Federal Motor Vehicle Safety Standards; Anti-Ejection Glazing for Bus Portals; Bus Emergency Exits and Window Retention and Release, 86255-86285 [2024-24462]

Agencies

• National Highway Traffic Safety Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 89, Number 210 (Wednesday, October 30, 2024)]
[Rules and Regulations]
[Pages 86255-86285]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-24462]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2024-0061]
RIN 2127-AL36


Federal Motor Vehicle Safety Standards; Anti-Ejection Glazing for 
Bus Portals; Bus Emergency Exits and Window Retention and Release

AGENCY: National Highway Traffic Safety Administration (NHTSA), 
Department of Transportation (DOT).

ACTION: Final rule.

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SUMMARY: This final rule establishes Federal Motor Vehicle Safety 
Standard (FMVSS) No. 217a, ``Anti-ejection glazing for bus portals; 
Mandatory applicability beginning October 30, 2027,'' to drive the 
installation of advanced glazing in over-the-road buses (motorcoaches) 
and other large buses to reduce passenger and driver ejections. This 
final rule, issued pursuant to the Moving Ahead for Progress in the 
21st Century Act (MAP-21), specifies impactor tests of the glazing 
material of side and roof windows. The impactor and impact speed 
simulate the loading from an average size unrestrained adult male 
impacting a window on the opposite side of a large bus in a rollover.

DATES: 
    Effective date: December 30, 2024.
    Compliance date: The compliance date for FMVSS No. 217a and the 
amendments to FMVSS No. 217 is October 30, 2027. Optional early 
compliance with the standards is permitted.
    Reconsideration date: If you wish to petition for reconsideration 
of this rule, your petition must be received by December 16, 2024.

ADDRESSES: Petitions for reconsideration of this final rule must refer 
to the docket and notice number set forth above and be submitted to the 
Administrator, National Highway Traffic Safety Administration, 1200 New 
Jersey Avenue SE, Washington, DC 20590. Note that all petitions 
received will be posted without change to https://www.regulations.gov, 
including any personal information provided.
    Docket: For access to the docket to read background documents or 
comments received, go to https://www.regulations.gov at any time or to 
1200 New Jersey Avenue SE, West Building, Room W12-140, Washington, DC 
20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. Telephone: (202) 366-9826.
    Privacy Act: The petition will be placed in the docket. Anyone is 
able to search the electronic form of all documents 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.). You may review DOT's complete Privacy Act 
Statement in the Federal Register published on April 11, 2000 (Volume 
65, Number 70; Pages 19477-78) or you may visit https://www.transportation.gov/individuals/privacy/privacy-act-system-records-notices.
    Confidential Business Information: If you wish to submit any 
information under a claim of confidentiality, you should submit three 
copies of your complete submission, including the information you claim 
to be confidential business information, to the Chief Counsel, NHTSA, 
at the address given under FOR FURTHER INFORMATION CONTACT. In 
addition, you should submit two copies, from which you have deleted the 
claimed confidential business information, to Docket Management at the 
address given above. When you send a submission containing information 
claimed to be confidential business information, you should include a 
cover letter setting forth the information specified in our 
confidential business information regulation (49 CFR part 512).

FOR FURTHER INFORMATION CONTACT: For technical issues, you may contact 
Mr. Dow Shelnutt, Office of Crashworthiness Standards, Telephone: (202) 
366-8779, Facsimile: (202) 493-2739. For legal issues, you may contact 
Mr. Matthew Filpi, Office of the Chief Counsel, Telephone: (202) 366-
2992, Facsimile: (202) 366-3820. The mailing address of these officials 
is: The National Highway Traffic Safety Administration, 1200 New Jersey 
Avenue SE, Washington, DC 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary
II. Background
    a. NHTSA's Approach to Motorcoach Safety
    b. U.S. DOT Motorcoach Safety Action Plan
    c. Congressional Action: MAP-21 and the Motorcoach Enhanced 
Safety Act
    d. NHTSA's 2013 Motorcoach Seat Belt Final Rule
    e. NHTSA's 2021 Motorcoach Structural Integrity Final Rule
    f. Data and Safety Need for Strengthening Motorcoach Window 
Glazing
    g. The 2016 NPRM

[[Page 86256]]

III. NHTSA's Statutory Authority
    a. National Traffic and Motor Vehicle Safety Act (Safety Act)
    b. MAP-21 (Incorporating the Motorcoach Enhanced Safety Act of 
2012)
IV. The Final Rule and Response to Comments
    a. Establishing FMVSS No. 217a and New Requirements
    b. Differences Between the NPRM and the Final Rule
V. Summary of Comments and Agency Responses
    a. Overview of Comments
    b. Applicability
    c. Occupant Injury Protection
    d. Test Procedures and Equipment
    e. Performance Requirements
    f. Organization of the Standard and Language Used in the 
Standard
    g. Compliance Date
    h. Retrofitting
    i. Definitions and Descriptions
    j. Costs and Benefits
VI. Overview of Costs and Benefits
VII. Regulatory Notices and Analyses

I. Executive Summary

    In 2007, NHTSA published a comprehensive plan on possible 
improvements in motorcoach safety.\1\ NHTSA's motorcoach safety plan 
identified four specific areas to most expeditiously achieve our goals: 
requiring seat belts (minimizing passenger and driver ejection from the 
motorcoach), improved roof strength, emergency evacuation, and fire 
safety. This final rule is another step in the agency's efforts to 
improve over-the-road bus (OTRB \2\) and large bus \3\ safety. This 
final rule establishes a new FMVSS, FMVSS No. 217a, ``Anti-Ejection 
Glazing for Bus Portals; Mandatory applicability beginning October 30, 
2027,'' to mitigate partial and complete ejection of passengers from 
windows on the side and roof of motorcoaches and large buses and to 
ensure that emergency exits remain operable after a rollover crash.
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    \1\ Docket No. NHTSA-2007-28793, NHTSA's Approach to Motorcoach 
Safety.
    \2\ An over-the-road bus is characterized by an elevated 
passenger deck located over a baggage compartment.
    \3\ Generally, certain buses with a gross vehicle weight rating 
(GVWR) greater than 26,000 pounds (lb) (11,793.4 kilograms (kg)).
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    This final rule fulfills a statutory mandate in the Motorcoach 
Enhanced Safety Act of 2012 (Motorcoach Enhanced Safety Act), which was 
incorporated and passed as part of MAP-21. The Motorcoach Enhanced 
Safety Act required the DOT to prescribe regulations that address 
passenger ejection in motorcoaches.\4\ Additionally, MAP-21 required 
DOT to consider requiring advanced glazing standards for motorcoach 
portals.
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    \4\ In section 32702(6) of MAP-21, a motorcoach is defined as an 
over-the-road bus, not including transit buses or school buses.
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    The Motorcoach Enhanced Safety Act emphasizes anti-ejection safety 
countermeasures, particularly advanced glazing. Section 32703(b)(2) of 
MAP-21 directs the Secretary to consider requiring advanced glazing 
standards for each motorcoach portal and to consider other portal 
improvements to prevent partial and complete ejection of motorcoach 
passengers, including children. Section 32703(b)(2) also states that in 
prescribing such standards, the Secretary shall consider the impact of 
such standards on the use of motorcoach portals as a means of emergency 
egress. MAP-21 requires NHTSA to adopt a final rule if NHTSA determines 
that such standards meet the requirements and considerations in 
subsections (a) and (b) of section 30111 of the National Traffic and 
Motor Vehicle Safety Act.\5\ As discussed in this final rule, NHTSA has 
made such a determination regarding an FMVSS for motorcoaches and 
certain large buses.
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    \5\ MAP-21, section 32703(b) and (b)(1).
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    The May 6, 2016, Notice of Proposed Rulemaking (NPRM) \6\ was among 
the rulemakings issued pursuant to NHTSA's 2007 Approach to Motorcoach 
Safety and DOT's Departmental Motorcoach Safety Action Plan.\7\ Both of 
these agency documents recognized that there was work to be done in 
protecting the public from death and serious injury in OTRB and large 
bus crashes. Although there are relatively few OTRB and large bus 
crashes when compared to other vehicle types, OTRB and large bus 
crashes tend to be serious when they do occur because they generally 
carry large numbers of passengers. Since producing these safety plans, 
NHTSA has promulgated several final rules targeted at protecting OTRB 
and large bus passengers. These final rules include a requirement that 
all seats on OTRBs and large buses be equipped with seat belts, a 
requirement that all OTRBs and large buses be equipped with electronic 
stability control, and requirements for improved structural integrity 
of OTRBs and large buses. This final rule is designed to work in tandem 
with these other requirements to further improve OTRB and large bus 
occupant safety.
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    \6\ 81 FR 27904.
    \7\ In 2009, DOT also issued a Motorcoach Safety Action Plan 
that addressed additional factors, such as driver fatigue and 
operator maintenance schedules. An update to the Departmental plan 
was issued in December 2012 https://www.fmcsa.dot.gov/sites/fmcsa.dot.gov/files/docs/Motorcoach-Safety-Action-Plan-2012.pdf.
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    While the agency's previous rulemakings in this area are expected 
to improve OTRB and large bus safety, passenger ejection in OTRB and 
large bus crashes remains a concern. Although seat belts are now 
required on OTRBs and large buses, not all states require that 
passengers wear seat belts on OTRBs and the agency believes seat belt 
use is generally low among large bus passengers. Additionally, while 
the structural integrity requirements enhance occupant safety by 
providing a ``survival space'' in a rollover, they do not mitigate 
glazing breakage during the crash, which would create ejection portals. 
This final rule is designed to ensure window glazing remains intact 
during a crash and windows do not open, even if a passenger is thrown 
against the glazing during the crash.
    To accomplish this safety objective, the new FMVSS No. 217a 
specifies certain benchmarks that OTRB and large bus window glazing 
must meet when it is contacted by an impactor projected at the window 
at a specified speed. In the adopted test, a 26 kilogram (kg) (57 pound 
(lb)) impactor is propelled from inside a test vehicle toward the 
window glazing at 21.6 kilometers per hour (km/h) (13.4 miles per hour 
(mph)). Each side window and glass panel/window on the roof would be 
subject to any one of three impacts, as selected by NHTSA in a 
compliance test: (a) an impact near a latching mechanism, discrete 
attachment point, or (for windows without latches) the center of the 
lower window edge of an intact window; (b) an impact at the center of 
the daylight opening \8\ of an intact window; and (c) an impact at the 
center of the daylight opening of a pre-broken glazing. The windows 
would have to prevent passage of a 102-millimeter (mm) (4 inch) 
diameter sphere both during and after the impact. Additionally, 
emergency exits are required to remain operable after each impactor 
test. The impactor and impact speed simulate the loading from an 
average size unrestrained adult male thrown from one side of a large 
bus and impacting a window on the opposite side of the bus in a 
rollover.
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    \8\ Center of daylight opening is the center of the total 
unobstructed window opening that would result from the removal of 
the glazing.
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    These requirements would ensure that glazing is securely bonded to 
window frames, no potential ejection portals are created due to 
breaking of the glass, the windows remain closed when impacted, and 
emergency exits remain operable after the crash. The test with the pre-
broken glazing would encourage the installation of advanced glazing. 
The requirement would also help ensure the advanced glazing reasonably 
retains occupants within the structural sidewall of the bus in a crash.

[[Page 86257]]

    The requirements in FMVSS No. 217a apply to OTRBs and all new large 
buses, with limited exceptions. The standard does not apply to school 
buses, prison buses, buses with perimeter seating, or transit buses 
that are not OTRBs. The FMVSS No. 217a requirements generally apply to 
those buses that are also required to meet the rollover structural 
integrity requirements of FMVSS No. 227, ``Bus rollover structural 
integrity.'' School bus derivative buses that meet the school bus roof 
crush requirements of FMVSS No. 220, ``School bus rollover 
protection,'' instead of FMVSS No. 227, would also need to meet FMVSS 
No. 217a.
    This final rule adds a new requirement to FMVSS No. 217, ``Bus 
emergency exits and window retention and release,'' that emergency exit 
window latches may not protrude more than 1 inch into the window 
opening when the window is open to minimize the potential for the latch 
protrusions to hinder the emergency egress of passengers. This 
requirement applies to all new buses that are currently subject to 
FMVSS No. 217, including new school buses.
    NHTSA has decided not to require existing large buses to meet the 
requirements adopted today for new buses. Most of the commenters did 
not support a retrofitting requirement. Upgraded window glazing on 
older buses without the requisite improved structural integrity in 
accordance with FMVSS No. 227 may not mitigate occupant ejections 
because the advanced glazing could simply pop out of the portal due to 
excessive structural deformation in a crash. The agency has also 
decided not to require retrofitting of buses with improved latch 
designs and window glazing materials. NHTSA believes it is not 
practical to retrofit improved latch systems on windows of existing 
buses because of the unique condition (including pre-existing damage or 
deformation) of each existing window structure and latching mechanism.
    NHTSA estimates that this rulemaking will be cost beneficial. The 
agency estimates the annual cost of this rule to be $0.96 million and 
annual undiscounted equivalent lives saved \9\ to be between 0.37 and 
1.91. The main contributor to the cost of this rule is estimated as the 
material costs for manufacturers to upgrade their window units from a 
tempered/tempered double-glazed window unit to, at minimum, a 
laminated/tempered double-glazed window unit. This improvement in 
window unit construction would not result in a considerable weight 
change. As outlined in the Final Regulatory Evaluation (FRE), NHTSA 
projects that the rule would cost between $0.50 million to $4.30 
million per equivalent life saved (Table 1). The net benefit/cost 
impact ranges from a net benefit of $1.92 million to $18.44 million 
(Table 2).
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    \9\ For details concerning equivalent lives saved, reference the 
FRE docketed with this final rule.

                                                 Table 1--Net Cost to Society Per Equivalent Life Saved
                                                              [In millions of 2022 dollars]
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                                                                         15% belt use rate                               90% belt use rate
                                                         -----------------------------------------------------------------------------------------------
                                                           Undiscounted         3%              7%         Undiscounted         3%              7%
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Material Costs..........................................           $0.96           $0.96           $0.96           $0.96           $0.96           $0.96
Equivalent Lives Saved \A\ \B\..........................          1.9191          1.5064          1.1491           0.374          0.2936          0.2240
Cost per Equivalent Life Saved..........................           $0.50           $0.64           $0.84           $2.58           $3.28           $4.30
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Notes:
A--These values from the FRE account for serious injuries (MAIS 3-5) by utilizing a relative injury factor.
B--MAIS = Maximum AIS, AIS = Abbreviated Injury Scale, MAIS 0 = No Injury, MAIS 1 = Minor, MAIS 2 = Moderate, MAIS 3 = Serious, MAIS 4 = Severe, MAIS 5
  = Critical, MAIS 6 = Maximum (untreatable)


                                                            Table 2--Annualized Net Benefits
                                                              [In millions of 2022 dollars]
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                                                                         15% belt use rate                               90% belt use rate
                                                         -----------------------------------------------------------------------------------------------
                                                           Undiscounted         3%              7%         Undiscounted         3%              7%
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Benefits from comprehensive costs avoided...............          $24.72          $19.40          $14.80           $4.82           $3.78           $2.88
Material costs..........................................            0.96            0.96            0.96            0.96            0.96            0.96
Net benefits............................................           23.75           18.44           13.84            3.85            2.82            1.92
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II. Background

    Since the early 2000s, NHTSA has made a concerted effort to improve 
OTRB safety. These types of buses often carry children and the elderly, 
which are two of the most vulnerable groups in motor vehicle crashes. 
Although transportation via OTRBs is generally a safe form of travel, 
the agency decided to better protect the public against unreasonable 
risk of death or injury in high-occupancy vehicles through a series of 
rulemakings. In many cases, crashes involving OTRBs result in 
rollovers, which can significantly damage the vehicle and create 
ejection portals that allow part or all of an occupant's body to be 
ejected from the vehicle during a crash.
    The agency has promulgated regulations that significantly reduce 
the risk that passengers will be ejected from OTRBs in the event of a 
rollover crash.\10\ This final rule represents yet another effort to 
significantly mitigate the risk of serious injury or death resulting 
from occupant ejection in OTRB crashes. It is the third rule targeted 
at minimizing the risk of ejection from OTRBs during a crash that the 
agency has promulgated over the past fifteen years. With this final 
rule, the agency will have taken yet another large stride in improving 
the safety of OTRBs, which means safer transportation for a significant 
number of children, the elderly, and lower

[[Page 86258]]

income individuals. What follows in this background section is a brief 
summary of NHTSA's efforts in the recent past to improve OTRB safety, 
as well as a discussion about how the proposal and this final rule were 
developed.
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    \10\ 78 FR 70415 (Nov. 25, 2013); 80 FR 36049 (Jun 23, 2015); 86 
FR 74270 (Dec 29, 2021).
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a. NHTSA's Approach to Motorcoach Safety

    In 2007, NHTSA undertook a comprehensive review of motorcoach 
safety issues and the course of action that the agency could pursue to 
address them. The agency considered various prevention, mitigation, and 
evacuation approaches in developing the plan. The agency considered 
issues such as: cost and duration of testing, development, and data 
analysis; likelihood that the effort would lead to the desired and 
successful conclusion; target population and possible benefits that 
might be realized; and anticipated cost of implementing the ensuing 
requirements into the bus fleet. The results were published as 
``NHTSA's Approach to Motorcoach Safety.'' This document outlined four 
critical areas that the agency believed significantly contributed to 
fatalities and serious injuries associated with motorcoaches: (1) 
passenger ejection, (2) rollover structural integrity, (3) emergency 
egress, and (4) fire safety. This was the first of two documents that 
the Department produced on motorcoach safety.

b. U.S. DOT Motorcoach Safety Action Plan

    In 2009, DOT issued a Departmental Motorcoach Safety Action Plan, 
which outlined a department-wide strategy to enhance motorcoach safety. 
In addition to the four priority action items specified in NHTSA's 2007 
``NHTSA's Approach to Motorcoach Safety,'' the DOT plan identified 
other strategies the Department would pursue to enhance motorcoach 
safety, such as issuing rules regarding electronic stability control 
systems, event data recorders, and programs addressing driver fatigue 
and operator maintenance.

c. Congressional Action: MAP-21 and the Motorcoach Enhanced Safety Act

    On July 6, 2012, President Obama signed MAP-21, which incorporated 
the Motorcoach Enhanced Safety Act in Subtitle G. The Motorcoach 
Enhanced Safety Act included a number of mandates, including 
requirements that DOT issue the following regulations, among others: a 
requirement that seat belts be installed in motorcoaches, a requirement 
mandating improved roof strength and crush resistance standards, and 
requirements that mitigate the likelihood of occupant ejection from 
motorcoaches in the event of a crash.
    As described in more detail below, NHTSA has issued several 
regulations over the past fifteen years that have improved motorcoach 
safety and satisfied Congress's statutory mandates in the Motorcoach 
Enhanced Safety Act. This final rule contributes to the agency's effort 
to further satisfy Congress's mandate to create anti-ejection safety 
countermeasures and fits with NHTSA's other motorcoach related 
rulemakings described below.

d. NHTSA's 2013 Motorcoach Seat Belt Final Rule

    On November 25, 2013, NHTSA published a final rule (``seat belt 
final rule'') that amended FMVSS No. 208, ``Occupant crash 
protection,'' to require that all new OTRBs as well as new buses with a 
gross vehicle weight rating (GVWR) greater than 11,793 kg (26,000 lb) 
have lap/shoulder seat belts for each passenger seating position. This 
rule fulfilled the mandated rulemaking in the Motorcoach Enhanced 
Safety Act, which directed DOT to ``prescribe regulations requiring 
safety belts to be installed in motorcoaches at each designated seating 
position.'' In addition to satisfying the seat belt mandate in the 
Motorcoach Enhanced Safety Act, this rule was also the agency's first 
step toward satisfying another mandate in the Motorcoach Enhanced 
Safety Act, which directed the Secretary to issue regulations that 
mitigate the risk of ejection from motorcoaches. At the time, NHTSA 
estimated that seat belts, when used, would be 77 percent effective in 
preventing fatal injuries in motorcoach rollover crashes, primarily by 
preventing ejection.
    The agency remains confident that the seat belt requirement is 
effective in mitigating ejection risk in crashes involving OTRBs and 
other large buses. However, seat belt usage rates by motorcoach 
occupants are uncertain. As an agency, NHTSA has the authority to 
mandate that OTRBs and other large buses have seat belts installed at 
each passenger designated seating position, but the agency does not 
have the authority to mandate usage of seat belts by passengers.\11\ 
The agency recognized at the time that the seat belt rule would not 
completely mitigate the risk of ejection, and the agency also 
recognized that there would be additional risks to belted passengers in 
OTRB and other large bus rollover crashes due to the lack of structural 
integrity requirements for those vehicles.
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    \11\ Laws requiring the use of seat belts in passenger vehicles 
are set by states.
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e. NHTSA's 2021 Motorcoach Structural Integrity Final Rule

    On December 29, 2021, NHTSA promulgated a final rule (``structural 
integrity final rule'') that established FMVSS No. 227, ``Bus rollover 
structural integrity.'' \12\ This new standard requires that buses 
provide a ``survival space'' in a rollover test to protect occupants 
from significant collapse of the bus structure around them. 
Additionally, the new standard requires that emergency exits remain 
closed during the rollover test. FMVSS No. 227 provides two significant 
safety benefits: (1) it protects occupants--belted and unbelted--from 
being harmed due to significant deformation of the bus structure or 
large falling objects such as luggage racks; and (2) it protects belted 
and unbelted occupants by minimizing the risk that emergency exits 
become ejection portals that passengers could be partially or 
completely ejected through.
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    \12\ 86 FR 74270 (Dec. 29, 2021); Partial grant of petitions for 
reconsideration, 88 FR 77523 (Nov. 13, 2023).
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    The structural integrity final rule satisfies the mandate in the 
Motorcoach Enhanced Safety Act that required the Secretary of 
Transportation to issue a regulation improving roof strength and crush 
resistance standards. Additionally, like the seat belt rule, the 
structural integrity final rule also contributes to satisfying the 
ejection mitigation mandate in the Motorcoach Enhanced Safety Act.
    Although the promulgation of FMVSS No. 227 is expected to improve 
safety outcomes in large bus rollover crashes when it goes into effect, 
the agency understands that occupants will still be at risk of ejection 
due to potential breakage of window glazing on large buses. Without a 
requirement that window glazing and latches on buses meet certain 
performance criteria, occupants could still be thrown against the 
window, break the window in the process, and be ejected through the 
broken window. This type of ejection is what spurred the agency to 
initiate this advanced glazing rulemaking.
    NHTSA's strategy has been first to seek improvements to the 
rollover structural integrity of motorcoaches (roof strength and crush 
resistance) and then to pursue measures that would drive use of 
advanced glazing. This ordered approach is based on findings from a 
NHTSA funded study \13\ that

