of
over 100,000 injuries annually in the United States. Additionally,
despite decades of industry and agency research into whiplash, the
understanding of the biological mechanisms that cause these injuries
remain limited. This has restricted NHTSA's ability to develop
objective updated performance standards for seat backs, such as updated
strength requirements or a comprehensive dynamic test for rear impact
protection. In particular, factors like test speed and what metrics of
seat back and head restraint performance to test (i.e., strength only
vs. anthropomorphic test dummy injury metrics) remain unclear. These
and other related issues present a challenge to updating FMVSS No. 207
in a manner that is objective, practicable, and meets the need for
safety.
---------------------------------------------------------------------------
\12\ The severity of injury is ranked in accordance with the
Abbreviated Injury Scale (AIS). An AIS level 3 injury is a serious
injury, level 4 a severe injury, and levels 5 and 6 are critical and
fatal injuries, respectively. www.aaam.org.
\13\ Prasad, Priya, et al. ``Relationships between passenger car
seat back strength and occupant injury severity in rear end
collisions: Field and laboratory studies.'' SAE transactions (1997):
3935-3967.
\14\ Parenteau, Chantal S., and David C. Viano. ``Serious head,
neck and spine injuries in rear impacts: frequency and sources.''
IRC-21-10, IRCOBI Conference. 2021.
---------------------------------------------------------------------------
This ANPRM is part of NHTSA's ongoing effort to meet this
challenge. Here, we detail a unified approach to occupant protection in
rear impacts. Although IIJA mentions only FMVSS No. 207, NHTSA is
considering integrating FMVSS Nos. 207 and 202a because of the clear
connection between head rests and seat backs. An integrated approach
would enable NHTSA to comprehensively evaluate the performance of the
seating system for rear impact protection and better balance
considerations relevant to both high speed (severe injuries) and low-
speed (whiplash injury prevention) impacts. As part of this approach,
NHTSA is considering a quasi-static test or a dynamic test requirement
with at least two (low and high) impact severity ranges. This ANPRM
discusses many considerations associated with each approach and seeks
comment on them, including choice of anthropomorphic test device (ATD),
performance criteria (such as ATD metrics), test severities, and crash
pulse delivery methods.
This ANPRM has four main areas of focus. In section II, NHTSA
details the safety problem in rear impact occupant protection. In
section III, NHTSA describes the regulatory and research history of
seat backs, and in section IV, NHTSA summarizes a literature review in
this area to provide context for the ANPRM.\15\ In section V, NHTSA
discusses the Cantor, Saczalski, and CAS petitions. Finally, in section
VI, NHTSA describes the unified approach with regard to FMVSS No. 207
and FMVSS No. 202a, and in section VII, NHTSA describes its research
efforts in this area and the knowledge gaps that may need to be filled
prior to implementing this unified approach. Throughout the document,
we seek comment on a variety of topics to inform a determination about
what upgrade, if any, to FMVSS No. 207 (and FMVSS No. 202a) can meet
the requirements of the Safety Act with the aim of improving occupant
protection in rear impact collisions.
---------------------------------------------------------------------------
\15\ The research in the public domain on the area of seat back
strength is extensive, and this document does not attempt to fully
synthesize it.
---------------------------------------------------------------------------
II. Occupant and Seat Back Dynamics and Field Data on Rear Impact
Crashes
Controlled interaction of the occupant with the seat back is the
primary countermeasure to injury in motor vehicle rear collisions. In
these crashes, the seat back supports the occupant during sudden
forward acceleration, when a range of injury risks may be generated.
Because it is necessary to provide a broad range of injury protections,
the rear impact protection issue has been framed as both a balance and
competition between high and low-severity protection measures. To
introduce the issue, this section begins with a brief discussion of
rear impact seat back dynamics and follows with a survey of field data
regarding rear impacts.
In front row seats, the seat back frame is typically connected to
the lower seat structure, or pan, by a mechanical joint. When a seat
back is subjected to an inertial load from the occupant during a rear
collision, the seat back frame rotates and bends rearward around this
joint. When asymmetric loading on the seat back occurs, this dynamic
can result in twisting of the seat back around its longitudinal axis.
The force acting on the seat back is proportional to the occupant's
mass and forward acceleration. As the seat back rotates rearward, the
force applied to the seat back becomes less perpendicular to the seat
back plane as the applied force is further defined by transverse forces
made up of seat back-occupant friction and pocketing,\16\ seat belt
restraints, and other factors that maintain occupant seat
retention.\17\ These actions have long been understood to absorb
energy, reduce forces acting on the seat occupant, and disperse
acceleration of
[[Page 58001]]
the occupant over time.18 19 When the force applied to the
seat back exceeds the material's elastic limit, it begins to deform in
a way that permanently bends the seat (plastic deformation). For some
rear impacts, this deformation may exceed the seat structure's ability
to substantially oppose the applied force, resulting in seat back
failure due to significant material bending or fracture, at which point
the seat back is said to fail. At the point of seat back failure or
significant seat back deformation, seat occupants in rearward seat rows
may be exposed to injury risk due to contact with the front seat back
or front occupants. Paradoxically, the restraining force applied by the
front seat on its occupant can lead to injury, just as a seat belt can
injure an occupant in a frontal crash. The following sub-section
examines field data to further lay out the current understanding of the
risks to vehicle occupants in rear impacts. Later sections will provide
additional discussion on the literature regarding rear impact injuries
and protection. The literature outlines a continued debate around how
best to protect occupants, the uncertain understanding of how certain
injuries occur in rear impacts, and varied approaches and developments
in technology for rear impact protection.
---------------------------------------------------------------------------
\16\ Pocketing refers to displacement of the occupant's torso
into the relatively pliable interior of a seat back.
\17\ Seat retention refers to the occupant restraint system's
ability to keep the occupant coupled to the seat.
\18\ Anderson JO. Dynamics of Occupants in Automotive Accidents
Involving Rear Impacts. Warren, MI: Research Laboratories General
Motors Corporation; 1961. Report No. R-34-1295.
\19\ Severy DM, Mathewson J, Bechtol O. Controlled automobile
rear-end collisions and investigation of related engineering and
medical phenomena. Can Serv Med J. 1955;11:727-759.
---------------------------------------------------------------------------
A. FARS and CRSS Data Analysis
In general, rear collisions result in fewer fatalities and serious
injuries when compared to other impact directions. Table II.1 shows
overall crash statistics for the sum of light vehicles (passenger cars
and light trucks) in year 2020 organized by impact directions and
injury severities. NHTSA compiled this data set in the 2020 Traffic
Safety Facts from FARS (Fatality Analysis Reporting System) and CRSS
(Crash Report Sampling System).\20\ We note that the data include all
vehicle rows. The data show that rear impacted light vehicles accounted
for 24.1% of crashed light vehicles and 21.8% of vehicles with injured
occupants, but only 7.2% of vehicles with fatalities in 2020.
---------------------------------------------------------------------------
\20\ National Center for Statistics and Analysis. (2022,
October). Traffic Safety Facts 2020: A compilation of motor vehicle
crash data (Report No. DOT HS 813 375). National Highway Traffic
Safety Administration.
Table II.1--Passenger Cars and Light Trucks Involved in Crashes, by Initial Point of Impact, Crash Severity, and Crash Type for Year 2020
--------------------------------------------------------------------------------------------------------------------------------------------------------
Crash severity
-------------------------------------------------------------------------------------------------------
Crash type by initial point of impact Fatal Injury Property damage only Total
-------------------------------------------------------------------------------------------------------
Number Percent Number Percent Number Percent Number Percent
--------------------------------------------------------------------------------------------------------------------------------------------------------
Single-Vehicle Crashes:
Front....................................... 10,883 67.9 358,800 77.1 791,913 73.1 1,161,597 74.2
Left Side................................... 890 5.6 21,960 4.7 54,317 5.0 77,167 4.9
Right Side.................................. 886 5.5 33,795 7.3 85,283 7.9 119,965 7.7
Rear........................................ 222 1.4 16,334 3.5 84,915 7.8 101,473 6.5
Noncollision................................ 1,714 10.7 27,237 5.9 40,898 3.8 69,849 4.5
Other/Unknown............................... 1,430 8.9 7,157 1.5 25,991 2.4 34,580 2.2
-------------------------------------------------------------------------------------------------------
Total................................... 16,025 100.0 465,285 100.0 1,083,319 100.0 1,564,629 100.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
Multiple-Vehicle Crashes:
Front....................................... 15,987 62.9 1,183,348 54.3 2,354,919 49.3 3,554,254 50.9
Left Side................................... 3,221 12.7 224,185 10.3 522,635 10.9 750,041 10.7
Right Side.................................. 2,649 10.4 206,256 9.5 486,970 10.2 695,875 10.0
Rear........................................ 2,772 10.9 561,310 25.8 1,395,634 29.2 1,959,717 28.1
Noncollision................................ 76 0.3 702 0.0 2,474 0.1 3,253 0.0
Other/Unknown............................... 704 2.8 2,787 0.1 17,515 0.4 21,007 0.3
-------------------------------------------------------------------------------------------------------
Total................................... 25,409 100.0 2,178,589 100.0 4,780,149 100.0 6,984,146 100.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
All Crashes:
Front....................................... 26,870 64.9 1,542,149 58.3 3,146,832 53.7 4,715,850 55.2
Left Side................................... 4,111 9.9 246,145 9.3 576,953 9.8 827,209 9.7
Right Side.................................. 3,535 8.5 240,051 9.1 572,254 9.8 815,839 9.5
Rear........................................ 2,994 7.2 577,646 21.8 1,480,551 25.3 2,061,189 24.1
Noncollision................................ 1,790 4.3 27,939 1.1 43,372 0.7 73,101 0.9
Other/Unknown............................... 2,134 5.2 9,945 0.4 43,507 0.7 55,586 0.7
-------------------------------------------------------------------------------------------------------
Total................................... 41,434 100.0 2,643,874 100.0 5,863,467 100.0 8,548,775 100.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
Of the over 2 million rear impacted light vehicles in 2020, only
0.15% (2994/2,061,189) involved fatalities, as compared with 0.57%
(26,870/4,715,850) of the 4.7 million front impacted light vehicles and
0.47% (7646/1,643,048) of the 1.6 million side impacted light vehicles
involved fatalities; a fatal rear collision is typically associated
with a high [Delta]V \21\ collision.\22\ However, the injury rate in
light vehicles that underwent a rear collision in 2020 is comparable to
other crash directions, as 30% of rear impacted light vehicles involved
injury, while 33% of frontal and 30% of side impacted light vehicles
involved injury.
---------------------------------------------------------------------------
\21\ [Delta]V is defined as the maximum change in velocity of
the struck vehicle after impact.
\22\ Wang, J.-S. (2022, May). MAIS(05/08) injury probability
curves as functions of [Delta]V (Report No. DOT HS 813 219) National
Highway Traffic Safety Administration.
---------------------------------------------------------------------------
The count of occupant injury and fatality for different collision
directions is classified by vehicle type for year 2020 in table II.2
Traffic Safety Facts from FARS and CRSS. Restricting the discussion to
light vehicles (passenger cars and light trucks), 6.1% of passenger car
occupants and 4.6% of light truck occupants killed were due to rear
[[Page 58002]]
impacts. The combined light vehicle total was 5.4%. In contrast to the
light vehicle fatality rate, the percentage of fatalities in rear
impacted large trucks was only 2.9%. This would be consistent with the
expectation that rear impact [Delta]V for large trucks would be on
average smaller than for light vehicles.\23\
---------------------------------------------------------------------------
\23\ [Delta]V is inversely proportional to the struck vehicle
weight. Large trucks (including single-unit trucks and truck
tractors) have a gross vehicle weight rating (GVWR) greater than
10,000 pounds. Passenger cars and light trucks (including pickups,
vans, and utility vehicles) have a GVWR not greater than 10,000
pounds.
Table II.2--Vehicle Occupants Killed and Injured, by Initial Point of Impact and Vehicle Type for Year 2020
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vehicle type
--------------------------------------------------------------------------------------------------------
Injury severity/initial point of impact Passenger Light Large Other/
cars trucks trucks Buses unknown Subtotal Motorcycles Total
--------------------------------------------------------------------------------------------------------------------------------------------------------
Occupants Killed:
Front...................................... 7,724 5,997 523 6 273 14,523 3,444 17,967
Left Side.................................. 1,849 1,129 35 1 53 3,067 300 3,367
Right Side................................. 1,633 840 50 0 52 2,575 259 2,834
Rear....................................... 822 474 24 1 70 1,391 242 1,633
Other...................................... 160 106 16 2 12 296 32 328
Noncollision............................... 581 1,309 146 2 280 2,318 858 3,176
Unknown.................................... 703 497 37 4 125 1,366 444 1,810
--------------------------------------------------------------------------------------------------------
Total.................................. 13,472 10,352 831 16 865 25,536 5,579 31,115
--------------------------------------------------------------------------------------------------------------------------------------------------------
Occupants Injured:
Front...................................... 696,221 440,711 21,175 1,958 3,023 1,163,087 41,952 1,205,039
Left Side.................................. 121,449 74,875 4,058 2,623 596 203,600 6,623 210,222
Right Side................................. 109,313 77,510 4,429 920 447 192,620 5,863 198,483
Rear....................................... 273,123 194,857 9,136 1,096 698 478,909 4,765 483,675
Other...................................... 5,600 3,584 1,228 0 38 10,451 289 10,740
Noncollision............................... 15,248 21,698 4,895 1 2,012 43,854 23,010 66,864
Unknown.................................... 381 274 13 23 34 725 26 751
--------------------------------------------------------------------------------------------------------
Total.................................. 1,221,335 813,509 44,934 6,620 6,849 2,093,246 82,528 2,175,774
--------------------------------------------------------------------------------------------------------------------------------------------------------
Further, according to the 2020 Traffic Safety Facts, 22.3% of
passenger vehicle injuries occurred in rear impacts (light trucks =
24.0%, heavy trucks = 20.3%). For each vehicle type, the proportion of
fatalities for rear impacts is significantly lower than the
corresponding proportion of injuries for rear impacts, compared to
other initial impact directions. The rear impact proportion of
fatalities in light trucks and heavy trucks is lower than in passenger
cars, but the rear impact proportion of injuries in light trucks is
slightly greater than in passenger cars and heavy trucks. The disparity
in rear collision proportion of injuries for different vehicle types is
discussed in the literature review below.
B. CISS Data Analysis
NHTSA also examined the Crash Investigation Sampling System (CISS)
data files for the years 2017-2020 to determine the number of rear
impacts compared to other crash modes and determine the injury risk
(number of injured occupants divided by the number of exposed
occupants) of vehicle occupants in rear impacts. These data are limited
because CISS currently reports only police reported, tow-away crashes,
and, as will be explained later, most rear impacts are not tow-aways.
The data were divided into different crash types: rollover, frontal,
side, rear, other, and unknown. In addition, for rear impacts, the data
were segmented by the change in velocity of the impacted vehicle
([Delta]V). All data presented here are weighted to represent national
estimates. The maximum abbreviated injury scale \24\ (MAIS) for each
injured occupant is presented so that an occupant with multiple
injuries is counted only once in the analysis. An occupant was counted
as having a whiplash injury (MAIS 1 neck injury) even if they had other
AIS 1 injuries. Crashes with fire have been excluded from the sample.
If an occupant had a whiplash injury but also had a MAIS 2+ injury,
they were not added to the whiplash injury count. As was the case for
the FARS and CRSS data above, we have not restricted the data by
seating row.
---------------------------------------------------------------------------
\24\ The severity of injury is reported in CISS 2017-2020 using
the 2015 Abbreviated Injury Scale, where AIS 1 are minor injuries,
and the 2-6 categories are moderate, serious, severe, critical, and
fatal injuries, respectively.
---------------------------------------------------------------------------
The total annualized number of involved individuals was estimated
to be 4.5 million, including crash types categorized as ``unknown'' and
``other.'' Rear impact crashes accounted for only 373,237 or 8.3% of
all tow-away crash involving individuals in the CISS database (Figure
II.1). Only rollover crashes yield fewer occupants involved in tow-away
crashes. Looking at the proportion of occupants with serious and higher
severity injuries (MAIS 3-6) by crash type, we see that MAIS 3-6 are
underrepresented in rear impacts (4.3% = 3,814/88,437) and
overrepresented in rollover (19.7% = 17,415/88,437). By contrast
whiplash injury is overrepresented in rear impacts (15.8% = 31,206/
197,060) as compared to the number of towed rear impacts.
[[Page 58003]]
[GRAPHIC] [TIFF OMITTED] TP16JY24.006
[[Page 58004]]
Figure II.2 and Figure II.3 show the risk of MAIS 3-6 and whiplash
injury \25\ for each towed crash mode. The risk of MAIS 3-6 injury in
rear impacts is 1.0% (= 3,814/373,237), which is about 60% of the next
highest risk (1.7% for side). The whiplash injury risk in rear impacts
is approximately 8.4% (= 31,206/373,237), which is about 1.5 times the
next highest risk (5.7% for rollover). These whiplash injury rates do
not consider non-towed crashes, where the majority of whiplash injuries
are known to occur.\26\
---------------------------------------------------------------------------
\25\ Risk of MAIS 3-6 injuries in a crash mode is equal to the
number of occupants with MAIS 3-6 injuries in that crash mode
divided the total number of occupants (injured and uninjured) in
that crash mode. Similar computation is done to determine risk of
whiplash injuries.
\26\ Final Regulatory Impact Analysis for FMVSS No. 202 Head
Restraints for Passenger Vehicles, Docket NHTSA-2004-19807.
[GRAPHIC] [TIFF OMITTED] TP16JY24.007
[[Page 58005]]
[GRAPHIC] [TIFF OMITTED] TP16JY24.008
[[Page 58006]]
Figure II.4 shows the distribution of towed rear impacts by the
change in velocity of the rear impacted vehicle. Most of the crashes
are in the 11-20 kilometers per hour (km/h) (6.8-12.4 miles per hour
(mph)) [Delta]V range. Table II.3 provides tabulated annual occupant
injuries in rear collisions according to injury severity and [Delta]V.
For occupants in a known [Delta]V rear impact crash, the majority of
injuries are estimated to be no injury (MAIS 0) in all [Delta]V ranges.
The most probable known [Delta]V range for injury of any type is the
11-20 km/h (6.8-12.4 mph) category, which is consistent with this being
the most common impact speed range. More than three-quarters of MAIS 3+
rear impact injuries occur above 31 km/h (19.3 mph). Figure II.5 gives
the risk of MAIS 2 and MAIS 3+ injuries as a function of impact
[Delta]V in towed rear crashes. The highest risk for MAIS 2 injuries is
8.4% (= 891/10,630) for 51+ km/h (31.7+ mph) [Delta]V crashes. The
highest risk for MAIS 3+ is 7.0% (= 1,572/22,425) for the 31-40 km/h
(19.3-24.9 mph) [Delta]V range. Figure II.6 shows that for whiplash,
the highest risk is 11.7% (= 2,624/22,425) for injury in towed crashes
occurring in the 26-35 km/h (16.2-21.8 mph) range. The risk at 51+ km/h
is similar at 11.1% (= 1,183/10,630) and at other speeds is between
2.8% and 9.7%.
[GRAPHIC] [TIFF OMITTED] TP16JY24.009
Table II.4--Annual Rear Impact Injury by [Delta]V
[2017-2020 CISS]
----------------------------------------------------------------------------------------------------------------
MAIS 1 no
[Delta]V (km/h) MAIS 0 Whiplash whiplash MAIS 2 MAIS 3-6 Total
----------------------------------------------------------------------------------------------------------------
Unknown........................... 101,022 12,637 13,950 4,495 789 132,893
0-10.............................. 22,057 675 913 59 0 23,704
11-20............................. 88,352 7,680 15,469 2,793 474 114,769
21-30............................. 46,618 6,302 10,429 1,455 249 65,052
31-40............................. 13,085 2,624 4,157 988 1,572 22,425
41-50............................. 1,811 107 1,661 94 92 3,764
51+............................... 5,173 1,183 2,746 891 638 10,630
-----------------------------------------------------------------------------
Total Known [Delta]V.......... 177,095 18,569 35,375 6,279 3,025 240,345
Total......................... 278,117 31,206 49,325 10,775 3,813 373,237
----------------------------------------------------------------------------------------------------------------
[[Page 58007]]
[GRAPHIC] [TIFF OMITTED] TP16JY24.010
[GRAPHIC] [TIFF OMITTED] TP16JY24.011
Figure II.6 provides the whiplash injury rates for towed crashes.
CISS does not collect injury data for non-towed crashes. In 2004, using
State data, the Final Regulatory Impact Analysis for the upgrade of
FMVSS No. 202 found four times as many whiplash injuries in all crashes
compared to those in tow-away crashes. NHTSA plans to update
[[Page 58008]]
this analysis to accurately represent the current whiplash injury risk.
Older field data, however, are still useful to provide a sense of the
very large proportion of whiplash injuries that occur at low speed.
With historical data, we can attempt to generate estimates that
include non-towed whiplash. Between 1982 and 1986, non-towed crash data
were collected. Table II.5 shows the distribution of an approximation
of whiplash injuries occurring in towed and non-towed impacts for the
1982-86 National Automotive Sampling System (NASS) data. The greatest
ratio of non-towed to towed whiplashes was 20 times for the 0-10 km/h
(0-6.2 mph) [Delta]V range. The next highest ratio was for the 11-20
km/h (6.8-12.4 mph) range at 8 times.\27\ As expected, this ratio drops
significantly at higher speeds because there are fewer non-towed
crashes at these speeds. If we use the ratio of NASS data for non-towed
to towed crashes as a multiplier for the CISS towed whiplash injury
estimates in each speed range to attempt to account for the non-towed
whiplash injuries in the newer data set, the result is column four in
table II.5. If we distribute proportionally the cases of whiplash
injuries where the impact speed was unknown to the known cases, the
result is given in the fifth column. In this column we see that more
than three-quarters (125,221/161,623) of all whiplash injuries occur at
impact [Delta]V less than 20 km/h (12.4 mph). For only towaway rear
impacts (not shown graphically) this [Delta]V limit captures 45%
(8,355/18,570) of whiplash injuries. The whiplash injury distribution
is shown graphically in Figure II.7. This estimate is provided to give
a general sense of how considering whiplash injury only in tow-away
crashes significantly underestimates overall whiplash injury
distribution, particularly for lower speed crashes. This estimate comes
with a large degree of uncertainty because it is based on historical
NASS data.
---------------------------------------------------------------------------
\27\ We note that these ratios are approximations from a
slightly different [Delta]V segmentation.
Table II.5--Adjustments to Whiplash Injuries To Account for Non-Towed Crashes
----------------------------------------------------------------------------------------------------------------
Ratio total to Towed whiplash Compensated Unknown
[Delta]V (km/h) towed (82-86 injury (2017-2020 whiplash [Delta]V
NASS) CISS) injury distributed
----------------------------------------------------------------------------------------------------------------
Unknown................................... 5.1 12,637 64,553 ..............
0-10...................................... 19.8 675 13,339 22,210
11-20..................................... 8.1 7,680 61,868 103,011
21-30..................................... 2.8 6,302 17,550 29,220
31-40..................................... 1.1 2,624 2,768 4,609
41-50..................................... 1.0 107 110 184
51+....................................... 1.0 1,183 1,183 1,972
---------------------------------------------------------------------
Total Known [Delta]V.................. ............... 18,570 96,819 ..............
Total................................. ............... 31,207 161,372 161,372
----------------------------------------------------------------------------------------------------------------
[GRAPHIC] [TIFF OMITTED] TP16JY24.012
[[Page 58009]]
C. Field Data Analyses From Relevant Literature
In an earlier 1997 study of the National Automotive Sampling
System-Crashworthiness Data System (NASS-CDS) across years 1980-1994,
Prasad \28\ found that rear impact collisions accounted for 11% of all
possible struck vehicle scenarios. The distribution of crashes
indicated that 50% of all rear impacts occur at [Delta]Vs of 21 km/h
(13 mph) or less, 86% occur at [Delta]Vs less than 32 km/h (20 mph) and
94% occur at [Delta]Vs of 40 km/h (25 mph) or less. Furthermore, when
examining the distribution of injuries, it was found that less than 1%
of rear end collisions resulted in severe injury of AIS 3 or more.
---------------------------------------------------------------------------
\28\ Prasad, Priya, et al. ``Relationships between passenger car
seat back strength and occupant injury severity in rear end
collisions: Field and laboratory studies.'' SAE transactions (1997):
3935-3967.
---------------------------------------------------------------------------
In another study, Parenteau \29\ examined 1999 to 2015 NASS-CDS
crash data to investigate the risk for MAIS 3+ outcomes including
fatalities in crashes involving vehicles from model year (MY) 2000 and
later. The risk for severe injury was lowest in rear crashes. The
authors found head trauma to be the most likely severe injury for
frontal passengers in rear collisions, followed by thorax and spinal
injuries. The severe injuries were mostly the result of contact with
the windshield, head restraint, and B-pillar. Many of these severe
injuries develop from a seat retention issue (such as not wearing a
seat belt) in which the occupant decouples from the seating system. It
is unclear to what extent seat strength and retention issues overlap.
The most severe injuries were attributed to forward intrusion of rear
components.
