Federal Motor Vehicle Safety Standards; Electronic Stability Control Systems, 54712-54753 [06-7598]

Agencies

• National Highway Traffic Safety Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 71, Number 180 (Monday, September 18, 2006)]
[Proposed Rules]
[Pages 54712-54753]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 06-7598]



[[Page 54711]]

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Part II





Department of Transportation





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National Highway Traffic Safety Administration



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49 CFR Parts 571 and 585



Federal Motor Vehicle Safety Standards; Electronic Stability Control 
Systems; Proposed Rule

Federal Register / Vol. 71, No. 180 / Monday, September 18, 2006 / 
Proposed Rules

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Parts 571 and 585

[Docket No. NHTSA-2006-25801]
RIN 2127-AJ77


Federal Motor Vehicle Safety Standards; Electronic Stability 
Control Systems

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

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: As part of a comprehensive plan for reducing the serious risk 
of rollover crashes and the risk of death and serious injury in those 
crashes, this document proposes to establish a new Federal motor 
vehicle safety standard (FMVSS) No. 126 to require electronic stability 
control (ESC) systems on passenger cars, multipurpose vehicles, trucks 
and buses with a gross vehicle weight rating of 4,536 Kg (10,000 
pounds) or less. ESC systems use automatic computer-controlled braking 
of individual wheels to assist the driver in maintaining control in 
critical driving situations in which the vehicle is beginning to lose 
directional stability at the rear wheels (spin out) or directional 
control at the front wheels (plow out).
    Based on our own crash data studies, NHTSA estimates that the 
installation of ESC will reduce single-vehicle crashes of passenger 
cars by 34 percent and single vehicle crashes of sport utility vehicles 
(SUVs) by 59 percent, with a much greater reduction of rollover 
crashes.
    Preventing single-vehicle loss-of-control crashes is the most 
effective way to reduce deaths resulting from rollover crashes. This is 
because most loss of control crashes culminate in the vehicle leaving 
the roadway, which dramatically increases the probability of a 
rollover. NHTSA estimates that ESC has the potential to prevent 71 
percent of passenger car rollovers and 84 percent of SUV rollovers in 
single-vehicle crashes.
    NHTSA estimates that ESC would save 5,300 to 10,300 lives and 
prevent 168,000 to 252,000 injuries in all types of crashes annually if 
all light vehicles on the road were equipped with ESC systems. ESC 
systems would substantially reduce (by 4,200 to 5,400) of the more than 
10,000 deaths each year on American roads resulting from rollover 
crashes.
    About 29 percent of model year (MY) 2006 light vehicles sold in the 
U.S. were equipped with ESC, and manufacturers intend to increase the 
number of ESC installations in light vehicles to 71 percent by MY 2011. 
This rule would require a 100 percent installation rate for ESC by MY 
2012 (with exceptions for some vehicles manufactured in stages or by 
small volume manufacturers). Of the overall projected annual 5,300 to 
10,300 highway deaths and 168,000 to 252,000 injuries prevented, we 
would attribute 1,536 to 2,211 prevented fatalities (including 1,161 to 
1,445 involving rollover) to this proposed rulemaking, in addition to 
the prevention of 50,594 to 69,630 injuries.

DATES: You should submit your comments early enough to ensure that 
Docket Management receives them not later than November 17, 2006.

ADDRESSES: You may submit comments identified by DOT DMS Docket Number 
above by any of the following methods:
     Web Site: https://dms.dot.gov. Follow the instructions for 
submitting comments on the DOT electronic docket site.
     Fax: 1-202-493-2251.
     Mail: Docket Management Facility; U.S. Department of 
Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, 
Washington, DC 20590
     Hand Delivery: Room PL-401 on the plaza level of the 
Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal Holidays.
     Federal eRulemaking Portal: Go to https://
www.regulations.gov. Follow the online instructions for submitting 
comments.
    Instructions: All submissions must include the agency name and 
docket number or Regulatory Identification Number (RIN) for this 
rulemaking. For detailed instructions on submitting comments and 
additional information on the rulemaking process, see the Public 
Participation heading of the Supplementary Information section of this 
document. Note that all comments received will be posted without change 
to https://dms.dot.gov, including any personal information provided. 
Please see the Privacy Act heading under Regulatory Notices.
    Docket: For access to the docket to read background documents or 
comments received, go to https://dms.dot.gov at any time or to Room PL-
401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., 
Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal Holidays.

FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may call Mr. 
Patrick Boyd, Office of Crash Avoidance Standards at (202) 366-2272. 
His FAX number is (202) 366-7002.
    For legal issues, you may call Mr. Eric Stas, Office of the Chief 
Counsel at (202) 366-2992. His FAX number is (202) 366-3820.
    You may send mail to both of these officials at National Highway 
Traffic Safety Administration, 400 Seventh Street, SW., Washington, DC 
20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary
II. Safety Problems Addressed by the Proposed Standard
    A. Single-Vehicle Crash and Rollover Statistics
    B. The Agency's Comprehensive Response to Rollover
III. Electronic Stability Control Systems
    A. How ESC Prevents Loss of Vehicle Control
    B. Additional Features of Some ESC Systems
IV. Effectiveness of ESC
    A. Human Factors Study on the Effectiveness of ESC
    B. Crash Data Studies of ESC Effectiveness
V. Agency Proposal
    A. Definition of ESC
    B. Performance Test of ESC Oversteer Intervention and Stability 
Criteria
    C. Responsiveness Criteria
    D. Other Issues
    1. ESC Off Switches
    2. ESC Activation and Malfunction Symbols and Telltale
    3. ESC Off Switch Symbol and Telltale
    E. Alternatives to the Agency Proposal
VI. Leadtime
VII. Benefits and Costs
    A. Summary
    B. ESC Benefits
    C. ESC Costs
VIII. Public Participation
IX. Regulatory Analyses and Notices

I. Executive Summary

    As part of a comprehensive plan for reducing the serious risk of 
rollover crashes and the risk of death and serious injury in those 
crashes, this rule proposes to establish Federal Motor Vehicle Safety 
Standard (FMVSS) No. 126, Electronic Stability Control Systems, which 
would require passenger cars, multipurpose passenger vehicles (MPVs), 
trucks, and buses that have a gross vehicle weight rating (GVWR) of 
4,536 kg (10,000 pounds) or less to be equipped with an ESC system that 
meets the requirements of the standard. ESC systems use automatic, 
computer-controlled braking of individual wheels to assist the driver 
in maintaining control (and the vehicle's intended heading) in 
situations where the vehicle is beginning to lose directional stability 
(e.g., where the driver misjudges the severity of a curve

[[Page 54713]]

or over-corrects in an emergency situation). In such situations (which 
occur with considerable frequency), intervention by the ESC system can 
assist the driver in preventing the vehicle from leaving the roadway, 
thereby preventing fatalities and injuries associated with crashes 
involving vehicle rollover or collision with various objects (e.g., 
trees, highway infrastructure, other vehicles).
    Based upon current estimates regarding the effectiveness of ESC 
systems, we believe that an ESC standard could save thousands of lives 
each year, providing potentially the greatest safety benefits produced 
by any safety device since the introduction of seat belts. The 
following discussion highlights the research and regulatory efforts 
that have culminated in the present proposal.
    Since the early 1990's, NHTSA has been actively engaged in finding 
ways to address the problem of vehicle rollover, because crashes 
involving rollover are responsible for a disproportionate number of 
fatalities and serious injuries (over 10,000 of the 33,000 fatalities 
of vehicle occupants in 2004). Although various options were explored, 
the agency ultimately chose to add a rollover resistance component to 
its New Car Assessment Program (NCAP) consumer information program in 
2001. In response to NCAP's market-based incentives, vehicle 
manufacturers made modifications to their product lines to increase 
their vehicles' geometric stability and rollover resistance by 
utilizing wider track widths (typically associated with passenger cars) 
on many of their newer sport utility vehicles (SUVs) and by making 
other improvements to truck-based SUVs during major redesigns (e.g., 
introduction of roll stability control). This approach was successful 
in terms of reducing the much higher rollover rate of SUVs and other 
high-center-of-gravity vehicles, as compared to passenger cars. 
However, manipulating vehicle configuration alone cannot entirely 
resolve the rollover problem (particularly when consumers continue to 
demand vehicles with greater carrying capacity and higher ground 
clearance).
    Accordingly, the agency began exploring technologies that could 
confront the issue of vehicle rollover from a different perspective or 
line of inquiry, which led to today's proposal. We believe that our 
proposed ESC requirement offers a complementary approach that would 
provide substantial benefits to drivers of both passenger cars and LTVs 
(light trucks/vans). Undoubtedly, keeping vehicles from leaving the 
roadway is the best way to prevent deaths and injuries associated with 
rollover, as well as other types of crashes. Based on its crash data 
studies, NHTSA estimates that the installation of ESC systems will 
reduce single vehicle crashes of passenger cars by 34 percent and 
single vehicle crashes of sport utility vehicles (SUVs) by 59 percent. 
Its effectiveness is especially great for single-vehicle crashes 
resulting in rollover, where ESC systems were estimated to prevent 71 
percent of passenger car rollovers and 84 percent of SUV rollovers in 
single vehicle crashes (see section VII).
    In short, we believe that preventing single-vehicle loss-of-control 
crashes is the most effective way to reduce rollover deaths, and we 
believe that ESC offers considerable promise in terms of meeting this 
important safety objective while maintaining a broad range of vehicle 
choice for consumers. In fact, among the agency's ongoing and planned 
rulemakings, it is the single most effective way of reducing the total 
number of traffic deaths. It is also the most cost-effective of those 
rulemakings.
    We note that this proposal is consistent with recent congressional 
legislation contained in section 10301 of the Safe, Accountable, 
Flexible, Efficient Transportation Equity Act: A Legacy for Users of 
2005 (SAFETEA-LU).\1\ That provision requires the Secretary of 
Transportation to ``establish performance criteria to reduce the 
occurrence of rollovers consistent with stability enhancing 
technologies'' and to ``issue a proposed rule * * * by October 1, 2006, 
and a final rule by April 1, 2009.''
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    \1\ Pub. L. 109-59, 119 Stat. 1144 (2005).
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    The balance of this notice explains in detail: (1) The size of the 
safety problem (see section II); (2) how ESC systems would act to 
mitigate that safety problem (see section II); (3) the basics of ESC 
operation (see section III); (4) findings from ESC-related research 
(see section IV);(5) the specifics of our regulatory proposal (see 
section V); (6) lead time and phase-in requirements (see section VI), 
and (7) costs and benefits associated with this proposal (see section 
VII). The following section summarizes the key points of the proposal.