[[Page 86259]]

found the integrity of the bus structure has a profound impact on the 
effectiveness of glazing as an anti-ejection safety countermeasure. 
Without a threshold standard for bus structural integrity, a twisting 
motion of a bus in a rollover could simply pop out any advanced glazing 
used in the windows and negate the potential benefits of the glazing in 
mitigating occupant ejection.
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    \13\ Motor Coach Glazing Retention Test Development for Occupant 
Impact During a Rollover (Martec Study), Final Report published on 
August 2006, Docket No. NHTSA-2002-11876-15.
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f. Data and Safety Need for Strengthening Motorcoach Window Glazing

Overview of Window Glazing
    In the context of motor vehicles, ``glazing'' is a general term 
used to describe the material used in vehicle windows. The glazing in 
motor vehicles typically consists of either glass, which can be 
tempered or laminated, or transparent plastics, such as acrylic or 
polycarbonate.
    The agency expects that manufacturers will often use laminated 
glass to meet the new requirements adopted in this final rule. A single 
pane of laminated glass contains two glass layers held together by an 
interlayer, typically made of polyvinyl butyral (PVB). The PVB 
interlayer retains a strong bond with the outer layers of glass so that 
in the event the glass breaks or cracks, large shards of sharp glass do 
not become free and risk cutting or seriously injuring people. 
Laminated glass may crack or splinter upon impact with the ground, but 
it can still provide a barrier to retain passengers within the bus if 
the glazing is retained within the window frame, the PVB interlayer is 
not excessively torn or punctured, and the window latch remains closed.
    Tempered glass is also often used for windows on vehicles and 
buses. Several OTRB manufacturers currently use tempered glass as their 
glazing of choice for windows. Tempered glass is processed with 
controlled thermal or chemical treatments. These treatments strengthen 
the glass and create balanced internal stresses so that when the glass 
does break, it breaks or crumbles into smaller granular chunks instead 
of large, jagged shards. Tempered glass is stronger than laminated 
glass, but an occupant impacting the window during a rollover event and 
the bus impact with the ground can potentially shatter tempered glass, 
causing the glazing to vacate the window frame and creating an ejection 
portal.
    In most passenger cars, a single layer of glazing is used for the 
windows or windshield. However, multiple layers of glazing are often 
used in the side windows of buses.\14\ For example, a bus may have a 
double-glazed tempered/tempered side window, which means within one 
window frame, there is an interior-side pane of tempered glass and an 
exterior-side pane of tempered glass with an air gap in between the 
two. This setup is a type of ``double-glazed'' window because there are 
two layers of glazing in the window frame. Based on NHTSA's research 
and industry feedback from the NPRM, the most common type of glazing 
used in motorcoach side windows is a double-glazed tempered/tempered 
window unit.
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    \14\ OTRB manufacturers generally use this type of window for 
thermal and sound insulation purposes. Having an ``air gap'' between 
the window panes acts as a thermal barrier, making it easier to keep 
the bus a comfortable temperature. The air gap also prevents 
vibrations from passing through as easily, resulting in a quieter 
ride for occupants.
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    Under section 32702 of MAP-21, ``advanced glazing'' means glazing 
installed in a portal on the side or the roof of a motorcoach that is 
designed to be highly resistant to partial or complete occupant 
ejection in all types of motor vehicle crashes. This rulemaking puts in 
place a series of performance tests to prevent partial and complete 
ejection of bus occupants. These tests, described below in this 
preamble, include striking the unbroken and broken glazing with an 
impactor and measuring both the excursion distance of the impactor 
during impact and any resulting openings in the glazing after the 
impact.
Data and Safety Need
    There were 73 OTRB and 38 large bus fatal crashes in the 14-year 
period from 2006 through 2019. Among these 111 OTRB and large bus 
crashes, 52 were rollovers, 53 were frontal crashes, and 6 were side 
crashes. The anti-ejection glazing requirements in this final rule are 
expected to reduce ejections in all of these crash types. Of the 73 
OTRBs involved in fatal crashes, 88 percent had a GVWR greater than 
11,793 kg (26,000 lb).
    NHTSA analyzed data from the agency's Fatality Analysis Reporting 
System (FARS) from 2006 through 2019 to analyze fatal bus crashes 
within the United States. During this period there were 111 fatal 
crashes involving all OTRBs regardless of GVWR and other applicable 
non-OTRBs with a GVWR greater than 11,793 kg (26,000 lb), resulting in 
a total of 284 occupant fatalities (an average of 20.3 total occupant 
fatalities per year). Tables 3 and 4 show the breakdown of the number 
of crashes and fatalities by bus body type, GVWR, and crash type, 
respectively. Fatalities resulting from other events such as fires or 
occupants jumping from a bus were not included.
    The OTRB and large bus fatalities were further categorized into two 
groups representing drivers and passengers. Passenger fatalities were 
significantly higher than driver fatalities, accounting for 84 percent 
of the total fatalities, and were particularly prevalent in the OTRB 
category. Rollover events accounted for 66 percent of all passenger 
fatalities (compared to 20 percent of driver fatalities). Rollover 
events are also the deadliest crash type, with 166 total fatalities in 
52 crashes, resulting in 3.2 fatalities per crash.

                                     Table 3--OTRB & Large Bus Fatal Crashes
                                                [FARS 2006-2019]
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                                                     Rollover          Front           Side            Total
----------------------------------------------------------------------------------------------------------------
Over-the-road Bus...............................              40              30               3              73
Large Bus GVWR >11,793 kg.......................              12              23               3              38
                                                 ---------------------------------------------------------------
    Total.......................................              52              53               6             111
----------------------------------------------------------------------------------------------------------------


[[Page 86260]]


                                                Table 4--OTRB & Large Bus Occupant Fatalities in Crashes
                                                                    [FARS 2006-2019]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         OTRB             Large Bus GVWR >11,793                   Total
                                                              --------------------------            kg            --------------------------------------
                          Crash type                                                    --------------------------
                                                                  Driver     Passenger      Driver     Passenger      Driver     Passenger       All
--------------------------------------------------------------------------------------------------------------------------------------------------------
Rollover.....................................................            7          134            2           23            9          157          166
Front........................................................           23           39           13           26           36           65          101
Side.........................................................            1            9            0            7            1           16           17
                                                              ------------------------------------------------------------------------------------------
    Total....................................................           31          182           15           56           46          238          284
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Occupant fatalities were further broken down based on ejection 
(Table 5) and ejection path. Occupant ejection is highly correlated 
with fatality. For all OTRB and large bus occupant fatalities, 39 
percent were associated with ejection.\15\ Additionally, 71 percent of 
ejected occupant fatalities occurred in rollover crashes, highlighting 
the importance of ejection mitigation in rollover crashes. Rollovers 
remain the largest cause of occupant fatalities, for both ejected and 
non-ejected passengers, in OTRB and large bus crashes. However, anti-
ejection glazing will help prevent occupant ejection in all crash 
types. During frontal impacts and side impacts, occupants are still at 
risk of ejection, as shown in Table 5. Any impact where the side 
windows break presents a risk of at least partial ejection for 
passengers. Partial ejection from a vehicle carries the additional risk 
of entrapment, as the partially ejected body part can be pinned under 
the bus, which can cause serious injury and prevent the immediate 
extraction of the passenger from the crash scene. Bus side windows can 
shatter upon impact even from frontal crashes, as evidenced during 
NHTSA's 35 mph frontal crash test of a 2000 Motor Coach Industries 
motorcoach in 2009.\16\
---------------------------------------------------------------------------

    \15\ Ejection data include both complete and partial ejections.
    \16\ See https://www.nhtsa.gov/research-data/research-testing-databases#/vehicle/6934.

                                            Table 5--OTRB & Large Bus Occupant Fatalities by Ejection Status
                                                                    [FARS 2006-2019]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       OTRB                 Large Bus GVWR > 11,793 kg                 Total
                       Crash type                        -----------------------------------------------------------------------------------------------
                                                               Eject         No Eject          Eject         No Eject          Eject         No Eject
--------------------------------------------------------------------------------------------------------------------------------------------------------
Rollover................................................              70              71               9              16              79              87
Front...................................................              21              41               6              33              27              74
Side....................................................               5               5               1               6               6              11
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................              96             117              16              55             112             172
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The aforementioned data show that crashes involving ejections 
present a high risk of death to the occupants of these buses. The 
majority of fatalities occur in rollovers, and approximately 48 percent 
of rollover occupant fatalities are associated with ejection.
    In nearly all the OTRB and large bus fatal rollover events 
discussed above, there was a significant amount of structural damage to 
the roof and side structure of the vehicles, as well as open window 
portals.\17\ This is a prime example of why this final rule works in 
tandem with the structural integrity final rule. The structural 
integrity final rule will ensure that the structure of the bus does not 
cause harm to occupants or create ejection portals via emergency exits, 
and this final rule will take the final step of increasing use of 
advanced glazing that prevents partial or complete ejection of 
motorcoach passengers and further ensures the integrity of glazing 
mounting.
---------------------------------------------------------------------------

    \17\ See NTSB report HAB-16/01 for September 21, 2014, OTRB 
rollover crash near Red Lion Delaware; see also NTSB report HAR-18/
03 for May 14, 2016, OTRB rollover crash near Laredo Texas.
---------------------------------------------------------------------------

g. The 2016 NPRM

NPRM Proposals
    On May 6, 2016, NHTSA published an NPRM that proposed the 
establishment of FMVSS No. 217a, with the goal of reducing the 
potential for occupant ejection in a crash. The NPRM proposed a new 
dynamic impact test that would be used to drive the installation of 
advanced glazing in high-occupancy buses. In this test, a 26 kg (57 lb) 
impactor would be propelled from inside a test vehicle toward a window 
glazing at 21.6 km/h (13.4 mph). The impactor and impact speed were 
chosen because they represent what the impact force would be from an 
average-sized unrestrained adult male striking the window on the 
opposite side of a large bus in a rollover. Each side window, rear 
window, and glazing panel/window on the roof would be subject to one of 
three impacts, as selected by NHTSA in a compliance test: (a) an impact 
near a latching mechanism of an intact window; (b) an impact at the 
center of the daylight opening of an intact window; and (c) an impact 
at the center of the daylight opening of a pre-broken window. The 
window would need to prevent passage of a 102 mm (4 inch) diameter 
sphere both during and after the impact to pass the test. In the 
proposed tests, the agency would assess the window during the impact by 
determining whether any part of the window passes a reference plane 
defined during a pre-test set up procedure. Furthermore, in the 
proposed test for the pre-broken glazing, the maximum displacement of 
the impactor at the center of the daylight opening of subject windows 
would be limited to 175 mm (6.9 inches).

[[Page 86261]]

    In the NPRM, NHTSA also proposed to limit the protrusions of 
emergency exit latches into the openings of windows to ensure they do 
not unduly hinder emergency egress. This proposal was supported by a 
recommendation from the National Transportation Safety Board (NTSB), 
which had submitted a letter to NHTSA describing a crash (``Gray Summit 
crash'') \18\ where occupants' clothing was caught on a window latch as 
they were trying to egress the vehicle. A detailed description of the 
Gray Summit crash can be found in the NPRM for this final rule. The 
NPRM proposed a limit that would set the maximum protrusion of a window 
latch into emergency exit openings of windows at 1 inch when the 
emergency exit window is open.
---------------------------------------------------------------------------

    \18\ NTSB/HAR-11/03 PB2011-916203; Multivehicle Collision 
Interstate 44 Eastbound Gray Summit, Missouri, August 5, 2010; 
December 2011.
---------------------------------------------------------------------------

    The NPRM proposed to apply the advanced glazing requirements to: 
(a) all new OTRBs (regardless of GVWR); and (b) all new buses other 
than OTRBs with a GVWR greater than 11,793 kg (26,000 lb), with the 
exception of school buses, prison buses, transit buses, and perimeter 
seating buses. For the applicable bus types, the proposed applicable 
windows included bus side and rear windows, and windows/glazing panels 
on the roof of the vehicle with a minimum dimension measured through 
the center of its area of 279 mm (11 inches) or greater. The NPRM 
proposed a different applicability for the emergency exit window latch 
protrusion requirement--the NPRM proposed that this requirement would 
apply to buses covered by the new FMVSS No. 217a as well as all buses 
subject to FMVSS No. 217, ``Bus emergency exits and window retention 
and release.'' \19\
---------------------------------------------------------------------------

    \19\ FMVSS No. 217 S3 says the standard ``applies to buses, 
except buses manufactured for the purpose of transporting persons 
under physical restraint.'' Accordingly, the NPRM proposed that the 
latch requirement apply to all buses except buses used for 
transporting persons under physical restraint.
---------------------------------------------------------------------------

Martec Study
    As discussed in the NPRM, in 2003, NHTSA and Transport Canada 
entered into a joint program that focused on improving glazing and 
window retention on OTRBs to prevent occupant ejection.\20\ This 
program is referenced in the NPRM and the sections below as the 
``Martec study,'' and the data gathered from the study is the basis for 
many of the proposals being adopted as part of this final rule. For the 
purposes of the NPRM, the agency used this study to develop a test 
procedure that realistically represented the impact loads from an 
unrestrained occupant onto motorcoach glazing during a rollover event.
---------------------------------------------------------------------------

    \20\ Motor Coach Glazing Retention Test Development for Occupant 
Impact During a Rollover (Martec Study), Final Report published on 
August 2006, Docket No. NHTSA-2002-11876-15.
---------------------------------------------------------------------------

III. NHTSA's Statutory Authority

    NHTSA is issuing this final rule pursuant to and in accordance with 
its authority under the National Traffic and Motor Vehicle Safety Act 
and the relevant provisions of MAP-21.

a. National Traffic and Motor Vehicle Safety Act (Safety Act)

    Under 49 United States Code (U.S.C.) Chapter 301, Motor Vehicle 
Safety (49 U.S.C. 30101 et seq.), the Secretary of Transportation is 
responsible for prescribing motor vehicle safety standards that are 
practicable, meet the need for motor vehicle safety, and are stated in 
objective terms (section 30111(a)). ``Motor vehicle safety'' is defined 
in the Safety Act (section 30102(a)(8)) as ``the performance of a motor 
vehicle or motor vehicle equipment in a way that protects the public 
against unreasonable risk of accidents occurring because of the design, 
construction, or performance of a motor vehicle, and against 
unreasonable risk of death or injury in an accident, and includes 
nonoperational safety of a motor vehicle.'' ``Motor vehicle safety 
standard'' means a minimum standard for motor vehicle or motor vehicle 
equipment performance (section 30102(a)(9)). When prescribing such 
standards, the Secretary must consider all relevant available motor 
vehicle safety information (section 30111(b)(1)). The Secretary must 
also 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 (section 30111(b)(3)) and 
the extent to which the standard will further the statutory purpose of 
reducing traffic accidents and associated deaths and injuries (section 
30111(b)(4)). The responsibility for promulgation of FMVSSs is 
delegated to NHTSA (49 CFR 1.95).

b. MAP-21 (Incorporating the Motorcoach Enhanced Safety Act of 2012)

    NHTSA is issuing this final rule in accordance with MAP-21, which 
incorporates the Motorcoach Enhanced Safety Act of 2012 into Subtitle 
G.\21\ Section 32703(b) of MAP-21 requires the Secretary (NHTSA by 
delegation) to prescribe regulations that would address certain aspects 
of motorcoach crash performance within 2 years if the agency determines 
that the standards would meet the requirements and considerations of 
section 30111(a) and (b) of the National Traffic and Motor Vehicle 
Safety Act.\22\
---------------------------------------------------------------------------

    \21\ The Motorcoach Enhanced Safety Act of 2012 is incorporated 
into the Moving Ahead for Progress in the 21st Century Act, Public 
Law 112-141 (Jul. 6, 2012).
    \22\ Id. Sec.  32703(b).
---------------------------------------------------------------------------

    Two subsections of section 32703(b) are particularly relevant to 
this final rule. Subsection (b)(1) specifies that the Secretary is to 
establish improved roof and roof support standards that ``substantially 
improve the resistance of motorcoach roofs to deformation and intrusion 
to prevent serious occupant injury in rollover crashes involving 
motorcoaches.'' Subsection (b)(2) directs the Secretary to ``consider 
advanced glazing standards for each motorcoach portal and [to] consider 
other portal improvements to prevent partial and complete ejection of 
motorcoach passengers, including children.'' \23\
---------------------------------------------------------------------------

    \23\ While this final rule is mainly aimed at addressing the 
rollover structural integrity of specific large bus types, the 
reduced deformation of the bus structure would ensure that any 
advanced glazing installed on portals would be retained on their 
mounting and reduce the risk of occupant ejection in rollover 
crashes. Further, the requirement that emergency exits should not 
open during the rollover test would also ensure that the exits do 
not become ejection portals. Thus, both subsection (b)(1) and 
subsection (b)(2) are relevant to this rule.
---------------------------------------------------------------------------

    MAP-21 contains other provisions pertaining to this rulemaking. 
Section 32702 states that ``motorcoach'' has the meaning given to the 
term ``over-the-road bus'' in section 3038(a)(3) of the Transportation 
Equity Act for the 21st Century (TEA-21).\24\ Section 3038(a)(3) of 
TEA-21 (see 49 U.S.C. 5310 note) defines ``over-the-road bus'' as ``a 
bus characterized by an elevated passenger deck located over a baggage 
compartment.'' However, section 32702 of MAP-21 excludes transit buses 
and school buses from the ``motorcoach'' definition.\25\
---------------------------------------------------------------------------

    \24\ Moving Ahead for Progress in the 21st Century Act, Public 
Law 112-141, 32702(6).
    \25\ Id. Sec.  32702(6)(A)-(B).
---------------------------------------------------------------------------

    Under Sec.  32702, ``portal'' means any opening on the front, side, 
rear, or roof of a motorcoach that could, in the event of a crash 
involving the motorcoach, permit the partial or complete ejection of 
any occupant from the motorcoach, including a young child. Section 
32703(b)(2) also states that in prescribing such standards, the 
Secretary shall consider the impact of such standards on the use of 
motorcoach portals as a means of emergency egress.

[[Page 86262]]

    MAP-21 further directs the Secretary to apply any regulation 
prescribed in accordance with section 32703(b) to all motorcoaches 
manufactured more than 3 years after the date on which the regulation 
is published.\26\ In addition, the Secretary may assess the 
feasibility, benefits, and costs of applying any requirement 
established under section 32703(b)(2) to ``motorcoaches manufactured 
before the date on which the requirement applies to new motorcoaches'' 
(retrofit).\27\ Finally, MAP-21 also authorizes the Secretary to 
combine the required rulemaking actions as the Secretary deems 
appropriate.\28\
---------------------------------------------------------------------------

    \26\ Id. Sec.  32703(e)(1).
    \27\ Id. Sec.  32703(e)(2), ``Retrofit Assessment for Existing 
Motorcoaches.''
    \28\ Id. Sec.  32706.
---------------------------------------------------------------------------

IV. The Final Rule and Response to Comments

a. Establishing FMVSS No. 217a and New Requirements

    This final rule adopts most of the proposals from the 2016 NPRM 
(the differences between the NPRM and this final rule are highlighted 
in the section below). As discussed in the NPRM, this final rule 
establishes a new standard within 49 CFR part 571 that will now be 
referred to as FMVSS No. 217a. This new standard will set out 
requirements that windows in certain types of buses must meet when 
evaluated by the dynamic test procedure described in the 2016 NPRM. 
Additionally, the new requirements will allow for only a 1-inch maximum 
protrusion for emergency exit window latches when the emergency exit 
window is open. Although there are some differences between the final 
rule and the NPRM, after reviewing the public comments to the NPRM, the 
agency has decided to adopt many of the proposals from the 2016 NPRM.

b. Differences Between the NPRM and the Final Rule

    This final rule makes amendments to several of the proposals in the 
2016 NPRM based on the comments the agency received. The most notable 
change between the 2016 NPRM and this final rule is in the 
applicability of FMVSS No. 217a. This final rule excludes all perimeter 
seating buses, even if those buses are also OTRBs, from the 
requirements in FMVSS No. 217a since these buses are also excluded from 
the structural integrity requirements in FMVSS No. 227 and therefore 
could lack the requisite integrity to retain advanced glazing within 
the window frame. Additionally, the final rule excludes all rear 
windows from FMVSS No. 217a requirements because the field data does 
not indicate an ejection risk from rear windows. Other differences 
between the 2016 NPRM and the final rule are minor updates to the 
regulatory text which include: (1) an adjustment to the location within 
FMVSS No. 217 for the new regulatory text that adds the emergency exit 
latch protrusion requirement; (2) new figures to the FMVSS No. 217a 
regulatory text to clarify the window pre-breakage procedure and the 
emergency exit opening space; and (3) adjustments to the FMVSS No. 217a 
regulatory text regarding the window pre-breakage procedure to specify 
steps to take if the electric staple gun used to pierce the glazing 
does not produce holes or perceivable damage to the glazing.