---------------------------------------------------------------------------
\29\ Parenteau, Chantal S., and David C. Viano. ``Serious head,
neck and spine injuries in rear impacts: frequency and sources.''
IRC-21-10, IRCOBI Conference. 2021.
---------------------------------------------------------------------------
Most rear collisions lead to a relatively low [Delta]V of the
struck vehicle and this contributes to moderating injury of the vehicle
occupants. The characteristics of the struck vehicle affect the injury
severity and fatality risk of the occupants. As discussed in the next
section, the majority of reported rear collision injuries are cervical
injuries with or without clear pathology, while a small percentage of
rear collisions are associated with high [Delta]V and severe injuries.
III. Statutory and Regulatory Background
A. The Safety Act and the Infrastructure, Investment and Jobs Act
Congress enacted the Safety Act for the purpose of ``reduc[ing]
traffic accidents and deaths and injuries resulting from traffic
accidents.'' \30\ To accomplish this, the Safety Act authorizes the
Secretary of Transportation to promulgate FMVSSs as well as to engage
in other activities such as research and development. The Secretary has
delegated the authority for implementing the Safety Act to NHTSA.\31\
The Safety Act requires that FMVSSs ``be practicable, meet the need for
motor vehicle safety, and be stated in objective terms.'' \32\ To meet
the Safety Act's requirement that standards be ``practicable,'' NHTSA
must consider several factors, including technological and economic
feasibility.\33\
---------------------------------------------------------------------------
\30\ 49 U.S.C. 30101.
\31\ 49 CFR 1.94.
\32\ 49 U.S.C. 30111(a). The Secretary must also (1) consider
relevant available motor vehicle safety information; (2) consult
with the agency established under the Act of August 20, 1958 (Pub.
L. 85-684, 72 Stat. 635), and other appropriate State or interstate
authorities (including legislative committees); (3) consider whether
a proposed standard is reasonable, practicable, and appropriate for
the particular type of motor vehicle or motor vehicle equipment for
which it is prescribed; and (4) consider the extent to which the
standard will carry out the purpose of the Safety Act to reduce
traffic accidents and deaths and injuries resulting from traffic
accidents. 49 U.S.C. 30111(b).
\33\ See, e.g., Paccar, Inc. v. Nat'l Highway Traffic Safety
Admin., 573 F.2d 632, 634 n.5 (`` `Practicable' is defined to
require consideration of all relevant factors, including
technological ability to achieve the goal of a particular standard
as well as consideration of economic factors.'') (citations and
quotations omitted). Technological feasibility considerations
counsel against standards for which ``many technical problems have
been identified and no consensus exists for their resolution . . .''
while economic feasibility considerations focus on whether the cost
on industry to comply with the standard would be prohibitive. Simms
v. Nat'l Highway Traffic Safety Admin., 45 F.3d 999, 1011 (6th Cir.
1995); See, e.g., Nat'l Truck Equip. Ass'n v. Nat'l Highway Traffic
Safety Admin., 919 F.2d 1148, 1153-54 (6th Cir. 1990).
---------------------------------------------------------------------------
In IIJA, Congress required NHTSA to issue this ANPRM to update
FMVSS No. 207. The statute further states that if the Secretary
determines a final rule complies with the Safety Act, a rule shall be
issued with a compliance date not later than 2 motor vehicle model
years after the model year the rule goes into effect.\34\ Under this
requirement, NHTSA is required to issue a final rule only if it meets
the requirements of the Safety Act, namely that it is practicable,
meets the need for safety, and is objective. In determining whether to
proceed with the rulemaking, NHTSA must also consider all of the
factors set forth in 49 U.S.C. 30111(b).
---------------------------------------------------------------------------
\34\ IIJA, section 24204 (2021).
---------------------------------------------------------------------------
B. Regulatory History of FMVSS No. 207 and FMVSS No. 202, and
Associated Research/Analyses
1. 1963--SAE Recommended Practice for Seats
The basis of the current FMVSS No. 207 standard is a recommended
practice established by SAE International on November 1, 1963: SAE
J879--Passenger Car Front Seat and Seat Adjuster. SAE J879 established
uniform test procedures and minimum performance requirements for motor
vehicle seats and seat adjusters.
J879 defined two test procedures. The first procedure, ``Simulated
Occupant Loading,'' tested rearward seat back strength. It required a
seat back to withstand a rearward moment of 480 Nm (4,250 in-lb) that
was generated via a static load applied to the uppermost cross member
of the seat back frame. However, this moment was calculated ``about the
rear attachments of the seat frame to the seat adjusters.'' The July 1,
1968, revision to J879, J879B--Motor Vehicle Seating Systems, modified
the moment to 373 Nm (3,300 in-lb) measured about the H-point, and the
direction of the force was specified to be perpendicular to the seat
back frame angle. The other procedure, ``Simulated Inertial Loading,''
established a 20 g minimum strength requirement for horizontal inertial
seat loadings, applied in both the forward and rearward direction. This
specification was designed to ensure that seat anchorages were
strengthened to the point where the seats would remain attached to the
vehicle body structure (typically the floor), preventing their inertia
from releasing them and creating a ram-like action within the passenger
compartment. During these tests, the seat back is braced to the seat
base to isolate the seat attachment to the vehicle.
2. 1967--Publication of FMVSS No. 207, Seating Systems
In February 1967, FMVSS No. 207 was enacted, and it went into force
beginning with MY 1969 passenger cars.\35\ It was later extended to
multipurpose vehicles, trucks, and buses in 1972.\36\
---------------------------------------------------------------------------
\35\ 32 FR 2415 (Feb. 3, 1967).
\36\ 36 FR 22945 (Dec. 2, 1971).
---------------------------------------------------------------------------
FMVSS No. 207 mostly mirrored the 1963 version of SAE J879.
However, the minimum rearward moment requirement was set at 373 Nm
(3,300
[[Page 58010]]
in-lb) as measured about the H-point.\37\ Additionally, provisions were
added for seats that folded forward to allow access to rear seats and
to assure that seats had a positive restraining device (latch) to
prevent them from swinging forward during a frontal crash. This
prevented adverse inertial forces by a flailing seat back to the back
of an occupant as they pitched forward during a frontal collision. The
additional requirement also helped protect unrestrained rear seat
occupants during frontal crashes or a hard breaking event who might
otherwise get thrown over a pitched-forward seat back and could suffer
injuries due to head impacts with the windshield or dash panel.
---------------------------------------------------------------------------
\37\ The rulemaking that established FMVSS No. 207 did not
discuss why it set a rearward moment with a different reference
point and value than recommended by the 1963 version of SAE J879.
See 32 FR 2415.
---------------------------------------------------------------------------
The new provision required the latch (and, hence, the seat back
itself) to withstand a forward load of 20 times the weight of the seat
back. The load was applied to the seat back at its center of gravity.
There was a concurrent revision to SAE J879 in July 1968. SAE also
changed the moment value and its reference point in J879 to be
consistent with FMVSS No. 207. However, the SAE requirement applied the
force generating the moment in a direction perpendicular to the seat
back instead of horizontally (see Figure III.1). The result of this
change was that a slightly higher force must be applied in FMVSS No.
207 to achieve the same moment level.\38\ Since then, the requirements
of FMVSS No. 207 and SAE J879B have not changed.
---------------------------------------------------------------------------
\38\ The magnitude of the force increase is equal to the inverse
of the cosine of the angle of the seat back from the vertical. So a
seat back with a 25 deg angle would have a 1.1 (1/cos(25)) times
greater load applied in FMVSS No. 207 than in SAE J879.
[GRAPHIC] [TIFF OMITTED] TP16JY24.013
3. 1968--Publication of FMVSS No. 202, ``Head Restraints''
In 1968, NHTSA issued FMVSS No. 202, ``Head restraints,'' requiring
head restraints on cars manufactured after January 1, 1969.\39\ The
standard specified that the head restraint must sustain an 890 N (200
lb-f) rearward load applied 65 mm (2.5 in) below the top of the head
restraint, while deflecting less than four inches (102 mm) and without
a seat back failure. The standard also specified that the top of the
head restraint must be at least 700 mm (27.5 in) above the H-point as
measured along the torso reference line of the J826 manikin.\40\ This
effectively placed a 565 Nm (5,000 in-lb) moment minimum strength
requirement on the seat back while also placing a lower bound on seat
back stiffness because this moment must be achieved within a specified
amount of deflection. Thus, between FMVSS Nos. 202 and 207, all
requirements for seat back strength were set forth through static
loads.
---------------------------------------------------------------------------
\39\ 33 FR 2945 (Feb. 12, 1968).
\40\ SAE J826-1995: Devices for Use in Defining and Measuring
Vehicle Seating Accommodation; 49 CFR 571.10; 73 FR 58896 (Oct. 8,
2008).
---------------------------------------------------------------------------
4. 1969--Report on Seat Safety Studies at ITTE
Following the issuance of FMVSS No. 207, Derwyn Severy, a principal
investigator at the Institute of Transportation and Traffic Engineering
(ITTE) at UCLA, published a paper \41\ at the 13th Stapp Car Crash
Conference advocating safer seat designs (``Stapp paper''). The ITTE
had been conducting field investigations and crash tests throughout the
1960s as they worked to develop design concepts for vehicle seats.
---------------------------------------------------------------------------
\41\ Severy, Derwyn M.; Brink, Harrison M.; Baird, Jack D;
Blaisdell, David M.; ``Safer Seat Designs,'' Proceedings of the 13th
Stapp Car Crash Conference Society of Automotive Engineers;
Warrendale, PA December 2-4, 1969; Boston, MA.
---------------------------------------------------------------------------
The 1969 Stapp paper provided the basis for several seat design
recommendations. Included were recommendations to increase the seat
back strength requirement to 11,300 Nm (100,000 in-lb) and limit the
seat back rotation to 10 degrees in a quasi-static test. According to
Severy, this load level was consistent with collision-induced forces
caused by the seat inertial forces augmented by a 50th percentile male
occupant in a 30 g rear-end crash.
In 1976, Severy published a follow-on paper on seat design.\42\ In
it, he offered his observations on safety improvements in production
seats brought about by the 1968 standard: ``that laboratory tests
established that production seats from cars large and small, foreign
and domestic, and from vehicles 30 years old to new, have seat back
strengths remarkably alike and that substantially exceed the required
FMVSS No. 207 criteria.'' Severy additionally stated that production
seats were incapable of effectively resisting motorist inertial forces
for any but light impact exposures without experiencing excessive yield
and/or component separation.
---------------------------------------------------------------------------
\42\ Severy, D.M., Blaisdell, D.M., and Kerkoff, J. F.;
``Automotive Seat Design and Collision Performance,'' 1976 SAE
Transactions, Sec. 4, Vol. 85.
---------------------------------------------------------------------------
[[Page 58011]]
5. 1974--Notice of Proposed Rulemaking (NPRM) To Revise FMVSS No. 207
In February 1974, Carl Nash of the Public Interest Research Group
petitioned NHTSA to implement a dynamic requirement for seat backs. He
asked NHTSA to add a rear impact test into FMVSS No. 208, ``Occupant
crash protection,'' with acceptance criteria based on head rotation of
a seated crash test dummy. Nash also called on NHTSA to consolidate
FMVSS No. 202 with FMVSS No. 207 because of the close relationship
between head restraints and seats in mitigating injuries in rear
impacts.
In March 1974, NHTSA published an NPRM that included proposed seat
back requirements that essentially mirrored Nash's request.\43\
However, instead of amending FMVSS No. 208, NHTSA proposed to add the
dynamic barrier test to a new, revised version of FMVSS No. 207. The
test was to be conducted using the same moving barrier apparatus as
that of the FMVSS No. 301 rear impact test for fuel system integrity,
which had been proposed a year earlier.\44\ Although a seated dummy was
specified, NHTSA did not propose any requirements based on dummy head
rotation as requested by Nash. Instead, NHTSA proposed a maximum seat
back rotation of 45 degrees. The proposal also integrated the
requirements of FMVSS No. 202 into a single, consolidated standard.
---------------------------------------------------------------------------
\43\ See, 39 FR 10268 (Mar. 19, 1974).
\44\ See 38 FR 22417 (Aug. 20, 1973).
---------------------------------------------------------------------------
To support a decision for a final rule, NHTSA contracted with the
University of New Mexico to conduct rear impact tests. Sled tests were
run on yielding vs. rigid seat backs using post-mortem human subjects
(PMHS).\45\ At the time, NHTSA was concurrently investigating whether
to revise FMVSS No. 202 to better mitigate the effects of whiplash. In
consideration of this, rigid and yielding seats were tested with and
without a head restraint. Sled tests were run by simulating a crash in
which a stationary vehicle is struck from the rear by another vehicle
having the same mass and travelling at a speed of 51 km/h (32 mph). The
investigators observed that with no head restraint, rigid seats
produced higher whiplash effects than yielding seats in low-speed rear
impacts. Also, ramping was exacerbated in rigid seats with no head
restraint. Thus, the results were deemed to be inconclusive as to
whether yielding seats or rigid seats reduced the risk of injury. In
addition to the work at the University of New Mexico, other basic
research was being conducted on the more general topic of human injury
tolerance to rearward forces and the biofidelity of the neck response
of test dummies in rear impacts.46 47 It is noteworthy that
NHTSA commissions another study in 1974 on the safety of occupants of
large school buses (school buses with gross vehicle weight rating
(GVWR) greater than 4,536 kilogram (kg) (10,000 pounds (lb))) prior to
issuance of FMVSS No. 222.\48\ Following this study, NHTSA developed
the concept of seating compartmentalization for school buses, which led
to the following conclusion regarding the seating system: ``The seats
and restraining barriers must be strong enough to maintain their
integrity in a crash yet flexible enough to be capable of deflecting in
a manner which absorbs the energy of the occupant.'' \49\ At least in
the context of larger school buses, NHTSA found there was a benefit to
yielding seats that maintain structural integrity in order to maintain
occupant compartmentalization when occupants were not protected by seat
belts. Based on this conclusion, NHTSA developed a force-deflection
requirement for the forward and rearward directions for large school
bus seat backs.\50\ The rearward requirement protects occupants in a
rear collision, analogous to the rear impact issue discussed in this
document.\51\
---------------------------------------------------------------------------
\45\ Hu, Anthony S., Stewart P. Bean, and Roger M. Zimmerman.
Response of belted dummy and cadaver to rear impact. No. 770929. SAE
Technical Paper, 1977.
\46\ Ewing, Channing L., et al. ``Effect of duration, rate of
onset and peak sled acceleration on the dynamic response of the
human head and neck.'' Proceedings: Stapp Car Crash Conference. Vol.
20. Society of Automotive Engineers SAE, 1976.
\47\ Muzzy, W. H. I., and Leonard Lustick. ``Comparison of
kinematic parameters between hybrid II head and neck system with
human volunteers for minus-Gx acceleration profiles.'' Proceedings:
Stapp Car Crash Conference. Vol. 20. Society of Automotive Engineers
SAE, 1976.
\48\ 39 FR 27584 (July 30, 1974).
\49\ 72 FR 65509 (Nov. 21, 2007).
\50\ 49 CFR 571.222--Standard No. 222; School bus passenger
seating and crash protection.
\51\ A rear impact into a large school bus is a much less severe
impact environment for the occupants of the bus than that of
occupants of a light vehicle experiencing an equivalent rear impact.
---------------------------------------------------------------------------
6. 1978--NHTSA Publishes a Request for Comment on Rulemaking Priorities
On March 16, 1978, NHTSA published a Request for Comments on the
agency's plan to prioritize ongoing rulemaking efforts.\52\ In
establishing priorities for the plan, NHTSA stated that limited
resources needed to be focused on rules with the largest safety
benefits. It identified the 1974 proposal to require stiffer seats as
one of several open rulemakings with low priority and proposed to
terminate it. In 1979, when the plan was issued, the 1974 proposal was
terminated.\53\ No public comments were received in response to the
request for comments.
---------------------------------------------------------------------------
\52\ 43 FR 11100 (June 7, 1978).
\53\ 44 FR 24591 (Apr. 26, 1979), ``Five Year Plan for Motor
Vehicle and Fuel Economy Rulemaking''.
---------------------------------------------------------------------------
Over the next several years, NHTSA continued to investigate the
safety of occupants in rear impacts. Beginning in 1979, NHTSA conducted
over 30 full-scale rear-impact crash tests on vehicles with
instrumented dummies seated in the front seats. The FMVSS No. 301
barrier was driven into the stationary vehicles at speeds ranging from
48-56 km/h (30 to 35 mph). These rear impact crash tests are catalogued
online.\54\
---------------------------------------------------------------------------
\54\ https://www.nhtsa.gov/research-data/research-testing-databases#/vehicle/.
---------------------------------------------------------------------------
7. 1989--NHTSA Receives Petitions for Rulemaking on Revisions to FMVSS
No. 207
In 1989, Kenneth J. Saczalski and Alan Cantor submitted their first
petitions for rulemaking on this subject to NHTSA.55 56
Saczalski sought an increase in the seat back moment requirement in
FMVSS No. 207 from 373 Nm (3,300 in-lb) to 6,330 Nm (56,000 in-lb),a
factor of 17 increase. The aim was to reduce the incidence of injuries
due to ramping and ejection in rear-end crashes. On July 24, 1989,
NHTSA notified Saczalski that his petition was granted.
---------------------------------------------------------------------------
\55\ Docket 89-20-No.1-001 or Docket NHTSA-1996-1817-0002. Both
petitions have significant overlap to the 2014 Saczalski and 2015
Cantor petitions discussed in this document.
\56\ The previous NHTSA Seat Dockets, 89-20 Notices 1-3, are now
available on the Docket Management System (DMS) at NHTSA-1998-1817,
-4047 and -4064, respectively.
---------------------------------------------------------------------------
Cantor's 1989 petition asked NHTSA to amend FMVSS No. 207 to
eliminate occupant ramping during a rear impact. Cantor did not provide
a standardized test procedure to measure and assess ramping, nor did he
describe a practicable countermeasure that could prevent ramping.
Nonetheless, on February 28, 1990, NHTSA notified Cantor that his
petition was granted.
After granting these petitions, NHTSA published another request for
comments (1989 RFC) on the need for amending the seat back performance
requirement in FMVSS No. 207 and opened a docket to receive comments on
the petitions and pertinent issues.\57\ In his comments submitted to
this docket, Saczalski provided additional recommendations.\58\ He
asked NHTSA
[[Page 58012]]
to also include a dynamic rear impact crash test using the FMVSS No.
301 barrier and a 95th percentile male dummy in the seat.
---------------------------------------------------------------------------
\57\ 54 FR 40897 (Oct. 4, 1989). Originally NHTSA Docket 89-20-
No. 1, and later transferred to Docket NHTSA-1996-1817.
\58\ Docket NHTSA-1996-1817-0002.
---------------------------------------------------------------------------
Most comments from the automotive industry on the 1989 Saczalski
and Cantor petitions opposed any new seat back stiffness requirements.
They argued that real-world crash data did not indicate that a safety-
related problem existed. General Motors, for example, cited its own
field data to conclude that any benefits associated with seat standard
changes for rear impact protection were very limited.\59\ Ford cited a
study of real-world crashes to conclude that a safety need did not
exist.\60\ The authors of that analysis had also reviewed test data
from prior studies (including those of Severy, et al). They concluded
that rigid seat backs would probably exacerbate injuries because
yielding seats absorb energy safely as they deform, thus reducing
injurious forces borne by the occupant, including whiplash-causing
forces. Occupant rebound from a rear impact and a subsequent hard
thrust forward was also cited as a negative effect of rigid seats.
Furthermore, a follow-up study by two of the same authors concluded
that ramping is more likely to occur in a rigid seat regardless of
whether a seat belt is used or a head restraint is in place.\61\ On the
other hand, Mercedes-Benz supported an upgrade to FMVSS No. 207.\62\ It
noted that seats in Mercedes vehicles were specifically designed to
reduce the danger to front and rear occupants during rear impacts as a
result of excessive rearward seat back deformation and the resultant
interaction between occupants.
---------------------------------------------------------------------------
\59\ Docket NHTSA-1996-1817-0010.
\60\ Docket NHTSA-1996-1817-0004.
\61\ James, M.B., Strother, C.E., Warner, C.Y., Decker, R.L., &
Perl, T.R. (1991). Occupant protection in rear-end collisions: I.
Safety priorities and seat belt effectiveness. SAE transactions,
2019-2027.
\62\ Docket NHTSA-1996-1817-0015.
---------------------------------------------------------------------------
At the time, NHTSA commissioned a study on injury incidence to
support a rulemaking decision.\63\ This analyzed the problem using NASS
real-world crash data. The study confirmed that seat back yield in
severe rear crashes does occur.\64\ Severe crashes were found to be
infrequent, however, amounting to approximately 5% of all rear impacts.
The study also showed that impacts with components in the rear seat
compartment and ejections are a relatively small portion of the
injuries. Injuries due to occupant impacts to components in the rear
seat compartment accounted for 2.8% (unrestrained occupant) and 0.1%
(restrained occupant) of the most severe injury to front seated
occupants in rear impacts, and only 3.2% of all harm to unrestrained
occupants in rear impacts involved occupant ejection.
---------------------------------------------------------------------------
\63\ ``Current Issues of Occupant Protection in Car Rear
Impacts,'' February 1990, Data Link, Inc., NHTSA Docket 89-20-No. 1-
21 or Docket Management System NHTSA-1996-1817-22.
\64\ This study considered severe crashes as those with a
vehicle change in velocity greater than 15 mph, CDC extent of damage
(exterior vehicle damage) greater than 3, and at least one occupant
with a maximum AIS of 3 or greater or with hospitalization or
fatality.
---------------------------------------------------------------------------
The study also concluded that current seat designs provided
reasonable safety in rear-end crashes, and that seat belts are
effective in reducing injuries. The report suggested that new head
restraint designs offered the best possibility to mitigate the largest
portion of injuries in rear-end crashes.
Additionally, Transport Canada submitted a report to the docket of
23 case studies of real-world rear impacts, all of which involved
vehicles that experienced seat back failures, and 11 of which resulted
in occupant ejections.\65\ Of the cases involving a rear seat
passenger, four of the five rear passengers sustained injuries
attributed to seat back failure of the front seat.
---------------------------------------------------------------------------
\65\ NHTSA Docket 89-20-No. 1-018 or Docket Management System
NHTSA-1996-1817-019.
---------------------------------------------------------------------------
NHTSA provided a summation of the comments and reports in a 1992
summary report.\66\ This document was placed in the docket for the
safety plan discussed below. The report concluded that improving
seating system performance may be more complex than simply increasing
the strength of the seat back, and that a proper balance in seat back
strength and compatible interaction with head restraints and seat belts
must be obtained to optimize injury mitigation.
---------------------------------------------------------------------------
\66\ NHTSA Docket 89-20-No. 3-001 or Docket Management System
NHTSA-1998-4064-001.
---------------------------------------------------------------------------
8. 1992-2000 NHTSA Publishes a Request for Comment on Possible
Revisions to FMVSS No. 207, Grants Two Petitions and Conducts Research
In November 1992, the agency published another Request for Comment
on more recent research findings and a proposed plan to address seat
back performance.\67\ At that time, the agency had refrained from
upgrading FMVSS No. 207 until significant results from research were
obtained, though the rulemaking action resulting from the 1989 petition
grants was still open. The first document the agency placed in the
docket was a report summarizing agency findings up to that point. The
1992 report stated that four categories of performance issues need to
be addressed as part of potential future changes to FMVSS No. 207.\68\
These four categories are:
---------------------------------------------------------------------------
\67\ 57 FR 54958 (Nov. 23, 1992).
\68\ ``Summary of Safety Issues Related to FMVSS No. 207,''
(1992), NHTSA-1998-4046-001.
(1) Seating system integrity: the ability of the seat and its
anchorage to the vehicle to withstand crash forces without failure.
(2) Energy absorbing capability: the extent to which the seat
and its attachment components absorb energy and the manner in which
the seat and its attachment components release energy during
rebound.
(3) Compatibility of a seat and its head restraint: The concern
in this category is that any change in seat back energy absorbing
capability could exacerbate head or neck injuries if the geometry
and energy absorbing capability of the head restraint is not also
changed.
(4) Seat belt restraint system: a seating system and its seat
belt restraint system must complement each other to prevent injury.
Over the ensuing 10-year period, the agency conducted extensive
physical testing of seat backs, performed computer modeling of seated
occupants in rear impacts, and conducted dynamic testing of
instrumented test dummies in vehicle seats. At the same time, NHTSA
also assessed how new requirements for head restraints could mitigate
whiplash injury in lower-speed rear-end crashes. The details of those
efforts are outlined in several NHTSA reports provided in docket folder
NHTSA-1998-4064 (document numbers 24-27, 31).
NHTSA also granted two more petitions related to seat back
strength: King (March 1998) \69\ and Hogan (December 1998).\70\ King
petitioned for a dynamic test using the FMVSS No. 301 rear impact test
procedure. Hogan stated that conformance to the current regulation was
being used in litigation as a defense for the performance of
contemporary seat designs, and therefore asked NHTSA to ``suspend''
FMVSS No. 207 until such time that the standard could be improved.
---------------------------------------------------------------------------
\69\ NHTSA-1998-4377-0001.
\70\ NHTSA-1999-5482-0008.