A. Proposed Requirements for ESC Systems

    Consistent with the congressional mandate in section 10301 of 
SAFETEA-LU, NHTSA is proposing to require all light vehicles to be 
equipped with an ESC system with, at the minimum, the capabilities of 
current production systems. We believe that a requirement for such ESC 
systems would be practicable in terms of both ensuring technological 
feasibility and providing the desired safety benefits in a cost-
effective manner. Although vehicle manufacturers have been increasing 
the share of the light vehicle fleet equipped with ESC, we believe that 
given the relatively high cost of this technology, a mandatory standard 
is necessary to maximize the safety benefits associated with electronic 
stability control, and is consistent with the mandate arising out of 
SAFETEA-LU.
    In order to realize these benefits, we have tentatively decided to 
require vehicles both to be equipped with an ESC system meeting 
definitional requirements and to pass a dynamic test. The definitional 
requirements specify the necessary elements of a stability control 
system that would be capable of both effective oversteer and understeer 
intervention. These requirements are necessary due to the extreme 
difficulty in establishing a test adequate to ensure the desired level 
of ESC functionality.\2\ The test is necessary to ensure that the ESC 
system is robust and meets a level of performance at least comparable 
to that of current ESC systems. These requirements are summarized 
below.
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    \2\ Without an equipment requirement, it would be almost 
impossible to devise a single performance test that could not be met 
through some action by the manufacturer other than providing an ESC 
system. Even a battery of performance tests still might not achieve 
our intended results, because although it might necessitate 
installation of an ESC system, we expect that it would be unduly 
cumbersome for both the agency and the regulated community.
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     Consistent with the industry consensus definition of ESC 
contained in the Society of Automotive Engineers (SAE) Surface Vehicle 
Information Report J2564 (rev. June 2004), we are proposing to require 
vehicles covered under the standard to be equipped with an ESC system 
that:
    (1) Augments vehicle directional stability by applying and 
adjusting the vehicle's brakes individually to induce correcting yaw 
torques to a vehicle;
    (2) Is computer-controlled, with the computer using a closed-loop 
algorithm \3\ to limit vehicle oversteer and to limit vehicle 
understeer when appropriate;
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    \3\ A ``closed-loop algorithm'' is a cycle of operations 
followed by a computer that includes automatic adjustments based on 
the result of previous operations or other changing conditions.