V. Summary of Comments and Agency Responses

a. Overview of Comments

    NHTSA received 11 unique comments on the NPRM. Comments were 
submitted by large bus manufacturers, including IC Bus (ICB), Van Hool 
N.V. (Van Hool), Prevost and Nova Bus divisions (Prevost), and Blue 
Bird Body Company (BBBC); a motorcoach operator, Greyhound Lines, Inc. 
(Greyhound); industry groups, including Enhanced Protective Glass 
Automotive Association (EPGAA), and School Bus Manufacturers Technical 
Council (SBMTC); a U.S. government agency, the NTSB; glazing 
manufacturers, including SABIC Innovative Plastics US LLP (SABIC) and 
Exatec, LLC (Exatec); and a consumer advocacy group, The Advocates for 
Highway and Auto Safety (Advocates).
    Most commenters expressed support for an FMVSS on advanced anti-
ejection glazing and emergency exit latches that do not hinder 
passenger egress, but views differed on how these concepts should be 
implemented. For example, Greyhound, Prevost, and Van Hool expressed 
concern that advanced glazing, specifically laminated glass, may 
increase the potential for head and neck injuries of belted passengers. 
Additionally, several commenters stated that the NPRM did not account 
for all costs associated with the proposed rule.
    Most commenting bus manufacturers and SBMTC requested that certain 
bus types or window types be excluded from applicability under this 
rulemaking, including entertainer buses, school buses, school bus-
derivative buses, driver's windows, windows in doors, rear windows, and 
windows that are partially blocked by equipment or seating. Conversely, 
NTSB requested more bus types be included in the rulemaking, such as 
medium-sized buses with a GVWR of 11,793 kg (26,000 lb) or less, not 
including school buses.
    Exatec, ICB, and SABIC all expressed concerns that the proposed 
glass pre-breakage procedure did not properly account for advanced 
glazing that may not break upon application of a line load by the 
electric staple gun.
    No commenters supported mandating a retrofit for the glazing 
requirements, but NTSB did support a retrofit requirement for the 
minimum latch protrusion. A detailed discussion of comments and the 
agency's responses can be found below.

b. Applicability

Bus Types
    NHTSA proposed to apply the FMVSS No. 217a window glazing dynamic 
impact test requirements to generally the same group of vehicles 
covered by the bus rollover structural integrity NPRM published in 
August 2014.\29\ NHTSA noted that both requirements should apply to 
high occupancy vehicles associated with an unreasonable risk of fatal 
rollover involvement. According to the data, these vehicles are 
generally OTRBs regardless of GVWR, and other buses with a GVWR greater 
than 11,793 kg (26,000 lb). Accordingly, the NPRM proposed that buses 
subject to FMVSS No. 217a would be (a) new OTRBs (regardless of GVWR), 
pursuant to the Motorcoach Enhanced Safety Act of 2012, and (b) all new 
buses other than OTRBs with a GVWR greater than 11,793 kg (26,000 lb). 
Similar to the bus rollover structural integrity proposal, school 
buses, transit buses, and perimeter seat buses (as defined in the 
August 2014 NPRM) \30\ were excluded from the FMVSS No. 217a proposed 
requirements. Prison buses were also excluded from FMVSS No. 217a 
proposed requirements because prison buses have bars over the windows 
that would impede the impactor for the glazing dynamic impact tests.
---------------------------------------------------------------------------

    \29\ 79 FR 46090 (Aug. 6, 2014).
    \30\ Per the August 2014 NPRM: Transit bus means a bus that is 
equipped with a stop-request system sold for public transportation 
provided by, or on behalf of, a State or local government and that 
is not an over-the-road bus; Perimeter-seating bus means a bus with 
7 or fewer designated seating positions rearward of the driver's 
seating position that are forward-facing or can convert to forward-
facing without the use of tools and is not an over-the-road bus.
---------------------------------------------------------------------------

    The December 29, 2022 final rule establishing FMVSS No. 227, ``Bus 
rollover structural integrity,'' excluded perimeter seating buses that 
are non-OTRBs as well as those that are OTRBs

[[Page 86263]]

from the requirements in FMVSS No. 227. The November 2023 final rule 
\31\ responding to petitions for reconsideration of the December 2022 
final rule expanded the definition of transit buses to include buses 
with a stop-request system sold for public transportation provided by, 
or on behalf of, the federal government. As detailed later in this 
section, this final rule adopts the 2015 NPRM proposals for 
applicability of FMVSS No. 217a but extends the exclusions to include 
perimeter seating buses that are OTRBs and the expanded definition of 
transit buses. These buses excluded from FMVSS No. 217a requirements 
are also excluded from FMVSS No. 227 and so may lack the requisite 
structural integrity to ensure any advanced glazing in windows does not 
pop out of its frame in a crash and thereby negate the potential 
benefits of the advanced glazing.
---------------------------------------------------------------------------

    \31\ 88 FR 77523.
---------------------------------------------------------------------------

    Additionally, in the NPRM the agency proposed applying the 
emergency exit window latch protrusion requirement to the same buses 
covered by FMVSS No. 227 and all buses governed under FMVSS No. 217, 
which includes all school buses. The agency is adopting the window 
latch applicability proposal as part of this final rule.
Medium-Sized Buses
    NTSB commented that the final rule should include medium-sized non-
school buses with GVWRs in the range of 4,536-1,793 kg (10,001-26,000 
lb). It noted that these buses are typically built as body-on-chassis 
vehicles without an elevated passenger deck over a baggage compartment, 
so they do not fall within the ``over-the-road bus'' definition. NTSB 
cited the 2009 bus crash near Dolan Springs, Arizona,\32\ and a 2014 
bus crash in Davis, Oklahoma \33\ where passengers were ejected from 
medium-sized buses and died as a result. The NTSB's Davis, Oklahoma 
accident report stated that a lack of appropriate crashworthiness 
standards contributed to the severity of passenger injuries.
---------------------------------------------------------------------------

    \32\ Bus Loss of Control and Rollover, Dolan Springs, Arizona, 
January 30, 2009. Highway Accident Report NTSB/HAR-10/01 
(Washington, DC: NTSB 2010).
    \33\ Truck-Tractor Semitrailer Median Crossover Collision with 
Medium-Size Bus on Interstate 35, Davis, Oklahoma, September 26, 
2014. Highway Accident Report NTSB/HAR-15/03 (Washington, DC: NTSB 
2015).
---------------------------------------------------------------------------

Agency Response
    As proposed in the NPRM, the agency has decided that the 
requirements for FMVSS No. 217a will not be applicable to medium-sized 
non-OTRBs.\34\ NHTSA bases this decision on a review of data for 
medium-sized buses from 2006-2019 as shown below in Table 6. During 
this period there were 37 fatalities with some degree of ejection from 
crashes involving medium-sized buses. During the same period there were 
112 fatal ejections in OTRBs and large buses, even though the 
population of OTRBs and large buses is much smaller than the population 
of medium-sized buses. Specifically, approximately 2,200 large buses 
(including OTRBs) are produced annually, compared to approximately 
16,000 medium-sized buses.\35\ Although there may be certain risks of 
occupant ejection from medium-sized bus crashes, the agency has 
concluded that medium-sized buses do not pose a sufficient safety need 
to warrant application of FMVSS No. 217a to those buses.
---------------------------------------------------------------------------

    \34\ Medium-sized buses have a GVWR greater than 4,536 kg 
(10,000 lb) and less than or equal to 11,793 kg (26,000 lb).
    \35\ Medium-Size Bus Production and Sales Supplemental 
Information Report. Docket Item #30 from NTSB HWY17MH011 Highway 
Investigation. https://data.ntsb.gov/Docket?ProjectID=94934.

              Table 6--Fatal Crashes and Ejected Fatalities for Large Buses and Medium-Sized Buses
                                                [FARS 2006-2019]
----------------------------------------------------------------------------------------------------------------
                                                                                    Avg. annual     Avg. annual
                            Bus size                                Avg. annual      ejection       fleet sales
                                                                   fatal crashes    fatalities         \36\
----------------------------------------------------------------------------------------------------------------
Large Bus (greater than 26,000 lb GVWR) and all OTRBs...........             7.9             8.0           2,200
Medium-Size Bus (GVWR of 10,000-26,000 lb)......................             5.9             2.6          16,000
----------------------------------------------------------------------------------------------------------------

    Data show a considerable disparity between the rate of fatal 
ejections for large buses (OTRBs and other buses covered by this final 
rule) versus medium-sized buses. Not only are large buses involved in 
34 percent more fatal crashes on average annually, but they also have 3 
times as many ejected occupant fatalities annually compared to medium-
sized buses.
---------------------------------------------------------------------------

    \36\ Medium-Size Bus Roadway Departure, Return, and Rollover 
Bryce Canyon City, Utah September 20, 2019. Accident Report NTSB/
HAR-21/01 PB2021-100917.
---------------------------------------------------------------------------

    School buses and transit buses in the medium-sized bus range have a 
very low rate of fatal ejections in rollover events. The bus rollover 
structural integrity requirements for FMVSS No. 227 only apply to OTRBs 
and buses other than OTRBs with a GVWR greater than 26,000 lb, meaning 
that if the agency were to apply this final rule to medium-sized buses, 
occupants in those buses would not receive the protections afforded by 
FMVSS No. 227.\37\ One of the reasons the agency promulgated FMVSS No. 
227 was because windows were popping out of place during rollover 
events, creating ejection portals. Since medium-sized buses do not have 
to comply with FMVSS No. 227, requiring medium-sized buses to utilize 
enhanced glazing may not be effective in mitigating ejection because 
the advanced glazing may pop out of the window due to excessive 
structural deformation during a crash and thereby create an ejection 
portal. Accordingly, it would be illogical from a safety standpoint to 
make medium-sized buses subject to FMVSS No. 217a, but not to FMVSS No. 
227. Thus, the agency has decided not to make medium-sized buses 
applicable under this final rule.
---------------------------------------------------------------------------

    \37\ FMVSS No. 227 has several express exemptions; the standard 
does not apply to school buses, school bus derivative buses, transit 
buses, prison buses, and perimeter-seating buses.
---------------------------------------------------------------------------

Entertainer Buses
    The NPRM proposed to exclude perimeter seating buses from the final 
rule with the exception of, however, if perimeter seating buses that 
met the definition of an OTRB. Prevost commented that entertainer buses 
should be completely exempt under the final rule, regardless of whether 
they fit the definition of an OTRB. Buses referred to as entertainer 
buses are generally built from an OTRB shell and can contain interior 
features such as kitchens, bathrooms, bedrooms, lounge areas, dining 
areas, generators, and slide out portions of the structure. The window 
configuration may or may not be the same as those of other OTRBs built 
as typical passenger vehicles.

[[Page 86264]]

    Prevost commented that reducing the number of ejection-related 
fatalities is an important aspect of motorcoach safety and must be 
inherent to the design. Prevost further agreed with the intent of the 
proposed regulation to mitigate the creation of ejection portals, and 
to create uniformity throughout the industry products. However, Prevost 
requested special consideration for an exemption from the proposed 
requirements for entertainer buses. Prevost stated that an 
``entertainer coach is very different from the passenger motorcoach 
both in design and application. From a design perspective, they have 
fewer and smaller passenger windows, offering relatively less chance of 
a potential, partial, or full ejection.''
Agency Response
    The agency believes that the term ``entertainer bus'' is not a term 
of art to be used in the standard. The buses that Prevost described in 
its comment are likely considered perimeter-seating buses, a bus type 
that NHTSA defined in the NPRM \38\ and excluded from compliance in the 
proposal, unless the perimeter seating bus in question fits the 
definition of an OTRB. After reviewing Prevost's comment, NHTSA has 
decided to maintain that under this final rule the new standard will 
not be applicable to perimeter-seating buses. Further, to align the 
application of FMVSS No. 217a with FMVSS No. 227, perimeter-seating 
buses that also meet the definition of an OTRB will also be excluded 
from FMVSS No. 217a.
---------------------------------------------------------------------------

    \38\ According to the NPRM, perimeter-seating bus means a bus 
with 7 or fewer designated seating positions rearward of the 
driver's seating position that are forward-facing or that can 
convert to forward-facing without the use of tools and is not an 
over-the-road bus.
---------------------------------------------------------------------------

    As stated in the FMVSS No. 227 motorcoach structural integrity 
final rule, the agency does not find a reason to distinguish between 
OTRBs with perimeter seating and non-OTRBs with perimeter seating.\39\ 
The safety data indicate no relevant differences between these vehicles 
based on safety need. In other words, OTRBs with perimeter seating do 
not present a greater risk of injury compared to non-OTRBs with 
perimeter seating.
---------------------------------------------------------------------------

    \39\ 86 FR 74284-74285.
---------------------------------------------------------------------------

    Furthermore, as discussed above, the advanced glazing requirements 
are most effective when paired with the improved structural integrity 
required by FMVSS No. 227. Therefore, the agency is excluding OTRBs 
with perimeter seating to mirror the decision made in the final rule 
for FMVSS No. 227. Many of the safety benefits gained from advanced 
glazing are dependent on sufficiently strong vehicle structural 
elements, meaning it would not make sense to apply advanced glazing 
requirements to a set of vehicles that do not have to comply with the 
more stringent structural integrity requirements of FMVSS No. 227.
    Lastly, to synthesize the definition with this decision in this 
final rule, the agency has decided to amend the definition of a 
perimeter seating bus in the regulatory text by deleting the phrase 
``and is not an over the road bus'' from the end of the proposed 
definition.
School Bus Derivative Buses
    ICB recommended that commercial buses built from school bus designs 
should not have to meet the ejection mitigation requirements of the 
proposed rule. ICB noted that its commercial buses are ``much 
different'' from a traditional motorcoach, meaning the data and studies 
NHTSA used for the NPRM potentially would not apply to their buses. ICB 
stated that the operating environment of its commercial buses derived 
from school buses is more closely related to that of school buses than 
the operating environment and conditions of OTRBs, meaning that the 
routes ICB commercial buses are used on are generally routes involving 
lower speeds and frequent stops. ICB wrote ``[t]he commercial variants 
of school buses are typically used in applications such as church 
buses, college campus buses, local shuttles and tours, emergency 
responders, and parks and recreation departments.''
Agency Response
    The agency disagrees with ICB's generalization of school bus 
derivative bus designs and their operating environments. NHTSA is 
therefore not excluding school bus derivative buses from FMVSS No. 217a 
as part of this final rule. The agency is basing this decision on the 
fact that school bus derivative buses are available for use in 
intercity travel and are offered for sale with motorcoach-style 
features, such as larger windows than school buses. While these buses 
are not required to comply with FMVSS No. 227, ``Bus rollover 
structural integrity,'' these buses are required to comply with FMVSS 
No. 220, ``School bus rollover protection,'' and FMVSS No. 221, 
``School bus body joint strength.'' When the agency defined the term 
``school bus derivative bus'' in FMVSS No. 227, the agency defined 
these buses as ``a bus that meets Federal motor vehicle safety 
standards for school buses regarding emergency exits (Sec.  571.217), 
rollover protection (Sec.  571.220), bus body joint strength (Sec.  
571.221), and fuel system integrity (Sec.  571.301).'' To meet the 
regulatory definition of a school bus derivative bus, the bus must 
comply with specific school bus requirements--including the structural 
integrity requirements of FMVSS Nos. 220 and 221--even if the bus is 
not used for school-related purposes.
    One of the agency's concerns when it promulgated the structural 
integrity final rule was the possibility of window glazing popping out 
of place and creating ejection portals. The school bus structural 
integrity standards, FMVSS No. 220 and FMVSS No. 221, ensure the 
windows in school bus derivative buses are less likely to ``pop out,'' 
similar to FMVSS No. 227 for OTRBs and other large buses. Thus, the 
agency believes it is reasonable for school bus derivative buses to be 
subject to the new FMVSS No. 217a but not to FMVSS No. 227.
    ICB requested that commercial buses built from school bus designs 
should not have to meet the ejection mitigation requirements of the 
proposed rule. Although some of the commercial buses derived from 
school bus designs are similar to school bus vehicles not subject to 
the proposed rule, it is the use patterns of the buses that makes them 
distinct from school buses. School buses are typically used for local 
transportation of students from home to school and from school back 
home. Like transit buses, school buses are typically operated at lower 
rates of speed with frequent starts and stops. The commercial buses 
derived from school bus designs are sold to groups that use the buses 
for both intracity and intercity travel. Some of these buses utilize 
larger windows and coach-style seating, making them even more like 
OTRBs.
    A school bus is defined in 49 CFR 571.3 as ``a bus that is sold, or 
introduced in interstate commerce, for purposes that include carrying 
students to and from school or related events, but does not include a 
bus designed and sold for operation as a common carrier in urban 
transportation.'' In other words, the definition of a ``school bus'' is 
use-based--if it looks like a school bus and operates for school bus 
purposes, it is a school bus and must comply with school bus 
requirements. If it looks like a school bus, but is not used for school 
bus purposes, it is not a school bus and does not have to comply with 
all school bus requirements. This distinction in the FMVSS is a 
critical reason why the agency believes school bus derivative buses 
should be covered under FMVSS No. 217a. Forcing manufacturers to comply 
with two separate structural integrity requirements would be illogical. 
However, unlike structural integrity,

[[Page 86265]]

there is not an existing vehicle-level school bus-specific advanced 
glazing standard. Therefore, NHTSA has decided not to exclude school 
bus derivative buses from the dynamic impact test requirements of FMVSS 
No. 217a. If a school bus derivative bus weighs greater than 11,793 kg 
(26,000 lb), it will have to comply with FMVSS No. 217a.
Transit Buses
    As part of this final rule, NHTSA is adopting a slightly altered 
definition of the term ``transit bus.'' The definition proposed in the 
NPRM read: ``a bus that is equipped with a stop-request system sold for 
public transportation provided by, or on behalf of, a State or local 
government and that is not an over-the-road bus.''
    In considering how to define the term for this final rule, the 
agency considered its response to petitions for reconsideration of the 
final rule for FMVSS No. 227, ``Bus rollover structural integrity,'' 
concerning the definition of a transit bus. To ensure consistency among 
standards, NHTSA has decided to adopt the definition adopted in the 
agency's response to petitions for reconsideration of FMVSS No. 227. 
This definition of ``transit bus'' differs from the definition proposed 
in the NPRM.
    In the petitions for reconsideration for the structural integrity 
final rule, petitioners argued that buses that are manufactured as 
transit buses but sold to entities that are not state or local 
governments (or operated on behalf of state or local governments) are 
not considered transit buses. The entities that the petitioners 
described are either private operators or the federal government. The 
petitioners stated that these transit-type buses are operated in a 
similar manner as transit buses operated by state or local governments 
and should therefore be included in the definition of ``transit bus.''
    In NHTSA's responses to petitions for reconsideration of FMVSS No. 
227,\40\ the agency partially granted the petitioners' request for 
adjusting the transit bus definition. NHTSA amended the transit bus 
definition by including transit-type buses operated by the federal 
government, but not including transit-type buses operated by private 
entities. NHTSA determined the federal government utilizes transit-type 
buses in a similar manner as other public transit agencies, but private 
operators may utilize these buses in higher-risk driving patterns. This 
amended definition is also being adopted as part of this final rule 
establishing FMVSS No. 217a. The amended definition of transit bus is 
now:
---------------------------------------------------------------------------

    \40\ 88 FR 77523.
---------------------------------------------------------------------------

    ``Transit bus means a bus that is equipped with a stop-request 
system sold for public transportation provided by, or on behalf of, a 
Federal, State, or local government and that is not an over-the-road 
bus.''
Emergency Exit Latch Protrusion Limit Requirements Applicability
    Two commenters requested clarification on the applicability of the 
emergency exit latch protrusion limit requirement proposed in the NPRM. 
ICB commented that it understands the protrusion limits are applicable 
to all buses, including school buses. SBMTC stated that the protrusion 
limit requirements should apply to all school buses, regardless of 
GVWR. To support its request, SBMTC also noted that the NTSB-requested 
latch protrusion limits are from a crash involving a school bus.
Agency Response
    To clarify, in the NPRM, NHTSA proposed that the emergency exit 
latch protrusion requirement be applicable to the buses to which the 
dynamic impactor test would apply (OTRBs regardless of GVWR and other 
large buses, except transit buses, prison buses, school buses, and 
perimeter-seating buses, and school buses). NHTSA also requested 
comment on the merits of requiring all buses subject to FMVSS No. 217 
to meet the requirement. After reviewing the comments, the agency has 
decided to adopt this proposal as part of this final rule. To avoid 
confusion over the applicability of this emergency exit window latch 
protrusion requirement, NHTSA is creating a new paragraph in FMVSS No. 
217 as part of this final rule.
    The NPRM proposed adding the protrusion limits into FMVSS No. 217 
S5.4.1 and S5.4.2.2. The first section, S5.4.1, applies to emergency 
exits on all buses except certain emergency exits on certain school 
buses outlined in S5.2.3. The other amended section, S5.4.2.2, applies 
only to school buses with a GVWR of 10,000 lb or less. The preamble of 
the NPRM states ``the maximum latch plate protrusion requirement would 
be applicable to the buses to which the impactor tests would apply. . . 
. However, NHTSA is also proposing to extend the maximum latch plate 
protrusion requirement to other buses as well . . . . NHTSA is 
proposing to extend the proposed requirement to school buses also.'' 
\41\ The proposed amendment did not clearly indicate which bus types 
would need to comply with the protrusion limits. As stated in the NPRM, 
NHTSA's intent was for the protrusion limits to apply to all school 
buses, regardless of GVWR. Therefore, the changes proposed in the NPRM 
for FMVSS No. 217 S5.4.1 and S5.4.2.2 will not be implemented. Instead, 
the requirement will be adopted in a different location in FMVSS No. 
217, which is reflected in the amended regulatory text at the end of 
this final rule.
---------------------------------------------------------------------------

    \41\ 81 FR at 27921-27922.
---------------------------------------------------------------------------