---------------------------------------------------------------------------
In comments posted in dockets NHTSA-1996-1817 \71\ and NHTSA-1998-
4064,\72\ most in the automobile industry argued that seat back
deformation was protective to the occupant by absorbing some crash
energy. However, there was recognition that better seat back
performance requirements could improve occupant safety in rear impacts
greater than 40 km/h (25 mph). Greater control of
[[Page 58013]]
occupant kinematics in severe rear crashes was thought to enhance
occupant safety, even for belted occupants, by controlling rearward
deflection of the seat back. Further comments presented by the
Advocates for Highway and Auto Safety expressed concern about the harm
caused by bodily impact with vehicle structures and noted the
importance of negating excessive seat back rotation, ramping, and
occupant rebound. One individual consultant described the consultant's
opinion regarding the deficiency of FMVSS No. 207 and the impact that
the standard may have had on automotive seat designs from that time.
Another consulting firm expressed concern about the level of
deformation that occurs due to the force applied to seat backs of that
time in rear impacts and its effect on the effectiveness of the
restraint systems in higher severity rear impacts.
---------------------------------------------------------------------------
\71\ These were originally posted to NHTSA Docket 89-20-No 1,
and subsequently transferred to Docket NHTSA-1996-1817.
\72\ These were originally posted to NHTSA Docket 89-20-No 3,
and subsequently transferred to Docket NHTSA-1998-4064.
---------------------------------------------------------------------------
The comments and research at the time affirmed that the issues of
seat back, head restraint, and belt retention were inextricably linked
to overall occupant safety. For example, in studies such as the 1997
Prasad,\73\ 1977 University of New Mexico study, and 1976 Severy study,
the disbenefits of a rigid seat were particularly evident in seats with
baseline head restraints.\74\ In the 1997 Prasad study for example, the
authors found that stiffer seats led to higher neck and lumbar spine
loads in rear impact tests. One complicating factor from this period is
that most of the laboratory tests were performed with Hybrid II or
Hybrid III 50th percentile male (HIII-50M) dummies, which are seated
dummies designed based on human indices measured in frontal crashes.
The torso and pelvis of these dummies do not articulate well in rear
impacts, and such articulation is needed to faithfully exhibit ramping.
While a larger size ATD would more fully exercise a seat back in a rear
impact, the additional use of a smaller ATD with female-specific
characteristics may have provided a more comprehensive assessment of
occupant kinematics and injury risk for different seat designs in these
earlier studies. Comments posted in the docket also emphasized the rear
impact protection points NHTSA made in the 1992 study, in particular
the need for energy absorption of the seat back, while also recognizing
that performance requirements may enhance rear impact protection.
---------------------------------------------------------------------------
\73\ See below in Review of Additional Literature, Occupant
Dynamics, for an in-depth discussion of the findings.
\74\ The term ``baseline'' indicates head restraints
manufactured prior to the 2004 update of the head restraint
standard. These provided much less protection than those mandated by
today's Federal standard. 69 FR 74848 (Dec. 14, 2004).
---------------------------------------------------------------------------
9. 2004--NHTSA Issues Final Rule Upgrading FMVSS No. 202, Head
Restraints
NHTSA's research on rear impact crashes and head restraints led the
agency in January 2001, to address the problem of whiplash injuries by
proposing to upgrade the head restraint standard, FMVSS No. 202.\75\ At
the time, the agency estimated that approximately 800,000 whiplash
injuries occurred annually in all crash types, resulting in a total
annual cost of $5.2 billion. Whiplashes in rear impacts were estimated
to be about 270,000 annually.
---------------------------------------------------------------------------
\75\ 66 FR 968 (Jan. 4, 2001).
---------------------------------------------------------------------------
After considering public comments on the proposal, NHTSA published
the final rule on December 14, 2004.\76\ It was estimated to reduce the
number of whiplash injuries by about 17,000 per year. The revised
standard imposed an increased head restraint height requirement such
that all outboard front seat head restraints must be capable of
adjusting to at least 800 mm (31.5 in) and not have an adjustment
position below 750 mm (29.5 in). It also imposed a minimum backset \77\
measurement that required the head restraint to be closer to the back
of a seated occupant's head. The updated standard maintained the
requirement for the head restraint to withstand a 200 lb-f or 890 N
rearward force applied 65 mm (2.5 in) below its top, when adjusted to
its highest position, which must be at least 800 mm. Thus, this imposes
an effective rearward strength requirement on seat backs of 654 Nm
(5,790 in-lb), where 654 = 890*(0.8-0.065). This is a factor of 1.75
greater than the rearward strength requirement of FMVSS No. 207.
---------------------------------------------------------------------------
\76\ 69 FR 74848 (Dec. 14, 2004).
\77\ Backset is defined as minimum horizontal distance between
the rear of a representation of the head of a seated 50th percentile
male occupant and the head restraint, as measured by the head
restraint measurement device. 49 CFR 571.202(a).
---------------------------------------------------------------------------
10. 2004--NHTSA Terminates Rulemaking on FMVSS No. 207, Seating Systems
By the time NHTSA finalized the head restraint regulation in 2004,
it was clear to the agency that additional research and data analyses
were needed to allow a fully informed decision on any change to the
seat back strength requirement in FMVSS No. 207. A year earlier,
researchers at Johns Hopkins University Applied Physics Laboratory
completed a study commissioned by NHTSA, which strongly suggested that
seat back stiffness plays a role in whiplash injury risk in low-speed
rear impacts.\78\ The main finding was that the risk of whiplash injury
cannot be related to a single design factor, such as head restraint
height. The study concluded that altering the seat back design could
have an effect on the occurrence of whiplash. Additional analyses were
needed to assure that a NHTSA-imposed seat back requirement would not
create a greater risk of whiplash. Since it was not clear when such
analyses would be complete, on November 16, 2004, NHTSA terminated the
FMVSS No. 207 rulemaking proceeding that had been open since 1989.\79\
NHTSA was unable to fully establish that a need for a stronger seat
back existed, establish a definitive link between injury reductions and
potential new regulatory seat back requirements, or show that new
requirements under consideration would not exacerbate risk of neck
injuries due to whiplash, roof contacts, or rebound. However, NHTSA did
not make a finding that an FMVSS No. 207 amendment was not warranted.
Instead, NHTSA stated that further study is needed to make a definitive
determination of the relative merits of different potential rulemaking
approaches and that research on seat back issues would continue.
---------------------------------------------------------------------------
\78\ Kleinberger M, Voo LM, Merkle A, Bevan M, Chang S: The Role
of Seatback and Head Restraint Design Parameters on Rear Impact
Occupant Dynamics. Proceedings of 18th International Technical
Conference on the Enhanced Safety of Vehicles, Paper #18ESV-000229,
Nagoya, Japan, May 19-22, 2003.
\79\ 69 FR 67068 (Nov. 16, 2004).
---------------------------------------------------------------------------
11. Further Regulatory Changes Since 2004
There have been two prominent regulatory changes regarding occupant
safety in rear-end crashes that have been fully implemented since NHTSA
terminated the rulemaking on FMVSS No. 207: a revision to FMVSS No.
202, and a revision to FMVSS No. 301, the fuel system integrity
standard. FMVSS No. 202 is the standard focused on neck injury
protection in rear impacts. Regarding FMVSS No. 301, while the stated
purpose of the standard is to reduce incidence of fire and fuel
ingestion incidents, it utilizes a test procedure that represents a
relatively severe rear impact in the field and has been recommended by
petitioners as a viable basis for an upgrade to FMVSS No. 207.
Additionally, some researchers have reported that vehicles compliant
with the updated FMVSS No. 301 have shown significant reduction in
fatality risk in rear impact.\80\ Therefore, as part
[[Page 58014]]
of our analysis of the need for new seat back strength requirements,
NHTSA considers the effects that these changes have had on seat
performance and occupant injury risk in moderate-to-severe rear-end
crashes.
---------------------------------------------------------------------------
\80\ Viano, David C., and Chantal S. Parenteau. ``Effectiveness
of the revision to FMVSS 301: FARS and NASS-CDS analysis of
fatalities and severe injuries in rear impacts.'' Accident Analysis
& Prevention 89 (2016): 1-8.
---------------------------------------------------------------------------
(a) FMVSS No. 202a, ``Head Restraints''
FMVSS No. 202a was issued in 2004 and applied an updated set of
safety requirements for head restraints beginning with model year
2010.\81\ Although the new requirements were not specifically intended
to strengthen seat backs, the head restraint upgrade resulted in an
increase in the minimum acceptable seat back strength.
---------------------------------------------------------------------------
\81\ 49 CFR 571.202a. See also 69 FR 74848 (Dec. 14, 2004). Many
requirements became effective on September 1, 2009, while others, in
particular those regarding rear head restraints, came into effect
the following year. Please review S2 of the standard for further
details.
---------------------------------------------------------------------------
FMVSS No. 202a requires a fully extended head restraint to
withstand an 890 N (200 lb-f) rearward load. Although this load was not
changed in FMVSS No. 202a, the minimum height of the head restraint was
raised from 700 mm to 800 mm. Thus, the effective torque requirement on
the seat back increased from about 565 Nm (5,000 in-lb) to 654 Nm
(5,790 in-lb).\82\
---------------------------------------------------------------------------
\82\ Agency testing of pre-FMVSS No. 202a seats showed seat back
strength well in excess of 654 Nm, so there was no need for
manufacturers to increase seat back strength to meet the new head
restraint requirements of FMVSS No. 202a, see Docket document no.
NHTSA-1998-4064-0026.
---------------------------------------------------------------------------
FMVSS No. 202a also introduced a new optional dynamic test for head
restraints. In the dynamic test, the entire vehicle is tested on a sled
with a seated HIII-50M dummy and subjected to a 17.3 km/h (10.75 mph)
rear impulse. The dummy's rearward head rotation with respect to its
torso must be limited to 12 degrees for the dummy in all outboard
designated seating positions. Though inertial forces of the occupant
acting on the seat back in FMVSS No. 202a testing are much lower
compared to those associated with an FMVSS No. 301 test pulse, FMVSS
No. 202a's dynamic test may have potentially resulted in stronger seat
back designs for those seats certified to this option because a stiffer
seat back with an adequately positioned head restraint would capture
the head motion before the limits are exceeded. Neither NHTSA nor, to
our knowledge, the petitioners, however, have studied whether the
upgrade to FMVSS No. 202a has resulted in injury reductions other than
whiplash.
(b) Upgrade to FMVSS No. 301, Fuel System Integrity
On November 13, 2000, NHTSA proposed a more stringent rear impact
offset test using a lighter deformable barrier.\83\ A final rule was
published on December 1, 2003, and the new requirements for the fuel
systems were phased in during MYs 2007-2009.\84\ Although the fuel
containment requirements remained the same as the previous version of
FMVSS No. 301, the crash test was generally more rigorous for most
passenger cars. Vehicles that passed the new rear impact requirements
were found to provide protection against crashes in which the impact
produced a 33 to 50 percent higher [Delta]V (which corresponds to 110
percent more energy being dissipated in the crash) compared to the
previous test.\85\
---------------------------------------------------------------------------
\83\ 65 FR 67693 (Nov. 13, 2000).
\84\ 68 FR 67068 (Dec. 1, 2003).
\85\ Pai, Jia-Ern. ``Evaluation of FMVSS NO. 301, `Fuel System
Integrity,' as upgraded in 2005 TO 2009.'' National Center for
Statistics and Analysis, National Highway Traffic Safety
Administration. Washington, DC (2014).
---------------------------------------------------------------------------
In a post-regulatory assessment, NHTSA compared the structure of
pre- and post-standard vehicles. NHTSA observed substantial structure
upgrades in the newer vehicles, which may mitigate intrusion of vehicle
structures into the rear seat occupant compartment. For example, in the
2016 study, Viano and Parenteau found MY 2008 and onward FMVSS No. 301
compliant vehicles to have a 27.1-32.8% reduction in fatality risk in
rear impacts compared to 1996-2001 MY vehicles. Two considerations
limit the conclusions that can be drawn from this data. First, injury
risk was estimated irrespective of post-crash fire. Thus, some of the
injury risk reduction could be a reduction in the incidence of fire.
Second, the authors noted that the changes in rear structures occurred
while front seats were transitioning to higher retention designs, which
may contribute to the reduction in fatality risk.
(c) NCAP
In 2007 NHTSA published a notice requesting comments on an agency
report titled ``The New Car Assessment Program (NCAP) Suggested
Approaches for Future Program Enhancements.'' \86\ With regard to rear
impact protection, NHTSA proposed that it could provide consumers with
basic information on rear crashes such as safe driving behavior, proper
adjustment of head restraints, real-world safety data by vehicle
classes, and links to the Insurance Institute of Highway Safety (IIHS)
rear impact test results. The agency further proposed that a dynamic
rear impact test, which addresses those injuries not covered by the
agency's current standards, could be investigated and incorporated into
the ratings program. Several organizations and manufacturers
recommended that NHTSA evaluate the effectiveness, cost, and safety
benefits of a rear impact test before incorporating such a test into
NCAP. Industry comments suggested that NHTSA should also evaluate the
effectiveness of the FMVSS No. 202a update and that incorporating rear
impact safety into NCAP would be better directed toward areas not fully
addressed by the current regulation. Commentors suggested that NHTSA
should study whiplash-type injuries and countermeasures and encourage
public education on the proper adjustment of the head restraint. NHTSA
concluded that a dynamic test would not be premature at that time since
such an option existed in FMVSS No. 202a. However, NHTSA noted that the
test dummy used by IIHS is not used for testing FMVSS compliance, and
some of the injury criteria used for the assessment had not been
correlated with real-world injury. Ultimately, the agency did not
incorporate rear impact protection information into the NCAP program.
---------------------------------------------------------------------------
\86\ 72 FR 3473 (Jan. 25, 2007).
---------------------------------------------------------------------------
IV. Review of Additional Literature
NHTSA, industrial, academic, and non-profit researchers have
conducted significant research into the rear impact protection of seat
backs and head restraints, and research is ongoing. Researchers have
investigated occupant dynamics in rear impacts, development of safer
seats for the occupant in rear impacts, and occupant injury mechanisms
in rear impacts.
A. Occupant Dynamics
Occupant dynamics and protection in rear collisions is a complex
multivariable problem. The ideal safe seat for one occupant in a
certain rear collision scenario may not be the ideal safe seat for
another occupant or for a different scenario. For example, research
suggests that females have a higher risk of whiplash injury compared to
males and respond differently to a rear impact.87 88 89 90
Additionally, other
[[Page 58015]]
occupant characteristics, such as weight, can play a significant role
in rear impact injury risk, as shown in the NASS-CDS case number 2011-
49-57 noted by Viano and Parenteau.\91\ This case outlines a rear
collision with an estimated [Delta]V between 35 and 39 km/h (21.7 and
24.2 mph). The 141 kg (311 lb) driver of the rear impacted 2008 model
passenger vehicle suffered critical head and neck injuries after
decoupling from the rotated driver seat back and colliding with the
rear seat back. The 68 kg (150 lb) right front passenger of the same
struck vehicle, however, had no documented injury.\92\ The injury
severity suffered by the driver in this case is rare in rear impacts.
Viano and Parenteau found passengers with injuries of MAIS 4 or greater
severity, including fatalities, represented 0.08% of passengers with
injury in rear collisions in MY 2008 and newer vehicles. A quantitative
description of seat back response is complicated by the potential
sensitivity of response to a range of initial conditions and external
factors including head posture,\93\ awareness,\94\ seat belt use and
seat geometry including initial seat back recline angle,\95\ details of
the crash pulse,96 97 and specific occupant characteristics
such as weight distribution. The initial posture and location of the
occupant is also thought to influence injury risk. Many occupants in
rear collisions are believed to be out-of-position (e.g., seated off-
center), and out-of-position occupants are thought to have a higher
probability of injury in rear impacts than symmetrically or normal-
positioned occupants.98 99 100
---------------------------------------------------------------------------
\87\ Berglund A, Alfredsson L, Jensen I, et al. Occupant- and
crash-related factors associated with the risk of whiplash injury.
Ann Epidemiol 2003;13:66-72.
\88\ Carlsson, Anna. Addressing female whiplash injury
protection-a step towards 50th percentile female rear impact
occupant models. Chalmers Tekniska Hogskola (Sweden), 2012.
\89\ Viano, David C. ``Seat influences on female neck responses
in rear crashes: a reason why women have higher whiplash rates.''
Traffic injury prevention 4.3 (2003): 228-239.
\90\ Linder, Astrid, and Mats Y. Svensson. ``Road safety: the
average male as a norm in vehicle occupant crash safety
assessment.'' Interdisciplinary Science Reviews 44.2 (2019): 140-
153.
\91\ Viano, David C., and Chantal S. Parenteau. ``Effectiveness
of the revision to FMVSS 301: FARS and NASS-CDS analysis of
fatalities and severe injuries in rear impacts.'' Accident Analysis
& Prevention 89 (2016): 1-8.
\92\ Comparisons such as these should be made with care because
the driver and passenger seat may not be structurally identical,
with the driver seat sometimes having more and powered adjustments
compared to the passenger seat.
\93\ Lenard, James, Karthikeyan Ekambaram, and Andrew Morris.
``Position and rotation of driver's head as risk factor for whiplash
in rear impacts.'' J Ergonomics S 3.2 (2015).
\94\ Siegmund, Gunter P., et al. ``Awareness affects the
response of human subjects exposed to a single whiplash-like
perturbation.'' Spine 28.7 (2003): 671-679.
\95\ Kang, Yun-Seok, et al. ``Effects of seatback recline and
belt restraint type on PMHS responses and injuries in rear-facing
frontal impacts.'' SAE International journal of transportation
safety 10.2 (2022): 09-10.
\96\ Hynes, Loriann M., and James P. Dickey. ``The rate of
change of acceleration: Implications to head kinematics during rear-
end impacts.'' Accident Analysis & Prevention 40.3 (2008): 1063-
1068.
\97\ Siegmund, Gunter P., et al. ``The effect of collision pulse
properties on seven proposed whiplash injury criteria.'' Accident
Analysis & Prevention 37.2 (2005): 275-285.
\98\ Strother, Charles E., Michael B. James, and John Jay
Gordon. ``Response of out-of-position dummies in rear impact.'' SAE
transactions (1994): 1501-1529.
\99\ Benson, Brent R., et al. ``Effect of seat stiffness in out-
of-position occupant response in rear-end collisions.'' SAE
transactions (1996): 1958-1971.
\100\ Burnett, Roger A., Chantal S. Parenteau, and Samuel D.
White. ``The effect of seatback deformation on out-of-position
front-seat occupants in severe rear impacts.'' Traffic Injury
Prevention (2022): 1-5.
---------------------------------------------------------------------------
Some research suggests that limiting seat back rotation can have
detrimental effects, particularly regarding neck injuries. In the 1997
Prasad study of real-world rear impacts, the authors concluded that a
revision to severely limit seat back rotation would have detrimental
effects. The study analyzed the 1980-94 NASS database to compare injury
rates in pickup trucks with passenger vehicles in rear impacts. This
allowed for comparison between yielding seat performance with the
rotationally stiff seats of pickup trucks (stiffness is due to the
small gap between seat and cab). A higher rate of occupant injury in
rear collisions across all [Delta]Vs was observed in pickup trucks. The
authors inferred that rotationally rigid seats could have an increased
rate of injury in rear impacts. The 1997 Prasad study further analyzed
a series of sled tests to investigate the relationship between seat
stiffness and anthropomorphic test device (ATD) kinematics for rear
impact [Delta]V of 16, 24, and 40 km/h (9.9, 14.9, and 24.9 mph). After
assessing the range of sampled speeds and ATD measurements, Prasad
hypothesized that (all else being equal) stiffening of the baseline
1996 production seats can result in an overall increase in whiplash
type injuries at low-to-moderate speeds and a greater potential for
serious neck injury at higher speeds, in addition to other conclusions.
This study, however, has limitations. Many of the pickups in the crash
data analyzed may not have had head restraints because trucks were not
required to have head restraints until MY 1993. Moreover, a
rotationally rigid seat represents the extreme end of the debate around
the seat strength set by FMVSS No. 207. While modern production seats
are characterized by a seat strength many times the value set by FMVSS
No. 207, these seats also display a degree of balance between high and
low-speed rear impact protection and the characteristic of rearward
rotation of the seat back.
Other research suggests that optimizing seat back design, including
stiffness, can reduce injury risks in rear impact. In a 1996 study,
Svensson, et al.\101\ analyzed the influence of seat back properties on
neck injury using the HIII ATD with a Rear Impact Dummy (RID)-neck in
low-speed rear collision sled testing. The study found that it was
possible to significantly reduce harmful head-neck motion of the ATD by
optimizing the head-to-head restraint gap, seat back frame stiffness,
and characteristics of the seat-back cushion.
---------------------------------------------------------------------------
\101\ Svensson, Mats Y., et al. ``The influence of seat-back and
head-restraint properties on the head-neck motion during rear-
impact.'' Accident Analysis & Prevention 28.2 (1996): 221-227.
---------------------------------------------------------------------------
A separate statistical analysis involving 20 years of the NASS
database by Burnett \102\ found that front seat occupants are
significantly more protected in rear collisions compared to other crash
directions, even for the most severe rear impacts where major seat
yielding and occupant decoupling from the seat can occur. The study
also conducted quasi-static mechanical testing and rear impact sled
tests of seven production seats to investigate the correlation between
mechanical parameters and ATD kinematics. The study found no
significant correlation between the seat strength and any of the
recorded ATD metrics, while seat stiffness and an energy absorption
parameter were nonlinearly correlated with ATD metrics.
---------------------------------------------------------------------------
\102\ Burnett, Roger, et al. ``The influence of seatback
characteristics on cervical injury risk in severe rear impacts.''
Accident Analysis & Prevention 36.4 (2004): 591-601.
---------------------------------------------------------------------------
B. Rear Impact Protection Technology
This section discusses some seat designs intended to improve rear
impact protection that have been incorporated over the years.
In 1998, a set of design guidelines was published by Volvo Cars and
Autoliv, Inc. for seats that emphasized the importance of controlling
an occupants' absolute and relative head and torso kinematics
throughout the rear impact process, to protect against neck and other
injuries.\103\ The Volvo Cars' Whiplash Protection System (WHIPS) was
introduced in 1998 and is built around these guidelines. In a
significant rear collision, the first generation WHIPS seat back
rotation point moves rearward and later transitions to rearward
rotation. During seat back rotation, a mechanical linkage
[[Page 58016]]
irreversibly absorbs rotational energy, so there is less energy
directed into the occupant and rebound is reduced. The seat back will
then continue to rotate and deflect rearward as a typical production
seat. According to data reported by Volvo, the first generation WHIPS
seat reduced soft tissue neck injury risk by 21% to 47% as compared to
prior seats.\104\
---------------------------------------------------------------------------
\103\ Lundell, Bjorn, et al. ``The WHIPS seat-a car seat for
improved protection against neck injuries in rear-end impacts.''
Proc. 16th ESV Conference, Paper. Vol. 98. 1998.
\104\ Jakobsson, Lotta, Irene Isaksson-Hellman, and Magdalena
Lindman. ``WHIPS (Volvo cars' Whiplash Protection System)--the
development and real-world performance.'' Traffic injury prevention
9.6 (2008): 600-605.
---------------------------------------------------------------------------
Another technology for whiplash injury protection is active head
restraints that was introduced by Saab in the late 1990s.\105\ These
systems aim to reduce the head restraint contact time by actively
shifting the head restraint forward in a rear impact through a
mechanical linkage in the seat structure activated when the seat
occupant moves rearward into the seat. Data acquired by the NCAP
program for MY2023 show that 21 vehicle models representing 4 percent
of vehicle sales are reported as having active head restraints or
provide the option. At least one automotive supplier is working on an
electromechanical system that moves the head restraint up to 40 mm
forward when a rear sensor in the vehicle anticipates a rear
impact.\106\
---------------------------------------------------------------------------
\105\ Wiklund, Kristina; Larsson, H[aring]kan (1 February 1998).
``Saab Active Head Restraint (SAHR)--Seat Design to Reduce the Risk
of Neck Injuries in Rear Impacts.'' Journal of Passenger Cars.
\106\ ``Can a high-tech headrest reduce whiplash injuries,''
Automotive News, August 14, 2022, https://www.autonews.com/suppliers/high-tech-headrest-designed-reduce-whiplash-injuries.
---------------------------------------------------------------------------
In the early 1990s, General Motors (GM) Research and Development
Center undertook an in-depth study of seat characteristics to improve
occupant safety in rear impacts. In general, the GM seat design
fostered movement of the pelvis rearward and into the lower portion of
the seat back frame in a way that would preclude ramping and reduce the
moment arm on the seat back. A key design component was to balance the
stiffness of the seat resisting the rearward movement of the pelvis
against the ability of the seat back frame to resist backward rotation.
GM established their own quasi-static test for the purposes of assuring
that a given seat met the design parameters. It was a destructive test
that made use of a 50th percentile male dummy loaded rearward into the
seat back through the lumbar joint. The dummy was free to move up,
down, and sideways during rear loading. The test also allowed the seat
back to rotate rearward and twist in a manner similar to what was
observed in sled testing. Eventually, GM's seat design targets were
published by SAE International.\107\ The targets were derived from
various measurements taken during their quasi-static test. The targets
contained many more parameters than FMVSS No. 207's single requirement
to withstand a 373 Nm (3,300 in-lb) moment (see table 1 for a list of
the parameters). Notably, the GM parameters included a criterion that
limited the seat stiffness to no more than 25 kN/m, while attempting to
assure that the seat had sufficient energy absorbing properties. GM
stressed that simply raising the FMVSS No. 207 moment beyond 373 Nm
would not achieve a desirable seat design. According to GM, increasing
only the seat back's stiffness would reduce the beneficial effects of
yielding.
---------------------------------------------------------------------------
\107\ Viano, David C. ``Role of the seat in rear crash safety.''
Warrendale, PA: Society of Automotive Engineers, 2002. 514 (2002).
---------------------------------------------------------------------------
A seat design feature that was rare 25 years ago, but appears to be
much more common in modern seats is a dual recliner
system.108 109 A dual recliner system places gear mechanisms
controlling the static recline angle on both sides of the seat. This
improvement significantly strengthened production seats and reduced
longitudinal axis twisting.\110\ The agency does not have an estimate
of the current level of implementation of dual recliners and requests
that commenters provide these data.
---------------------------------------------------------------------------
\108\ About one third of the seats tested by the agency in 1998
were dual recliners. This was a convenience sample not intended to
be representative of the fleet. Molino L (1998), Determination of
Moment-Deflection Characteristics of Automobile Seat Backs, NHTSA,
November 25, 1998. See Regulations.gov, Docket document no. NHTSA-
1998-4064-0026.
\109\ Viano, David C., et al. ``Occupant responses in
conventional and ABTS seats in high-speed rear sled tests.'' Traffic
injury prevention 19.1 (2018): 54-59.
\110\ Herbst, B.R., Meyer, SE, Oliver, A.A., and Forrest, S.M.
Rear impact test methodologies: quasistatic and dynamic. Proceedings
of 21st International Technical Conference on the Enhanced Safety of
Vehicles, 2009. Stuttgart, Germany.
---------------------------------------------------------------------------
An IIHS study of contemporary production seats claims that a wide
range of seating systems have achieved a balance between low-speed
protection while maintaining structural integrity at higher speeds and
occupant retention.\111\ This study conducted rear impact sled testing
on 26 modern production seats at a [Delta]V of 36.5 km/h (22.7 mph)
using a 78 kg (172 lb) Hybrid III 50th percentile male dummy. The
maximum dynamic seat back rotation ranged from 15[deg] to 47[deg] from
the initial angle and the dummy was retained by all seat backs. During
testing, the vertical displacements of the dummies was between 41 mm to
144 mm. The authors concluded that a majority of tested production
seats provided adequate occupant retention at a [Delta]V of 36.5 km/h
(22.7 mph), but with a range of performance metrics. Moreover, all 26
seats tested by IIHS had ``Good'' ratings for low-speed rear impact
protection as determined by a separate IIHS test using the BioRID dummy
at a [Delta]V of 16 km/h (10 mph).
---------------------------------------------------------------------------
\111\ Edwards, Marcy A., et al. ``Seat design characteristics
affecting occupant safety in low-and high-severity rear-impact
collisions.'' IRCOBI Conference, Florence, Italy, IRC-19-11. 2019.
---------------------------------------------------------------------------
C. Non-Contact Injuries
This section outlines a segment of the literature concerning non-
contact neck and thorax injuries resulting from rear collisions.
1. Neck Injuries
The term whiplash has been used since the 1920s to describe various
symptoms or signs of cervical spine injury in motor vehicle accidents.
The first case series studies on motor vehicle whiplash injury were
published in the early 1950s.\112\ Later in the 1960s, studies were
conducted on the mechanisms of whiplash injury.\113\ These and related
efforts developed the notion that the whiplash injury rate could be
reduced by preventing hyperextension of the neck. The initial version
of FMVSS No. 202 mandated head restraints as a countermeasure to this
type of neck injury.\114\ After the mandate was introduced, a
statistical analysis of crash data sets found modest improvements in
the whiplash injury rates.\115\ A 1982 NHTSA report of rear impacts in
passenger cars, for example, found that integral head restraints
reduced whiplash injury risk by 17% while adjustable restraints reduced
the risk by 10%.\116\ A Swedish study found
[[Page 58017]]
a similar 20% decrease in neck injuries as a result of the head
restraint.\117\ However, the persistence of frequent whiplash injury
motivated later studies of cervical spine dynamics in rear collisions.
---------------------------------------------------------------------------
\112\ Gay, James R., and Kenneth H. Abbott. ``Common whiplash
injuries of the neck.'' Journal of the American Medical Association
152.18 (1953): 1698-1704.
\113\ MacNab, Ian. ``Whiplash injuries of the neck.''
Proceedings: American Association for Automotive Medicine Annual
Conference. Vol. 9. Association for the Advancement of Automotive
Medicine, 1965.
\114\ NHTSA, FMVSS No. 202 Head Restraints for Passenger
Vehicles Final Rule, Final Regulatory Impact Analysis, Nov. 2004,
Docket No. NHTSA-2004-19807.
\115\ O'Neill, Brian, et al. ``Automobile head restraints--
frequency of neck injury claims in relation to the presence of head
restraints. American journal of public health 62.3 (1972): 399-406.
Nygren, Ake, Hans Gustafsson, and Claes Tingvall. Effects of
different types of headrests in rear-end collisions. No. 856023. SAE
Technical Paper, 1985.
\116\ Kahane, Charles J. An Evaluation of Head Restraints, NHTSA
Publication No. DOT HS 806 108, Washington, DC, 1982, pp. 154-160
and 181-197.
\117\ Nygren, Ake, Hans Gustafsson, and Claes Tingvall. Effects
of different types of headrests in rear-end collisions. No. 856023.
SAE Technical Paper, 1985.
---------------------------------------------------------------------------
In 1995, the Quebec Task Force on Whiplash Associated Disorders
categorized whiplash injuries into five grades, 0 to IV, in order of
increasing severity. For convenience, we will continue to refer to
whiplash associated disorders as whiplash injuries. The Quebec study
determined that 90% of insurance claims fell within grades 0 and I
where there was no clear pathology based on existing technology, but
symptoms may include neck pain, headache, memory loss, jaw pain,
hearing disturbance, and dizziness. Grades II and III include
musculoskeletal and neurological signs; grade IV contains cervical
fractures and dislocations. The most severe soft tissue whiplash type
injury occurring in grade IV is typically characterized by disc
herniation and is often accompanied by facet-joint hematoma, peripheral
spinal nerve and spinal cord contusion or articular process
fracture.\118\ The findings of a study on very low velocity rear
collisions \119\ led the authors to conclude that a biomechanical
``limit of harmlessness'' for whiplash exists for rear collision
[Delta]V between 10 to 15 km/h. The author goes on to explain that this
is the speed range below which there were no anatomical signs of
injury, but did not rule out ``psychological injury.''
---------------------------------------------------------------------------
\118\ Davis, Charles G. ``Mechanisms of chronic pain from
whiplash injury.'' Journal of forensic and legal medicine 20.2
(2013): 74-85.
\119\ Castro, W.H., et al. Do whiplash injuries occur in low-
speed rear impacts? European spine journal: official publication of
the European Spine Society, the European Spinal Deformity Society,
and the European Section of the Cervical Spine Research Society 6.6
(1997): 366-375.
---------------------------------------------------------------------------
Basic research of rear collision neck kinematics indicate that neck
and head dynamics occur through a complex process. The neck may
experience compression, tension, shear, torsion, retraction,
protraction, flexion, and extension to varying degrees and at different
points in time. Studies on cervical spine kinematics in rear collisions
by Svensson, et al.\120\ and McConnell, et al.\121\ in 1993, Geigl, et
al.\122\ in 1994 and Panjabi, et al.\123\ in 1998 noted that the neck
displayed an unnatural S-shaped curve in the early stages of the
kinematics due to retraction, and Panjabi hypothesized that neck injury
may occur before head contact with the head restraint. In a study by
Feng, et al.,\124\ the authors described early rear impact neck
dynamics through a series of kinematic spinal processes. The authors
noted that rear impact forces are at first distributed across the
occupant's torso through the seat back and then are transmitted to the
neck and head. These initial forces impose torso straightening and
likely movement of the occupant's torso up the seat back. The authors
hypothesize that axial compression is generated in the spinal column,
which travels up the neck to the head. As the head moves upwards axial
tension is then proposed to develop in the neck through
disproportionate movement of the head and neck due to a constrained
torso. As these first actions evolve the head lag phenomenon (also
described in an earlier 1976 study \125\) or retraction develops
through a delay between the forward motion of an occupant's torso and
head. Retraction leads to shear in the cervical column and curvature of
the neck is reduced. These theorized actions occur before the head
contacts the head restraint.
---------------------------------------------------------------------------
\120\ Svensson, Mats Y., et al. Rear-end collisions-a study of
the influence of backrest properties on head-neck motion using a new
dummy neck. No. 930343. SAE Technical Paper, 1993
\121\ McConnell, Whitman E., et al. Analysis of human test
subject kinematic responses to low velocity rear end impacts. No.
930889. SAE Technical Paper, 1993.
\122\ Geigl, B.C., et al. ``The movement of head and cervical
spine during rear end impact.'' Proceedings of the International
Research Council on the Biomechanics of Injury conference. Vol. 22.
International Research Council on Biomechanics of Injury, 1994.
\123\ Panjabi, Manohar M., et al. ``Mechanism of whiplash
injury.'' Clinical Biomechanics 13.4-5 (1998): 239-249.
\124\ Luan, Feng, et al., ``Qualitative analysis of neck
kinematics during low-speed rear-end impact.'' Clinical Biomechanics
15.9 (2000): 649-657.
\125\ Ewing CL., Thomas D., Lustick L., Muzzy W.H., et al. The
Effect of Duration, Rate of Onset and Peak Sled Acceleration on the
Dynamic Response of the Human Head and Neck. Proceedings of the 20th
Stapp Car Crash Conference, Dearborn, MI, Society of Automotive
Engineers, Inc., 1976.
---------------------------------------------------------------------------
2. Thorax Injuries in High-Speed Rear Impacts
A recent NHTSA research study was conducted with 14 PMHS tests in
rear facing seats in frontal collisions at a [Delta]V of 56 km/h for
different recline angles and seat types to investigate thorax
injuries.\126\ The structure supporting the seat back was rigidized to
avoid unpredictable permanent deformations of the seat during the
event. The goal of the study was to examine non-standard seating
configuration for vehicles with automated driving systems (ADS) with
reclined rear-facing seats in a frontal collision. It may also,
however, provide some insight into rear impact dynamics because the
loading is rearward with respect to the seat back orientation.
Additionally, the 56 km/h [Delta]V test is very severe for a rear
impact. The CISS data reported in section II.B indicates this speed
represents more than 95% of all towaway rear impacts. The authors found
that rib fractures occurred in the PMHSs due to a complex combination
of chest compression and expansion with upward shear loading. The
majority of rib fractures occurred after peak chest compression when
the abdominal contents shifted rearward and upward into the thorax due
to the ramping motion of the PMHS, which created a combined loading
(compression/tension and shear) to the thorax. Similar magnitudes of
rib strains were observed regardless of seat types, while strain modes
varied according to recline angle and seat type. Fewer injuries were
seen with a more upright 25-degree seat back, compared to a more
typical initial seat angle of 45-degree seat back.
---------------------------------------------------------------------------
\126\ Kang YS, et al. ``Thoracic responses and injuries to post-
mortem human subjects (PMHS) in rear-facing seat configurations in
high-speed frontal impacts,'' Twenty-Seventh Enhanced Safety of
Vehicles Conference (2023).
---------------------------------------------------------------------------
D. Summary
While progress has been made in understanding rear impact injuries,
the literature continues to point toward the need for a greater
understanding before conclusions can be drawn about the exact
mechanisms of injury and the risk factors involved, particularly in
regards to whiplash.\127\ Likewise, important safety improvements have
been made in production seats over the last 50 years and a greater
understanding of the relationship between seat back characteristics and
injury has been achieved, but questions remain with respect to
precisely quantifying protective characteristics. The continued
uncertainty around how best to protect occupants as well as the varied
approaches and developments in rear impact technology suggests that, as
NHTSA considers amendments to FMVSS Nos. 207 and 202a, there is value
in preserving industry flexibility in seat back and head restraint
design and strength parameters to allow further
[[Page 58018]]
research into and development of these systems.
---------------------------------------------------------------------------
\127\ Holm, Lena W., et al. ``The burden and determinants of
neck pain in whiplash-associated disorders after traffic collisions:
results of the Bone and Joint Decade 2000-2010 Task Force on Neck
Pain and Its Associated Disorders.'' Journal of manipulative and
physiological therapeutics 32.2 (2009): S61-S69.
---------------------------------------------------------------------------
V. Petitions for Rulemaking at Issue in This Document
A. Statutory and Regulatory Background
Under 5 U.S.C. 553(e), 49 U.S.C. 30162(a)(1) and 49 CFR part 552,
interested persons can petition NHTSA to initiate a rulemaking
proceeding. Upon receipt of a properly filed petition, the agency
conducts a technical review of the petition, material submitted with
the petition, and any additional information.\128\ After conducting the
technical review, NHTSA determines whether to grant or deny the
petition.\129\ The Safety Act states that all FMVSS requirements must
be practicable, meet the need for motor vehicle safety, and be stated
in objective terms.\130\ Accordingly, NHTSA will initiate a rulemaking
only if the agency believes that the proposed rule would meet these
criteria. If a petition is granted, a rulemaking proceeding is promptly
initiated in accordance with statute and NHTSA procedures. A grant of a
petition and a commencement of a rulemaking proceeding do not, however,
signify that the rule in question will be issued. That decision is made
on the basis of all available information developed in the course of
the rulemaking proceeding, in accordance with statutory criteria.\131\
If a petition under this section is denied, the reasons for the denial
are published in the Federal Register.\132\
---------------------------------------------------------------------------
\128\ 49 U.S.C. 30162(a)(1); 49 CFR 552.6.
\129\ 49 CFR 552.8; see also 49 U.S.C. 30162(c).
\130\ 49 U.S.C. 30111(a).
\131\ 49 CFR 552.9; see also 49 U.S.C. 30162(c).
\132\ 49 CFR 552.10.
---------------------------------------------------------------------------
B. Petition of Kenneth J. Saczalski
On October 28, 2014, Kenneth J. Saczalski of ERST petitioned NHTSA
to amend FMVSS Nos. 207 (Seating systems), 213 (child restraint
systems), and 301 (Fuel system integrity). Saczalski requested that
NHTSA increase the static strength requirement for seat backs by a
factor of six and implement a new dynamic requirement. The dynamic
requirement would assess the seat back of a vehicle by performing a
rear impact crash test with a 50th percentile male ATD positioned in
the seat. The petition also suggested adding a rear impact requirement
to FMVSS No. 213, ``Child restraint systems,'' and implementing a new
requirement for rear seats that would resist the forces of loose cargo
that may be stowed behind the rear seats.
1. FMVSS No. 207, Seating Systems
Saczalski seeks an amendment to FMVSS No. 207, S4.2(d) to increase
the rearward force that occupant seats must withstand from a 373 Nm
(3,300 in-lb) moment measured about the H-point to a 2,260 Nm (20,000
in-lb) moment measured from the pivot intersection of the seat back
structure and the seat cushion frame.\133\ While this ostensibly
represents an increase by a factor of six, because FMVSS No. 202a
effectively requires seat backs to withstand a 654 Nm (5,790 in-lb)
moment, this would only increase the performance requirement by a
factor of 3.5 above current requirements, if measured about the H-
point. The actual factors would be closer to a factor of 5.4 above the
required FMVSS No. 207 moment and 3.1 above the FMVSS No. 202a
requirement, depending on the relative position of the seat pivot with
respect to the H-point.\134\
---------------------------------------------------------------------------
\133\ ``Rearward force'' means the force against the rear side
of an occupant seat, regardless of orientation. For a forward-facing
seat, this would mean a force applied in the rearward longitudinal
direction, whereas with a rear-facing seat, this would mean a force
applied in the forward longitudinal direction.
\134\ Selecting the seat pivot point as the location for the
moment measurement reduces the force needed to produce a given
moment. Assuming a vertical distance of 535 mm from the H-point to
the location of force application and a vertical distance of 595 mm
from the seat pivot to the force location results in a 10% reduction
in force for the same moment measure about the pivot compared to the
H-point.
---------------------------------------------------------------------------
Saczalski also made a more general request that FMVSS No. 207 seat
strength testing be conducted ``to ultimate strength levels'' that
establish a seat's capacity to withstand crash forces. According to
Saczalski, testing must be repeated to examine strength variations
relating to adjustable seat components, such as height adjusters.
Saczalski does not, however, provide a specific set of performance
requirements or tests that he asserts should be conducted. Saczalski
also requested that NHTSA add a requirement that seats not experience a
``sudden load collapse'' (i.e., a failure of structural components that
causes the occupant support loading to suddenly drop off) of 400 pounds
force or greater within a short span of rearward deformation. According
to Saczalski, this testing should be done using a ``torso body-block''
device that replicates the upper body weight of a 95th percentile male.
2. Use of FMVSS No. 301, ``Fuel System Integrity,'' To Test Seats
Saczalski petitioned NHTSA to implement a new seat back requirement
using the dynamic rear-end crash test prescribed in the latest revision
of the fuel system integrity test described in FMVSS No. 301. In this
test, a stationary vehicle is struck in the rear by a 1,368 kg (3,015
lb) deformable barrier travelling at 80 km/h (50 mph). The barrier
overlaps the rear end of the vehicle by 70%.
Saczalski asserted that a dynamic, full vehicle test is needed in
addition to the static requirements discussed above. The main purpose
of such a test would be to fully assess the safety of children in rear
seats who may be exposed to collapsing front seat backs. Saczalski
cites in his petition a 2008 study by Children's Hospital of
Philadelphia (CHoP).\135\ The study examined risk levels through an
epidemiological study of real-world crashes, and found that in a rear-
end crash, children seated directly behind a seat back that yielded
exhibited about twice the risk of injury as children seated behind a
seat back that did not yield. Saczalski has asked for a dynamic test to
be run with Hybrid III 95th percentile male dummies (HIII-95M) in the
front seats with 12-month-old dummies seated directly behind in
forward-facing child restraints.\136\ He recommends a pass/fail limit
on front seat back rotation of no more than 25 degrees rearward from
its initial seat back orientation. He also recommends that NHTSA impose
pass/fail requirements based on dummy measurements within the head,
neck, chest, and extremities. This would apply to the HIII-95M and the
12-month-old dummies. Saczalski recommends pass/fail requirements for
both dummies equivalent to ``their respective NHTSA injury reference
levels for the head, neck, chest, and extremities.'' \137\
---------------------------------------------------------------------------
\135\ Jermakian JS, Arbogast KB, Durban DR, Kallan NJ (2008),
Injury risk for children in rear impacts: role of the front seat
occupant, 52nd AAAM Annual Conference, Annals of Advances in
Automotive Medicine, October 2008.
\136\ The 12-month-old dummy, known as the (CRABI) dummy, is
already integrated into subpart P of part 572.
\137\ Injury reference values recommended by NHTSA for the CRABI
and HIII-95M, when used to assess air bags, are contained within:
Eppinger R, Sun E, Kuppa S, Saul R (2000), Supplement: development
of improved injury criteria for the assessment of advanced
automotive restraint systems-II, National Highway Traffic Safety
Administration, March 2000.
---------------------------------------------------------------------------
Saczalski also suggested that the test be run with 20 kg (44 lb)
simulated luggage cases in the trunk area, which he stated could push
the rear seat forward. According to Saczalski, such a requirement will
guard against injuries due to the intrusion of a rear seat occupied by
a child into a yielding front seat back.
[[Page 58019]]
3. FMVSS No. 213, Child Restraint Seats
Saczalski asked NHTSA to include a rear impact requirement for
child restraint systems within FMVSS No. 213, which does not contain
such requirements. He suggested using the same test and performance
criteria as the European standard for child restraint systems, United
Nations Economic Commission for Europe Regulation 44 (ECE R.44),\138\
but run at a higher test speed of 40 km/h.\139\ The ECE standard
contains requirements for various sized child dummies subjected to a 30
km/h rear impact. Like FMVSS No. 213, the European standard also
includes requirements for a frontal impact, but those are not discussed
in Saczalski's petition.
---------------------------------------------------------------------------
\138\ Uniform Provisions Concerning the Approval of Restraining
Devices for Child Occupants of Power-Driver Vehicles, (Child
Restraint Systems), ECE R.44, E/ECE/324/Rev (unece.org).
\139\ UNECE Regulation No. 44, Uniform provisions concerning the
approval of restraining devices for child occupants of power-driven
vehicles (``Child Restraint System'').
---------------------------------------------------------------------------
C. Petition of Alan Cantor
In a letter dated September 28, 2015, Alan Cantor of ARCCA
petitioned NHTSA to revise FMVSS No. 207 by implementing new
requirements for seat back strength involving a crash test with an ATD.
He also requested that NHTSA reinstate a provision to FMVSS No. 209,
``Seat belt assemblies,'' that he states would prevent occupant
injuries in rear impacts.
1. Use of FMVSS No. 301, ``Fuel System Integrity,'' To Upgrade FMVSS
No. 207
Cantor requested a dynamic test to assess seat back loading by
occupants of different sizes. He envisioned the use of the current
FMVSS No. 301 procedure with Hybrid III 50th Percentile male dummies
(HIII-50M). Additionally, Cantor requested that a test be performed at
oblique impact angles to assess the potential of excessive seat back
twisting that Cantor stated could facilitate rearward ramping and an
out-of-position orientation of the occupant in the seat during
subsequent impacts. A full vehicle test was also envisioned, but
alternatively Cantor suggested that a sled test could be run using an
impulse equivalent to that produced by the dynamic procedure. Cantor
did not request a change to the static requirements of FMVSS No. 207,
nor did he call for the use of rear seated child dummies in the
dynamic, full vehicle test. Under Cantor's rationale, the test with the
HIII-50M dummies would serve as the basis for a new set of FMVSS
requirements. The requirements would apply to front seats as well as
rear ``bucket'' seats, such as those within minivans, that he suggests
may also have a propensity to collapse.
2. Rearward Rotation Limit and Structural Symmetry Requirement
Cantor recommended a pass/fail limit for rearward seat back
rotation of no more than 15 degrees from its initial seat back
orientation (measured in real-time during the test). For the oblique
impacts, there would be a requirement that the differential rearward
deflection of the seat back is no more than 10 degrees between the left
and right sides. According to Cantor, this will assure structural
symmetry of the seat to prevent excess twisting of the seat under load,
which can lead to ramping or out-of-position orientation of an occupant
if subsequent impacts occur.
3. Additional Dynamic Testing and NCAP Implementation
Cantor also requested another dynamic test to assess seat back
loading to be performed with a Hybrid III 95th male dummy (HIII-95M)
and to incorporate results into the NCAP star rating for the vehicle.
This test would be performed in a manner similar to the current FMVSS
No. 301 procedure, but at an impact speed of the barrier that is 8 km/h
(5 mph) faster than the current FMVSS No. 301 speed. He argues that it
would serve to inform consumers on whether a given vehicle seat back
has the propensity to collapse. Cantor states it would also provide
incentive to manufacturers to develop enhancements to rear impact crash
protection.
Cantor recommended the same pass/fail limit for rearward seat back
rotation for the NCAP tests as he recommended for the FMVSS No. 301
impacts. Cantor did not specify how the results would be factored into
the NCAP rating.
4. FMVSS No. 209, Seat Belt Assemblies
Cantor requested that NHTSA restore S4.1(b), which NHTSA deleted in
a final rule published in 1999.\140\ This provision required the lap
belt portion of the seat belt be designed to remain on the pelvis under
all crash conditions. Cantor states that restoring S4.1(b) would assure
that vehicles will be equipped with seat belt technologies that prevent
ramping in rear impact crashes.
---------------------------------------------------------------------------
\140\ 64 FR 27203 (May 19, 1999).
---------------------------------------------------------------------------
D. NHTSA's Analysis of Saczalski and Cantor Petitions
NHTSA is denying in part the Saczalski and Cantor petitions as they
pertain to the following recommendations: Cantor's requested amendments
to NCAP and request to restore anti-ramping language to FMVSS No. 209,
and Saczalski's requests to add a rear impact test to FMVSS No. 213 and
a cargo test requirement to FMVSS No. 207. As part of this rulemaking
effort to update FMVSS No. 207 and to facilitate informed comment,
NHTSA is granting the petitions in part with regard to updating the
strength requirement in FMVSS No. 207, the structural symmetry
requirement requested by Cantor, and the possible development of new
test procedures for seat back strength under FMVSS No. 207. NHTSA notes
that, at this time, insufficient information has been provided to
support the petitioners' suggested specific strength levels or test
designs, but NHTSA seeks comment on this issue. The remainder of this
section provides NHTSA's opinions on the recommendations in the
petitions to provide context and information to support informed
comment on an update to FMVSS No. 207. Later in this document, we
discuss NHTSA's current thinking on an integrated and unified approach
to rear impact protection and seeks comment on that approach.