    The content of the changes is the same as what was proposed in the 
NPRM, but the location has changed to be in its own section that 
applies to all bus types within FMVSS No. 217. This change should 
alleviate any confusion concerning the applicability of the emergency 
latch protrusion requirement.
Applicable Window Types
    In the NPRM, NHTSA proposed applying the dynamic impact test 
requirements to all side windows, rear windows, and glazing panels/
windows on the roof of applicable buses that met the minimum size 
requirements. The Motorcoach Enhanced Safety Act directs the agency to 
consider requiring advanced glazing standards for ``each motorcoach 
portal'' (section 32703(b)(2)). The Act defines ``portal'' as ``any 
opening on the front, side, rear, or roof of a motorcoach that could, 
in the event of a crash involving the motorcoach, permit the partial or 
complete ejection of any occupant from the motorcoach, including a 
young child'' (section 32702(9)). NHTSA applied the proposed advanced 
glazing requirements to the portals the agency believed pose a valid 
risk of ejection. The agency estimates that side bus windows account 
for about 80 percent of portals (potential ejection routes) on buses.
    The NPRM proposed not applying the dynamic impact test requirements 
to the front windshield, roof hatches, or any doors that do not contain 
glazing of at least the minimum size. Accident data from real-world 
rollover crashes indicate that passenger ejections generally do not 
occur from the front windshield, emergency doors, or service doors. As 
proposed in the NPRM, the dynamic impact test procedure applies to 
windows that have a minimum dimension measured through the center of 
their area of 279 mm (11 in) or greater.
    The NPRM proposed to amend FMVSS No. 217 to specify in S5.4.1 of 
the standard that emergency exit latches and other related release 
mechanisms not protrude more than 25 mm (1 inch)

[[Page 86266]]

into the opening of an emergency exit when the window is opened to the 
minimum emergency egress opening (allowing passage of an ellipsoid 500 
mm (19.7 inches) wide by 330 mm (11.8 inches) high). The purpose of 
this proposed requirement was to limit the potential for objects such 
as latch plates to protrude into the emergency exit window opening 
space even when the protrusion still allows the exit window to meet the 
opening size requirements. These requirements were proposed in the NPRM 
to only apply to emergency exit windows.
Minimum Window Size
    Regarding minimum dimensions, ICB and Advocates provided comments 
and recommendations for changes to the requirements. Advocates 
expressed concern with the lack of evidence supporting the exemption 
from testing of windows with a maximum dimension of 11 inches or less. 
ICB stated that the minimum surface dimension should be 381 mm (15 in) 
based on a typical side passenger window size for school buses.
Agency Response
    The testing standard, as discussed in the Martec report, provides 
that the window glazing impact loading event is modelled after a 
motorcoach side rollover with an occupant from one side of the bus 
being thrown from their seat and impacting glazing on the opposite side 
of the bus.
    As stated in the NPRM: ``The window would be tested if it is large 
enough to fit the impactor face plus a 25 mm (1 inch) border around the 
impactor face plate edge without contact with the window frame. The 
dimensions of the dynamic impactor the agency proposed to use were 177 
mm by 212 mm (7 inches by 8.3 inches).'' The headform impactor used in 
FMVSS No. 217 has a 6-inch diameter, and the minimum required dimension 
measured through the center of the window is 8 inches for the window to 
be tested. Using a proportional relationship for the wider (8.3 inch) 
dimension of the impactor in FMVSS No. 217a results in a minimum 
required dimension measured through the center of the window's area of 
11 inches (279 mm).
    As discussed in the Martec report, the loading case was chosen as a 
representative loading situation so that a minimum level of protection 
would be provided for all bus occupants, drivers, and passengers, for 
all crash scenarios. The Martec study determined that the occupant 
impacting the opposite side window would primarily be through shoulder 
contact. The impactor was fabricated to represent the mass, stiffness, 
and contacting area of the United States side impact dummy (US-SID) 
shoulder. The minimum window dimension is based upon this impactor 
size. Testing a window smaller than the impactor would cause the 
vehicle structure around the window to be loaded during testing, thus 
lowering the force applied to the glazing material. Using an impacting 
face smaller than the proposed guided impactor face in order to 
evaluate smaller windows would not be representative of the loading 
analysis conducted. The agency does not agree with the request to 
evaluate other crash scenarios for occupant-to-window contact.
    ICB requested NHTSA increase the minimum window size to match the 
size of a typical school bus window, which ICB stated is 381 mm (15 
inches). As discussed later in the preamble, since school bus-sized 
windows are large enough to satisfy emergency exit requirements, they 
are large enough to become an ejection portal that could permit the 
partial or complete ejection of a passenger if the glazing is vacated 
from the opening. Therefore, NHTSA will not increase the minimum window 
surface dimension as ICB has requested.
Rear Windows
    ICB stated that the rear windows should be exempt from the anti-
ejection requirements of FMVSS No. 217a. ICB pointed out that in 
traditional motorcoaches there is typically not a rear window, and that 
most bus crash injuries and fatalities involve traditional 
motorcoaches. Additionally, ICB stated that it is not aware of any 
crash reports for ``a survivable rollover incident that would propel an 
occupant with such force to the rear of the vehicle that it would eject 
them through the rear glazing.'' ICB further stated that rear windows 
are usually partially blocked by forward facing seats, which makes it 
less likely for passengers to be ejected out the rear of a bus. ICB 
pointed to a sentence from the Martec report which ICB interpreted to 
imply that the impactor anvil test does not apply to rear-window 
glazing.
    BBBC stated that the rear windows should be exempt on ``large 
commercial buses that are constructed substantially the same as school 
buses'' because they are usually partially blocked by seats. 
Additionally, BBBC stated that since NHTSA's testing was only performed 
on side windows, additional research would be required before 
establishing performance requirements for the rear glazing.
Agency Response
    After reviewing the comments from ICB and BBBC, the agency further 
analyzed typical bus designs, ejection data, and fatal crash data. The 
agency has concluded that rear bus windows will be excluded from 
testing as part of this final rule.
    In the NPRM, NHTSA proposed applying the dynamic impact test 
requirements to all side windows, rear windows, and glazing panels/
windows on the roof of applicable buses that met the minimum window 
size requirements. The agency recognized that OTRBs typically have the 
bus engine in the rear, and therefore usually have no windows on the 
rear of the bus. However, the agency stated that nothing precludes bus 
designs from having windows in the rear of the bus that could be 
potential ejection portals.
    The crash type most likely to result in an ejection through the 
rear glazing would be a rear impact. As stated by ICB and BBBC and 
confirmed by NHTSA, there were no recorded fatalities in applicable 
buses from rear impact crashes in the 2006-2019 FARS data. While it is 
conceivable occupants could be ejected through the rear glazing in 
other crash types, it is less likely. Further, as BBBC indicated, rear 
windows in large buses that are not OTRBs are often substantially 
blocked by the rear seats. As a result, occupants are less likely to be 
ejected through the rear glazing. In the event of a partial ejection 
through a rear window, the occupant is less likely to experience 
serious injury or death, because there is a low likelihood the bus will 
roll onto its rear side.
    The requirements and evaluation procedures of FMVSS No. 217a are 
based upon analysis of unbelted passenger impacting side bus windows 
during a rollover crash scenario. This loading case was chosen as a 
representative loading situation so that a minimum level of protection 
would be provided for all bus occupants, drivers, and passengers, for 
all crash scenarios. Therefore, as a practical matter, NHTSA has 
decided rear windows will be exempt from the impact test requirements 
of FMVSS No. 217a.
Windows Mounted on Doors and Hatches
    ICB questioned whether the dynamic impact test requirements apply 
to all window glazing, including those in doors and emergency exit 
hatches. In their comments, ICB argued that ``NHTSA did not intend for 
the glazing anti-ejection requirements to be applicable to glazings in 
any door or

[[Page 86267]]

roof hatch emergency exit and we ask that NHTSA make that clear in the 
final rule.'' BBBC stated that the NPRM did not ``adequately convey 
NHTSA's intention to exclude windows that are part of a side or rear 
door.''
Agency Response
    Both BBBC and ICB stated that windows which are part of doors 
should be exempt from the anti-ejection requirements. NHTSA has 
observed that in current buses there are typically windows in the 
emergency exit doors and in regular doors. The agency stated in the 
NPRM that NHTSA would not be applying the proposed requirements to the 
front windshield, or to emergency exit doors, service doors, or roof 
hatches. The agency does not intend to apply the glazing ejection 
mitigation requirements to the structure securing side and rear doors 
to the vehicle. However, all bus windows are potential ejection portals 
if the glazing material breaks. If a window in a side door or roof 
hatch and has the requisite minimum dimensions of 279 mm (11 in) or 
greater measured through the center of its area, that window will be 
subject to the proposed anti-ejection requirements.
    The agency has concluded that this final rule is applicable to all 
side and roof window glazing that meet the minimum window dimensions. 
Furthermore, NHTSA wishes to clarify that the anti-ejection 
requirements proposed for FMVSS No. 217a do not apply to the non-window 
portion of doors, service doors, or roof hatches. Any window in a door, 
service door, or roof hatch would have to meet the anti-ejection 
requirements if such a window exceeds the minimum size (279 mm or 11 
inches) specified in S5 of FMVSS No. 217a.
School Bus Sized Windows
    SBMTC commented that school bus size windows used on commercial 
buses derived from school bus designs are too small to be covered by 
the proposed anti-ejection requirements. BBBC, ICB, and SBMTC claimed 
that since OTRBs have larger windows than the commercial buses derived 
from school buses, commercial buses with these windows should not be 
subject to the same requirements as traditional OTRBs. ICB indicated 
that it does ``install larger `non-typical' school bus windows in some 
of its commercial buses and [it is] not asking for any exemption for 
these larger bus windows.''
Agency Response
    First, as mentioned in the preceding paragraphs, if a bus derived 
from a school bus design is not a school bus and has a GVWR greater 
than 11,793 kg (26,000 lb), it will have to comply with FMVSS No. 217a. 
The fact that certain school bus derivative buses may have smaller 
windows does not change this requirement. Furthermore, FMVSS No. 217 
requires buses other than school buses to have emergency exit windows 
large enough to ``admit unobstructed passage, keeping a major axis 
horizontal at all times, of an ellipsoid generated by rotating about 
its minor axis an ellipse having a major axis of 50 centimeters and a 
minor axis of 33 centimeters.'' Since these school bus windows are 
large enough to satisfy emergency exit requirements, they are large 
enough to become an ejection portal that could permit the partial or 
complete ejection of a passenger if the glazing is vacated from the 
opening. FARS data from 2006-2019 include 26 fatal ejections from 
school buses with a GVWR greater than 26,000 lbs. This data shows that 
school bus sized windows can become ejection portals.
    Lastly, although school bus derivative buses may use the same sized 
windows as school buses, NHTSA believes that school bus derivative 
buses are more likely than school buses to be used in a manner that has 
a higher risk of crashes. Therefore, although school bus derivative 
buses may have smaller windows than traditional OTRBs, these windows 
are large enough for a passenger, especially a child or smaller adult, 
to be fully or partially ejected through if such a window is broken out 
from the surrounding bus structure. Accordingly, a bus being equipped 
with ``school bus sized'' windows will not create an exemption to FMVSS 
No. 217a under this final rule. If the windows are large enough to be 
tested with the impactor, the fact that the windows are ``school bus 
sized'' will not impact their applicability to this standard.
Driver Side Windows
    Both BBBC and ICB commented that because seat belts should protect 
bus drivers from ejection, driver side windows should be exempt from 
this final rule. ICB indicated that the seat belt usage rates for bus 
drivers is as high as or higher than the 84% rate for commercial truck 
drivers listed in a Federal Motor Carrier Safety Administration (FMCSA) 
study.\42\
---------------------------------------------------------------------------

    \42\ Safety Belt Usage by Commercial Motor Vehicle Drivers 
(SBUCMVD) 2013, U.S. Department of Transportation, Federal Motor 
Carrier Safety Administration (FMCSA).
---------------------------------------------------------------------------

Agency Response
    The agency has decided not to exempt driver side windows from the 
requirements under this final rule. FARS data from 2006-2019 show 9 
drivers were fatally ejected from school buses with a GVWR greater than 
26,000 lb.\43\ The numbers of ejected drivers are relatively low, but 
the risk is present in bus crashes. Also, advanced glazing in driver 
side windows will protect the drivers against partial ejections. Bus 
manufacturers will be able to use similar anti-ejection design features 
for driver side windows as those anti-ejection features used for the 
remaining bus windows. Under the final standard, if a bus driver side 
window meets the minimum size requirements, it will have to meet the 
requirements of FMVSS No. 217a.
---------------------------------------------------------------------------

    \43\ According to the 2006-2019 FARS data, 6 of these fatal 
driver ejections were through a side door opening, 1 was through a 
side window, 1 was through the windshield, and 1 was an unknown 
ejection path.
---------------------------------------------------------------------------

Blocked Windows
    SBMTC commented that some side wheelchair lift doors are 
``effectively blocked by the stowed wheelchair lift'' and that as a 
result, these windows do not pose a risk for ejection. ICB commented 
that NHTSA should exclude glazing in ``[d]oors, such as wheelchair lift 
doors, that have equipment or other items that would prevent or 
restrict passenger ejection.'' ICB also commented that doors with no 
adjacent seat should be exempted from the 217a requirements.
    Additionally, BBBC argued that NHTSA did not intend to apply the 
dynamic test requirements to glazing in wheelchair lift doors, ``which 
would have a wheelchair lift between the passenger and the window.'' 
BBBC also stated that in many of the buses it manufactures, the rear 
seats obstruct much of the rear window. BBBC stated these obstructed 
windows should be exempt from the dynamic impact test requirements.
Agency Response
    SBMTC, BBBC, and ICB stated that since wheelchair lift ramps block 
the window in the wheelchair access door, such windows should not have 
to meet the proposed anti-ejection requirements. The agency examined 
different wheelchair access doors and the wheelchair lift ramps in 
their stowed positions. Some lift ramps are stowed outside the bus in a 
storage compartment under the bus. Other configurations stow the ramp 
inside the bus in a folded position. These interior

[[Page 86268]]

ramps may partially block the door window.
    Windows that have no blockage will have to meet the anti-ejection 
requirements, since no part of the vehicle would block a passenger from 
contacting the window. Windows completely blocked by wheelchair lift 
ramps will not have to meet the anti-ejection requirements, since 
passengers would not be able to contact such windows. Windows that are 
partially blocked by wheelchair lift ramps would need to meet the anti-
ejection requirements if the daylight opening of such windows is large 
enough such that the minimum dimensions measured through the center of 
the daylight opening area is not less than 279 mm. Note that the 
definition of daylight opening states that the periphery includes 
surfaces 100 mm inboard of the window and 25 mm outboard of the window, 
not including gaskets, weather stripping, grab handles, or seats. Also, 
since bus passengers can walk about the bus while it is in motion, the 
agency does not agree with ICB's suggestion to restrict the anti-
ejection requirements to only those windows which have a seating 
position near that window glazing.
Emergency Exit Windows and Latches
    ICB agreed with the agency that the window latch release mechanism 
should not be a hindrance in evacuations through the emergency window 
exit. Both BBBC and ICB argued that the protrusion limits are intended 
to only apply to emergency exit windows, and not to other types of 
emergency exits such as doors or hatches. Both respondents specifically 
asked for the word ``window'' to be inserted into the sentence planned 
for the end of FMVSS No. 217, S5.4.1 so that their interpretation of 
the protrusion requirement applicability is specifically written into 
the standard.
Agency Response
    The NPRM was silent on protrusion concerns for emergency exit doors 
and roof hatches. The NPRM did discuss latch protrusion issues in the 
context of the emergency exit windows on the school bus involved in the 
Gray Summit crash. Additionally, no other respondents commented on the 
lack of concern for protrusions impeding passenger emergency egress 
through side door or roof exits. The confusion over which emergency 
exits are subject to the protrusion limits may stem from the section of 
regulatory text into which the protrusion limits were placed.
    FMVSS No. 217, S5.4.1 does not specifically list the emergency 
exits to which that section applies. Further, the title for FMVSS No. 
217 S5.4 is ``Emergency exit opening,'' not ``Window emergency exit 
opening.'' Window emergency exits are a subset of roof, side, and rear 
emergency exits. Placing the emergency window exit protrusion limits 
into a section covering multiple types of exits may have created 
confusion for the respondents that asked for this clarification. The 
protrusion limit for emergency exit window latches is also to be 
applied to school bus emergency exit windows, through addition of the 
similar text into S5.4.2.2 of FMVSS No. 217. However, to avoid 
additional confusion by including an emergency exit window specific 
provision into a section devoted to small school bus emergency exit 
doors, the agency has decided to place the emergency exit latch 
protrusion requirement at the end of S5.4.
    As mentioned above in the discussion on the protrusion limit 
applicability for all buses, the agency is relocating this requirement 
into a new subsection, FMVSS No. 217 S5.4.4, so that the requirement 
will be more easily understood as applicable to all buses included in 
FMVSS No. 217. This location also clarifies the application of the 
protrusion requirements is only for window emergency exits. The NPRM's 
proposed text additions to FMVSS No. 217 S5.4.1 and S5.4.2.2 are not 
being adopted and the new S5.4.4 contains the planned protrusion limit 
requirements. NHTSA is including the word ``window'' in the standard 
for clarification as ICB and BBBC suggested.

c. Occupant Injury Protection

    In the event of a rollover crash involving a large bus or OTRB, 
there is concern for more than just injury or death resulting from 
ejection from the bus; there is also a risk that passengers may suffer 
injuries from impacting reinforced glazing during a crash. While the 
main objective of this final rule is to protect occupants by preventing 
ejection through windows and glazing panels, the agency has also 
considered the impact forces bus occupants would experience when 
contacting the advanced glazing during a crash. Several commenters 
discussed this potential issue, and a summary of those comments along 
with the agency's responses can be found in the paragraphs below.
Rigidity of Advanced Glazing
    Greyhound, Prevost, and Van Hool suggested that advanced glazing 
would be too rigid, causing an increase in the number and severity of 
passenger injuries. Greyhound commented ``that NHTSA should consider 
technologies that reduce ejections while not increasing impact 
injuries.'' Van Hool stated that ``[t]he passenger on the rollover-side 
wearing the seat belt in a bus according to this NPRM might be 
victimized because in a single rollover his head will hit a surface 
that is strong enough to retain the body of a free-falling passenger of 
the other, non-rollover side.'' Prevost stated, based upon information 
in a 2007 Los Angeles Times article, that ``[laminated] glass could 
increase head and neck injuries to passengers who wear seat belts.''
Agency Response
    The agency shares the respondents' concerns for injuries caused by 
collisions with advanced glazing and window panels in OTRB and large 
bus crashes. However, the agency disagrees with the argument that 
advanced glazing may cause injuries which would not otherwise occur 
from a broken or unbroken tempered glazing panel.
    The Los Angeles Times article that Prevost referenced provided no 
supporting information for the conclusion that laminated glazing is 
harder than tempered glazing material. The agency has force deflection 
data from the bus glazing panel research conducted for this final rule, 
which can be seen in Table 7 below. In tests where the guided impactor 
struck the center of bus windows made of a single glazing panel, the 
tempered glazing panels had higher peak force levels and lower 
deflections than glazing panels made from laminated glass, 
polycarbonate, and acrylic. This test data indicates that tempered 
glass is harder and more rigid than the other glazing types, including 
laminate glass. The higher force levels and lower deflections indicate 
that a bus occupant hitting tempered glazing at high speeds could 
receive higher contact injuries than if they were to hit a different 
type glazing material.

[[Page 86269]]



             Table 7--Data From Bus Glazing Guided Impactor Testing \44\ Single Panel Window Glazing
----------------------------------------------------------------------------------------------------------------
                                        Actual impact                   Peak impactor
    Glazing configuration (bonding      velocity (km/  Peak force (N)  face excursion     Interior glass pane
               method)                       h)                             (mm)                 broken
----------------------------------------------------------------------------------------------------------------
Laminated glass (Rubber).............            21.5           4,780             116  Yes.
Laminated Glass (Rubber).............            21.2           5,879             106  Yes.
Tempered Glass (Rubber)..............            21.3           8,030              49  No.
Acrylic (Rubber).....................            21.4           6,211              66  No.
Tempered Glass (Glued)...............            20.8           8,518              41  No.
Laminated Glass (Glued)..............            20.9           7,592              57  Yes.
Polycarbonate (Glued)................            21.2           6,822              69  No.
----------------------------------------------------------------------------------------------------------------

    In the case of belted occupants, a belted occupant seated against 
the bus side wall is at risk of partial ejection of their upper torso, 
hands, arms, neck, and head if the window breaks. It is safer for any 
passenger to be retained inside the bus by an advanced glazing surface 
than to be partially outside the bus when it hits and/or slides along 
the pavement or ground. According to FARS data from 2006-2019, thirty-
nine percent of all large bus and OTRB fatalities were ejected, as 
detailed in Table 8 below. Because the vast majority of occupants in 
large bus and OTRB crashes are not ejected, this data and study prove 
that, in the event of a rollover crash, it is safer for an occupant to 
remain inside the vehicle than to be ejected, even though that may mean 
a potential collision with an unbroken advanced glazing panel.
---------------------------------------------------------------------------

    \44\ Duffy, S., & Prasad, A., National Highway Traffic Safety 
Administration, Motorcoach Side Glazing Retention Research, pg 18, 
(Report No. DOT HS 811 862) (Nov. 2013).