1. Analysis of Data and Research Provided by Cantor and Saczalski
Regarding Safety Need
In the past, NHTSA and petitioners on this topic have not been able
to demonstrate that a safety need exists regarding the seat back
strength requirement in FMVSS No. 207.\141\ In their petitions,
Saczalski and Cantor both implied that factors related to child safety
have given rise to a new safety need for stronger seat backs. NHTSA
acknowledges that there is evidence that, in some crash scenarios, seat
back deformation or rearward movement due to component failure can lead
to injury, but NHTSA believes that the petitioners have not provided
sufficient supporting data to demonstrate a worsening safety need
related to seat back strength compared to NHTSA's past determination.
NHTSA discusses the materials provided by petitioners below and seeks
comment on this question.
---------------------------------------------------------------------------
\141\ See discussion in section III.B.10 of this document and 69
FR 67068 (Nov. 16, 2004).
---------------------------------------------------------------------------
In support of his petition, Saczalski references the CHoP study.
NHTSA agrees with Saczalski that the 2008 CHoP study is useful for
understanding the levels of risk to which children in rear seats are
exposed, but the CHoP study did not determine that this risk was
associated with front seat back strength. The information submitted by
petitioners did not provide new or pertinent information to build upon
the
[[Page 58020]]
CHoP study or further demonstrate a safety need.
Saczalski provided NHTSA with his own publications, including one
from the 2014 annual meeting of the International Federation of
Automotive Engineering Societies (FISITA).\142\ This paper described 13
cases of infant fatalities in rear-end crashes in which the infant was
seated behind an occupied front seat. However, as with the CHoP study,
Saczalski's paper did not provide additional insight on whether the
fatalities were associated with front seat back strength. Moreover,
because most of the fatalities occurred in vehicles that were built
prior to MY 2000, the cases he cites may not reflect the lower level of
risk associated with new vehicles. Since then, improvements have been
made to FMVSS Nos. 202a, 301, and other standards that may impact the
conclusions reached in the CHoP study and Saczalski's paper. In
addition, changes in manufacturer's design targets and the more
frequent use of dual recliners may have resulted in seat designs that
are generally stronger.
---------------------------------------------------------------------------
\142\ Saczalski K, Pozzi M, Burton J, Saczalski T (2014),
Experimental and field accident analysis study of factors effecting
child occupant injury risk and safety in rear impacts, 2014 Annual
FISITA Meeting, Paper No. F2014-AST-013, 2014.
---------------------------------------------------------------------------
Saczalski also provided the results of several sled tests with
crash test dummies, which he argues demonstrate that the seat back of a
front-seated adult can collapse on a child sitting in the rear in a 48
km/h rear-end impact. While these tests may illustrate the potential
consequences of seat back deformation or failure, they simply reinforce
a finding of which NHTSA is already aware: that it is possible for some
seat backs to yield in a severe rear-end impact in a way that could
potentially injure occupants.
Finally, according to Saczalski, fatality counts within the Fatal
Accident Reporting System (FARS) from 2001-2011 show that fatalities in
infants (0-12 months) have doubled since 1990-2000, from which he
infers a worsening safety need.
NHTSA believes that the conclusion Saczalski draws from this data
is inaccurate. NHTSA has queried FARS for infant and adolescent
fatalities where the child was known to be restrained in a rear seat,
non-ejected, in a non-rollover, rear impact. Over the last 15 years
captured in the study, the average fatality rate is 7.7 per year,
ranging from 1 to 15 per year (See Figure V.1). There is a great deal
of scatter and no clear fatality trend over time. If the data are
expanded to all children up to an age of 5, the average fatality rate
is 31.9 per year, ranging from 22 to 60 (See Figure V.2). Again, there
is no clear trend in the data. The data for the 0-5-year-olds have less
scatter than that for the 0-12-month-olds. This latest data is not
supportive of a claim that there is a fatality risk that continues to
increase. NHTSA notes that these data provide an estimate of all-cause
mortality and therefore provide no insights into whether front row seat
performance contributed to the child's death.
BILLING CODE 4910-59-P
[GRAPHIC] [TIFF OMITTED] TP16JY24.014
[[Page 58021]]
[GRAPHIC] [TIFF OMITTED] TP16JY24.015
BILLING CODE 4910-59-C
2. Rear Structure Intrusion
Saczalski states in his petition that there are phenomena other
than front seat back failure and ramping that create risk to children
in rear seats. He notes that rear-seated children in rear-end
collisions are often injured by poorly designed rear structures that
push children forward into the front seat back. He supports this claim
using a 2008 study of NASS-CDS data, which looked at the risk to
children seriously injured in rear impacts and indicated that injury
caused by intrusion from the rear seating area is a larger problem than
deforming front seat.\143\ NHTSA appreciates the analysis done by
Saczalski and agrees that there is evidence to support a finding that
there is a safety risk to children in the rear seat in a rear impact
crash. NHTSA also agrees that this risk involves more factors than just
front seat back collapse, such as rear structure intrusion. NHTSA seeks
comment on the significance of the intrusion issue in the overall
context of rear impacts and whether a practicable solution to this
issue exists. NHTSA notes that the 2006 revision to FMVSS No. 301, Fuel
system integrity, which would not have been in place for the model
years of the vehicles Saczalski studied, may have induced changes to
rear vehicle structures that mitigated the intrusion problem.
---------------------------------------------------------------------------
\143\ Viano D, Parenteau C (2008), Field Accident Data Analysis
of 2nd Row Children and Individual Case Reviews, SAE Technical Paper
2008-01-1851.
---------------------------------------------------------------------------
NHTSA wishes to emphasize that Saczalski and Cantor do not appear
to have considered whether increasing the requirement for seat strength
would have any unintended negative safety impacts. This document
discusses at length the literature, such as the 1997 Prasad study,
which suggest a possible association between significantly stiffer
seats and increased incidence of whiplash and other non-contact
injuries. NHTSA seeks comment on these potential negative safety
impacts, which the agency believes is critical to understanding the
overall safety problem in occupant protection in rear impact and
whether changes to FMVSS No. 207 will meet a need for safety.
3. Cost and Practicability
Cantor argues in his petition that upgrading seat back strength
would not impose a major cost on manufacturers, claiming that many
modern vehicles have stronger seats compared to those in 1989 even in
absence of a change to FMVSS No. 207. To support this claim, he cites
his own testing, in which he claims to have studied newer vehicles
using the FMVSS No. 207 procedure and found that they ``tested out''
somewhere between 2.5 to 10 times the current compliance level (373
Nm). Based on his own testing, he concludes that it would not be cost
prohibitive for original equipment manufacturers that use less strong
seats to increase seat back strength, and he argues that an upgrade to
the standard is needed to assure all seat backs have a minimum
strength.
NHTSA does not believe that Cantor's examples of actual seat back
strength in the modern vehicles provide new or better data over what
was known to NHTSA in 2004, when NHTSA terminated a rulemaking to
increase seat back strength. The variance seen in Cantor's test results
is consistent with that seen in the Severy data from the 1960s. It was
also seen in data in a 1998 report prepared by NHTSA.\144\
---------------------------------------------------------------------------
\144\ Molino L (1998), Determination of Moment-Deflection
Characteristics of Automobile Seat Backs, NHTSA, November 25, 1998.
See Regulations.gov, Docket document no. NHTSA-1998-4064-0026.
---------------------------------------------------------------------------
NHTSA agrees that increasing seat back strength is technically
feasible. Any rulemaking action to change the seat back strength
requirement, however, must be practicable, meet the need for motor
vehicle safety, and be stated in objective terms. As part of this
analysis, a rulemaking action would assess whether this would be a
cost-effective way to increase overall motor vehicle safety.
E. Assessment of the Specific Recommendations by Cantor and Saczalski
In this section, NHTSA presents its assessment of specific matters
petitioned for by Cantor and Saczalski. The first section discusses the
matters on which NHTSA is granting the petitions and initiating
rulemaking and provides NHTSA's opinions on those specific petitioned-
for issues to facilitate informed comment. The second section covers
the issues on which NHTSA is
[[Page 58022]]
denying in part and provides the reasons for denial as required in 49
CFR part 552.
1. Matters on Which NHTSA Is Granting the Petitions
(a) Amend FMVSS No. 207 To Increase Seat Back Moment Requirement and
Alter Load Application Method
Saczalski asked NHTSA to raise the torque requirement about the
seat back pivot to 2,260 Nm (20,000 in-lb). This would raise the
current FMVSS No. 207 requirement of 373 Nm (3,300 in-lb) by a factor
of about 5.4 and by a factor of about 3.1 above the FMVSS No. 202a
requirement of 654 Nm (5,788 in-lb). In addition, Saczalski recommended
that the load be applied through a ``body block'' representing a 95th
percentile male, rather than to the upper member of the seat frame.
NHTSA is granting the petition on the torque requirement and static
test design issues in part, is initiating rulemaking to consider
whether to upgrade FMVSS No. 207 on these topics and seeks comment on
the analysis below.
Saczalski did not explain why a torque limit of 2,260 Nm was
preferable to other limits that NHTSA has considered previously (See
table V.1) and would not result in the potential safety harms discussed
above. Furthermore, Saczalski does not provide a compelling reason why
a body block test would be the most effective way to test rearward
moment strength statically. NHTSA notes that Saczalski is also
requesting a dynamic requirement, and he did not explain why amending
the FMVSS to use a body block for the static test would be necessary if
NHTSA were to accept his recommendation to incorporate a dynamic test
with a more biofidelic dummy.
Table V.1--Past Recommendations for Revising the Quasi-Static Seat Back Torque Requirement in FMVSS No. 207
--------------------------------------------------------------------------------------------------------------------------------------------------------
Current standard Recommendations
-----------------------------------------------------------------------------------------------------------------------
Test reference FMVSS No. 207 Saczalski (1989 Saczalski (2014
(since 1968) Severy (1969) NHTSA (1974 NPRM) petition) Viano \1\ (2003) petition)
--------------------------------------------------------------------------------------------------------------------------------------------------------
H-point moment, min............. 373 Nm (3,300 in- 11,300 Nm (100,000 373 Nm (3,300 in- 6327 Nm (56,000 in- 1700 Nm (15,000 in- 2260 Nm (20,000 in-
lb). in-lb). lb). lb). lb). lb).
Seat back requirement........... ``withstand'' .................. .................. ``withstand'' specifics given ``withstand''
torque. torque. below. torque.
Seat back rotation, max......... .................. 10 deg............ 40 deg............
Load drop limit, max............ .................. .................. .................. .................. 2000 N over 1780 N ``sudden''.
10[deg] rot.
Load application................ upper member of upper member of upper member of upper member of thru HIII-50M thru HIII-95M body
seat back frame. seat back frame. seat back frame. seat back frame. lower torso. block.
Seat stiffness, max............. .................. .................. .................. .................. 25 kN/m...........
Frame compliance, max........... .................. .................. .................. .................. 2.0 deg/kN........
Load limit, min................. .................. .................. .................. .................. 7.7 kN............
Seat twist, max................. .................. .................. .................. .................. 15 deg............
Dummy H-point upward displ., max .................. .................. .................. .................. 50 mm.............
(design target only).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Viano's quasi-static test equipment and procedure represents more of an alternate test method than a simple revision to FMVSS No. 207. Details are
described in Viano (2003), ``Resolving the debate between rigid (stiff) and yielding seats: seat performance criteria for rear crash safety,'' cited
earlier.
Saczalski also suggested that NHTSA impose a requirement so that,
when tested to failure, there is no sudden drop in load of 1,780 N (400
lb-f) or greater within a short span. NHTSA is also granting the
petition on this issue in part. NHTSA is aware of others who have
recommended similar changes in the past to assure a gradual deformation
of seat back components. NHTSA notes that Saczalski did not suggest an
objective and practicable test procedure. Depending on how a test is
carried out, a sudden load drop in a quasi-static test may not
necessarily indicate an unsafe design. Even a drop to zero is not
necessarily problematic if a slight perturbation in backward movement
brings the load back up. NHTSA seeks comment on this requirement. What
safety benefits could be obtained from such a requirement? Is there a
practicable and objective test procedure that can be developed?
(b) Structural Symmetry
To assure structural symmetry of the seat, Cantor petitioned for a
pass/fail limit for rearward seat back rotation of no more than 15
degrees from its initial seat back orientation (measured in real-time
during the test) and 10 degrees of differential rearward deflection
between the left and right sides for oblique impacts. NHTSA is granting
in part on this issue and seeks comment. In particular, does the
increased prevalence of dual recliners in the fleet remove any safety
benefits that may be gained from a structural symmetry requirement? If
not, what test procedures and anti-twisting standards should NHTSA
consider and why? NHTSA notes that Cantor does not provide data or
evidence supporting his proposed pass/fail limit or deflection amounts
proposed.
(c) Dynamic Rear Impact Test Design
Both Saczalski and Cantor petitioned NHTSA to add a new dynamic
crash test to FMVSS No. 207, which would test seat back performance
using a 1,368 kg (3,015 lb) deformable barrier that strikes the rear of
the vehicle at 80 km/h.\145\ NHTSA is granting the petitions in part on
this issue and seeks comment on the analysis below. NHTSA has
previously considered, in the 1974 NPRM, adding a new dynamic
requirement of the type recommended by Saczalski and Cantor. Table V.2
shows the various dynamic rear impact tests that have been proposed and
considered in the past.
---------------------------------------------------------------------------
\145\ This barrier test would be similar to the barrier test
that NHTSA included in its latest revision of the FMVSS No. 301; see
68 FR 67068 (Dec. 1, 2003).
[[Page 58023]]
Table V.2--Past Recommendations for a Dynamic Seat Back Strength Requirement
--------------------------------------------------------------------------------------------------------------------------------------------------------
Saczalski 1989 Saczalski 2015
Nash 1974 NPRM 1974 \1\ Cantor 1999 \2\ Viano 2002 \4\ Cantor 2015
--------------------------------------------------------------------------------------------------------------------------------------------------------
Test type.................... FMVSS No. 301 FMVSS No. 301 FMVSS No. 301 FMVSS No. 301 Sled test...... FMVSS No. 301 FMVSS No. 301
(1974). (1974). (1974). (1974). (2003). (2003).
Impactor speed \3\........... 48 km/h......... 48 km/h......... 48 km/h......... 48 km/h......... 30-36 km/h\3\.. 80 km/h........ 80 km/h.
Barrier specs................ 1814 kg rigid... 1814 kg rigid... 1814 kg rigid... 1814 kg rigid... ............... 1368 kg 1368 kg
deformable. deformable.
Impact angle................. +/- 30 deg...... 0 deg........... 0 deg........... 0 deg........... 0 deg.......... 0 deg.......... +/- 30 deg.
Impact overlap............... 100%............ 100%............ 100%............ 100%............ 100%........... 70%............ 70%.
Dummy size................... HII-50M......... HII-50M......... HIII-95M........ 50M2............ HIII-50M....... HIII-95M....... HIII-50M.
Rear seat dummy.............. ................ ................ ................ ................ ............... CRABI-12M in ...............
FFCS.
Seat back rotation, max...... No fail......... 40 deg.......... 40 deg.......... 15 deg.......... 35 deg......... 25 deg......... 15 deg.
Seat back twist, max......... ................ ................ ................ ................ 8 deg.......... ............... 10 deg.
Head, HIC.................... ................ ................ ................ unspecified ............... CRABI 390 ...............
value. [verbar] HIII
700.
Head/neck extension.......... 45 deg.......... ................ ................ ................ 45 deg......... n/a............ 10 deg.
Neck moment.................. 45 deg.......... ................ ................ unspecified 20 Nm.......... CRABI 17 Nm ...............
value. [verbar] HIII
179 Nm.
Neck x-displacement.......... ................ ................ ................ ................ 60 mm.......... n/a............ ...............
Neck y-displacement.......... ................ ................ ................ ................ 30 mm.......... n/a............ ...............
Chest deflection............. ................ ................ ................ ................ ............... CRABI 30 mm ...............
[verbar] HIII
70 mm.
Femur load................... ................ ................ ................ ................ ............... CRABI n/a ...............
[verbar] HIII
12.7 kN.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Contained within Saczalski's comments to NHTSA's 1989 Request for Comments. See Regulations.gov, Docket Document No. NHTSA-1996-1817-0024.
\2\ Contained within Cantor's presentation to NHTSA on November 18, 1999. Cantor recommended the use of a dummy designed with an articulated pelvis. See
Regulations.gov, Docket Document No. NHTSA-1998-4064-0030 for a copy of the presentation.
\3\ Except for the Viano (2003) recommendation, the impactor speed for each recommendation represents the speed of the moving barrier when it strikes
the stationary test vehicle. The Delta-V experienced by the test vehicle is about half of the impactor speed, depending on the mass of the vehicle.
For the Viano recommendation, the 30-36 km/h impulse for the sled test corresponds to the Delta-V range observed in FMVSS No. 301 rigid barrier tests
run at 54.2 km/h (33.2 mph).
\4\ Saczalski's 2015 petition recommended use of ``NHTSA injury reference values for the head, neck, chest, and extremities'' for the HIII-95 seated in
the front and the CRABI seated in the rear. For convenience, we have entered IARVs for the CRABI ``C'' and the HIII-95M ``H'' in the table above that
correspond to those that NHTSA recommended in Eppinger, 2000 (cited earlier)
(1) The Saczalski Petition
In his petition, Saczalski states that a dynamic test is needed,
but he does not explain the reason that he recommends using a
deformable barrier travelling at 80 km/h, a HIII-95M in the front seat,
and a rear seated CRABI in a forward-facing child restraint.
NHTSA believes that his recommendations are intended to represent
the crash Saczalski studied in his 2014 FISITA paper, a real-world
crash that involved an infant fatality in the rear seat.\146\ For the
paper, Saczalski reconstructed the crash by staging a crash test on the
same vehicle model (a 2004 Chrysler minivan) with a CRABI dummy in the
child restraint and an HIII-95M in the front seat. A crash pulse
generating a [Delta]V of 40 km/h was applied. The test resulted in seat
back yielding and head-to-head contact between the two dummies. This
produced a head injury criteria (HIC) of 3192 in the CRABI dummy, which
is well above the reference value of HIC = 390.
---------------------------------------------------------------------------
\146\ The crash Saczalski describes in a forward-facing child
restraint, and a rearward [Delta]V of 40 km/h. (Note: [Delta]V is
the change in velocity of a vehicle due to a crash or impulse. In
this instance, the 80 km/h barrier impact with a stationary vehicle
resulted in a [Delta]V of 40 km/h.)
---------------------------------------------------------------------------
Saczalski then re-ran the test but replaced the minivan's standard
front seat with a stronger seat removed from a 2004 Chrysler
convertible. This was a belt integrated seat design, where the torso
belt anchorage was attached to the seat back. For such a seat design,
the seat back attachment to the seat base must be much stronger than a
typical design because it must be capable of sustaining the seat belt
loading from frontal crashes. According to Saczalski, the replacement
seat did not yield significantly in the crash, resulting in no head-to-
head contact and a very low (HIC=36) HIC value of the CRABI dummy. In
addition, Saczalski presented a process by which he was able to develop
a predictive equation for determining HIC in the CRABI dummy as a
function of the front seat occupant mass and the impulse of the crash
([Delta]V), which involved running slight variations of the above-
described scenario multiple times using the same model of 2004 Chrysler
minivan. Based on Saczalski's findings, to avoid occupant to occupant
interaction in the particular crash he studied, the seat back of the
front seat would need to be strong enough to not excessively yield in a
crash that involves a [Delta]V of 40 km/h when the seat is occupied by
a HIII-95M dummy.
Saczalski's analysis in his FISITA paper is informative, but
insufficient to support a final rule implementing the test parameters
utilized and suggested in his petition. First, it is based on tests of
only a single vehicle model (a 2004 Chrysler minivan), two seat
designs, and a single child restraint system (CRS) model. Additional
data from a wider variety of vehicles, seats, and CRS models would be
needed to determine whether Saczalski's findings in his FISITA paper
are consistent across the U.S. fleet of passenger cars. Of particular
concern is the fact that the belt integrated seat design used as an
acceptably performing seat is relatively rare in the fleet (primarily
used in convertibles) and designed for seat belt loading in the frontal
direction.\147\
---------------------------------------------------------------------------
\147\ 2016-2016 estimates put convertible sales at approximately
1.9% in the U.S. Source: https://www.iseecars.com/most-convertibles-by-state-2017-study.
---------------------------------------------------------------------------
Second, the tests use a front seat test dummy, the HIII-95M, which
is not a regulated test tool and may not have the full scope of
necessary traits for rear impact testing at high speed. In particular,
the HIC response generated by the dummy may be of limited value for
analyzing the situation in question because the rear part of the
dummy's
[[Page 58024]]
head, which contacts the child dummy, is not designed to provide an
internal or external biofidelic impact.
Third, the predictive HIC equation on which Saczalski based his
recommended test setup does not use adequate statistical methods. It is
generated using only five data points, potentially making it
insufficiently robust. Moreover, it bases the prediction through two of
the more extreme data points, while ignoring the other three. As a
result, the predictive function fits the two selected points perfectly,
but very poorly fits the others. Finally, because standard regression
techniques were not applied, there were no statistical computations of
standard errors or other measures of fit, such as R-squared. Given
these shortcomings, NHTSA does not believe it could base its selection
of test parameters in a new dynamic seat back strength test on
Saczalski's data. NHTSA seeks comment on this analysis and whether
there is additional supporting data for Saczalski's proposed test
design.
(2) The Cantor Petition
Cantor similarly does not provide support for the test parameters
he chose in his recommendation for a dynamic rear-impact seat back
strength test. He argues that because the impulse created by the 80 km/
h barrier is appropriate for the FMVSS No. 301 fuel system integrity
standard, it would also be appropriate for setting a minimum seat back
requirement. This is a generalization that requires further
justification. Because the minimum requirements for seat back strength
and fuel system integrity do not address the same safety concerns,
NHTSA believes this is insufficient basis, on its own, to implement
this test parameters.
Finally, NHTSA would need to show that any dummy used in a new
dynamic test is chosen appropriately. The petitioners suggested the use
of a Hybrid III dummy (HIII-95M by Saczalski; HIII-50M by Cantor). As
stated, in regard to Saczalski's 2014 FISITA paper, the Hybrid III
dummies have significant biofidelity limitations when used for rear
impact analysis. NHTSA seeks comment on whether there is evidence
showing these limitations are acceptable and would lead to appropriate
seat designs if these dummies are chosen for a new dynamic test in
FMVSS No. 207.
2. Matters on Which NHTSA Is Denying the Petitions
(a) Incorporate a Cargo Stipulation Into FMVSS No. 207
Saczalski requested that NHTSA amend FMVSS No. 207 to include a
cargo stipulation in a dynamic vehicle test. Saczalski argued that
deformation of the rear of the vehicle caused by crash forces could
cause loose cargo stored in the rear (or trunk) to be pushed forward
into the back of the second row of seats, causing those seats and their
occupants to in turn be pushed forward into the back of the front row
seats.
NHTSA previously denied a similar request from Cantor in 2004, and
Saczalski did not provide additional field data or analysis to support
adding specifications for cargo placement.\148\ Without further
analysis, NHTSA is not considering incorporating a cargo stipulation in
FMVSS No. 207 at this time. This decision will allow NHTSA to focus its
resources more fully on the aspects of the petitions related to
rearward seat back strength.
---------------------------------------------------------------------------
\148\ Cantor sought inclusion of an unrestrained cargo test for
the safety of occupants in the rear seat. 71 FR 70477 (Dec. 5,
2006). 71 FR 70478. NHTSA denied that petition because the incidence
of injuries caused by loose luggage was very low and did not warrant
an amendment to a Federal safety standard, and Cantor did not
provide any field data demonstrating a correlation between cargo
intrusion and occupant safety.
---------------------------------------------------------------------------
(b) Amend FMVSS No. 209 To Require That Seat Belts Remain on Pelvis
Under All Conditions
Cantor requested NHTSA restore language, previously deleted in
1999, in FMVSS No. 209 requiring that the pelvic restraint portion of
both Type-1 and Type-2 seat belts remain on the pelvis under all
conditions.\149\ NHTSA is denying this request.
---------------------------------------------------------------------------
\149\ The paragraph in question, S4.1(b), read as follows:
``4.1(b) Pelvic restraint. A seat belt assembly shall provide pelvic
restraint whether or not upper torso restraint is provided, and the
pelvic restraint shall be designed to remain on the pelvis under all
conditions, including collision or roll-over of the motor vehicle.
Pelvic restraint of a Type 2 seat belt assembly that can be used
without upper torso restraint shall comply with requirement for Type
1 seat belt assembly in S4.1 to S4.4.''
---------------------------------------------------------------------------
Cantor states that restoration of this paragraph will prevent
ramping by assuring that manufacturers install a device that keeps the
lap belt portion of the seat belt on the pelvis under all crash
conditions. According to Cantor, technology that would prevent ramping
is already available on the market, including the following: a sliding/
cinching latch plate to prevent excess shoulder belt webbing from
transitioning to the lap belt portion and causing the lap belt to go
slack; an integrated seat in which both lap and shoulder belt anchors
are mounted to the seat; and seat belt pretensioners sensitive to rear
impacts and designed to work with an integrated seat with a belt
configuration as described above.
The agency removed this stipulation from the standard in 1999
because it was deemed redundant and unnecessary.\150\ FMVSS No. 208,
other provisions in FMVSS No. 209, and FMVSS No. 210 contained more
specific requirements that collectively have the effect of requiring
pelvic restraint and thereby reducing the likelihood of occupants
submarining \151\ during a crash. It was also deemed unenforceable
because the regulation did not provide an objective means to determine
that a lap belt complied with the requirement and was in fact
``designed'' to remain on the pelvis. In addition, NHTSA noted that the
meaning of the words, ``remain on the pelvis,'' was unclear. Because
these conditions and reasons have not changed since that action was
taken, NHTSA will not reinstate the requested language.
---------------------------------------------------------------------------
\150\ 64 FR 27203 (May 19, 1999).
\151\ ``Submarining'' refers to the tendency for a restrained
occupant to slide forward feet first under the lap belt during a
vehicle crash, which could result in serious abdominal, pelvic, and
spinal injuries.
---------------------------------------------------------------------------
(c) Add a Rear Impact Test to FMVSS No. 213, Child Restraint Systems
Saczalski requested that NHTSA revise FMVSS No. 213 by including a
rear impact requirement for child restraint systems like the one
described in ECE Reg. No. 44. Saczalski's only change from Reg. No. 44
is performing the rear impact test at a 40 km/h velocity instead of 30
km/h. Saczalski stated that such a revision is necessary to prevent
rear facing child restraint systems (CRSs) from folding rearward when
they become trapped between a rear seat and a yielding front seat back
during a rear impact crash.\152\
---------------------------------------------------------------------------
\152\ This condition was highlighted in Saczalski's 2014 FISITA
paper.
---------------------------------------------------------------------------
NHTSA is denying this request for change. NHTSA considered adopting
ECE Reg. No. 44's rear impact test into FMVSS No. 213 in the past.\153\
In a 2002 ANPRM, NHTSA discussed agency tests evaluating ECE Reg. No.
44's rear impact test conducted at 30 km/h (18.6 miles per hour), with
peak deceleration between 14 g and 21 g over a 70-millisecond time
period. The tests were dynamic sled testing performed by NHTSA in
research on FMVSS No. 202 and FMVSS No. 207, where NHTSA added a rear-
facing child restraint with a 12-month-old test dummy to a 1999 Dodge
Intrepid vehicle seat. One test, simulating a dynamic FMVSS No. 202
[[Page 58025]]
condition, was conducted at approximately 17.5 km/h (11 mph). The other
two tests were conducted at approximately 30.5 km/h (19 mph). In all of
the tests the 12-month-old dummy in the rear-facing child restraint was
able to easily meet the injury criteria of FMVSS No. 208, i.e. was
below the threshold for injury. After examining these data, comments to
the ANPRM, and data showing that fatalities for children in rear impact
crashes constitute a much smaller percentage of the total than other
crash modes, NHTSA decided to focus its resources on developing a side
impact test and not a rear impact test.\154\
---------------------------------------------------------------------------
\153\ NHTSA analyzed this issue in a rulemaking amending FMVSS
No. 213 pursuant to the Transportation Recall Enhancement,
Accountability and Document Act (TREAD Act), November 1, 2000,
Public Law 106-414, 114 Stat. 1800. The agency requested comments on
the merits of incorporating the rear impact test of ECE Reg. No. 44
into FMVSS No. 213 (ANPRM; 67 FR 21836, 21851 (May 1, 2002)).
\154\ NHTSA withdrew the rulemaking in a final rule, 68 FR
37620, 37624 (June 24, 2003). See also Report to Congress, ``Child
Restraint Systems, Transportation Recall Enhancement, Accountability
and Document Act,'' February 2004. chrome-extension://
efaidnbmnnnibpcajpcglclefindmkaj/https://www.nhtsa.gov/sites/nhtsa.gov/files/documents/tread.pdf.
---------------------------------------------------------------------------
NHTSA disagrees with Saczalski that there is a need to adopt a 40
km/h rearward impact test based on ECE Reg. No. 44. NHTSA does not
believe adopting such a rear impact test is warranted for a number of
reasons. First, rear impact fatalities among children restrained in
CRSs are generally in very severe crashes that result in significant
passenger compartment intrusion into the rear seating area. However,
the ECE Reg. No. 44 sled test requested by the petitioner does not
simulate such intrusion into the seating area. Second, the ECE test
protocol does not evaluate the circumstance about which Saczalski is
concerned. The rear impact test in ECE Reg. No. 44 does not have a
simulated front seat and therefore does not replicate the crash
scenario the petitioner seeks to evaluate. The standard seat assembly
in FMVSS No. 213 also does not include a simulated front seat, and it
is yet to be determined if a representative front seat could be
designed and whether it could be made to collapse in a compliance test
in a repeatable and reproducible manner.
Finally, the petitioner provides no information about a practicable
countermeasure that CRSs can provide that would prevent injuries and
fatalities if there is a front seat collapse and/or intrusion into the
rear seating area. NHTSA undertakes rulemakings on FMVSS No. 213
weighing various principles and considerations, in addition to the
considerations and requirements for FMVSS specified by the Safety Act,
statutory mandates, Executive Order (E.O.) 12866,\155\ and other
requirements for agency rulemaking. In making regulatory decisions on
possible enhancements to FMVSS No. 213, NHTSA considers the consumer
acceptance of cost increases to an already highly effective item of
safety equipment and whether an amendment could potentially have an
adverse effect on the sales of this product. The net effect on safety
could be negative if CRSs are not used as much because of cost
increases. NHTSA also weighs the effects of an amendment on the ease of
correctly using child restraints. We consider whether an amendment may
cause child restraints to become overly complex or frustrating for
caregivers, resulting in increased misuse or nonuse of the restraints.
The petitioner did not provide information that would enable NHTSA to
assess these practicability issues.
---------------------------------------------------------------------------
\155\ E.O. 12866, ``Regulatory Planning and Review,'' September
30, 1993, as amended by E.O. 14094.
---------------------------------------------------------------------------
Based on the forgoing, NHTSA is denying Saczalski's request to
amend FMVSS No. 213.
(d) NCAP Implementation
Cantor requested that NHTSA implement a rear-impact crash test into
the 5-star rating as part of his dual FMVSS/NCAP approach. NHTSA's
regulations at 49 CFR 552.3 state that a petition for rulemaking may be
filed respecting the issuance, amendment or revocation of a motor
vehicle safety standard. NCAP is not a motor vehicle safety standard.
Therefore, a petition for rulemaking is not the appropriate mechanism
for requests to amend the NCAP program. NHTSA therefore denies Cantor's
petition for rulemaking. After NHTSA's planned research is completed,
however, we will be in a better position to consider how best to
implement any necessary changes both in our standards and/or NCAP.
F. Conclusion of NHTSA Assessment of Cantor and Saczalski Petitions
In accordance with 49 CFR part 552 and after careful consideration,
Cantor's request to restore pelvic restraint language to FMVSS No. 209,
and Saczalski's request to add a rear impact test to FMVSS No. 213 and
to add a cargo test and requirement to FMVSS No. 207 are denied based
on the information presented above. This ANPRM provides the required
notification of the denial. As part of our effort to facilitate further
research and data development to support a potential rulemaking to
updated FMVSS No. 207, NHTSA grants in part both petitions regarding
updating the moment strength requirement in FMVSS No. 207 and the
development of updated static and dynamic test procedures for seat back
strength, and Cantor's petitioned-for request on structural symmetry.
NHTSA seeks comment on the issues discussed above.
G. Center for Auto Safety (CAS) Petition
On March 9, 2016, CAS petitioned NHTSA to amend FMVSS No. 208 and
FMVSS No. 213 to require additional warnings instructing parents to
place children in rear seating positions behind unoccupied front seats,
if possible, or behind the lightest front seat occupant.
CAS requested that FMVSS No. 208, S4.5.1(f), be amended so that the
vehicle owner's manuals be required to include the following language
(or similar):
``If possible, Children Should Be Placed in Rear Seating Positions
Behind Unoccupied Front Seats. In Rear-End Crashes, the Backs of
Occupied Front Seats Are Prone to Collapse Under the Weight of Their
Occupants. If This Occurs, the Seat Backs and Their Occupants Can
Strike Children in Rear Seats and Cause Severe or Fatal Injuries.''
CAS also requested that the label found at FMVSS No. 213, Figure
10, be amended to include the statement ``Place behind an unoccupied
front seat where possible.''
H. Analysis of CAS Petition
CAS requested that NHTSA add warning statements in the owner's
manual and on CRS labels to warn parents to ``Place behind an
unoccupied front seat where possible.'' Currently, the CRS label warns
of the potential injury that could result from placing a CRS in front
of an air bag but does not make any statement relating to where else in
the vehicle the CRS should not be placed. Moreover, the CRS label
instructs that ``The back seat is the safest place for children 12 and
under.'' \156\
---------------------------------------------------------------------------
\156\ FMVSS No. 213, Figure 10.
---------------------------------------------------------------------------
CAS does not provide analysis demonstrating a net benefit to
placing the child in a specific rear seat. Long established data show
that the rear seat is the safest place for children under the age of
13.\157\ Published NHTSA data shows that rear seats are 25-75 percent
more effective in reducing fatalities (compared to front seats) for
children 0-12 years old.\158\ However, the overall risk to CRS-seated
children in each rear position depends on many factors other than front
seat occupancy. These factors may include which side of the vehicle
[[Page 58026]]
is struck in a side impact (and where the CRS is placed in relation to
that impact) and the risks involved in more common frontal impacts. CAS
fails to provide sufficient data or other information to conclude that
the warning recommended in its petition would have any net benefit.
---------------------------------------------------------------------------
\157\ Braver, ER et al. Seating positions and children's risk of
dying in motor vehicle crashes. Inj Prev. 1998;4:181-187. Durbin, DR
et al. Effects of seating position and appropriate restraint use on
the risk of injury to children in motor vehicle crashes. Pediatrics.
2005;115:e305-e309.
\158\ Kuppa, S et al. Rear Seat Occupant Protection in Frontal
Crashes. 2005 Enhanced Safety of Vehicles Conference, Paper No. 05-
0212.
---------------------------------------------------------------------------
By contrast, there may be unintended safety harms that such a label
could generate. The suggested label could dilute the message about the
importance of placing children in the rear seat. It could be read by
some consumers as inconsistent with the label required by Figure 10 of
FMVSS No. 213 that the rear seat is the safest place for children aged
12 and under. Such inconsistency may confuse them and reduce the
efficacy of the current CRS label. The label could lead some caregivers
to install the child restraint system in a front seating position
rather than a rear seating position to avoid rear proximity to an
occupied front seat. This outcome could have severe consequences if the
rear-facing CRS were positioned in front of a deploying air bag.
Another unsafe outcome of such confusion could be some caregivers
deciding not to use a CRS at all with their child when the CRS cannot
be placed behind an unoccupied front seat. CAS did not provide any
assessment of the risk of unintended consequences related to the
petition for a label. The guidance recommended by CAS may result in the
continual removal and reinstallation of a CRS by parents, depending on
front seat occupancy, as they decide which seating position is safer.
Such actions could lead to fatigue, with some caregivers eventually
ignoring the instruction. Not only would that undermine the label's
purpose, but NHTSA is also concerned that caregivers may start to
ignore other instructions and warnings on the label, such as the
warning on the label required by Figure 10 not to place the CRS on the
front seat with an air bag. Such a warning is crucial to the safety of
the child and must be always followed.
Finally, NHTSA rejects CAS's request to add language to FMVSS No.
208, S4.5.1(f) and therefore required in owner's manuals, stating ``If
possible, Children Should Be Placed in Rear Seating Positions Behind
Unoccupied Front Seats. In Rear-End Crashes, the Backs of Occupied
Front Seats Are Prone to Collapse Under the Weight of Their Occupants.
If This Occurs, the Seat Backs and Their Occupants Can Strike Children
in Rear Seats and Cause Severe or Fatal Injuries.'' We are denying this
request for the same reasons discussed above, namely that CAS has not
provided supporting information demonstrating the benefit of the change
and has not provided analysis of unintended consequences that the
amendment may cause. We also emphasize that this language proposed for
the owner's manual, by focusing even more on the risk of seat back
collapse than the language proposed for the label, has added potential
to cause confusion beyond the language petitioned for the label.
Therefore, NHTSA will not incorporate the requested amendment.
For these reasons, NHTSA does not believe adopting CAS's
recommendation to change the CRS label or amend FMVSS No. 208,
S4.5.1(f) would be appropriate. The agency continues to promote the
message that the rear seat is the safest place for children. In
accordance with 49 CFR part 552 and after careful consideration, the
CAS petition for a labeling requirement to be added to FMVSS No. 213
and to amend FMVSS No. 208 is denied based on the information presented
above. This ANPRM provides the required notification of the denial.
VI. Unified Approach to Rear Impact Protection
A. Introduction
As NHTSA undertakes this process, our main considerations, as
always, are safety and the obligations the agency has under the Vehicle
Safety Act. IIJA requires that we publish this ANPRM to update FMVSS
No. 207. Throughout this rulemaking effort, we need to take into
account the Safety Act's imperative that FMVSS be practicable, meet the
need for motor vehicle safety, and be stated in objective terms. The
long-term and ongoing challenge to meeting these goals has been to
develop an update to FMVSS No. 207 and rear impact protection in
general that effectively balances the tradeoffs to improve overall
safety with a reasoned consideration of all factors involved. As far
back as 1974, NHTSA understood that there would be advantages in taking
a more unified approach to rear impact protection. The 1974 NPRM
preamble stated that consolidation of Standards 202 and 207 logically
reflects the relationship of the seat and its head restraint and would
improve the possibilities of eventually testing the whole seating
system with a dynamic test procedure.
In 1992, the agency again signaled that it continued to believe
that a unified approach was likely the best approach to rear impact
protection. In that report, the agency stated that there are four
categories of performance issues that need to be addressed as part of
future changes to FMVSS No. 207. These four categories are: (1) Seating
system integrity; (2) Seat energy absorbing capability; (3)
Compatibility of a seat and its head restraint; and (4) Seat and seat
belt working together. In the 2004 final rule to update FMVSS No. 202,
NHTSA again reiterated the ultimate goal of adopting a method of
comprehensively evaluating the seating system.
The four rear impact protection categories outlined in 1992
indicate the need to maintain a balance between energy absorbing and
stiffness characteristics and the fact that the severity and type of
occupant injuries varies with impact velocity in rear collisions. Low-
to-moderate velocity crashes represent the majority of rear collisions,
and these crashes are responsible for the majority of reported
injuries, mainly whiplash. At higher impact velocities the injury risks
for the occupant of a seat include bodily impact with vehicular
structures, severe thorax, pelvis, and neck injuries, and other
risks.\159\ Additionally, at higher impact velocities deformation of
the seat sufficient to allow interaction between front and rear
occupant rows and associated injuries can occur. The debate around
FMVSS Nos. 202a and 207 concerns how effective these standards are in
mitigating these risks and the inevitable tradeoffs.
---------------------------------------------------------------------------
\159\ We note that 2017-2020 CISS data indicates that at all
rear impact crash speeds whiplash remains more frequent than any
MAIS 2+ injury.
---------------------------------------------------------------------------
NHTSA seeks comment broadly on an update to the FMVSS regarding
occupant protection in rear impacts. Even if it has been clear for many
years that the ideal approach to rear impact safety would incorporate
consideration of both moderate and severe rear impacts, is there a
sound scientific basis for a reasonable update to the standards for
rear impact protection and are the necessary technical tools available
for a sound rulemaking proposal? Can we have a high degree of
confidence that any such proposal will be generally beneficial? In the
following section, we further analyze, discuss, and seek comment on
potential paths forward for an update to rear impact protection
required by the FMVSSs, with emphasis on a unified approach.
B. FMVSS No. 207
Generally, the discussion around FMVSS No. 207 has been a narrow
focus on seat back strength. However, occupant protection in rear
impact involves many other issues. Some, such as Prasad in 1997 and
Burnett in 2004,
[[Page 58027]]
suggested that seat back strength has limited correlation with occupant
dynamics prior to seat back failure. Such conclusions, however, were
drawn from older designs whose seat strength is much lower than some
have proposed for a FMVSS No. 207 upgrade.\160\ Nonetheless, in its
present form, the standard provides limited guarantees on how an
occupant will respond to a rear collision prior to the seat back
failing. In fact, the FMVSS No. 202a requirements likely have a greater
influence on occupant protection because the majority of rear
collisions yield minor or no injuries and occur at relatively low
[Delta]Vs. For example, table II.3 shows NHTSA's estimate that in rear
collisions, 96% of injuries were MAIS 1-2 and, if [Delta]V was known,
76% of MAIS 1-2 injuries occurred at [Delta]V of 30 km/h or less.
Therefore, the present scope of FMVSS No. 207 is limited in the sense
that it focuses only on the first category of the four seat performance
categories for rear impact protection, i.e., seating system integrity.
---------------------------------------------------------------------------
\160\ See table VI.1, above.
---------------------------------------------------------------------------
Furthermore, a very high seat back strength requirement in FMVSS
No. 207 would likely result in a seat back with very high stiffness due
to the necessary structural reinforcements. Such seats may impose high
occupant loading due to rapid acceleration in higher speed rear
impacts.\161\ However, whether such loading is necessarily injurious,
the speeds at which such loading may be injurious, and whether the
trade-offs between stiffness and injury are inherent or can be
compensated for in other design elements, are all matters to be
considered. On the other hand, a seat back with very low strength may
quickly reach a rotation limit, or fail, at lower rear impact speeds.
---------------------------------------------------------------------------
\161\ The reader is referred to the increased risks as noted in
the 1997 Prasad study and concerns drawn out from the 1989 Request
for Comments. We note, however, that these conclusions are based on
seats that are now decades old. A more recent examination of this
can be found in 2023 Kang, for a very severe rear impact condition
and a rigid seat structure.
---------------------------------------------------------------------------
In striking this balance, manufacturers have, in general, settled
on seat back strength that has increased on average over the decades to
many times the value set by FMVSS No. 207.\162\ Viano, et al., for
example, noted that MY 1990s dual recliner seats had an average peak
moment strength of 1,970 Nm while MY 2000s era dual recliner seats had
an average peak moment strength of 2,360 Nm.\163\ As noted in the 2019
Edwards study,\164\ it appears as if some manufacturers have strived to
achieve balance in modern seating systems between low-speed whiplash
protection and structural integrity at higher speeds.
---------------------------------------------------------------------------
\162\ Saunders, J., Molino, L.N., Kuppa, S., and McKoy, F.L.
Performance of seating systems in a FMVSS No. 301 rear impact crash
test. Proceedings of 18th International Technical Conference on the
Enhanced Safety of Vehicles, 2003. Nagoya, Japan.
\163\ Viano, David C., et al. ``Occupant responses in
conventional and ABTS seats in high-speed rear sled tests.'' Traffic
injury prevention 19.1 (2018): 54-59.
\164\ Edwards, Marcy A., et al. ``Seat design characteristics
affecting occupant safety in low-and high-severity rear-impact
collisions.'' IRCOBI Conference, Florence, Italy, IRC-19-11. 2019.
---------------------------------------------------------------------------
Currently, FMVSS No. 207 addresses a segment of the overall rear
impact protection issue. In addition, the regulated seat strength set
by FMVSS No. 207 is considerably lower than the average seat strength
of modern production seats. The following section outlines different
approaches for updating the standard to enhance or broaden the scope of
rear impact protection, thereby further addressing the rear impact
protection points set by NHTSA.
C. Analysis of Approaches To Updating Standards for Occupant Protection
in Rear Impact
1. Seat Back Strength and Other Mechanical Properties
A foundational consideration for updating standards related to rear
impact protection is the strength of cantilevered seat backs in the
rearward direction, regardless of how the seat back strength is tested
or measured. The current strength level set by FMVSS No. 207 is far
below the average design strength of production seats. As a result,
manufacturers have great flexibility in seat back design. This
flexibility allows manufacturers to readily adopt new technology such
as active head restraints, and to allow their seat designs to quickly
evolve as the understanding of rear impact protection changes. Any
increase in the seat back strength requirement will reduce manufacturer
flexibility. Furthermore, any new strength requirement should reduce
injuries and adequately balance tradeoffs. As with any other regulatory
change, due consideration must be given to overall cost effectiveness
of proposed changes to the regulatory regime.
As a starting point, the required level of seat back strength
should limit the interaction between the occupants of different rows of
seats in a rear impact. It is not clear, however, what level of crash
severity is sufficient to protect against and for what size of
occupant. No seat strength requirement can protect all occupants in all
possible rear impact severities, but the selected strength should
attempt to be protective of as many occupants as possible within the
constraints of practicality and cost. Therefore, we seek comment on the
correct minimum seat back strength requirement. We further seek comment
on ways this parameter can be tested and measured. We also seek comment
on the benefits or harm generated by the manufacturer flexibility
allowed by a low minimum seat back strength requirement, and how NHTSA
should understand those benefits or harms as well as the cost to
manufacturers to comply with alternative elevated lower bound seat back
strength options.
Another issue is energy absorption. The energy absorption or force-
deflection characteristics of seat backs are currently not regulated by
FMVSS No. 207. Controlled deformation of the seat back allows the
occupant of a seat to ride-down a crash in a manner that may minimize
injury. However, if the seat back absorbs the crash energy elastically
rather than irreversibly,\165\ there may potentially be injurious
rebound of the occupant. Thus, remaining residual energy after occupant
ride-down may be an important consideration. We note that FMVSS No. 222
incorporates a rearward energy absorption and force deflection
requirement for school bus seat backs. We seek comment on whether a
similar requirement should be incorporated into FMVSS No. 207 and what
the performance level should be.
---------------------------------------------------------------------------
\165\ When the seat back deforms elastically it absorbs energy
like a spring and will return to its original position and shape
after the applied force is removed. When the applied force is
sufficient to cause yielding in the seat back there is irreversible,
also termed inelastic or plastic, deformation in the seat back which
permanently absorbs some energy; in which case the seat back will
not return to its original position and shape after the applied
force is removed.
---------------------------------------------------------------------------
Older seat designs have typically used a single recliner mechanism
to control seat back rotation. Because of the nature of such a design,
rearward seat back load is not uniformly restricted, leading to one
side of the seat back rotating more than the other; this lack of
structural symmetry may lead to a subsequent twisting of the seat back.
It has been theorized that such twisting reduces the ability of the
seat back to prevent occupant ramping. Both of the current petitions
discussed earlier in this ANPRM desired some limit to be placed on seat
twist. We seek comment on whether a similar requirement is needed, what
the performance level should be and how it should be measured.
We also seek comment on whether an updated FMVSS should regulate
other seat characteristics that may be related
[[Page 58028]]
to occupant ramping, such as pocketing and the coefficient of friction
of the upholstery. We also seek comment on any other seat
characteristics that should be regulated for rear impact protection.
2. Test Parameters
This section discusses and requests comment on means of testing or
measuring seat parameters. We first discuss the benefits and
limitations of a quasi-static approach. Afterward, we discuss and seek
comment on a dynamic testing regime that utilizes two testing speeds to
cover the variety of rear impact occupant protection scenarios.
3. Quasi-Static Testing
One approach to update FMVSS No. 207 is to increase the required
seat back moment while retaining the current test procedure of loading
the upper frame member or some other part of the seat back. This is
appealing in its simplicity but has some potential shortcomings. First,
the required moment is specified to be applied through a horizontal
force and a distance from the seating reference point. This works well
as an initial condition and within the required moment value, which
typically results in a relatively small amount of seat back rotation.
Depending on the increase in moment value, however, significant seat
back deformation could occur during testing. In this circumstance,
maintaining a horizontal load throughout the test becomes a serious
challenge.
In addition, it is not clear that loading the seat back at the
upper crossmember is the best way to quasi-statically load the seat
back. Over the years, several different methods of loading the seat
back have been developed that may better achieve the goals of the
test.\166\ For example, NHTSA has tested seat backs to failure by
modifying the FMVSS No. 207 procedure such that the loading arm rotates
with the seat back and the initial direction of loading perpendicular
to the seat back as specified by SAE J879.\167\ Some methods involve
the use of body-blocks or counter balanced ATDs, pushed or pulled into
the seat back, which loads the seat back in a manner more closely
related to how a human may load the seat back. Such methods can also
measure force-deflection in addition to strength.
---------------------------------------------------------------------------
\166\ Burnett, R; Viano, D; Parenteau, C; (2022) ``Quasi-Static
Methods to Evaluate Seat Strength in Rear Impacts.'' Traffic Injury
Prevention.
\167\ Molino, L (1998): Determination of Moment-Deflection
Characteristics of Automobile Seat Backs. NHTSA Technical Report,
DOT Docket Management System NHTSA-1998-4064.
---------------------------------------------------------------------------
However, existing quasi-static test procedures are also limited
because they can tell us how the seat reacts when it is loaded, but
they cannot tell us whether the seat's characteristics are potentially
injurious to or protective of the occupant in certain rear impacts.
Thus, the value of the quasi-static method may be limited if the
relationship between mechanical seat properties and occupant response
in a rear impact is not well understood. This may lead to a lack of
optimization and the potential introduction of harmful seat behavior.
We seek comment on the use of quasi-static testing in an updated
rear impact occupant protection regime. Could changes be made to quasi-
static procedures or loading devices that would help discern the effect
of the seat design on the seat's occupant? Is this important to fully
understand how changes to seat strength or other seat design parameters
will affect the occupant prior to determining what level of increase in
minimum seat back strength is sufficient? Is this information necessary
to develop objective measures, tests, and strength requirements for
seat backs?