                         Table 8--Occupant Fatalities by Ejection Status FARS 2006-2019
                            [Large buses (GVWR greater than 26,000 lb) and all OTRBs]
----------------------------------------------------------------------------------------------------------------
                            Bus type                                Not ejected       Ejected          Total
----------------------------------------------------------------------------------------------------------------
Van-based.......................................................               1               0               1
Large Van.......................................................               0               0               0
Intercity Bus...................................................             117              96             213
Other Bus.......................................................              46              13              59
Unknown Bus.....................................................               8               3              11
----------------------------------------------------------------------------------------------------------------

Other Means of Injury Prevention
    In Greyhound's comment, it urged the agency to consider alternative 
technologies to prevent passenger ejection and reduce injuries. 
Greyhound suggested that the advanced glazing will not prevent 
fatalities due to ejection. Greyhound suggested that there are ``other 
technologies, including those in use in the automotive and trucking 
industries, which may have a higher likelihood of retaining passengers 
in the vehicle in rollover/tipover events.''
Agency Response
    NHTSA is always willing to consider specific proposals that may 
enhance passenger safety in the agency's final rules. However, in this 
instance, Greyhound did not provide a name or description of the 
``other technologies'' that may be more effective than advanced glazing 
in mitigating the risk of passenger ejection in OTRB and large bus 
crashes. Additionally, Greyhound may have overlooked several general 
aspects of occupant movement during a crash. All occupants come to a 
stop at some point during a crash; the main question is how occupants 
stop. The answer to this question plays a significant role in 
determining the extent of passenger injuries or even risk of death in 
rollover crashes. The proposed requirements of this rule provide 
partial ejection protection for belted occupants seated against bus 
windows as well as protection against partial or complete ejections of 
unbelted passengers that may fall or move into the ejection portal 
created by a broken window. As stated above, the agency welcomes 
comments about other technologies or vehicle safety countermeasures 
that others believe would be more beneficial than the requirements 
proposed in the NPRM. However, in this case, there simply is not enough 
detail in Greyhound's comment to compare ``other technologies'' to the 
proposals in the NPRM. The agency is confident that the new 
requirements adopted in this final rule will be highly effective in 
mitigating the risk of passenger ejection during rollover crashes 
involving large buses and OTRBs.

d. Test Procedures and Equipment

    Multiple commenters discussed the dynamic impact test procedure and 
the equipment used to conduct the dynamic impact test. The agency has 
decided to adopt a few of the recommendations made in the comments, 
which means the adopted test procedure will be slightly different from 
the test procedure proposed in the NPRM. Specifically, the agency is 
amending the proposed regulatory text for the window pre-breakage 
procedure as well as the edge impact test procedure for increased 
clarity.
Guided Impactor Specifications
    Two of the commenters asked for more details to be provided for the 
guided impactor test equipment. BBBC requested that NHTSA change the 
word ``mass'' to the phrase ``mass to bring total mass of impactor to 
26 kg'' in the proposed Figure 1 of the regulatory text, which 
illustrates the guided impactor. Additionally, BBBC and SBMTC requested 
more details on the foam used on the impactor face.
Agency Response
    The impactor design being adopted as part of this final rule is the 
same impactor design proposed in the NPRM. The agency has decided not 
to change the language for the proposed impactor

[[Page 86270]]

test as BBBC requested, as the agency does not believe that these 
changes are necessary to provide the clarity BBBC requested. Instead, 
NHTSA has made a few changes to the impactor design figure, shown below 
as Figure 1, which will be included in the regulatory text as well as a 
separate technical supporting document that can be found in the docket 
for this rulemaking (Technical Support Document). The changes to the 
figure are designed to provide additional clarity, and the agency 
believes these changes will resolve any confusion BBBC had regarding 
the mass of the impactor design.
[GRAPHIC] [TIFF OMITTED] TR30OC24.017

    The changes between this figure and the figure proposed in the NPRM 
include (1) changing the term ``mass'' to ``ballast mass,'' (2) 
changing the term ``foam'' to ``SID arm foam,'' (3) adding the ``thrust 
bearing rod'' to the figure, and (4) labeling the ``impactor face 
bearing.'' This figure now illustrates and names all components of the 
impactor that contribute to the overall mass of 26 kg (57 lb). The 
Technical Support Document includes more details and figures that 
provide example masses for each component.
    As proposed in the NPRM, the agency is adopting the requirement 
that the total mass of the impactor be 26 kg (57 lb), which represents 
the effective mass measurements from the Martec study. The impactor is 
designed to represent the torso of the SID. To clarify, when the 
regulatory text says that the impactor must be a total mass of 26 kg 
(57 lb), it is referring to the mass of the entire impactor assembly, 
not just one component of the impactor. In Figure 1 above--which will 
also be adopted as part of the regulatory text--the agency has decided 
to show the entire impactor assembly, and has labeled one component of 
the impactor as the ``ballast mass.'' The agency believes the 
clarification of the ``total mass of the impactor'' combined with 
labeling the ballast mass will alleviate any confusion BBBC had on the 
mass issue.
    Regarding the foam used on the impactor face, in an effort to 
provide greater clarity, the agency is able to share the following 
additional details. The foam used on the impact side of the impactor 
plate is the 50th percentile male side impact dummy (SID) arm foam. SID 
arm foam is composed of a piece of urethane foam, conforming to the 
properties listed in the Technical Support Document. Additional details 
of the foam can be found in the Technical Support Document, and a copy 
of the engineering drawing, SID-069, is also in the docket of this 
final rule.
Window Pre-Breakage Test Procedure
    In the NPRM, NHTSA proposed a breaking specification and method 
that involves applying a line load to the glazing, to simulate the 
damage the glazing could experience in a rollover prior to impact by an 
occupant. The line loads would be applied at set distances on both the 
interior and exterior glass plies of the laminated glazing. The window 
breaking procedure would damage but not destroy laminated glazing, 
while it would obliterate tempered glazing. Since tempered glazing 
would be obliterated, this proposal would have the effect of 
prohibiting manufacturers from having applicable bus windows made 
solely from tempered glazing.
    The first step in the proposed test procedure is to mark the 
glazing surface on the occupant-side interior glass in a horizontal and 
vertical grid of points separated by 75 mm (3 inches), with the first 
point coincident with the geometric center of the daylight opening. 
Next, the grid on the opposite side of the glazing would be marked. For 
most glazing, the grid on the opposite side of the glazing would be 
staggered to avoid tearing the PVB interlayer. For laminates, ``the 
opposite side of the glazing'' means the opposing glass ply directly 
opposite of the PVB interlayer. ``Staggered'' means that the 75 mm (3 
inch) offset pattern has a 75 mm x 75 mm (3 inch x 3 inch) pattern on 
the occupant-side interior glass and the same pattern, offset by 37.5 
mm (1.5 inch) horizontally and vertically, on the outside exterior 
glass surface.
    For windows that are a single-pane unit, NHTSA would use the grid 
pattern on the occupant-side interior surface and the staggered grid 
pattern on the outside exterior surface of the glazing.
    For double-glazed windows, the agency proposed using a grid pattern 
on the occupant-side interior surface of the interior pane and on the 
outside of the exterior pane. For double-glazed windows that consist of 
one pane of tempered glass, that pane would be broken and removed, and 
the remaining glazing (that is not of tempered glass) would be pre-
broken on both sides

[[Page 86271]]

(occupant interior and outside exterior) with the grid and staggered 
grid patterns, respectively. For double-glazed windows that do not 
consist of any tempered glass pane, it would not be practical to apply 
the 75 mm (3 inch) pre-break pattern to the insulated surface (inside 
the air gap) of the individual panes. For cases in which neither pane 
is tempered glass, both the occupant side of the interior pane and the 
outside of the exterior pane would be marked in the grid pattern, but 
the patterns would not be offset (one side would not use the staggered 
pattern) due to a lack of need. That is, for those windows there would 
be little likelihood of tearing the PVB interlayer even when the 
patterns are not offset.
    The agency proposed breaking the defined grid points using an 
unloaded electric staple gun, since the device worked well for that 
purpose in our developmental testing. The staple gun would apply a 12.7 
mm (0.5 inch) line load (with a thickness of 1.3 mm (0.05 inches)) (the 
size of a standard staple) onto the glazing with a force in the range 
of 3,500 newtons (N) (787 lb) to 5,000 N (1,124 lb) when the front nose 
opening of the staple gun is held parallel to the glazing surface. 
These staple gun specifications are intended to break the glass with a 
single punch without producing tears in the PVB interlayer. These line 
loads would be applied to the glazing starting with the inside surface 
of the glazing, and starting with the forwardmost, lowest hole in the 
pattern. NHTSA would continue applying the line loads 75 mm (3 inches) 
apart, moving rearward on the bus. When the end of a row is reached, 
the agency would move to the most forward hole in the next higher row, 
75 mm (3 inches) from the punched row. After completing the 
applications on the inside surface, the agency would repeat the process 
on the outside surface.
    When applying the line load, NHTSA would place a 100 mm (4 inch) by 
100 mm (4 inch) piece of plywood on the opposite side of the glazing as 
a reaction surface against the punch. If a particular window were 
constructed such that the inner laminated material is penetrated or 
damaged, the procedure would not be halted or invalidated. The impactor 
test would be conducted at the conclusion of the glazing breakage 
procedure. If punching a hole causes the glazing to disintegrate, as 
would occur when testing tempered glazing, the procedure would be 
halted for that item of glazing and the impactor test would be 
conducted on what glazing, if any, remains. If there is no glazing 
remaining after the hole-punching procedure, there would be a failure 
to comply since the window would not be able to restrain the impactor 
or prevent passage of the 102 mm (4 inch) diameter sphere.
    BBBC requested that the specific electronic staple gun used during 
the agency's research testing be specified in the final rule. ICB 
commented that it does not understand why the FMVSS No. 226 spring-
loaded center punch breakage method is not practical for this proposed 
regulation. SABIC, Exatec, and ICB each noted that it may not be 
possible to break or even force holes into all types of glazing, 
specifically glazing made from polycarbonate material. ICB also 
requested improved clarity through the addition of figures or diagrams 
for the glazing pre-breaking procedure.
Agency Response
    While the agency understands BBBC's preference for a glazing 
material breakage procedure identical to that used during the agency's 
testing, NHTSA does not believe it is necessary to specify a model of 
electronic staple gun to be used in the regulatory text and will not 
being doing so as part of this final rule. Instead, the agency has 
decided to specify the length over which the line load is to be applied 
as well as the force applied by the staple gun to the glazing. Although 
the agency did not list any force level in the NPRM's proposed 
regulatory text, NHTSA believes it will be useful to include the 
average force level (4,200 N (994 lb)) and standard deviation (850 N 
(191 lb)) obtained from sampling the Duo Fast Model EWC electric staple 
gun force levels as the target force in this final rule. This force was 
adequate to break the laminate glazing's glass layer without tearing 
the inner PVB material. For these reasons, NHTSA declines to accept 
BBBC's suggestion to list a specific electric staple gun model in the 
final rule.
    ICB questioned why NHTSA developed a new glass breakage procedure 
that differs from the existing glass breakage procedure in FMVSS No. 
226. As stated in NHTSA's ``Motorcoach Side Glazing Retention 
Research,'' \45\ ``[i]t was quickly determined that the automatic 
center punch used in FMVSS No. 226 was not practical for large bus 
windows and was not tested in this study.'' Due to the effort required 
to actuate the center punch and the large size of motorcoach windows, 
NHTSA determined the center punch used in the FMVSS No. 226 glazing 
pre-breaking procedure would not be a practical tool for the FMVSS No. 
217a glazing pre-breaking procedure. Accordingly, NHTSA developed the 
breakage procedure proposed in the NPRM and is adopting that procedure 
as part of this final rule.
---------------------------------------------------------------------------

    \45\ Duffy, S., & Prasad, A., National Highway Traffic Safety 
Administration, Motorcoach Side Glazing Retention Research, pg 18, 
(Report No. DOT HS 811 862) (Nov. 2013).
---------------------------------------------------------------------------

    SABIC, Exatec, and ICB each shared concerns that the glazing 
breakage procedure could effectively preclude usage of their 
polycarbonate glazing material. These commenters stated it may be 
possible that certain glazing types would receive little to no marking 
when attempting to break that glazing using the required glazing 
breakage procedure. Their stated concern is that if no hole can be 
made, then their glazing cannot pass the test. A similar concern was 
addressed in the final rule for FMVSS No. 226.
    Like FMVSS No. 226, the hole break pattern for FMVSS No. 217a will 
be marked onto the bus's window glazing, as shown in the regulatory 
text below, then the electric staple gun would be used once at each 
marked location. It is possible that certain glazing may have smaller, 
or no holes produced. Similar to the agency's response to the comment 
in response to the FMVSS No. 226 NPRM, NHTSA believes that even if 
certain glazing may have smaller, or no holes produced by the breakage 
procedure being adopted in this final rule, the window may still be 
weakened and should be tested in accordance with the rest of the 
procedures outlined for the impact test.
    Even though the agency has decided to adopt the pre-breakage test 
procedure as proposed in the NPRM as part of this final rule, NHTSA has 
decided to include an additional figure to the regulatory text to aid 
in the clarification of the glazing pre-breakage procedure as ICB 
requested. The combined proposed revision to FMVSS No. 217a is shown in 
the appendix of this final rule.
Edge Impact Test Procedure
    During agency review, NHTSA determined the edge impact test 
procedure could be improved with three distinct updates, which are 
described briefly here. The first update is to describe the impactor 
positioning for an additional glazing orientation. For the scenario 
where a window on the bus roof does not have a latch or other discrete 
attachment point, the agency has decided to define which edge with 
which to align the impactor. In order to be consistent with side 
windows that do not have a latch, the agency is using the rearmost edge 
of a roof window as the reference edge because if a latch were present, 
it would likely be located on the rearmost edge due to the

[[Page 86272]]

requirement in FMVSS No. 217 S5.2.3.2(b). Second, the agency determined 
a tolerance to properly define the lateral distance between the 
impactor face plate edge and the window frame. NHTSA is defining a 
tolerance of  2 mm based on the positioning of a similar 
impactor as described in FMVSS No. 226, ``Ejection mitigation.'' The 
third update is necessary to further clarify the alignment of the 
impactor face plate with respect to a latch. Due to varying latch 
designs, the center of the latch may not necessarily correspond to the 
center of the location where the latch attaches to the movable portion 
of the window. Because the location where the latch attaches to the 
movable portion of the window is where the latch is most likely to 
fail, the agency has decided to specify that location for the edge 
impact procedure by referencing the latch attachment point when 
aligning the impactor. The agency is adopting these three updates to 
the edge impact test procedure as part of this final rule.

e. Performance Requirements

Impact Testing Displacement Limits
    In the NPRM, NHTSA proposed to specify performance requirements for 
windows comprised of unbroken and broken glazing when the glazing is 
subjected to impactor testing. In NHTSA's impactor test of glazing near 
a latching mechanism and in the impactor test of glazing at the center 
of the daylight opening, an ``ejection reference plane'' would be 
determined prior to the test. The plane would be based on the passage 
of a 102 mm (4 inch) diameter sphere through a potential ejection 
portal of the window. The agency would require that no part of the 
window (excluding glazing shards) may pass this ``ejection reference 
plane'' during the dynamic impact test. If any part of the window 
glazing or window frame passes the plane, there would be a failure to 
comply.
    For unbroken glazing, the window would be subject to either of the 
following two impacts, as selected by NHTSA in a compliance test: (a) 
an impact near a latching mechanism, and (b) an impact at the center of 
the daylight opening. The displacement limit for these tests on the 
unbroken glazing was proposed to be 102 mm (4 inch) both during and 
after the test.
    For pre-broken glazing, the window would be subject to an impact 
test at the center of the daylight opening. The displacement limit for 
this test was proposed to be 175 mm (6.89 inch) during the test and 102 
mm (4 inch) after the test.
    Advocates expressed concerns that the pass/fail criteria for the 
rule had not been adequately supported. Advocates stated that the 6.9-
inch excursion limit and the 4-inch dynamic displacement limits are 
inadequate requirements. Advocates was concerned that ``[a]ny amount of 
excursion exposes the occupant in contact with the window to impacts 
with objects outside of the vehicle such as the roadway, and as such 
should be reduced the greatest extent possible.'' Advocates requested 
that the agency ``establish requirements that push the industry to 
adopt the safest reasonable practices, as opposed to the bare minimum 
or current average performance.''
    Regarding permitted deflections, ICB provided comments and 
recommendations for changes to the requirements. ICB stated that there 
should not be a deflection requirement based on the ejection reference 
plane as part of the requirement.
Agency Response
    The agency has decided not to adjust the proposed excursion limit 
of 175 mm for the pre-broken glazing impact test. Advocates stated that 
the agency used the International Code Council (ICC) guardrail spacing 
requirements as justification for 102 mm excursion limits in FMVSS No. 
226. Advocates are incorrect in this belief, as the final rule notice 
establishing FMVSS No. 226 noted that other FMVSSs (FMVSS No. 206 and 
FMVSS No. 217) as well as the ICC have a 100 mm maximum limit on a 
portal/opening to minimize the risk of an occupant being ejected or of 
a child passing through the portal/opening. The final rule establishing 
FMVSS No. 226 reported that test data highlighted an increased 
likelihood of large portals forming when excursions were over 100 mm. 
The agency believes that the 102 mm excursion limit based upon the 
ejection reference plane remains an appropriate requirement.
    Concerning the 175 mm displacement limit for the pre-broken glazing 
test, the agency asked for comments and additional data in the NPRM. 
NHTSA noted in the NPRM that this limit was based on two tests of a 
single production bus window design. It was also noted in the NPRM that 
results from laminate glazing testing conducted for the Martec study 
resulted in an average displacement of 175 mm for the impactor in the 
center of daylight opening impacts (using the 75 mm (3 inch) diagonally 
offset pattern).
    No other respondents commented either for or against the excursion 
limits. Advocates stated that ``excursion exposes the occupant in 
contact with the window to impacts with objects outside of the vehicle 
such as the roadway, and as such should be reduced the greatest extent 
possible.'' As discussed earlier, the manner in which occupants come to 
a stop during a crash will contribute to the extent and severity of 
their injuries. Based on data from NHTSA's ``Motorcoach Side Glazing 
Retention Research,'' \46\ where different configurations of pre-broken 
laminated glass window units were impacted at the Martec conditions, 
the thicker PVB layer resulted in lower excursion limits and higher 
impact force values for almost all of the pre-broken glazing 
configurations.
---------------------------------------------------------------------------

    \46\ Duffy, S., & Prasad, A., National Highway Traffic Safety 
Administration, Motorcoach Side Glazing Retention Research, pg 18, 
(Report No. DOT HS 811 862) (Nov. 2013).
---------------------------------------------------------------------------

    Advocates did not offer any additional data, studies, or 
suggestions for what a better, lower excursion limit should be for the 
pre-broken glazing test. Using the data at the agency's disposal, an 
excursion limit of 175 mm is reasonable and sufficient. NHTSA chose 
this excursion limit based on practicability, costs, and safety needs. 
Using a 100 percent thicker PVB layer yielded a 14 percent lower 
excursion limit in our testing. This method is effective for 
manufacturers to reduce the excursion limit if necessary to comply or 
for slight improvements. The NPRM requested comments on the 
practicability, costs, and potential benefits of using a lower 
excursion limit such as 146 mm, which is the average excursion found 
during the testing with the thicker PVB layer (using the same 75 mm 
diagonally offset breaking procedure). Advocates did not provide any 
comment on this aspect of the excursion limit, nor did any other 
commenter. Therefore, the agency will not adjust the proposed excursion 
limit of 175 mm for the pre-broken glazing impact test.
    ICB also expressed doubt regarding the appropriateness of 
deflection limits as part of the bus glazing anti-ejection 
requirements. ICB suggested that the glazing and window frame should be 
allowed to flex. The agency understands that window glazing, and 
perhaps even the window frame, will flex when hit by the guided 
impactor face. However, unlimited flexing, or displacement, is 
undesirable because glazing deflection past the ejection reference 
plane would allow tears to develop in glazing that could lead to an 
ejection portal. Additionally, the displacement limit provides a means 
of ensuring the

[[Page 86273]]

window does not open during the impact test, which would result in a 
portal for occupant ejection. Limiting the deflection to the ejection 
reference plane ensures that a minimum level of passenger retention 
will be maintained by the bus window glazing material. Therefore, the 
agency is not adopting ICB's recommendation to remove the deflection 
limit for the unbroken window test.
Emergency Exit Window Latch Protrusion
    The NTSB investigation into the Grey Summit bus crash noted that 
passenger egress through the emergency exits was hindered when 
passengers snagged their clothing on the emergency exit latch hardware 
protruding into the egress route.\47\ Several passengers in the lead 
school bus, and a witness who assisted in the evacuation, stated in 
post-crash interviews that emergency egress was hindered by the design 
of the emergency exit window. Particularly, the 4-inch by 3-inch 
emergency release latch plate for the emergency exit window was 
elevated about 1 inch from the window base and snagged the clothing of 
several passengers as they were exiting through the window opening.
---------------------------------------------------------------------------

    \47\ NTSB/HAR-11/03, https://www.ntsb.gov/investigations/AccidentReports/Reports/HAR1103.pdf,
---------------------------------------------------------------------------