The above discussion is primarily related to determining seat back
performance at higher severity levels. Any unified approach, however,
must also consider the frequent lower speed rear impacts correlated to
whiplash injury. Currently, FMVSS No. 202a requires the head restraint
to have a minimum height and maximum backset or optionally limit the
head to torso rotation of a Hybrid III dummy in a sled test. What
changes can be made to the test method and standard for head restraints
from a quasi-static requirement perspective that may improve the
protection against whiplash in moderate severity rear impacts and/or
create more synergistic total rear impact protection?
4. Dynamic Testing
Considering the limitations of quasi-static testing in an
environment with significant uncertainty regarding injury dynamics, a
dynamic assessment of seat behavior at multiple impact severities may
be a more effective method for achieving a unified and synergistic
approach to rear impact protection. As noted above, this approach has
been a feature of past efforts to update standard FMVSS No. 207 and is
also consistent with the four rear impact protection points. In this
section, we discuss and seek comment on various dynamic testing
approaches to achieve the goal of improved rear impact protection.
Topics of discussion include test speeds, seat performance measures,
ATD selection, and ATD performance measures.
To fully assess the four rear impact protection points, NHTSA is
considering a dynamic approach that contains both a low and high-speed
test. Each of these regimes place distinct requirements on the seating
system, and a dual speed regime can help ensure balance in rear impact
protection. NHTSA believes a two-tiered approach will preserve seat
design flexibility while improving protection for the occupant across a
range of rear impact severities.
NHTSA is considering which ATDs are best suited to use in rear-
impact dynamic testing, at both low and high-speed. A low-speed test
would assess the seating system's ability to protect against injuries
to the cervical spine. As mentioned previously, FMVSS No. 202a
currently includes a low-speed sled test option using the HIII-50M test
dummy. NHTSA is considering a similar test utilizing the BioRID 50th
percentile male dummy and believes this dummy provides significant
improvements over other ATD options. A high-speed test would assess the
rear impact regime where significant rearward rotation of the seat back
may occur, and occupant retention becomes a concern as well as contact
with rear seat occupants. An ATD used for this type of test should have
characteristics that replicate the interaction of the occupant with the
seat back. NHTSA is also considering BioRID for use in the higher speed
test but acknowledges that the two test severities require different
ATD capabilities. NHTSA is aware of a female rear impact dummy finite
element model, EvaRID FE, which is a scaled down version of the BioRID,
with mass and geometrical dimension representing a 50th percentile
female. The agency is also aware of the development of a prototype 50th
percentile female rear impact dummy known as the BioRID-P50F,\168\ and
is also interested in, and seeks comment on, the potential for its use
and to what extent its state of readiness is consistent with a
potential rulemaking proposal. The agency seeks comment on which ATDs
would be most appropriate to use in both low and high-speed rear impact
testing of seats, and whether using two different sized ATDs (for
example, BioRID and BioRID-P50F) in one or both of these test
configurations would
[[Page 58029]]
offer a more comprehensive assessment of seat performance.
---------------------------------------------------------------------------
\168\ The physical BioRID-P50F dummy is currently in prototype
stage and not available for evaluation by the agency.
---------------------------------------------------------------------------
(a) Low-Speed Test
An upgraded low-speed test would assess the energy absorption
characteristics and compatibility of the seat and head restraint with
respect to occupant protection in low severity rear impacts. The
primary concern in low-speed rear impacts are cervical spine injuries
associated with whiplash. Therefore, a low-speed test should promote
best practices that mitigate whiplash beyond what is currently achieved
by FMVSS No. 202a by ensuring compliance with a standard that
establishes a minimum level of injury prevention. During the rulemaking
establishing FMVSS No. 202a, the agency acknowledged commenters'
criticism of the biofidelity sufficiency of the HIII-50M used in 202a,
particularly its neck, in the rearward direction.\169\ Thus, it is
appropriate for the agency to explore the use of alternative ATDs such
as BioRID, which may more accurately replicates spinal, torso and head
motion. As discussed below, this comes with challenges in determining
an acceptable and repeatable biomechanical measurement. Below, we
discuss and seek comment on certain considerations relevant to a low-
speed test: test pulse and injury criteria and test repeatability.
---------------------------------------------------------------------------
\169\ 69 FR 74873 (Dec. 14, 2004); The agency concluded at that
time that the HIII-50M was sufficient to discern between acceptably
safe head restraint systems and those that allow unacceptable levels
of head-to-torso rotation. Nonetheless, the agency stated it was
likely ``to revisit the decisions made in [the] final rule about
dynamic performance values and the test device as more advanced
dummies are developed and the injury criteria achieve broader
consensus.''
---------------------------------------------------------------------------
First, we consider the appropriate test pulse. The low-speed regime
is typically associated with rear impact [Delta]V between 16 and 24 km/
h. The dynamic sled test option in FMVSS No. 202 has a [Delta]V target
of 17.3 0.6 km/h. The Euro NCAP whiplash assessment uses
low, medium and high severity sled acceleration corridors with target
[Delta]Vs of 16.10, 15.65 and 24.45 km/h. The IIHS dynamic whiplash
rating uses a simulated rear impact conducted on a sled using a
[Delta]V of 10 mph. In addition to the issues outlined below, NHTSA
seeks comment on the test pulse for a low-speed rear impact test, such
as [Delta]V and acceleration profile.
Next, we consider injury criteria and test repeatability. Current
low-speed testing practices present challenges with well-defined injury
criteria and repeatability of the tests. The understanding of whiplash
injury mechanisms continues to evolve, and contemporary ATD injury
criteria are therefore derived from nonlinear statistical correlations
with biomechanical data. Because of this evolving understanding,
existing dynamic whiplash assessments use a range of ATD measures. For
example, the 2009 EuroNCAP dynamic whiplash ratings system \170\
calculates a rear impact seat performance rating using a combination of
seven measures from rear impact sled testing using the BioRID ATD.
These measures are:
---------------------------------------------------------------------------
\170\ van Ratingen, Michiel, et al. ``The Euro NCAP whiplash
test.'' 21st international technical conference on the enhanced
safety of vehicles. 2009.
NIC (neck injury criteria),
Nkm (shear force and bending moment),
Head rebound velocity,
Fx upper neck shear,
Fz upper neck axial force,
T1 acceleration up to head contact, and
Head restraint contact time
Any assessment based on a threshold value of these parameters
should accurately assess the injury risk. To be objective, the ATD
metrics of a low-speed test should also be based on a fundamental
understanding of the biomechanical injury mechanisms. For example, NIC
is based on the principle of neck retraction prior to the head
contacting the head restraint, described earlier in the Neck injuries
subsection, leading to injurious pressure waves in the spinal
canal.\171\ An injury threshold of 15 m\2\/s\2\ for the NIC was
suggested \172\ after analyzing human volunteer results \173\ to find a
lower bound of injury tolerance. However, the predictive basis of ATD
metrics for low-speed injury are usually based on a statistical
nonlinear analysis of biomechanical data and shows varying degrees of
success in predicting real world outcomes. In the 2019 Edwards
study,\174\ the authors compared low-speed BioRID measurements with
insurance claim data. The standard whiplash metrics, such as those
listed above, did not have a significant correlation with the insurance
claim data for all the seats analyzed. The longitudinal pelvis
displacement of the BioRID dummy into the seats, an atypical metric in
whiplash assessments, had the most significant correlation with
insurance data. NHTSA has also studied intervertebral rotations in low-
speed rear impacts using PMHS and ATD occupants.175 176 177
NHTSA found the intervertebral rotations of the PMHS subjects to be
comparable with BioRID rotations \178\ and the PMHS intervertebral
rotations were found to correlate with PMHS subluxation injuries (an
incomplete or partial dislocation of a joint or organ).\179\ The use of
ATD injury metrics in assessing low-speed rear impact injury risk is
still developing, and further investigation is needed to develop
metrics or ratings systems with a direct relationship to real world
whiplash injury. NHTSA's forthcoming research discussed later will
explore various ATD whiplash criteria.
---------------------------------------------------------------------------
\171\ Aldman, B.: An analytical approach to the impact
biomechanics of head and neck injury.'' Proceedings of the 39th
American Association for Automotive Medicine Conference; October 6-
8, 1986, Montreal, QC. 1986.
\172\ Bostr[ouml]m, Ola, et al. ``A new neck injury criterion
candidate-based on injury findings in the cervical spinal ganglia
after experimental neck extension trauma.'' Proceedings of The 1996
International Ircobi Conference On The Biomechanics Of Impact,
September 11-13, Dublin, Ireland. 1996.
\173\ Eichberger, Arno, et al. ``Comparison of different car
seats regarding head-neck kinematics of volunteers during rear end
impact.'' Proc. IRCOBI Conf. 1996.
\174\ Edwards, Marcy A., et al. ``Seat design characteristics
affecting occupant safety in low-and high-severity rear-impact
collisions.'' IRCOBI Conference, Florence, Italy, IRC-19-11. 2019.
\175\ Moorhouse K, Kang Y, Donnelly B, Herriott R, Bolte JH.
(2012, Nov). Evaluation of The Internal and External Biofidelity of
Current Rear Impact ATDs to Response Targets Developed from
Moderate-speed Rear Impacts of PMHS. STAPP Car Crash Journal, 56,
12S-21.
\176\ Kang Y, Moorhouse K, Donnelly B, Herriott R, Bolte JH.
(2012, Nov). Biomechanical Responses of PMHS in Moderate-speed Rear
Impacts and Development of Response Targets for Evaluating the
Internal and External Biofidelity of ATDs. STAPP Car Crash Journal,
56, 12S-20.
\177\ Kang Y, Moorhouse K, Herriott R, Bolte JH. (2013, May).
Comparison of Cervical Vertebrae Rotations for PMHS and BioRID II in
Rear Impacts. Traffic Injury Prevention, 14 (Supplement 1), S136-
S147.
\178\ Kang Y, Moorhouse K, Icke, K., Stricklin, J., Herriott R,
Bolte J.H. Rear Impact Head and Cervical Spine Kinematics of BioRID
II and PMHS in Production Seats (2015, Sept). International Research
Council on Biomechanics of Injury (IRCOBI), IRC-15-38, 246-260.
\179\ Kang Y, Moorhouse K, Icke K, Herriott R, Bolte JH. (2014,
Sept). Head and Cervical Spine Responses of Post Mortem Human
Subjects in Moderate Speed Rear Impacts. International Research
Council on Biomechanics of Injury (IRCOBI), Berlin, Germany. IRC-14-
33, 268-285.
---------------------------------------------------------------------------
Multiple studies have shown lack of reproducibility in low-speed
impacts. In 2007, a study compared the measurements of a BioRID-IIg
dummy in rear impact sled tests run across 18 identical production
seats.\180\ The authors were concerned that because the loads in a low-
speed rear impact test are very low, there could be high variability in
results due to small changes in the test setup. The study ran tests at
3
[[Page 58030]]
different severities with 6 equivalent repetitions at each severity.
The authors found that the ATD metrics displayed high variability
across the equivalent tests. The dummy rebound velocity showed the
least variability with 2.76%, 1.83% and 1.23% coefficient of variation
in the low, medium, and high severity tests. The NIC had greater
variability with a 9.18%, 10.5%, and 13.83% coefficient of variation.
The neck shear Fx, however, had very high variability with a 21.04%,
27.86%, and 32.57% coefficient of variation across like tests. After
computing the ranking score for each of the 6-test series, the authors
found the scores to vary by 26% from lowest to highest. Because of
variability in the measurements and ranking scores the authors called
into question the discriminatory power of the scoring system and noted
the lack of robustness in the scoring system. This study underlines the
challenge in developing a low-speed rear impact testing approach with
high reproducibility. Note that the values of a characteristic for a
rating system or standard might be set in such a way as to account for
the variability associated with the test.
---------------------------------------------------------------------------
\180\ Bortenschlager, Klaus, et al. ``Review of existing injury
criteria and their tolerance limits for whiplash injuries with
respect to testing experience and rating systems.'' Proceedings of
the 20th International Technical Conference on Enhanced safety of
vehicles, Lyon, France. 2007.
---------------------------------------------------------------------------
The precise understanding of how whiplash injuries occur is
evolving, but not complete. We seek comment on this approach. Are the
ATD measurements described above sufficiently objective and correlated
with whiplash injury? If so, can a low-speed test be conducted in a
repeatable and reproducible manner that would ensure objective results
and positive safety outcomes that are equitably distributed across all
occupant types? Do practicable countermeasures for whiplash injuries
exist to meet such a regulatory requirement? Would the requirement work
synergistically with a high-speed dynamic requirement?
(b) High-Speed Test
A high-speed test would assess rear impact protection at a severity
where significant rearward deflection of the seat back may occur, and
occupant retention becomes a concern. This test would assess all four
of the rear impact protection points. The high inertial forces placed
on a seat back would test seating system integrity and energy
absorption capabilities of the seat back through rearward rotation and
deflection, as well as the ability of the seat belt restraint system to
maintain retention and support an occupant in rebound. Finally,
compatibility of the seat and head restraint would be assessed through
appropriate ATD injury limits. The assessment would likely include neck
(whiplash or higher-level injury), thorax, spine, and pelvis results,
but could include other body regions as well.
Occupant injuries in a high-speed rear impact are primarily severe
head, neck, and thorax injuries and have clear pathology. Research
conducted by NHTSA has shown that severe thorax injuries, i.e., rib
fracture, may also occur in a retained seat occupant through inertia
and interaction with the seat back in very high-speed rear collisions
and rigid seat supporting structures.\181\
---------------------------------------------------------------------------
\181\ Kang, Yun-Seok, et al. ``Biomechanical responses and
injury assessment of post mortem human subjects in various rear-
facing seating configurations.'' Stapp car crash journal 64 (2020):
155-212.
---------------------------------------------------------------------------
Seat retention provides continual support to the occupant and is
important to avoid severe contact injuries and injurious occupant
kinematics. A lack of occupant retention may also lead to severe
injuries to passengers other than the forward row occupants through
occupant-to-occupant interaction. A high-speed test would assess
seating protection against injury through data from an ATD and related
seating retention metrics. The occupant retention metrics of concern
may include the maximum dynamic seat back rotation angle and ATD
displacement measures. NHTSA seeks comment on the appropriate occupant
retention metrics and ATD injury criteria at high-speed. We request
comment on how the availability of specific ATDs might limit or inform
the selected measurements.
The forces applied to seat backs in rear impacts range over a
continuum of severities. The applied inertial forces are proportional
to the seat base acceleration induced by the crash pulse, the
occupant's mass, and acceleration. The distribution of occupant mass
along the seat back influences the torque generated at the seat back
recliner mechanism, and the torque is proportional to the occupant's
mass. A high-speed test would need to set a test severity within the
range of potential real-world severities for which practicable
countermeasures may be available. Extreme forces on the seat back due a
rear impact are a relatively rare occurrence in the real-world, with
the highest forces requiring both a relatively high [Delta]V and
occupant mass. As noted in our analysis of 2017--2020 CISS data
reported in Figure II.4, 94% of rear towaway collisions occur at
[Delta]V of 40 km/h (24.9 mph) or less. Table II.2 indicated that the
most probable [Delta]V range for MAIS 3+ injuries in rear impacts was
the 31-40 km/h (19.3-24.9 mph) range. For some seat designs, a dynamic
test in the [Delta]V range of 35 to 40 km/h (21.7 to 24.9 mph) that is
conducted with a 50th percentile male ATD would likely lead to
significant rotation of the seat back and occupant movement along the
seat back, as described in the 2019 Edwards study.\182\ The authors
also noted that within the context of a 50th percentile male ATD and
37.5 km/h (23.3 mph) [Delta]V rear impact sled test, a degree of
balance was achieved between low and high-speed rear impact protection
in a range of production seats, as measured by the low-speed ratings
system, seat back rotation, and occupant displacement in the high-speed
test. Such a dynamic test conducted with a 95th percentile male ATD or
at higher [Delta]V, however, would lead to greater forces on the seat
back with a greater potential for plastic deformation of the seat
structure, a more extreme test of retention, and potential interaction
with rear seats. The high-speed test [Delta]V would ideally be high
enough to be sufficiently representative of real-world crashes to
generate practicable and, ideally, cost effective countermeasures for
protection against higher level injuries. NHTSA seeks comment on the
appropriate test severities for a possible high-speed test and the
appropriate ATD to utilize.
---------------------------------------------------------------------------
\182\ Edwards, Marcy A., et al. ``Seat design characteristics
affecting occupant safety in low-and high-severity rear-impact
collisions.'' IRCOBI Conference, Florence, Italy, IRC-19-11. 2019.
---------------------------------------------------------------------------
Positioning of the ATD in the seat may be an important factor in a
high-speed test. Studies such as the 1994 Strother and James cited
above, have shown occupant posture to influence injury outcome in rear
impacts. In addition, the sensitivity of an ATD itself to positioning
may be a factor to explore. For example, how sensitive are results to
atypical positions like leaning on the arm rest, creating an off-center
midsagittal plane for the ATD? NHTSA seeks public comment on the
appropriate positioning of the ATD in a high-speed rear impact test and
whether and/or what type of out-of-position testing should be
performed.
A well-designed high-speed rear impact test would account for all
four of NHTSA's rear impact protection points in the context of high
inertial forces leading to significant rearward deflection of the seat
back. The performance measures of concern may include retention
measures such as maximum dynamic seat back rotation angle, but also ATD
injury metrics relating to thorax and neck injury. In addition to these
concerns, NHTSA seeks comment regarding what objective rear impact
protection metrics are of most concern in a high-speed rear impact
test. Does existing ATD
[[Page 58031]]
technology adequately replicate occupant kinematics at high-speeds?
What ATD injury metrics would be most objective and relevant?
(c) Rear Impact Delivery Methods
Another factor to consider for a dynamic testing approach is how
the crash pulse should be delivered to the seat base. There are two
basic approaches to consider: a sled (with the seat mounted to either
the vehicle floor plan or a rigid platform) or moving barrier to
vehicle approach. This section explores the advantages and
disadvantages of each approach.
In experimental study of rear impacts, the most common method for
crash pulse delivery is a sled-based method. In this approach, a
moveable sled is accelerated with a high degree of accuracy on a linear
track. Mounted on the sled may be a rigid platform to which the vehicle
seat is attached. With appropriate mounting hardware, many types of
seats can be accommodated without significant modification to the
setup. However, the mounting of the seat to a rigid platform may not
transmit loading to the seat identically to how it would be transmitted
if the seat were mounted to the vehicle floor pan. Thus, a more
realistic approach would be to mount a floor pan to the sled and mount
the seat to the floor pan. Such an approach can be expanded to mount
all or portions of the vehicle body and interior to the sled,
potentially allowing for multiple ATDs in multiple rows of seats. The
agency uses a vehicle body mounted sled test approach currently for the
optional dynamic testing in FMVSS No. 202a.
Sled-based methods are relatively low cost and deliver a highly
repeatable pulse that can be readily applied to all seats. This removes
a degree of uncertainty about test repeatability. However, a sled pulse
only approximates a real-world crash pulse. A sled offers one-
dimensional translational motion, while actual rear impact crash test
may contain three-dimensional translational motion and rotation of the
vehicle, albeit likely relatively small accelerations in the vertical
and lateral direction. While a sled-based approach is advantageous from
a cost and repeatability standpoint, it may discount case-specific
design considerations. In addition, for higher speed impacts, if seats
were designed around a universal rear impact sled pulse, some seats may
in turn be over-designed and others under-designed relative to their
actual need for rear impact protection. This is because the design of
rear impact protection in seats could consider vehicle factors, e.g.,
vehicle weight and/or stiffness of the vehicle.
A vehicle approach would deliver a rear impact to a motor vehicle
using a moving barrier, similar to tests conducted under FMVSS No. 301.
In fact, while conducting FMVSS No. 301 tests outlined in the 2003
Saunders study, the agency has added instrumentation to seat backs and
placed HIII-50M ATDs in the front seats to assess the performance of
seat backs. As is the case with the vehicle body being mounted to a
sled, this approach would test rear impact protection in the context of
the entire vehicle. However, it differs in that the acceleration pulse
delivered to the seat will be a function of the vehicle's structural
deformation. In a real collision, the seat base acceleration depends on
vehicular factors, e.g., vehicle mass and structural characteristics,
and therefore the moving barrier to vehicle approach would be closer to
reality compared to a typical sled-based approach. A moving barrier to
vehicle approach is more of a consideration for higher speed impacts,
where the vehicle characteristics would have a greater influence on the
crash pulse. A sled-based approach could tune the sled pulse to the
actual vehicle crash pulse, if it were known, or use some adjustment to
the pulse that considers vehicle-based factors. Nonetheless, a barrier
impact approach would place a greater load on seats of lighter and
stiffer vehicles because [Delta]V has positive correlation with these
features if all else is equal.
The barrier impact approach places the seat in the full vehicle
environment. However, a sled-based approach allows the possibility of
the seat mounted on a platform in isolation. Whether a full vehicle or
isolated seat is tested is less likely to influence testing outcomes in
low-speed testing. However, high-speed testing will cause much more
seat back deformation. In certain vehicle environments, such as
convertibles, two-door cars, standard cab pickup trucks, and vehicles
with rigid second row seating, there may be structures near the seat
back which could restrict its rearward movement. Such restrictions
could be advantageous with respect to meeting seat back rotation
limits. How such restrictions would influence risk of injury, however,
is not obvious.
In summary, a sled-based method using a rigid platform and a
generic sled pulse is the most cost effective and simplest method for
inertial loading of a seat. Sled testing using the vehicle floor and
even more of the actual vehicle would likely increase cost and perhaps
complexity. The use of generic sled pulses, whether for lower or higher
speed impact simulation may also potentially allow for greater
repeatability, while sacrificing closeness to reality. Sled testing
using a vehicle specific crash pulse would add some complexity and the
need for knowledge of the crash pulse. A moving barrier to vehicle test
would be the option but would deliver the best approximation to the
real-world impact while simplifying crash pulse generation. It would
have instrumentation measurement complexity similar to sled testing.
Additionally, a moving barrier to vehicle test may also introduce more
avenues for test-to-test variability, part of which can be attributed
to vehicle build variability. NHTSA seeks comment on the different
approaches for delivering a rear impact crash pulse.
(d) Characteristics and Performance Measures Needed for a Rear Dummy
As discussed above, fostering the synergistic performance of seats
suggests dynamic testing should sample at least two different [Delta]V
regimes: including a low-speed and high-speed test. A different ATD
could be used for each test to adequately assess the range of occupant
kinematics that occur as [Delta]V is varied. The primary ATD
performance measures of concern for a low-speed test relate to whiplash
injuries and as noted earlier, important characteristics include the
ability to replicate torso straightening and neck kinematics. These
factors are also important for biofidelity in a high-speed test along
with thoracic compression, spine flexibility, and pelvic rotation.\183\
---------------------------------------------------------------------------
\183\ Hagedorn, A., Stammen, J., Ramachandra, R., Rhule, H. et
al., ``Biofidelity Evaluation of THOR-50M in Rear-Facing Seating
Configurations Using an Updated Biofidelity Ranking System,'' SAE
Int. J. Trans. Safety 10(2):291-375, 2022.
---------------------------------------------------------------------------
The HIII-50M has long been widely used for rear impact protection
research, even though this dummy was developed and validated for
frontal crash testing. Nonetheless, the HIII-50M has provided an
effective means of ballasting the seat and measurements of dummy
kinematics and loading. Over time, significant progress has been made
on the development of the BioRID ATD, which is designed specifically
for rear impacts. BioRID performance has thus far been focused on low-
speed testing to assess neck injury risk but has more recently been
evaluated in higher speed rear impact conditions. Additionally, dynamic
sled tests are used by ratings groups, academic researchers and
industrial researchers to assess the performance of seating systems in
a rear impact, and results are compared with adult volunteers in low-
speed tests and
[[Page 58032]]
PMHS at higher speeds to validate modern ATD
measurements.184 185 These efforts have built a better
technological basis for a dynamic test compared to the past.
---------------------------------------------------------------------------
\184\ Willis, Claire, Jolyon Carroll, and Adrian Roberts. ``An
evaluation of a current rear impact dummy against human response
corridors in both pure and oblique rear impact.'' Proceedings of the
19th International Technical Conference of the Enhanced Safety of
Vehicles, Paper. No. 05-0061. 2005.
\185\ Croft, Arthur C., and Mathieu MGM Philippens. ``The RID2
biofidelic rear impact dummy: A pilot study using human subjects in
low-speed rear impact full scale crash tests.'' Accident Analysis &
Prevention 39.2 (2007): 340-346.
---------------------------------------------------------------------------
The BioRID 50th percentile male dummy was developed by a Swedish
team in the 1990s.\186\ The development was in response to low-speed
rear impact testing using human volunteers indicating that torso
straightening, and angling of the lower spine were essential for
accurate cervical spine dynamics,\187\ \188\ and the determination that
existing ATDs of that era did not properly simulate the cervical
vertebrae motions. Therefore, development focused on an ATD with more
realistic spinal motion, particularly in the neck, and one that would
simulate torso straightening.\189\ The BioRID dummy has an articulated
mechanical spine and is primarily intended to replicate spinal motion
in low-speed rear impacts. BioRID vertebrae are connected by linear pin
joints and a tension cable. This mechanical system shows comparatively
high torsional, shear, compression, and tension inter-vertebral forces
in rear impacts.\190\ NHTSA has evaluated the BioRID and believes it is
the best available 50th percentile male ATD for the low-speed rear
impact test discussed in this ANPRM, but seeks comment on this topic.