    The additional requirements as outlined in the NPRM proposed to 
limit how far emergency exit latches may protrude into the emergency 
exit opening. The NPRM for this rule proposed that emergency exit latch 
protrusions cannot extend more than 1 inch into the opening of the 
window when the window is opened to the minimum emergency egress 
opening specified under FMVSS No. 217. This opening is described in 
S5.4.1 as ``large enough to admit unobstructed passage, keeping a major 
axis horizontal at all times, of an ellipsoid generated by rotating 
about its minor axis an ellipse having a major axis of 50 centimeters 
and a minor axis of 33 centimeters.'' The NPRM proposed making all 
buses governed under FMVSS No. 217 applicable under this requirement.
    The NTSB agreed that emergency exit window latches need to be 
functional after a crash to ensure passengers can egress through all 
viable exits; consequently, the NTSB supported testing the latches 
after impact tests. Advocates also supported the agency's proposals to 
minimize emergency exit latch protrusions and to require these latches 
to remain operable following the impact testing.
    Concerning the 1-inch protrusion limit proposed in the NPRM, both 
the NTSB and Advocates requested a lower limit for allowable 
protrusion. NTSB noted that the emergency latch in the Gray Summit 
crash protruded 1 inch into the emergency exit opening; therefore the 
proposed 1-inch maximum limit would not have prevented clothes from 
snagging in that crash scenario. NTSB noted that the manufacturer has 
since decreased the height of its buses' emergency release latch plate 
so that it does not protrude into the window opening more than 0.5 
inches. Advocates stated in their comments that there exist ``flush-
mount [latch] designs that entail no protrusion at all.'' However, they 
added that these latches are implemented in non-motorcoach designs. 
NTSB stated that, if NHTSA allows any degree of latch protrusion, the 
latch should be designed to eliminate its potential to snag clothing or 
otherwise impede evacuation.
    SBMTC suggested NHTSA should provide a formal definition of 
``opening'' as used in the proposal that ``emergency exit latches, or 
other related release mechanisms, shall not protrude more than 25 mm 
into the opening of the emergency exit when the window is in the open 
position.'' ICB commented that the ``protrusion requirement applies to 
a latch or latch mechanism that is attached and remains with the bus 
body structure and not to a latch or latch mechanism that is attached 
to and moves with the exit window itself.'' ICB wrote that the 
protrusion limit applies to anywhere in the window opening, even if the 
opening is larger than required for the passage of the ellipsoid 
specified in S.5.4.1. ICB also asked if ``a latch or latch mechanism, 
that is spring loaded and protrudes more than 25 mm into the window 
opening in order to release the window, but then returns to a position 
that protrudes less than 25 mm, would be compliant with this 
requirement.''
Agency Response
    The agency has decided that it cannot justify a reduction in the 
emergency exit window latch protrusion requirements based on the 
comments and data provided in response to the NPRM. It is unknown at 
this time what the financial burden on the industry would be to require 
emergency exit latches to be replaced with flush-mount designs or 
reduced protrusions. It is also unproven at this time whether flush-
mount latch designs would withstand the impact forces from the FMVSS 
No. 217a impact tests without additional modifications. The commenters 
did not provide information on the current status of latch designs used 
in different bus types, or what changes would be needed to comply with 
their suggested lower protrusion limits. Therefore, although we 
acknowledge that a one-inch protrusion may hinder egress in certain 
cases, NHTSA is denying the requests to reduce the emergency exit 
window latch protrusion limit.
    ICB is correct that the protrusion limits apply only to the latch 
components that remain with the bus structure. The latch protrusion in 
the Grey Summit bus crash that snagged on occupants' clothing was 
mounted to the bottom of the window frame. Latches and related 
components that protrude into the window opening from the fixed bus 
structure are difficult for occupants to avoid when attempting to climb 
through the window opening during an emergency. This difficulty results 
in a high likelihood of the protrusion snagging onto occupants' 
clothing. If the latch components are located on the portion of the 
emergency exit window that opens, the occupant would likely be able to 
reduce the risk of snagging any protrusion by opening the window 
farther. Thus, the protrusion limits apply only to the latch components 
that remain with the bus structure when the emergency exit window is in 
the open position to allow passage of the ellipsoid specified in S5.4.1 
of FMVSS No. 217.
    ICB stated the protrusion limit applies to anywhere in the window 
opening even when the window is opened beyond what is required by 
S5.4.1 of FMVSS No. 217. This statement is incorrect. As proposed in 
the NPRM, the protrusion limit only applies to the window opening when 
the emergency exit is opened to the amount necessary to admit 
unobstructed passage of the ellipsoid specified in S5.4.1 of FMVSS No. 
217.
    ICB asked if ``a latch or latch mechanism, that is spring loaded 
and protrudes more than 25 mm into the window opening in order to 
release the window, but then returns to a position that protrudes less 
than 25 mm,'' would be compliant with this requirement. An emergency 
exit opening system in which part of the latch mechanism protrudes into 
the opening space while the window latch lock is being released would 
be acceptable, as long as the latch components are all below the 
protrusion limit once the window is opened to the amount specified in 
S5.4.1. For example, a lever handle could protrude more than an inch 
into the opening while it is being moved from the closed position to 
the open position. However, once the lever is in the position to allow 
the window to be opened, all parts of

[[Page 86274]]

the lever and its attachment bracket must protrude less than one inch 
from the structure to which it is attached.
Force Required To Open Emergency Exits
    NTSB stated that from its accident investigations it ``found that 
some passengers have difficulty in opening motorcoach windows and 
evacuating from them because of the weight of the windows and the 
challenge of keeping them open.'' NTSB cited results from its crash 
investigations that support this concern. NTSB also requested that 
NHTSA take action in this, or a future, rulemaking to address the ease 
of opening such windows and their ability to remain open independently. 
NTSB stated ``[s]uch action is needed to improve evacuation from 
emergency exit windows for motorcoaches and school buses.''
Agency Response
    While NHTSA shares the NTSB's concern for the capability of school 
bus occupants to easily open emergency exits, this aspect of emergency 
egress is not within the scope of this rulemaking. Therefore, NHTSA 
will not be mandating requirements concerning the force required to 
open emergency exits on school buses as part of this final rule.

f. Organization of the Standard and Language Used in the Standard

    Several commenters provided feedback on the organization of the 
proposed standard, as well as the language used in the proposed 
standard. In response to these comments, the agency has decided to make 
several amendments to the proposed organization and language of the 
standard, which will be adopted as part of this final rule. The 
amendments to the proposed organization and language are highlighted in 
several of the agency response sections below.
Merging FMVSS No. 217a Into FMVSS No. 217
    ICB suggested ``that there should not be a separate and distinct 
regulation for FMVSS 217a Anti-Ejection Glazing for Bus Portals.'' ICB 
stated that it would be better to have all bus window and glazing 
requirements included in FMVSS No. 217. However, ICB did note that it 
is ``helpful to keep the latch protrusion requirements separate from 
the anti-ejection requirements.''
Agency Response
    The agency has chosen to keep the bus anti-ejection requirements 
and procedures in a separate standard. Having FMVSS No. 217a separate 
from FMVSS No. 217 serves to highlight the differences in the two 
standards. Additionally, having the bus glazing anti-ejection 
requirements in a separate standard avoids confusion with existing 
FMVSS No. 217 requirements and procedures. This separation is useful 
for school bus applicability, since the planned FMVSS No. 217a has no 
applicability to school buses whereas FMVSS No. 217 does have specific 
requirements for school buses.
102 mm Sphere Application Force and Passage
    Section 5.2(b) in the NPRM's proposed regulatory text states that 
``[e]ach piece of window glazing and each surrounding window frame 
shall be retained by its surrounding structure in a manner that 
prevents the formation of any opening large enough to admit the passage 
of a 102 mm diameter sphere under a force, including the weight of the 
sphere, of up to 22 newtons.'' This wording is different from the 
language used in S5.1(b) and S5.3(b). Those two sections use the phrase 
``. . . when a force of no more than 22 newtons is applied with the 
sphere at any vector . . .'' The text in S5.1(b) and S5.3(b) correctly 
states a 22 N force is applied to the glazing by the sphere. To be 
consistent, the agency has decided that the same wording in S5.1(b) and 
S5.3(b) will be used in S5.2(b). Additionally, the agency has decided 
to amend S5.1(b), S5.2(b), and S5.3(b) so that ``passage'' is amended 
to ``complete passage.'' This change is based upon agency feedback 
recommending improved clarity in the regulatory text for compliance 
purposes. It was noted that without usage of the word ``complete,'' 
there would be no distinction between minimal, partial, and complete 
passage of the sphere through the glazing. The amended language is 
reflected in the final regulatory text for FMVSS No. 217a.
Testing Requirements Organization
    ICB requested separate sections in the standard for each impact 
test (center impact, edge impact, and pre-broken glazing impact tests) 
with the requirements for each type of test in that section.
Agency Response
    After reviewing the organization of the three types of tests 
(center impact, edge impact, and pre-broken glazing impact tests), the 
agency concluded that the requirements for each are already in separate 
sections. Within the proposed regulatory text for FMVSS No. 217a, S5.1 
includes the requirements for the edge impact test, S5.2 includes 
requirements for the center impact test, and S5.3 includes requirements 
for the pre-broken glazing impact test. Accordingly, NHTSA does not see 
any need to adjust the organization of these requirements as part of 
this final rule.

g. Compliance Date

    When the NPRM for this rule was published, NHTSA proposed a 
compliance date of 3 years after publication of a final rule. Based on 
research from NHTSA's Vehicle Research and Test Center, the agency 
believes that some manufacturers would need to redesign their emergency 
exit latch systems or adopt a design that would meet the proposed 
requirements. Also, manufacturers would have to transition from double-
glazed tempered/tempered windows to a new setup that has at least one 
layer of laminated glass or advanced glazing that can meet the proposed 
requirements. The agency has determined that a 3-year lead time after 
publication of a final rule is appropriate as some design, testing, and 
development will be necessary to certify compliance to the new 
requirements.
    The rollover structural integrity final rule has a compliance date 
of December 30, 2024, which is 3 years after the publication date of 
December 29, 2021. Similarly, the agency proposed a compliance date of 
3 years after publication of the final rule for this advanced glazing 
rulemaking. Since the two rulemakings were initially being developed 
concurrently, and since the anti-ejection requirements are dependent 
upon the rollover structural integrity requirements, the agency 
proposed in the NPRM to make the compliance date of the two rulemakings 
the same. The agency also proposed that, to enable manufacturers to 
certify to the new requirements as early as possible, optional early 
compliance with the standard would be permitted. EPGAA commented that 
the glazing industry should have no issue supporting the three-year 
phase-in period since ``the manufacturing technology and capacity 
already exist to produce advanced glazing solutions.'' BBBC stated that 
making the compliance date the same for the two rulemakings (FMVSS No. 
227 and FMVSS No. 217a) is preferred only if the date is a minimum of 3 
years after the publication of both final rules. ICB also requested 
alignment of the implementation time for FMVSS No. 227 and FMVSS No. 
217a. Van Hool stated that it would prefer to extend the crash 
requirements for the retention of glazing and the opening of emergency 
exits after the crash.

[[Page 86275]]

Agency Response
    Since the rollover structural integrity final rule was published 
significantly earlier than this anti-ejection glazing final rule, the 
agency has decided not to align the compliance date of the two 
standards. The agency agrees with EPGAA that the MAP-21 mandated lead 
time of 3 years is sufficient for the necessary design, testing, and 
development to comply with this standard. To align the compliance dates 
of FMVSS No. 227 and a final rule for advanced glazing, the agency 
would either need to delay the compliance date of FMVSS No. 227 or 
accelerate the compliance date of advanced glazing final rule 
establishing FMVSS No. 217a. As stated in the NPRM, NHTSA believes a 
lead time of 3 years is an appropriate amount of time to account for 
the changes required to comply with this anti-ejection glazing 
standard. The agency will not decrease the lead time of this standard 
to align the compliance date with FMVSS No. 227. Additionally, the 
structural integrity improvements due to compliance with FMVSS No. 227 
will benefit occupants during a rollover crash even if the anti-
ejection glazing improvements have not yet been implemented. Therefore, 
the agency will not delay the compliance date of FMVSS No. 227 to align 
with a final rule establishing FMVSS No. 217a as BBBC and ICB have 
requested.
    The agency is unclear about what Van Hool was requesting in it 
comment on the compliance date. If Van Hool was asking for additional 
lead time, it did not state how much additional time it was requesting 
before implementation of improved passenger anti-ejection benefits. 
Accordingly, NHTSA has decided not to grant Van Hool's request.
    For the reasons discussed above, NHTSA is adopting the 3-year 
compliance date as proposed in the NPRM as part of this final rule.

h. Retrofitting

    Greyhound and ICB agreed with the agency that it would make little 
sense to require retrofitting of bus windows without improving the 
structural integrity of the bus. Greyhound indicated that any 
requirements for enhanced window standards should apply only to buses 
manufactured after the implementation date of those standards. NTSB 
requested NHTSA consider requiring retrofit of existing buses for 
improved window latch design, stating that ``NHTSA has identified 
simple countermeasure latch designs that reduce latch openings when the 
window is struck near the latch.''
Agency Response
    The agency has decided to not require retrofitting of buses with 
improved latch designs and window glazing materials as part of this 
final rule. As stated in the NPRM, the simple countermeasure for latch 
designs was to add a washer screwed onto the top of the existing MCI E/
J-series striker post. The agency has no data to determine if this fix 
would work for other latch systems, or if other redesigns to those 
latch systems would be necessary. For example, it is not known if the 
other buses have enough strength at the latch anchorage locations of 
each window for the improved latch system. Every window system would 
require analysis and most likely testing to verify its capability to 
successfully manage the new loads. Each window structure would need to 
be inspected for pre-existing damage that would cause the improved 
latch system to fail when subjected to the new loads. Therefore, NHTSA 
disagrees with the NTSB's argument that a simple countermeasure exists 
for retrofitting all existing buses. It is not practical to retrofit 
improved latch systems onto existing buses because of the unique nature 
of each existing window structure and latching mechanism.
    Additionally, NHTSA retains its plan to not require retrofitting of 
advanced glazing into existing buses. The agency agrees with Greyhound 
and ICB that it makes little sense to upgrade the window glazing 
without also improving the bus structure in accordance with FMVSS No. 
227. Therefore, NHTSA will not require retrofitting for any 
requirements of this standard.

i. Definitions and Descriptions

Daylight Opening
    BBBC commented that the proposed S4 definition of ``daylight 
opening'' through its use of the terms ``horizontal'' and ``vertical'' 
assumes the opening is essentially purely horizontal or vertical, 
respectively. While BBBC stated that openings are usually one or the 
other, BBBC recommended that NHTSA consider how to apply that 
definition to an opening that may be in a plane that is not purely 
vertical or horizontal, such as one 45 degrees to either plane.
    Replying to the questions asked in the NPRM concerning Executive 
Order (E.O.) 12866 and E.O. 13563, ICB and SBMTC requested improved 
clarity through the addition of figures and diagrams for various terms, 
including daylight opening and periphery. ICB stated that the 
definition for daylight opening given in the NPRM is ``confusing and 
overly complicated.'' It also asked for clarification concerning the 
items to be included in the daylight opening measurement and further 
suggested that any window frame, weather stripping, or flexible gasket 
material should not be included in portal size measurements.
Agency Response
    NHTSA is adopting the proposed definition of daylight opening; 
however the specifications for daylight opening for rear windows have 
been deleted.\48\ Due to the number of comments received concerning the 
definition of daylight opening, NHTSA has elected to add figures and 
additional details in the Technical Support Document to aid in 
understanding the definition as part of this final rule. This Technical 
Support Document is included in the docket for this final rule. For the 
purposes of FMVSS No. 217a, ``daylight opening'' is the opening 
generated when the visible glazing, including flexible material, is 
removed from the window. It is the opening bounded by the bus 
structure's window frame. ``Daylight opening'' applies to all side and 
roof windows of the vehicle, including emergency exit windows. 
``Daylight opening'' is used to help determine where the FMVSS No. 217a 
guided impactor will hit.
---------------------------------------------------------------------------

    \48\ Since the impact tests no longer apply to rear windows in 
this final rule, there is no need for defining daylight opening for 
rear windows.
---------------------------------------------------------------------------

    BBBC commented that the proposed definition for daylight opening 
does not account for window openings that are not purely vertical or 
horizontal. BBBC is correct that while most windows are oriented 
vertically or horizontally, there are applications where the window may 
be installed at an angle or consist of curved glazing. The agency 
believes the proposed definition of daylight opening properly accounts 
for these situations where the window is not purely horizontal or 
vertical. The proposed definition specifies the orientation of the 
``daylight opening'' to be based on the bus's longitudinal axis and 
whether the window is on the bus's side wall or roof. If the window is 
installed at an angle or uses curved glazing, the daylight opening 
would still be measured based on the proposed definition depending on 
whether the window is located in the bus side wall or roof. Therefore, 
whether a window is purely vertical or horizontal, the daylight opening 
would be determined in the same manner. The Technical Support Document 
provides illustrations and examples for determining the daylight 
opening for curved glazing. The Technical Support Document also 
addresses the comments from ICB and SBMTC, which requested

[[Page 86276]]

additional figures and clarification surrounding the definition of 
daylight opening and periphery.
Portal
    ICB commented that a portal is related to the opening created in 
the bus structure when the window is opened. ICB stated that the term 
``portal'' is confusing and that the term be replaced with ``opening.''
Agency Response
    NHTSA has decided not to replace the term ``portal'' with 
``opening'' as part of this final rule. The definition of a portal 
according to the proposed FMVSS No. 217a text is ``an opening that 
could, in the event of a crash involving the vehicle, permit the 
partial or complete ejection of an occupant from the vehicle, including 
a young child.'' This definition comes directly from MAP-21. An opening 
is a more general term, and a portal is a specific type of opening. A 
portal can be any type of opening in a bus wall, floor, or roof that 
could allow even a partial ejection of an occupant in the event of a 
crash. Some examples of a portal include an open window or door, a 
broken window with some glazing removed, a hole in the bus wall, or an 
open roof hatch. While there are no minimum dimensions associated with 
portals, it must be large enough to admit at least partial passage of 
an occupant, even if they are a smaller child. NHTSA will not replace 
the word ``portal'' with ``opening,'' because an opening does not have 
to be large enough to admit at least partial passage of an occupant.
Miscellaneous Comments on Clarification of Terms
    In addition to the clarifications discussed above, ICB requested 
improved clarity through the addition of figures and diagrams for 
measuring minimum surface dimension of an opening and glazing pre-
breaking procedures.
Agency Response
    NHTSA believes these topics are discussed in sufficient detail in 
the NPRM and in this final rule. Additional details for the glazing 
breaking procedures, the latch protrusion into the emergency exit when 
the window is in the open position, and how to measure minimum surface 
dimension of an opening are items that will be included in the agency's 
compliance test procedures for this rule.

j. Costs and Benefits

    In the NPRM and Preliminary Regulatory Evaluation (PRE), NHTSA 
anticipated that tempered glazing would not meet the requirements of 
the dynamic impact tests, particularly the pre-broken impact test, and 
the agency believed the double-glazed tempered/tempered windows would 
need to be replaced, at minimum, with a single-glazed laminated window. 
Thus, the cost and benefit estimates assumed the manufacturers would be 
upgrading from double-glazed tempered/tempered glazing to single-glazed 
laminated glazing.
    The target population for total lives saved was based on fatalities 
from rollover crashes in applicable buses and was reduced by the 
expected lives saved due to Electronic Stability Control (ESC), seat 
belt usage, and rollover structural integrity. The NPRM noted that 
advanced glazing would also prevent fatalities in other crash types, 
but it did not include those crash types in the estimation due to lack 
of need to further justify the rule.\49\
---------------------------------------------------------------------------

    \49\ 81 FR 27925.
---------------------------------------------------------------------------

    For the governing scenario of replacing double-glazed tempered/
tempered glazing with single-glazed laminated glazing, NHTSA estimated 
the costs and benefits as summarized in Table 9 below. NHTSA determined 
replacing a double-glazed tempered/tempered glazing with a single-
glazed laminated glazing would result in a weight decrease and cost 
increase.\50\ For additional details and the calculations associated 
with these data, refer to the PRE included in the docket with the NPRM.
---------------------------------------------------------------------------

    \50\ The agency estimated that a fully framed and assembled 
double-glazed tempered/tempered window (approximately 25 square 
feet) costs $340. Likewise, the agency estimated that a fully framed 
and assembled single-glazed laminated window (approximately 25 
square feet) costs $353.75. The incremental cost of choosing a 
single-glazed laminated window over a double-glazed tempered/
tempered window is $13.75 per window or $165.00 per bus assuming 12 
windows. The weight of the double-glazed tempered/tempered window 
units used in NHTSA's testing were 100 lb and 110 lb (avg of 105 
lb). The single-glazed laminated window unit weighed 77 lb. This 
difference results in an average weight savings of 28 lb per window 
unit. Assuming an average of 12 windows per bus results in 336 lb of 
weight savings per bus.

                          Table 9--Advanced Glazing Annual Costs and Benefits From PRE
----------------------------------------------------------------------------------------------------------------
                          Costs                                                  Benefits
----------------------------------------------------------------------------------------------------------------
                  Item                      Value ($M)               Item                       Amount
----------------------------------------------------------------------------------------------------------------
Material................................          $0.191  Lives Saved \A\...........  0.33-1.54 lives per year.
                                                          Fuel Savings \B\..........  0.04 mpg.
----------------------------------------------------------------------------------------------------------------
Notes:
\A\ Range is dependent on seat belt usage, from 15 percent usage to 84 percent usage.
\B\ Fuel savings due to weight savings estimated at 336 lb per vehicle.

    According to the PRE and NPRM, the main cost associated with the 
requirements in this rule would be the material costs for the new 
glazing types and window units. The agency also anticipated that 
modifications to the window latch systems would be needed to meet the 
dynamic impact test requirements. Applying these material costs to the 
population of new, large buses and motorcoaches produced annually 
resulted in approximately $191,000.\51\
---------------------------------------------------------------------------

    \51\ The agency estimated that there are 2,200 new over-the-road 
and applicable large buses manufactured annually. NHTSA estimated 
that MCI manufactures about 47.7 percent of the market population 
and already includes laminated glazing as part of its production 
window options. Assuming 12 windows per bus, the cost to equip 
laminated glass instead of tempered glass is $13.75 per window, and 
the cost of latch improvements is $0.05 per window, the total annual 
incremental cost for new buses covered under this proposal is 
$191,169 (= 2,200 x 0.477 x $0.60 + 2,200 x 0.523 x $165.60) in 2013 
dollars.
---------------------------------------------------------------------------

    Switching from a double-glazed tempered/tempered window unit to a 
single-glazed laminated window unit would reduce the overall weight of 
the window unit. This weight reduction would result in improved fuel 
economy for each bus. The weight of the double-glazed tempered/tempered 
window units used in NHTSA's testing were 100 lb and 110 lb (avg of 105 
lb). The single-glazed laminated window unit weighed

[[Page 86277]]

77 lb. This difference resulted in an average weight savings of 28 lb 
per window unit. Assuming an average of 12 window units per bus 
resulted in 336 lb of weight savings per bus. Based on the calculations 
outlined in the PRE, this change resulted in an increase of 0.04 mpg 
per bus. Projecting that fuel economy benefit over the life of each 
affected bus produced annually resulted in approximately $2.90 million 
worth of fuel economy savings at a 3% discount rate.\52\ Table 10 below 
summarizes the costs and benefits of the rule as outlined in the PRE.
---------------------------------------------------------------------------

    \52\ A typical large bus travels 56,000 miles per year and has 
an average fuel economy of 6.1 mpg. With the 47.7 percent current 
compliance rate, an estimated 1,151 buses would benefit from this 
fuel economy increase.

                                Table 10--Summary of Annualized Costs and Benefits due to the Anti-Ejection Glazing NPRM
                                                         [Costs are in millions of 2013 dollars]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         15% belt use rate                               84% belt use rate
                                                         -----------------------------------------------------------------------------------------------
                                                           Undiscounted         3%              7%         Undiscounted         3%              7%
--------------------------------------------------------------------------------------------------------------------------------------------------------
Equivalent Lives Saved..................................            1.60            1.37            1.03            0.34            0.29            0.22
Net Cost \A\............................................         ($5.57)         ($4.30)         ($3.20)         ($3.98)         ($3.05)         ($2.25)
Cost per Equivalent Lives Saved.........................         ($3.48)         ($3.14)         ($3.11)        ($11.71)        ($10.52)        ($10.23)
Benefits from Comprehensive Costs Avoided...............          $15.44          $13.22           $9.95           $3.30           $2.82           $2.12
Net Benefits............................................          $21.02          $17.52          $13.15           $7.28           $5.87           $4.37
--------------------------------------------------------------------------------------------------------------------------------------------------------
Notes: \A\ Net costs are negative because the fuel savings are expected to outweigh the material costs.

Glazing Construction for Compliance
    BBBC, Prevost, Van Hool, SBMTC, and ICB expressed concerns that 
usage of laminated glazing could result in increased weight and cost 
per bus, leading to increased fuel usage and possibly resulting in 
reduced seating capacity in buses close to their weight limit. Prevost 
questioned the agency's assumption that double-glazed tempered/tempered 
windows could be replaced with a single pane of laminated glazing. Van 
Hool and Prevost expressed concern for changes in thermal properties, 
which would directly influence costs associated with heating and 
cooling of the bus interiors. Prevost also obtained a price quotation 
for installing laminated glazing in its motorcoaches. According to 
Prevost, for equivalent sizes, shapes, and tinting, the estimated cost 
increase when compared to its current double-glazed tempered/tempered 
configuration was ``on the order of five thousand dollars ($5,000) per 
vehicle.'' ICB stated it uses single-paned tempered glazing for bus 
windows. According to ICB, replacing this material with single paned 
laminated glazing ``could add up to 200 lb of additional weight.'' Van 
Hool also stated that ``[d]ouble laminate or tempered/laminated glazing 
might do the trick at no expense for seating capacity, but with no gain 
either.''
    EPGAA agreed with the agency's conclusion that there is a weight 
reduction in direct replacement of laminated for tempered glazing in 
situations where the overall thickness remains the same since the 
density of the plastic interlayer is about half that of glass. EPGAA 
expressed doubt that there will be a significant change in the desire 
of bus OEMs to employ double-glazed insulating assemblies for buses 
used in colder climate zones. EPGAA stated that the insulating units 
are employed to increase the interior glass temperature and thus reduce 
any propensity for condensation or fogging while increasing occupant 
thermal comfort. EPGAA stated that advanced glazing does not in itself 
create a significant impact in thermal performance compared to 
monolithic glass since it has a similar thermal conductivity.
    EPGAA commented that advanced glazing would offer a benefit through 
reduced sound transmission when compared to monolithic tempered glass, 
creating a quieter cabin. EPGAA also commented that advanced glazing 
would result in a significant reduction in UV exposure of occupants and 
interior components. EPGAA stated that with the addition of optional 
low emissivity or solar control layers the advanced glazing may also be 
used to significantly reduce the solar load and hence air conditioning 
load. EPGAA also stated that certain added layers may function to 
reduce condensation or fogging thresholds and could in some cases help 
to eliminate the need for the double-glazed insulating assemblies. 
EPGAA concluded that while the fuel savings based on reduction in use 
of insulating glass assemblies may be overestimated, there are unstated 
monetary savings associated with air conditioning load reduction as 
well as reduced UV exposure of occupants.
Agency Response
    Based on comments and feedback from the bus manufacturers and 
SBMTC, NHTSA understands most bus manufacturers will not be replacing 
double-glazed tempered/tempered windows with single-glazed laminated 
windows. Instead, it is more representative of the industry to assume 
the manufacturers will simply exchange at least one pane of tempered 
glazing with laminated glazing but keep the double-glazed window 
construction. In other words, the double-glazed tempered/tempered 
windows will likely be replaced with double-glazed laminated/tempered 
windows, where either the interior or exterior pane is laminated 
glazing. This replacement will maintain or improve the thermal and 
sound insulation properties that are experienced by occupants with the 
current glazing units. The cost-benefit analysis in this final rule 
uses this change as the governing scenario, instead of the scenario 
presented in the PRE.
    This change in governing scenario results in the removal of the 
weight reduction benefit that was estimated in the PRE. EPGAA stated in 
its comments that there is some weight reduction when directly 
replacing tempered glazing with laminated glazing due to the lower 
density of the PVB interlayer compared to glass. However, the laminated 
glazing is often thicker than the tempered glazing it replaces, and the 
PVB interlayer only makes up approximately 6 percent of the glazing 
thickness.\53\ Therefore, any weight difference is considered 
negligible for

[[Page 86278]]

the purposes of the cost and benefit calculations.
---------------------------------------------------------------------------

    \53\ Duffy, S., & Prasad, A., National Highway Traffic Safety 
Administration, Motorcoach Side Glazing Retention Research, pp. 10-
13 (Report No. DOT HS 811 862) (Nov. 2013). Washington, DC:.
---------------------------------------------------------------------------

    As Prevost commented, there are additional costs to consider if 
manufacturers would be replacing their current double-glazed window 
units with single-glazed laminated windows. Switching from a double-
glazed tempered/tempered window construction to a double-glazed 
laminated/tempered window construction will be more expensive for bus 
manufacturers than switching to a single-glazed laminated window as 
previously calculated. The agency estimates that a fully framed and 
assembled double-glazed tempered/tempered window (approximately 25 
square feet) costs $377.73. Likewise, NHTSA estimated that a fully 
framed and assembled double-glazed laminated/tempered window 
(approximately 25 square feet) costs $438.84. The incremental cost of 
choosing a double-glazed laminated/tempered window over a double-glazed 
tempered/tempered window is $61.11 per window or $733.32 per bus 
(assuming 12 windows per bus). As outlined in the costs and benefits 
section of this final rule, even with the higher costs associated with 
this governing scenario this final rule is still cost beneficial.
Previous Rulemakings
    Van Hool expressed concern that the possible positive influences of 
ESC on bus rollovers were not properly accounted for. Van Hool asked 
how effective an ESC system would be during a bus rollover. Further, 
Van Hool proposed that the severity of an unbelted occupant's contact 
with the opposite side glazing during a rollover would be mitigated by 
the effects of ESC.
    Prevost stated that it ``believe[s] that the estimated usage of 
seat belts is higher than what is listed in the NPRM.'' Prevost also 
stated that ``[s]eat belt usage is the single most important safety 
system to mitigate passenger ejection and we commend NHTSA on the 
attention they continue to give to this. We believe that pre-trip 
safety briefings will further increase the percentage of seat belt 
usage.'' Van Hool stated that any seat belt usage data is speculative 
at best and that the agency manipulated the seat belt estimates ``in 
order to make the numbers work.''
    Van Hool commented that the effects of the requirements from FMVSS 
No. 227 have not been taken into account and that there has not been 
enough consideration of the performance changes to the vehicle 
structure that will be created by bus designs changing to meet FMVSS 
No. 227. Van Hool stated that its bus windows do not break in a 
rollover test under Regulation No. 66 of the Economic Commission for 
Europe of the United Nations (ECE R.66). Van Hool stated the agency has 
not adequately proven that the FMVSS No. 217a impactor test represents 
rollover forces acting on the windows of future buses that fulfill the 
requirements of FMVSS No. 227 and/or ECE R.66.
Agency Response
    Details concerning the effectiveness of ESC for buses was discussed 
in both the agency's 2012 NPRM proposing to require ESC on heavy 
vehicles and a 2011 agency research note.\54\ The analysis estimated 
that ESC would be 40-56 percent effective against a rollover event. In 
other words, 44-60 percent of the rollover events would still occur, 
even with ESC installed in the heavy buses. Since ESC alone only 
partially mitigates the risk of rollover crashes, there remains a need 
to protect passengers from ejection conditions in applicable vehicles. 
NHTSA has accounted for the crash reducing effects of ESC when 
calculating the estimated lives saved from the advanced glazing 
requirements in this final rule.
---------------------------------------------------------------------------

    \54\ 77 FR 3076 NPRM for new FMVSS No. 136 (May 23, 2012); 
Effectiveness of Stability Control Systems for Truck Tractors, DOT 
HS 811 437 (Jan. 2011).
---------------------------------------------------------------------------

    The agency agrees with Prevost on the importance of seat belt usage 
in all motor vehicles. The agency examined seat belt usage rates of 15% 
and 84% in the NPRM. For the cost-benefit analysis in this final rule, 
the upper bound was increased to 90 percent. Nationally the seat belt 
usage rate in passenger vehicles has been approximately 90 percent very 
year from 2016 to 2021.\55\ Therefore, the agency analysis based on the 
90 percent usage rate in motorcoaches is reasonable as a conservative 
upper bound since usage rates in buses are not believed to be as high 
as passenger vehicles. NHTSA has accounted for a range of bus occupants 
using seat belts when calculating the estimated lives saved from the 
advanced glazing requirements in this final rule.
---------------------------------------------------------------------------

    \55\ Seat Belt Use in 2021--Overall Results, Traffic Safety 
Facts Research Note, Report number DOT HS 813 241 (Dec. 2021), 
https://crashstats.nhtsa.dot.gov/Api/Public/Publication/813241, last 
accessed December 18, 2023.
---------------------------------------------------------------------------

    The bus structural integrity rollover test used in FMVSS No. 227 
and ECE R.66 is an effective test to determine a bus's capability to 
maintain a survival space during a rollover event.\56\ However, in that 
test, ballast weight for each occupant is strapped to the seats for the 
FMVSS No. 227 evaluation. Windows are not intended to be evaluated 
under loading from moving objects in that test. While the increased 
structural rigidity is expected to reduce the number of fatal 
ejections, those requirements do not account for passengers being 
ejected through windows that have been broken by internal impacts. The 
rollover structural integrity FRE estimates a 74 percent effectiveness 
of ejection mitigation in preventing fatalities. It also states that 
the enhanced rollover structural integrity test procedure does not 
include a condition to simulate occupant loading, and therefore 
estimates a midpoint effectiveness of 37 percent for unrestrained 
ejected fatalities. As outlined above, this effectiveness is accounted 
for when calculating the expected number of lives saved from the 
requirements in this final rule.
---------------------------------------------------------------------------

    \56\ Matolcsy, M., ``The Severity of Bus Rollover Accidents,'' 
20th International Technical Conference for the Enhanced Safety of 
Vehicles, Paper 989, Lyon, France (2007). Available at: www-nrd.nhtsa.dot.gov/pdf/esv/esv20/07-0152-O.pdf.
---------------------------------------------------------------------------

Supporting Data
    Van Hool stated that ``the data driving this NPRM seems to be from 
1980-2004'' and that this data was collected well before seat belts 
were in use. Van Hool commented that if 2010-2015 data were used there 
would not be a strong case for requiring anti-ejection glazing. Van 
Hool commented that ``recently released FMCSA crash data indicates the 
lowest fatality rates given the higher numbers of coaches on the road 
and the highest number in miles traveled.''
    Van Hool also expressed doubt for the particular occupant loading 
chosen in the Martec study, and the agency's usage of that loading to 
develop the proposed anti-ejection requirements for this rule. Van Hool 
expressed a preference to use the structural integrity rollover test 
used in FMVSS No. 227 as the bus motion to study for window glazing 
loading during crashes. Van Hool stated a ``passenger could not be 
projected against the window, nor could he be ejected out of the bus 
through the opposite side.''
Agency Response
    The 1980-2004 data to which Van Hool refers was used for the Martec 
report, which was completed in 2006. The data presented in the report 
was the most recently available information at the time that study was 
conducted. Those crashes were investigated to identify the rollover 
events most likely to produce worst-case occupant to glazing impact 
loads. While the Martec report and its source data are over 10

[[Page 86279]]

years old, data indicate that passengers continue to be ejected from 
motorcoaches during rollover and other crashes. NHTSA did not rely on 
the Martec report data as the ``driving data'' for this rule. The 
driving data used for the NPRM and PRE was from 2004-2013. NHTSA has 
updated that data to be from 2006 to 2019 for the final rule.
    The Martec report stated that its objective was ``to improve the 
level of safety protection of passengers in motorcoach crashes by 
reducing the likelihood of ejection during vehicle collision or 
rollover, as such ejections are associated with a high probability of 
fatality.'' The report authors examined Transport Canada bus crash 
investigation reports and then chose to model the passenger motion in a 
bus during a crash where

. . . the bus rolled onto its side after yawing while trying to 
negotiate a sharp turn at elevated speed. The bus had a significant 
lateral velocity, the underside of the bus contacted the ground, 
furrowed into the sod, and the bus rolled over on its side. A rear 
hinged/latched emergency window (on the impacted side) was either 
dislodged during the crash or had been opened prior to the rollover, 
and there were fatalities due to ejections through the window 
opening.\57\
---------------------------------------------------------------------------

    \57\ Motor Coach Glazing Retention Test Development for Occupant 
Impact During a Rollover (Martec Study), Final Report published on 
August 2006, Docket No. NHTSA-2002-11876-15.

    The claim that a passenger could not move unobstructed to the 
opposite side of a bus during a vehicle rollover does not apply to all 
bus seating configurations. The Martec study appropriately used a 
severe bus crash event and conducted computer simulations to determine 
a possible window loading scenario caused by a passenger's unrestrained 
movement during such a crash event. With this bus glazing anti-ejection 
rule the agency is establishing requirements such that the retained 
windows will mitigate partial ejections of belted occupants seated next 
to the windows as well as retain the estimated 10 to 85 percent of 
unbelted occupants. The anti-ejection requirements will mitigate the 
occurrence of window portals being created by movement of unrestrained 
passengers. Accordingly, the agency will not be adopting Van Hool's 
recommendation to use the motion from a belted passenger in a rollover 
test as the load basis for window glazing anti-ejection requirements as 
part of this final rule.

VI. Overview of Costs and Benefits

    After accounting for the above comments from the NPRM, NHTSA 
analyzed the anticipated effects of a final rule and determined the net 
result is cost beneficial. The agency anticipates that tempered glazing 
will not meet the requirements of the dynamic impact tests, 
particularly the pre-broken impact test. Therefore, the governing 
scenario we use for the cost-benefit analysis assumes the manufacturers 
will replace at least one pane of their double-glazed tempered/tempered 
window units with laminated glass.
    For fatality data analysis, NHTSA used FARS data from 2006-2019. 
The agency decided not to use 2020 data for data summaries and averages 
due to the effect of the COVID-19 pandemic on the industry. NHTSA 
believes the 2020 data could disproportionately skew the costs and 
benefits analysis. For injury data analysis, NHTSA used the National 
Automotive Sampling System--General Estimates System (NASS-GES) data 
from 2006-2015 and Crash Report Sampling System (CRSS) data from 2016-
2019. The NASS-GES system was retired in 2016 and replaced by the CRSS 
system. The same 14-year period 2006-2019 was used to match the time 
frame of fatality data.
    The costs resulting from today's final rule are the material costs 
attributed to upgrading the window glazing material and improving the 
latching mechanisms as necessary. As discussed in the FRE for today's 
final rule, approximately 47.7 percent of motorcoach manufacturers 
currently use laminated glass in their window units. The remaining 52.3 
percent of motorcoach and large bus manufacturers are assumed to use 
double-glazed tempered/tempered window units, or some other glazing 
construction that may not comply with the performance requirements in 
this final rule. These windows will need to be upgraded to at least a 
double-glazed laminated/tempered glazing window unit construction. 
Additionally, NHTSA estimates that modifications to the window latch 
systems for all motorcoach and large bus manufacturers will be needed 
in order to meet the dynamic impact test requirements. Table 11 
summarizes the incremental costs associated with administering the 
upgrades necessary for compliance with today's final rule.

            Table 11--Incremental Costs From Replacing Tempered/Tempered Glazing With Laminated/Tempered Glazing and Upgraded Window Latches
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                 Total cost   Total cost
                                                                              Cost for    Number of                 Number of    to upgrade    assuming
                         Glazing type                            Cost per     improved    side glass    Cost per    applicable      all         47.7%
                                                                  window     latch per    positions     vehicle      vehicles    applicable   compliance
                                                                               window                                             vehicles       rate
--------------------------------------------------------------------------------------------------------------------------------------------------------
Double-glazed tempered/tempered..............................      $430.62        $0.00           12    $5,167.48        2,200  $11,368,457           NA
Double-glazed laminated/tempered.............................       500.28         0.06           12     6,003.40        2,200   13,209,144           NA
Incremental cost.............................................        69.66         0.06           12       835.92        2,200    1,840,687      963,477
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The benefits of today's final rule are calculated based on the 
number of expected equivalent lives saved \58\ from ejections during 
crashes involving the applicable buses. NHTSA calculated the fatal 
target population using FARS data from 2006-2019 and injury data from 
NASS-GES (2006-2015) and CRSS (2016-2019). The target population was 
estimated using both a 15 percent seat belt usage scenario and a 90 
percent seat belt usage scenario based on the 2021 large bus rollover 
structural integrity final rule. The resulting target population (i.e., 
unrestrained ejected \59\ occupants) estimated for today's final rule 
after accounting for the benefits from the other initiatives applicable 
to the same group of buses (seat belts, ESC, and structural integrity) 
is 6.38 fatalities at the 15 percent seat belt use rate and 1.18 
fatalities at the 90 percent seat belt use rate. Based on the various 
rollover tests on buses performed by the agency,

[[Page 86280]]

NHTSA believes that the required advanced glazing would maintain its 
retention capability in single and double \1/4\-turn bus rollover 
crashes. Accordingly, the agency expects that the requirements would 
result in 0.37 to 1.91 equivalent lives saved annually. Table 12 below 
summarizes the costs and benefits of today's final rule.
---------------------------------------------------------------------------

    \58\ For details concerning equivalent lives saved, reference 
the FRE docketed with this final rule.
    \59\ For the analysis, both complete and partial ejections are 
included as ``ejected occupants'' since the anti-ejection glazing is 
expected to reduce the risk of both ejection types.

                   Table 12--Summary of Annualized Costs and Benefits Due to Advanced Glazing
                                     [Costs are in millions of 2022 dollars]
----------------------------------------------------------------------------------------------------------------
                                          15% belt use rate                         90% belt use rate
        Discount rate        -----------------------------------------------------------------------------------
                               Undiscounted        3%           7%       Undiscounted        3%           7%
----------------------------------------------------------------------------------------------------------------
Equivalent Lives Saved \A\            1.9191       1.5064       1.1491          0.3740       0.2936       0.2240
 \B\........................
Material Costs..............           $0.96        $0.96        $0.96           $0.96        $0.96        $0.96
Cost per Equivalent Lives               0.50         0.64         0.84            2.58         3.28         4.30
 Saved......................
Benefits from Comprehensive            24.72        19.40        14.80            4.82         3.78         2.88
 Costs Avoided..............
Net Benefits................           23.75        18.44        13.84            3.85         2.82         1.92
----------------------------------------------------------------------------------------------------------------
Notes:
\A\ These values from the FRE account for serious injuries (MAIS 3-5) by utilizing a relative injury factor.
\B\ MAIS = Maximum AIS, AIS = Abbreviated Injury Scale, MAIS 0 = No Injury, MAIS 1 = Minor, MAIS 2 = Moderate,
  MAIS 3 = Serious, MAIS 4 = Severe, MAIS 5 = Critical, MAIS 6 = Maximum (untreatable).