NHTSA also seeks comment on the potential use of appropriate female
crash test dummies designed specifically for rear impact to offer a
more comprehensive assessment of seat performance.
---------------------------------------------------------------------------
\186\ Davidsson, Johan, et al. ``BioRID I: a new biofidelic rear
impact dummy. '' Proceedings of the International Research Council
on the Biomechanics of Injury conference. Vol. 26. International
Research Council on Biomechanics of Injury, 1998.
\187\ McConnell, Whitman E., et al. Analysis of human test
subject kinematic responses to low velocity rear end impacts. No.
930889. SAE Technical Paper, 1993.
\188\ Ono, Koshiro, and Munekazu Kanno. ``Influences of the
physical parameters on the risk to neck injuries in low impact speed
rear-end collisions.'' Accident Analysis & Prevention 28.4 (1996):
493-499.
\189\ L[ouml]vsund, Per, and Mats Y. Svensson. ``Suitability of
the available mechanical neck models in low velocity rear end
impacts.'' CNR-PFT2 ELASIS International Conference on Active and
Passive Automobile Safety in Capri, Italy. 1996.
\190\ Viano, David C., et al. ``Neck biomechanical responses
with active head restraints: Rear barrier tests with BioRID and sled
tests with Hybrid III.'' SAE Transactions (2002): 219-237.
---------------------------------------------------------------------------
For the higher speed rear impact test, NHTSA is examining the use
of BioRID as well as the HIII-50M and Test device for Human Occupant
Restraint 50th percentile male (THOR-50M) ATD.\191\ The BioRID has the
advantages articulated above, but there may be limits to the speed of
the crash environment that it can be used in and BioRID replicates only
two-dimensional motion of the spine with injury assessment being
limited to the cervical spine.
---------------------------------------------------------------------------
\191\ Hagedorn A, Stammen J, Ramachandra R, Rhule H, Thomas C,
Suntay B, Kang YS, Kwon HJ, Moorhouse K, Bolte IV JH. Biofidelity
Evaluation of THOR-50M in Rear-Facing Seating Configurations Using
an Updated Biofidelity Ranking System. SAE Int. J. Trans. Safety
10(2):2022, https://doi.org/10.4271/09-10-02-0013.
---------------------------------------------------------------------------
The HIII-50M and THOR-50M have limitations due to being designed
for frontal impacts. Nevertheless, these dummies are typically used in
studies of high-speed rear impact dynamics and have been used as seat
occupants in rear impact tests. In the case of high-speed tests these
ATDs enable the measurement of seat back rotation and retention by
acting as ballasts that impose a biofidelic inertial load on the seat
back. The 2019 Edwards study, for example, used the HIII-50M dummy for
the high-speed test. The HIII-50M is limited because it has a rigid
thoracic spine so its interaction with a seat back is significantly
different than a real occupant whose bendable spine conforms with the
seat cushion profile and structural cross members. The THOR-50M ATD, a
refinement of the TAD-50M thorax, integrated a new multi-directional
neck and instrumented pelvis, abdomen, and lower extremity concepts.
Both the HIII-50M and THOR-50M allow for the measurement of chest
injury risk. While a high-speed test that uses one of the male ATDs
discussed above is necessary to assess seating system integrity, a
comprehensive test of seat retention may also require a test using a
female ATD. NHTSA seeks comment on the ATDs to use for high-speed rear
impact tests.
NHTSA is exploring a low and high severity test as components of a
unified approach to updating FMVSS No. 207 and the ATD requirements of
these tests overlap with capabilities of the HIII-50M, THOR-50M, and
BioRID dummies. NHTSA seeks comment on the benefits and costs, in
particular the practicability and objectivity concerns, of using
different ATDs for different rear impact test severities versus the use
of a single ATD for both low and high-speed testing.
D. Crash Avoidance Technology
Over the last several years, automatic emergency braking (AEB) and
forward collision warning (FCW) have become more prevalent in the light
vehicle fleet. An AEB system uses various sensor technologies and sub-
systems that work together to detect when the vehicle is in a crash
imminent situation, to automatically apply the vehicle brakes if the
driver has not done so, or to apply more braking force to supplement
the driver's braking. A FCW system uses sensors that detect objects in
front of vehicles and provides an alert to the driver. FCW systems may
detect impending collisions with any number of roadway obstacles,
including vehicles. NHTSA has recently published a final rule requiring
that all new light vehicles be equipped with AEB and FCW systems.\192\
NHTSA anticipates that over time, AEB and FCW prevalence in the fleet
will increase and the technology will improve. Therefore, any future
rulemaking action related to the upgrade of rear impact protection
through modification of seat related standards will need to fully
consider the effects of crash avoidance technology such as AEB and FCW.
AEB and FCW are expected to reduce the incidence of high-speed rear
impact collisions, either through avoiding a collision entirely or
mitigating impact speeds into lower-speed collisions. If AEB and FCW
have this impact, their availability may in turn affect crash
frequencies and injury types relevant to this ANPRM, such as the
incidence of seat back failure in vehicles struck from the rear. AEB
and FCW may also reduce the incidence of low-speed rear impacts that
cause injuries such as whiplash in occupants of the struck vehicle.
However, it is possible that AEB and FCW, by mitigating some high-speed
impacts into lower-speed collisions, may increase the number of lower-
speed rear impacts. It is not clear what the net impact would be. NHTSA
seeks comment on how best to consider the effects of this technology on
the issues discussed in the ANPRM. In particular, how might a change in
frequency of rear impacts of different velocities impact the benefit-
cost considerations for regulatory changes discussed in this ANPRM,
such as the seat back strength requirement?
---------------------------------------------------------------------------
\192\ 89 FR 39686 (July 8, 2024). This final rule builds on a
voluntary commitment, announced by NHTSA in March 2016, by 20
vehicle manufacturers to make AEB a standard feature on nearly all
new light vehicles.
---------------------------------------------------------------------------
[[Page 58033]]
VII. NHTSA's Forthcoming Research
NHTSA is pursuing research to build a greater understanding of the
issues presented in this document. Based upon the current understanding
of these issues, the goals are to better define the scope of the
current rear impact safety problem, validate seated ATD measurements in
rear impacts, quantify rear impact injury risks, attempt to develop
injury risk curves, and analyze rear impact dynamics and testing
procedures. Because the understanding of the rear impact problem
continues to evolve, the priorities and objectives are subject to
change and likely to evolve as research progresses. Currently, the aim
is to identify sled test [Delta]Vs, test types (e.g., static versus
dynamic), test tools (e.g., loading fixture, ATDs) and performance
limits (e.g., strength requirements, displacement limits, injury
assessment reference values). It is anticipated that the research
outcomes will contribute to the determination of whether to propose an
update to FMVSS No. 202a and FMVSS No. 207 and, if the determination is
made to do so, provide the basis for such a proposal. The following
discussion outlines NHTSA's path forward for research activities
related to this ANPRM.
A. Field Data Analysis and Market Research
A study of rear impact field data will investigate the scope of the
rear impact safety problem. NHTSA intends to examine the incidence of
injuries to the seated front occupant, the types of injuries, the
degree to which modern occupied seat backs fail or become deformed (by
row), and which parts of the seat incur yielding (i.e., just the seat
back, the anchors and seat track, the vehicle floor, etc.). For higher
speed rear impacts, this is needed to identify the level of crash
severity that may represent a reasonable dynamic testing level. Overall
trends will be examined by analyzing aggregate field data and occupant
injury and multiple seat row interaction. An attempt will be made to
attribute vehicle occupant injury to seat performance. It is expected
that manual reviews of case file material will be necessary to discern
seat performance and failure mechanisms. NHTSA also intends to examine
how seat designs may have improved across the fleet or how second row
seats differ in performance from front row seats.
B. Test Procedure Assessment
NHTSA plans to conduct a sled-based study of rear impact seat back
and occupant dynamics to develop a greater knowledge base in the
performance of modern seats in both low and high-speed regimes and to
investigate the feasibility of a dynamic approach for updating FMVSS
No. 207 and rear impact protection in general.
1. High-Speed Test
The agency expects to perform high-speed sled tests across a range
of [Delta]Vs including the high-speed rear impact fuel integrity test
performed in FMVSS No. 301 and at speeds identified in the field data
analysis mention above that result in relatively high risks to vehicle
occupants. Through this testing, NHTSA will attempt to determine what
physical characteristics govern occupant protection and what severities
lead to substantial deformation of seat backs in high-speed rear
impacts. This testing will take a variety of configurations and serve a
variety of functions. One important question to be answered is what
deceleration pulse and/or [Delta]V will achieve the agency's regulatory
goals, particularly with respect to a front seat occupant intruding
into the rear seat occupant space. Another important research question
is whether the deceleration pulse and/or [Delta]V should be vehicle
specific or generic. It is expected that sled testing will be performed
with partial vehicles as well as platform mounted seats to decern the
effect of these two configurations of seat performance as well as to
assess the challenges related to testing a seat within a vehicle. This
testing will also help identify the important seat performance
characteristics and the best way to measure them. We expect to use
multiple ATDs and PMHS occupants in the seats for a variety of tasks
discussed below.
2. Exploratory Testing
NHTSA recently conducted exploratory high-speed rear impact sled
testing on a series of production seats to gain insight into
instrumentation and measurement needs for such tests. The test closely
resembled the 2019 high-speed rear impact tests from the IIHS
study,\193\ except that NHTSA used the THOR-50M as a normally
positioned occupant. NHTSA's crash pulse achieved a maximum sled
acceleration of 15.1 g after approximately 80 ms resulting in a
[Delta]V of 36 km/h (22.4 mph). The test series consisted of 6 total
sled tests involving the front driver seat of three different major
auto manufacturers in 2013 and 2018 MY used passenger vehicles. The
three models were tested with and without seat belt pretensioners. The
seats were instrumented with accelerometers, load cells, strain gages
and camera target standoffs and fixed to the sled buck with an initial
seat back recline angle of 25[deg]. The time-dependent seat back
rotation angle was determined by postprocessing film data and 6DX
(Diversified Technical Systems) sensor package measurements and are
shown in Figure VII.1 in the case of no pretensioners.
---------------------------------------------------------------------------
\193\ Edwards, Marcy A., et al. ``Seat design characteristics
affecting occupant safety in low-and high-severity rear impact
collisions.'' IRCOBI Conference, Florence, Italy, IRC-19-11. 2019.
---------------------------------------------------------------------------
BILLING CODE 4910-59-P
[[Page 58034]]
[GRAPHIC] [TIFF OMITTED] TP16JY24.016
[[Page 58035]]
[GRAPHIC] [TIFF OMITTED] TP16JY24.017
BILLING CODE 4910-59-C
The seat backs reached their maximum rearward rotation at
approximately twice the point of peak sled acceleration and then, upon
reversing, decayed to a final recline angle that is greater than the
initial recline angle. Seat I had the least rearward rotation and its
final recline angle was the least among the three models. Seat III had
the most rearward rotation and its final recline angle was the greatest
among the three models. The difference between the initial and final
recline angles are a product of irreversible deformation in the seat
frame and an indication of energy absorbed by the seat. In seat I and
to a lesser extent seat II, as the rotation angle decayed to the final
angle there was oscillation of the seat back about the final angle;
this is a characteristic of spring-mass-damper systems. Seat III had
significant twisting about the longitudinal axis as seen in the large
differences between the left and right seat back rotations. A post-test
visual tear down analysis found that in all seats the side bolsters
bent inward toward the occupant and deformation was also seen in the
lower seat frames and pans. This initial series of tests demonstrates
that rearward excursion and rotation are high-speed seat performance
metrics that can be reliably obtained in different seat models.
3. Low-Speed Test
To broadly assess the rear impact protection measures of a seat,
the performance should be compared in a low- and high-speed test to
analyze whether improvements in seat performance at high-speed impacts
sacrifice whiplash injury mitigation at low-speeds. Thus, it is
expected that seats will be tested in both a low- and a high-speed
test, to see how the performance compares in both rear impact
conditions. This study may determine if the design requirements for
low- and high-speed performance align or contradict one another.
As stated above, one important factor in test procedure development
will be exploring the appropriate low- and high-speed deceleration for
rear impact tests. A reasonable starting point for the lower speed test
is the head restraint optional dynamic test in FMVSS No. 202a. We are
aware of other sled pulses used for whiplash assessment by IIHS and
EuroNCAP, however, and will explore these as well. We will also explore
the need or acceptability of platform mounted seats versus in-vehicle
testing. Finally, a key factor for low-speed testing will be the ATD.
NHTSA expects to focus on the use of the BioRID for these tests.\194\
We also expect to assess various whiplash injury criteria.
---------------------------------------------------------------------------
\194\ See discussion at section IV.4., above, for additional
information related to use of the BioRID.
---------------------------------------------------------------------------
C. Parametric Modeling
A computational model of seat occupant dynamics in a rear impact
that is validated against experimental data could provide insight into
a range of safety issues. It is expected that both ATDs and human body
models will be used as seat occupants and the impact of various
occupant characteristics on injury risk can be determined, such as the
occupant size and gender. NHTSA may also study the extent to which seat
design specifications have a positive influence on injury risk. A
computational model can be run over a range of deceleration pulses and
seat characteristics to determine at which point significant seat
deformation and the onset of serious injuries to seat occupant occurs.
D. ATD and Injury Risk Function Development
Rear impact testing with PMHS seat occupants provides biomechanical
data for ATD evaluation as noted in the NHTSA citations above. By
comparing equivalent pairs of ATD and PMHS tests, more realistic injury
risk functions can be developed for the ATD seat occupant in a rear
impact. NHTSA has, for example, performed extensive work on low-speed
whiplash injury risk functions for the BioRID. NHTSA expects the BioRID
to be the focus of low-speed testing in this research; however, various
whiplash injury criteria will be explored.
[[Page 58036]]
For high severity research, further PMHS testing will provide the
injury information to correlate with ATD measurements in an injury risk
function. This information will also be correlated to seat performance
parameters to assist in identification of factors that influence injury
risk. Additionally, both BioRID and THOR-50M will be evaluated for
high-speed testing. The BioRID has a fully articulated spine but was
designed specifically for lower speed rear impacts. Thus, durability
and biofidelity in higher speed rear impacts will need to be evaluated.
The THOR-50M was not designed for rear impacts, but has thoracic
measurements not available in BioRID. However, its acceptability for
overall rear impact injury risk will need further consideration. Once
injury risk functions are developed, the ATD(s) will be used in a
broader evaluation of seats on the market against identified
performance metrics.
E. Cost Analysis
The purpose of a cost analysis is to determine the financial
implications of improving rear impact protection. A broad understanding
will be gained by performing a cost analysis in each aspect of NHTSA's
research initiative. A tear down analysis of tested seats provides an
indication of failure mechanisms and protective design measures. The
cost differential between good and poor performing seats could be
estimated by quantifying the difference in design measures determined
through tear down. The computational study could assess the overall
impact and cost of design changes within a seat; for example, if design
changes are made to a poorly performing seat for a high-speed test with
a specific occupant, would these changes in fact have a detrimental
impact in other scenarios? After the cost differential between good and
poor performing seats is well defined, then market research and
assessment of the fleet will determine the overall costs of improving
rear impact protection.
F. Summary
NHTSA is pursuing research to gain a greater understanding of the
modern rear impact protection issue that the agency regulates under
FMVSS Nos. 207 and 202a. An examination of recent rear impact field
data is helpful to define the overall safety issue and determine
whether any countermeasure to a problem is cost effective. This
document discusses a two-tiered dynamic testing approach. NHTSA is
pursuing sled testing of rear impacts to explore this dynamic approach
and has conducted an initial exploratory series of high-speed rear
impact tests described above. NHTSA has ongoing research in rear impact
sled testing using PMHS occupants that in turn supports an ATD based
assessment of rear impact injuries and dynamics. A computational
parametric study has also been proposed to broadly investigate rear
impact dynamics and various protection measures. If a rulemaking is
pursued, NHTSA will also perform research tasks to develop the
necessary cost and benefit estimates for upgraded rear impact
protection estimates. NHTSA would like this research to make decisive
contributions and therefore seeks comment on the research proposed
here. Would a greater impact be achieved if the agency's resources were
directed in another area of rear impact protection or more focused in a
critical area?
VIII. Public Participation
A. How can I inform NHTSA's thinking on this rulemaking?
Your comments will help us improve this rulemaking. NHTSA invites
you to provide different views on options NHTSA discusses above, new
approaches the agency has not considered, new data, descriptions of how
this ANPRM may affect you, or other relevant information.
NHTSA welcomes public review of all aspects of this ANPRM, but
requests comments on specific issues throughout this document. NHTSA
will consider the comments and information received in developing a
potential proposal for how to proceed with updating requirements for
motor vehicles. Your comments will be most effective if you follow the
suggestions below:
Explain your views and reasoning as clearly as possible.
Provide solid technical and cost data to support your
views.
If you estimate potential costs, explain how you arrived
at the estimate.
Tell NHTSA which parts of the ANPRM you support, as well
as those with which you disagree.
Provide specific examples to illustrate your concerns.
Offer specific alternatives.
Refer your comments to specific sections of the ANPRM,
such as the units or page numbers of the preamble.
B. How do I prepare and submit comments?
Your comments must be in writing. To ensure that your comments are
filed correctly in the Docket, please include the docket number of this
document located at the beginning of this notice in your comments.
Your primary comments should not be more than 15 pages long.\195\
You may attach additional documents to your primary comments, such as
supporting data or research. There is no limit on the length of the
attachments.
---------------------------------------------------------------------------
\195\ 49 CFR 553.21.
---------------------------------------------------------------------------
Please submit one copy of your comments (two if submitting by mail
or hand delivery), including the attachments, to the docket via one of
the methods identified under the ADDRESSES section at the beginning of
this document. If you are submitting comments electronically as a PDF
(Adobe) file, we ask that the documents submitted be scanned using an
Optical Character Recognition (OCR) process, thus allowing NHTSA to
search and copy certain portions of your submission.
Please note that pursuant to the Data Quality Act, for substantive
data to be relied upon and used by the agency, it must meet the
information quality standards set forth in the OMB and DOT Data Quality
Act guidelines. Accordingly, NHTSA encourages you to consult the
guidelines in preparing your comments. DOT's guidelines may be accessed
at www.transportation.gov/regulations/dot-information-dissemination-quality-guidelines.
C. How can I be sure that my comments were received?
If you submit comments by hard copy and wish Docket Management to
notify you upon its receipt of your comments, enclose a self-addressed,
stamped postcard in the envelope containing your comments. Upon
receiving your comments, Docket Management will return the postcard by
mail. If you submit comments electronically, your comments should
appear automatically in the docket number at the beginning of this
notice on https://www.regulations.gov. If they do not appear within two
weeks of posting, we suggest that you call the Docket Management
Facility at 202-366-9826.
D. How do I submit confidential business information?
NHTSA is currently treating electronic submission as an acceptable
method for submitting confidential business information to the agency
under part 512. If you claim that any of the information or documents
provided in your response constitutes confidential business information
within the meaning of 5 U.S.C. 552(b)(4), or are protected from
disclosure pursuant to 18 U.S.C. 1905, you may either submit your
request via email or request a secure file transfer
[[Page 58037]]
link from the Office of the Chief Counsel contact listed below. You
must submit supporting information together with the materials that are
the subject of the confidentiality request, in accordance with part
512, to the Office of the Chief Counsel. Do not send a hardcopy of a
request for confidential treatment to NHTSA's headquarters.
Your request must include a request letter that contains supporting
information, pursuant to Sec. 512.8. Your request must also include a
certificate, pursuant to Sec. 512.4(b) and part 512, appendix A.
You are required to submit one unredacted ``confidential version''
of the information for which you are seeking confidential treatment.
Pursuant to Sec. 512.6, the words ``ENTIRE PAGE CONFIDENTIAL BUSINESS
INFORMATION'' or ``CONFIDENTIAL BUSINESS INFORMATION CONTAINED WITHIN
BRACKETS'' (as applicable) must appear at the top of each page
containing information claimed to be confidential. In the latter
situation, where not all information on the page is claimed to be
confidential, identify each item of information for which
confidentiality is requested within brackets: ``[ ].''
You are also required to submit one redacted ``public version'' of
the information for which you are seeking confidential treatment.
Pursuant to Sec. 512.5(a)(2), the redacted ``public version'' should
include redactions of any information for which you are seeking
confidential treatment (i.e., the only information that should be
unredacted is information for which you are not seeking confidential
treatment). For questions about a request for confidential treatment,
please contact Dan Rabinovitz in the Office of the Chief Counsel at
[email protected].
E. Will the agency consider late comments?
NHTSA will consider all comments received to the docket before the
close of business on the comment closing date indicated above under the
DATES section. NHTSA will consider any late-filed comments to the
extent possible.
F. How can I read the comments submitted by other people?
You may read the comments received by Docket Management in hard
copy at the address given above under the ADDRESSES section. The hours
of the Docket Management office are indicated above in the same
location. You may also read the comments on the internet by doing the
following:
(1) Go to https://www.regulations.gov.
(2) Regulations.gov provides two basic methods of searching to
retrieve dockets and docket materials that are available in the system:
a. The search box on the home page which conducts a simple full-
text search of the website, into which you can type the docket number
of this notice and
b. ``Advanced Search,'' which is linked on the regulations.gov home
page, and which displays various indexed fields such as the docket
name, docket identification number, phase of the action, initiating
office, date of issuance, document title, document identification
number, type of document, Federal Register reference, CFR citation,
etc. Each data field in the advanced search function may be searched
independently or in combination with other fields, as desired. Each
search yields a simultaneous display of all available information found
in regulations.gov that is relevant to the requested subject or topic.
(3) Once you locate the docket at httsp://www.regulations.gov, you
can download the comments you wish to read. We note that because
comments are often imaged documents rather than word processing
documents (e.g., PDF rather than Microsoft Word), some comments may not
be word searchable.
Please note that, even after the comment closing date, NHTSA will
continue to file relevant information in the Docket as it becomes
available. Further, some people may submit late comments. Accordingly,
NHTSA recommends that you periodically check the Docket for new
material.
IX. Regulatory Analyses and Notices
A. Executive Order (E.O.) 12866, E.O. 13563, and E.O. 14094 and DOT
Regulatory Policies and Procedures
The agency has considered the impact of this rulemaking action
under Executive Order (E.O.) 12866, E.O. 13563, E.O. 14094, and the
Department of Transportation's regulatory procedures DOT Order 2100.6A.
This ANPRM was determined to be significant under E.O. 12866 and was
reviewed by the Office of Management and Budget.
This ANPRM presents possible avenues for updating regulations
regarding occupant protection in rear impact and seeks public comment
to develop information that may inform a future proposal. NHTSA is
using this ANPRM to solicit public feedback before potentially
proceeding with a proposed rule.
We have asked commenters to answer a variety of questions to elicit
practical information about alternative approaches and relevant
technical data, which will enable analysis of the costs and benefits of
a possible future proposal.
B. Paperwork Reduction Act
Under the Paperwork Reduction Act of 1995 (PRA), a person is not
required to respond to a collection of information by a Federal agency
unless the collection displays a valid OMB control number. This ANPRM
would not establish any new information collection requirements.
C. Privacy Act
DOT solicits comments from the public to better inform its
rulemaking process. DOT posts these comments, without edit, including
any personal information the commenter provides, to
www.regulations.gov, as described in the system of records notice (DOT/
ALL-14 FDMS), which can be reviewed at www.dot.gov/privacy. Please note
that anyone is able to search the electronic form of all comments
received into any of our dockets by the name of the individual
submitting the comment (or signing the comment, if submitted on behalf
of an association, business, labor union, etc.). For information on
DOT's compliance with the Privacy Act, please visit https://www.transportation.gov/privacy.
D. Plain Language
Executive Order 12866 requires each agency to write all rules in
plain language. Application of the principles of plain language
includes consideration of the following questions:
Have we organized the material to suit the public's needs?
Are the requirements in the document clearly stated?
Does the document contain technical language or jargon
that isn't clear?
Would a different format (grouping and order of sections,
use of headings, paragraphing) make the document easier to understand?
Would more (but shorter) sections be better?
Could we improve clarity by adding tables, lists, or
diagrams?
What else could we do to make the document easier to
understand?
If you have any responses to these questions, please include them
in your comments.
E. Regulation Identifier Number (RIN)
The Department of Transportation assigns a regulation identifier
number (RIN) to each regulatory action listed in the Unified Agenda of
Federal
[[Page 58038]]
Regulations. The Regulatory Information Service Center publishes the
Unified Agenda in April and October of each year. You may use the RIN
contained in the heading at the beginning of this document to find this
action in the Unified Agenda.
X. Conclusion
In accordance with 49 CFR part 552, NHTSA grants in part and denies
in part the petitions by Mr. Saczalski and Mr. Cantor and denies the
CAS petition.
Issued in Washington DC, under authority delegated in 49 CFR
1.95, 501.5, and 501.8.
Jack Danielson,
Executive Director.
[FR Doc. 2024-15390 Filed 7-15-24; 8:45 am]
BILLING CODE 4910-59-P