VII. Regulatory Notices and Analyses

E.O. 12866, E.O. 14904, E.O. 13563, and DOT Regulatory Policies and 
Procedures
    NHTSA has considered the potential impact of this final rule under 
E.O. 12866, E.O. 14094, E.O. 13563, DOT Order 2100.6A and the DOT's 
regulatory policies and procedures. This final rule is not considered 
to be significant under the DOT's regulatory policies and 
procedures.\60\
---------------------------------------------------------------------------

    \60\ 44 FR 11034 (Feb. 26, 1979).
---------------------------------------------------------------------------

    This final rule creates a new FMVSS (FMVSS No. 217a) and makes 
several changes to FMVSS No. 217. Specifically, the final rule creates 
a new standard that will establish requirements for advanced glazing in 
over-the-road buses and buses weighing over 26,000 lb. The final rule 
also creates a requirement establishing a minimum protrusion limitation 
requirement for emergency exit latches. The agency estimates that 
compliance with the final rule would result in an annual cost of $0.96 
million to manufacturers. More information on costs can be found in 
section VI above.
Regulatory Flexibility Act
    Pursuant to the Regulatory Flexibility Act (5 U.S.C. 601 et seq., 
as amended by the Small Business Regulatory Enforcement Fairness Act 
(SBREFA) of 1996), whenever an agency is required to publish a notice 
of rulemaking for any proposed or final rule, it must prepare and make 
available for public comment a regulatory flexibility analysis that 
describes the effect of the rule on small entities (i.e., small 
businesses, small organizations, and small governmental jurisdictions). 
The Small Business Administration's regulations at 13 CFR part 121 
define a small business, in part, as a business entity ``which operates 
primarily within the United States.'' (13 CFR 121.105(a)). No 
regulatory flexibility analysis is required if the head of an agency 
certifies that the rule will not have a significant economic impact on 
a substantial number of small entities. The SBREFA amended the 
Regulatory Flexibility Act to require federal agencies to provide a 
statement of the factual basis for certifying that a rule will not have 
a significant economic impact on a substantial number of small 
entities.
    NHTSA has considered the effects of this rulemaking action under 
the Regulatory Flexibility Act. According to 13 CFR 121.201, the Small 
Business Administration's size standards regulations used to define 
small business concerns, manufacturers of the vehicles covered by this 
final rule would fall under North American Industry Classification 
System (NAICS) No. 336111, Automobile Manufacturing, which has a size 
standard of 1,000 employees or fewer. NHTSA estimates that there are 26 
manufacturers of these types of vehicles in the United States 
(including manufacturers of motorcoaches, cutaway buses, second-stage 
motorcoaches, and other types of large buses covered by this final 
rule). Using the size standard of 1,000 employees or fewer, we estimate 
that approximately 10 of these 26 manufacturers would be considered 
small businesses.
    The agency does not believe that this final rule will have a 
significant economic impact on those small entities. First, the agency 
estimates that the incremental costs to each vehicle that currently 
does not comply with the requirements would be approximately $836 per 
unit to meet the final rule. This incremental cost will not constitute 
a significant impact given that the average cost of the vehicles 
covered by this final rule ranges from $200,000 to $400,000. Further, 
these incremental costs, which are very small compared to the overall 
cost of the vehicle, can ultimately be passed on to the purchaser and 
user.
    In addition, the agency believes that certifying compliance with 
the rule will not have a significant impact on the manufacturers. Small 
manufacturers have various options available that they may use in 
certifying compliance with the standard. Manufacturers are not required 
to use NHTSA's test as the basis for their certification. While the 
agency's test defined in the regulatory text will be an objective test 
capable of determining which vehicles meet the minimum requirements, 
manufacturers can use other methods in certifying the compliance of 
their own vehicles.
    For instance, a manufacturer could obtain advanced glazing windows 
from a glazing supplier and test the glazing on body sections of the 
vehicle. NHTSA used this approach in its motorcoach side glazing 
retention research program. The manufacturer could ``section'' the 
vehicle or otherwise obtain a body section representative of the 
vehicle, or test the glazing on test frames. It could base its 
certification on these tests, without testing a full vehicle.
    Unlike NHTSA, manufacturers certifying compliance of its own 
vehicles have more detailed information regarding their own vehicles 
and can use reasonable engineering analyses to determine whether its 
vehicles will comply with the requirements. We believe that a small 
manufacturer would be closely familiar with its own vehicle design and 
would be able to use modeling and relevant analyses on a vehicle-by-
vehicle basis to reasonably predict whether its design will meet the 
requirements of this final rule.

[[Page 86281]]

    We also note that the product cycle of the covered buses is 
significantly longer than those of other vehicle types. With a longer 
product cycle, we believe that the costs of certification for 
manufacturers would be further reduced as the costs of conducting 
compliance testing and the relevant analyses could be spread over a 
significantly longer period of time.
    Finally, we note that the requirements in this final rule may 
affect the operators of the buses that are the subject of today's final 
rule--some of which may be small businesses--but only indirectly as 
purchasers of these vehicles. As mentioned above, we anticipate that 
the impact on these businesses will not be significant because the 
expected price increase of the vehicles (those that do not comply with 
the requirements) used by these businesses is small ($836 for each 
vehicle valued between $200,000 and $400,000).
    For the aforementioned reasons, I hereby certify that this final 
rule will not have a significant economic impact on a substantial 
number of small entities.
Federalism
    NHTSA has examined this final rule pursuant to E.O. 13132 (64 FR 
43255; Aug. 10, 1999) and concluded that no additional consultation 
with states, local governments, or their representatives is mandated 
beyond the rulemaking process. The agency has concluded that the final 
rule does not have sufficient federalism implications to warrant 
consultation with state and local officials or the preparation of a 
federalism summary impact statement. The final rule does not have 
``substantial direct effects on the States, on the relationship between 
the national government and the States, or on the distribution of power 
and responsibilities among the various levels of government.''
    NHTSA rules can have preemptive effect in two ways. First, the 
National Traffic and Motor Vehicle Safety Act contains an express 
preemption provision: When a motor vehicle safety standard is in effect 
under this chapter, a state or a political subdivision of a state may 
prescribe or continue in effect a standard applicable to the same 
aspect of performance of a motor vehicle or motor vehicle equipment 
only if the standard is identical to the standard prescribed under this 
chapter. 49 U.S.C. 30103(b)(1). It is this statutory command by 
Congress that preempts any non-identical state legislative and 
administrative law address the same aspect of performance.
    The express preemption provision described above is subject to a 
savings clause under which ``[c]ompliance with a motor vehicle safety 
standard prescribed under this chapter does not exempt a person from 
liability at common law.'' 49 U.S.C. 30103(e). Pursuant to this 
provision, state common law tort causes of action against motor vehicle 
manufacturers that might otherwise be preempted by the express 
preemption provision are generally preserved.
    NHTSA rules can also preempt state law if complying with the FMVSS 
would render the motor vehicle manufacturers liable under state tort 
law. Because most NHTSA standards established by an FMVSS are minimum 
standards, a state common law tort cause of action that seeks to impose 
a higher standard on motor vehicle manufacturers will generally not be 
preempted. However, if and when such a conflict does exist--for 
example, when the standard at issue is both a minimum and a maximum 
standard--the state common law tort cause of action is impliedly 
preempted. See Geier v. American Honda Motor Co., 529 U.S. 861 (2000).
    Pursuant to E.O. 13132, NHTSA has considered whether this final 
rule could or should preempt state common law causes of action. The 
agency's ability to announce its conclusion regarding the preemptive 
effect of one of its rules reduces the likelihood that preemption will 
be an issue in any subsequent tort litigation. To this end, the agency 
has examined the nature (e.g., the language and structure of the 
regulatory text) and objectives of this final rule and finds that this 
final rule, like many NHTSA rules, prescribes only a minimum safety 
standard.
    Accordingly, NHTSA does not intend that this final rule preempt 
state tort law that would effectively impose a higher standard on motor 
vehicle manufacturers than that established by this final rule. 
Establishment of a higher standard by means of state tort law would not 
conflict with the minimum standard finalized in this document. Without 
any conflict, there could not be any implied preemption of a state 
common law tort cause of action.
National Environmental Policy Act
    NHTSA has analyzed this final rule for the purposes of the National 
Environmental Policy Act. The agency has determined that implementation 
of this action will not have any significant impact on the quality of 
the human environment.
Paperwork Reduction Act
    Under the procedures established by the Paperwork Reduction Act of 
1995, a person is not required to respond to a collection of 
information by a federal agency unless the collection displays a valid 
Office of Management and Budget (OMB) control number. This rulemaking 
will not establish any new information collection requirements.
Unfunded Mandates Reform Act (UMRA)
    The Unfunded Mandates Reform Act of 1995 (UMRA) requires federal 
agencies to prepare a written assessment of the costs, benefits and 
other effects of proposed or final rules that include a federal mandate 
likely to result in the expenditure by state, local or tribal 
governments, in the aggregate, or by the private sector, of more than 
$100 million annually (adjusted annually for inflation, with base year 
of 1995). UMRA also requires an agency issuing an NPRM or final rule 
subject to the Act to select the ``least costly, most cost-effective or 
least burdensome alternative that achieves the objectives of the 
rule.'' This final rule would not result in a federal mandate that will 
likely result in the expenditure by state, local or tribal governments, 
in the aggregate, or by the private sector, of more than $100 million 
annually (adjusted annually for inflation, with base year of 1995).
E.O. 12778 (Civil Justice Reform)
    When promulgating a regulation, agencies are required under E.O. 
12988 to make every reasonable effort to ensure that the regulation, as 
appropriate: (1) specifies in clear language the preemptive effect; (2) 
specifies in clear language the effect on existing federal law or 
regulation, including all provisions repealed, circumscribed, 
displaced, impaired, or modified; (3) provides a clear legal standard 
for affected conduct rather than a general standard, while promoting 
simplification and burden reduction; (4) specifies in clear language 
the retroactive effect; (5) specifies whether administrative 
proceedings are to be required before parties may file suit in court; 
(6) explicitly or implicitly defines key terms; and (7) addresses other 
important issues affecting clarity and general draftsmanship of 
regulations.
    Pursuant to this Order, NHTSA notes as follows. The preemptive 
effect of this final rule is discussed above. NHTSA notes further that 
there is no requirement that an individual submit a petition for 
reconsideration or pursue

[[Page 86282]]

other administrative proceedings before they may file suit in court.
National Technology Transfer and Advancement Act
    Under the National Technology Transfer and Advancement Act of 1995 
(NTTAA) (Pub. L. 104-113), all federal agencies and departments shall 
use technical standards that are developed or adopted by voluntary 
consensus standards bodies, using such technical standards as a means 
to carry out policy objectives or activities determined by the agencies 
and departments. Voluntary consensus standards are technical standards 
(e.g., materials specifications, test methods, sampling procedures, and 
business practices) that are developed or adopted by voluntary 
consensus standards bodies, such as the International Organization for 
Standardization and the Society of Automotive Engineers. The NTTAA 
directs us to provide Congress, through OMB, explanations when we 
decide not to use available and applicable voluntary consensus 
standards. There are no voluntary consensus standards developed by 
voluntary consensus standards bodies pertaining to this final rule.
Plain Language Requirement
    E.O. 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 rule clearly stated?
     Does the rule contain technical language or jargon that 
isn't clear?
     Would a different format (grouping and order of sections, 
use of headings, paragraphing) make the rule 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 rule easier to 
understand?
    NHTSA has considered these questions and attempted to use plain 
language in promulgating this final rule. If readers have suggestions 
on how we can improve our use of plain language, please write us.
Regulatory Identifier Number (RIN)
    The DOT assigns a RIN to each regulatory action listed in the 
Unified Agenda of Federal Regulations. The Regulatory Information 
Service Center publishes the Unified Agenda in April and October of 
each year. The RIN contained in the heading at the beginning of this 
notice may be used to find this action in the Unified Agenda.
Privacy Act
    In accordance with 5 U.S.C. 553(c), DOT solicits comments from the 
public to better inform its decision-making 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.transportation.gov/privacy. 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.). 
You may review DOT's complete Privacy Act Statement in the Federal 
Register published on April 11, 2000 (Volume 65, Number 70; Pages 
19477-78).

List of Subjects in 49 CFR Part 571

    Imports, motor vehicles, motor vehicle safety.

Amended Regulatory Text

    In consideration of the foregoing, NHTSA amends 49 CFR part 571 as 
follows:

PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS

0
1. The authority citation for part 571 continues to read as follows:

    Authority:  49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.95.


0
2. Section 571.217 is amended by
0
a. In paragraph S.4 removing the definition of ``Daylight opening'';, 
and
0
b. Adding paragraph S5.4.4 to read as follows:


Sec.  571.217  Standard No. 217; Bus emergency exits and window 
retention and release.

* * * * *
    S5.4.4 Protrusion Limit on Emergency Exit Window Latches and other 
related mechanisms
    For buses applicable under S3 of this standard, manufactured on or 
after October 30, 2027, any emergency exit window latch and other 
related release mechanisms shall not protrude more than 25 mm (1 inch) 
into the opening of the emergency exit window when that window is in 
the open position as described under S5.4.1 and S5.4.2.
* * * * *

0
3. Section 571.217a is added to read as follows:


Sec.  571.217a  Standard No. 217a; Anti-ejection glazing for bus 
portals; Mandatory applicability beginning October 30, 2027.

    S1. Scope. This standard establishes requirements to improve side 
and roof bus portals by way of glazing that is highly resistant to 
partial or complete occupant ejection in all types of crashes.
    S2. Purpose. The purpose of this standard is to reduce death and 
injuries resulting from complete and partial ejections of bus occupants 
through side and roof portals during rollovers and other crashes.
    S3. Application.
    (a) Subject to S3(b) of this section, this standard applies to:
    (1) Over-the-road buses manufactured on or after October 30, 2027, 
and
    (2) Buses, other than over-the-road buses, that have a gross 
vehicle weight rating (GVWR) greater than 11,793 kilograms (kg) 
manufactured on or after October 30, 2027.
    (b) This standard does not apply to school buses, transit buses, 
prison buses, and perimeter-seating buses.
    S4. Definitions.
    Daylight opening means, for openings on the side of the vehicle 
(other than a door opening), the locus of all points where a horizontal 
line, perpendicular to the vehicle longitudinal centerline, is tangent 
to the periphery of the opening. For openings on the roof of the 
vehicle, daylight opening means the locus of all points where a 
vertical line is tangent to the periphery of the opening. The periphery 
includes surfaces 100 millimeters (mm) inboard of the inside surface of 
the window glazing and 25 mm outboard of the outside surface of the 
window glazing. The periphery excludes the following: Any flexible 
gasket material or weather stripping used to create a waterproof seal 
between the glazing and the vehicle interior; grab handles used to 
facilitate occupant egress and ingress; and any part of a seat.
    Over-the-road bus means a bus characterized by an elevated 
passenger deck located over a baggage compartment.
    Perimeter-seating bus means a bus with 7 or fewer designated 
seating positions rearward of the driver's seating position that are 
forward-facing or can convert to forward-facing without the use of 
tools.
    Portal means an opening that could, in the event of a crash 
involving the vehicle, permit the partial or complete ejection of an 
occupant from the vehicle, including a young child.
    Prison bus means a bus manufactured for the purpose of transporting 
persons subject to involuntary restraint or

[[Page 86283]]

confinement and has design features consistent with that purpose.
    Stop-request system means a vehicle-integrated system for passenger 
use to signal to a vehicle operator that they are requesting a stop.
    Transit bus means a bus that is equipped with a stop-request system 
sold for public transportation provided by, or on behalf of, a Federal, 
State, or local government and that is not an over-the-road bus.
    S5. Requirements. When tested according to the procedures specified 
in S6 of this section and under the conditions specified in paragraph 
S7 of this section, each applicable bus shall meet the following 
requirements specified in this section. The requirements of this 
paragraph S5 n do not apply to portals other than side and roof 
portals, and do not apply to a side or roof portal whose minimum 
surface dimension measured through the center of its area is less than 
279 mm.
    S5.1 Edge impact.
    (a) When the ejection impactor described in S8 of this section 
contacts the target location specified in S6.1.1 of this section of 
each side or roof daylight opening of a vehicle at 21.6 km/h  0.4 km/h, no portion of the window (excluding glazing shards) 
may pass the ejection reference plane defined under the procedures of 
S6 of this section.
    (b) Each piece of window glazing and each surrounding window frame 
shall be retained by its surrounding structure in a manner that 
prevents the formation of any opening large enough to admit the 
complete passage of a 102 mm diameter sphere when a force of no more 
than 22 newtons (N) is applied with the sphere at any vector in a 
direction from the interior to the exterior of the vehicle.
    S5.2 Center impact.
    (a) When the ejection impactor described in paragraph S8 of this 
section contacts the target location specified in paragraph S6.1.2 of 
this section of each side or roof daylight opening of a vehicle at 21.6 
km/h  0.4 km/h, no portion of the window (excluding glazing 
shards) may pass the ejection reference plane defined under the 
procedures of paragraph S6.3 of this section.
    (b) Each piece of window glazing and each surrounding window frame 
shall be retained by its surrounding structure in a manner that 
prevents the formation of any opening large enough to admit the 
complete passage of a 102 mm diameter sphere when a force of no more 
than 22 N is applied with the sphere at any vector in a direction from 
the interior to the exterior of the vehicle.
    S5.3 Center impact to pre-broken glazing.
    (a) When the ejection impactor described in S8 of this section 
contacts the target location specified in S6.1.3 of this section of 
each side or roof daylight opening of a vehicle at 21.6 km/h  0.4 km/h, no portion of the impactor may displace more than 175 
mm past where the surface of the glazing had been in an unbroken 
condition.
    (b) Each piece of window glazing and each surrounding window frame 
shall be retained by its surrounding structure in a manner that 
prevents the formation of any opening large enough to admit the 
complete passage of a 102 mm diameter sphere when a force of no more 
than 22 N is applied with the sphere at any vector in a direction from 
the interior to the exterior of the vehicle.
    S5.4 Post-Impact Emergency Exit Release and Operability.
    After the impacts described in paragraphs S5.1, S5.2, and S5.3 of 
this section, each emergency exit provided in accordance with Standard 
No. 217 (Sec.  571.217) shall be capable of releasing and opening 
according to the requirements specified in that standard.
    S6. Test procedures.
    S6.1 Target locations.
    S6.1.1 Edge impact. Position the impactor face on the glazing 
adjacent to a latch or discrete attachment point such that, when viewed 
perpendicular to the glazing surface, the center of the impactor face 
plate is as close as practicable to the center of the latch attachment 
point or discrete attachment point with the impactor face plate either 
horizontal or vertical, whichever orientation provides the shortest 
distance between the two centers, while maintaining at least a 25 mm 
 2 mm distance between the impactor face plate edge and the 
window frame. ``Window frame'' includes latches, handles, attachments, 
and any solid structures other than the glazing material or flexible 
gaskets. If the window does not have any latches or discrete attachment 
points (e.g., it is fully rubber bonded or glued), position the 
impactor as follows:
    (a) For side windows, directly above the center of the lower window 
edge, with the impactor face plate either horizontal or vertical, 
whichever orientation provides the shortest distance between the two 
centers, with the bottom edge of the impactor face plate 25 mm  2 mm above the daylight opening periphery when viewed 
perpendicular to the glazing surface.
    (b) For roof glazing panels or roof windows, directly forward of 
the center of the rearmost window edge, with the impactor face plate 
either horizontal or vertical, whichever orientation provides the 
shortest distance between the two centers, with the rearmost edge of 
the impactor face plate 25 mm  2 mm forward of the daylight 
opening periphery when viewed perpendicular to the glazing surface.
    S6.1.2 Center impact.
    Position the center of the impactor face, with the long axis of the 
impactor face plate either vertical or horizontal, at the center of the 
daylight opening area of the window with the glazing intact.
    S6.1.3 Center impact to pre-broken glazing.
    Position the center of the impactor face, with the long axis of the 
impactor face plate either vertical or horizontal, at the center of the 
daylight opening area of the window with the glazing pre-broken 
following the procedure in paragraphs S6.2.1 and S6.2.2 of this 
section.
    S6.2 Window glazing pre-breaking procedure.
    S6.2.1 Breakage pattern. Locate the geometric center of the 
daylight opening. Mark the surface of the window glazing in a 
horizontal and vertical grid of points separated by 75 mm  
2 mm with one point coincident within  2 mm of the 
geometric center of the daylight opening (Figure 2).
    (a) If the window is a single-pane unit, then both the occupant 
space interior and outside exterior surfaces of the glass pane are 
marked with the 75 mm grid pre-break pattern. The patterns are offset 
diagonally from one another (the points on one surface of the glass 
pane are offset 37.5 mm  2 mm horizontally and 37.5 mm 
 2 mm vertically from the points on the contralateral 
surface of the glass pane).
    (b) If the window is an insulated unit or double-glazed window, 
then both the occupant space side of the interior pane and the outside 
of the exterior pane are marked with the 75 mm grid prebreak pattern.
    (1) If one of the glass panes is constructed of tempered or 
toughened glass, the insulated surface of the remaining glass pane 
(within the air gap) is marked with the 75 mm grid pre-break pattern. 
The patterns are offset diagonally from the remaining glass pane's 
contralateral surface.
    (2) If neither pane is tempered glass, then both the occupant space 
side of the interior pane and the outside of the exterior pane are 
marked with the 75 mm grid pre-break pattern. The patterns are not 
diagonally offset from one another. The insulated surfaces of the glass 
panes (within the air gap) are not marked.
    S6.2.2 Breakage method.

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    (a) Use a 100 mm  10 mm x 100 mm  10 mm 
piece of rigid material as a reaction surface on the opposite side of 
the glazing to prevent to the extent possible the window surface from 
deforming by more than 10 mm when pressure is being applied by the 
staple gun.
    (b) Start with the inside surface of the window and forwardmost, 
lowest mark made as specified in S6.2.1 of this section. Use an 
electric staple gun without any staples to apply a load along a line of 
12 to 14 mm onto the glazing. The applied force shall be 4,200 N  850 N. Apply the line load only once at each marked location, 
even if the glazing does not break or no perceptible mark or hole 
results.
    (c) Continue applying the line load with the electric staple gun by 
moving rearward in the grid until the end of a row is reached. Then 
move to the forwardmost mark on the next higher row and apply the line 
load. Continue in this pattern until the line load has been applied to 
all grid points on the inside surface of the glazing.
    (d) Repeat the process on the outside surface of the window.
    (e) If applying the line load causes the glazing to disintegrate, 
halt the breakage procedure and proceed with the next step in the 
compliance test.
    S6.3 Determination of ejection reference planes.
    (a) For side windows, the ``ejection reference plane'' is a 
vertical plane parallel to the longitudinal vertical center plane of 
the bus passing through a point located at a lateral distance of 102 mm 
from the lateral most point on the glazing and surrounding frame, with 
the window in the closed position.
    (b) For roof glazing panels/windows, the ``ejection reference 
plane'' is a horizontal plane passing through a point located at a 
vertical distance of 102 mm from the highest point on the glazing and 
surrounding frame, with the window/panel in the closed position.
    S7. Test conditions.
    During testing, the ambient temperature is between 18 degrees C. 
and 29 degrees C., at any relative humidity between 10 percent and 70 
percent.
    S8. Guided impactor.
    The impactor test device has the dimensions shown in Figure 1 of 
this section. It has a total impactor mass of 26 kg  1.0 kg 
and a spring stiffness of 258 N/mm  39 N/mm. The impactor 
is propelled in the horizontal direction in impacts to the side 
daylight openings and is propelled vertically in impacts to the roof 
daylight openings.
[GRAPHIC] [TIFF OMITTED] TR30OC24.018


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[GRAPHIC] [TIFF OMITTED] TR30OC24.019


    Issued in Washington, DC, under authority delegated in 49 CFR 
1.95 and 501.5.
Sophie Shulman,
Deputy Administrator.
[FR Doc. 2024-24462 Filed 10-29-24; 8:45 am]
BILLING CODE 4910-59-P