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    (3) Has a means to determine vehicle yaw rate \4\ and to estimate 
its sideslip \5\;
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    \4\ ``Yaw rate'' means the rate of change of the vehicle's 
heading angle measured in degrees/second of rotation about a 
vertical axis through the vehicle's center of gravity.
    \5\ ``Sideslip'' means the arctangent of the lateral velocity of 
the center of gravity of the vehicle divided by the longitudinal 
velocity of the center of gravity.
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    (4) Has a means to monitor driver steering input, and
    (5) Is operational over the full speed range of the vehicle (except 
below a low-speed threshold where loss of control of the vehicle is 
unlikely).
     The proposed ESC system as defined above would also be 
required to be capable of applying all four brakes individually and to 
have an algorithm that utilizes this capability. The system would also 
be required to be operational during all phases of driving, including 
acceleration, coasting, and deceleration (including braking), and it 
would be required to remain operational when the antilock brake system 
or traction control system is activated.
     We are also proposing to require vehicles covered under 
the standard to meet a performance test that would satisfy the 
standard's stability criteria and responsiveness criterion when 
subjected to the Sine with Dwell steering maneuver test. This test 
involves a vehicle coasting at an initial speed of 50 mph while a 
steering machine steers the vehicle with a steering wheel pattern as 
shown in Figure 2. The test maneuver is then repeated over a series of 
increasing maximum steering angles. This test maneuver was selected 
over a number of other alternatives, because we tentatively decided 
that it has the most optimal set of characteristics, including severity 
of the test, repeatability and reproducibility of results, and the 
ability to address lateral stability and responsiveness (see section 
V.B).
    The maneuver is severe enough to produce spinout for most vehicles 
without ESC. The stability criteria for the test measure how quickly 
the vehicle stops turning after the steering wheel is returned to the 
straight-ahead position. A vehicle that continues to turn for an 
extended period after the driver steers straight is out of control, 
which is what ESC is designed to prevent. The stability criteria are 
expressed in terms of the percent of the peak yaw rate after maximum 
steering that persists at a period of time after the steering wheel has 
been returned to straight ahead. They require that the vehicle yaw rate 
decrease to no more than 35 percent of the peak value after one second 
and that it continues to drop to no more than 20 percent after 1.75 
seconds. Since a vehicle that simply responds very little to steering 
commands could meet the stability criteria, a minimum responsiveness 
criterion is applied to the same test. It requires that the ESC-
equipped vehicle must move laterally at least 1.83 meters (half a 12 
foot lane width) during the first 1.07 seconds after the initiation of 
steering (a discontinuity in the steering pattern that is convenient 
for timing a measurement).
     Because the benefits of the ESC system can only be 
realized if the system is functioning properly, we are proposing to 
require a telltale be mounted inside the occupant compartment in front 
of and in clear view of the driver and be identified by the symbol 
shown for ``ESC Malfunction Telltale'' in Table 1 of FMVSS No. 101, 
Controls and Displays. The ESC malfunction telltale would be required 
to illuminate not more than two minutes after the occurrence of one or 
more malfunctions that affect the generation or transmission of control 
or response signals in the vehicle's ESC system. Such telltale must 
remain continuously illuminated for as long as the malfunction(s) 
exists, whenever the ignition locking system is in the ``On'' (``Run'') 
position. (Vehicle manufacturers would be permitted to use the ESC 
malfunction telltale in a flashing mode to indicate ESC operation.)
     In certain circumstances, drivers may have legitimate 
reasons to disengage the ESC system or limit its ability to intervene, 
such as when the vehicle is stuck in sand/gravel or when the vehicle is 
being run on a track for maximum performance. Accordingly, under this 
proposal, vehicle manufacturers would be permitted to include a driver-
selectable switch that places the ESC system in a mode in which it 
would not satisfy the performance requirements of the standard (e.g., 
``sport'' mode or full-off mode). However, if the vehicle manufacturer 
chooses this option, it would be required to ensure that the ESC system 
always returns to a mode that satisfies the requirements of the 
standard at the initiation of each new ignition cycle, regardless of 
the mode the driver had previously selected. The manufacturer would be 
required to provide an ``ESC Off'' switch and a telltale that is 
mounted inside the occupant compartment in front of and in clear view 
of the driver and which is identified by the symbol shown for ``ESC 
Off'' in Table 1 of FMVSS No. 101. Such telltale must remain 
continuously illuminated for as long as the ESC is in a mode that 
renders it unable to meet the performance requirements of the standard, 
whenever the ignition locking system is in the ``On'' (``Run'') 
position.
     We are not proposing to require the ESC system to be 
equipped with a roll stability control function (or a separate system 
to that effect). Roll stability control systems involve relatively new 
technology, and there is currently insufficient data to judge the 
efficacy of such systems. However, the agency will continue to monitor 
the development of roll stability control systems. Vehicle 
manufacturers may supplement the ESC system we are proposing to require 
with a roll stability control system/feature.

B. Leadtime and Phase-In

    In order to provide the public with what are expected to be the 
significant safety benefits of ESC systems as rapidly as possible, 
NHTSA is proposing to require all light vehicles covered by this 
standard to be equipped with a FMVSS No. 126-compliant ESC system by 
September 1, 2011. We are proposing that compliance would commence on 
September 1, 2008, which would mark the start of a three-year phase-in 
period. Subject to the special provisions discussed below, the proposed 
phase-in schedule for FMVSS No. 126 would be as follows: 30 percent of 
a vehicle manufacturer's light vehicles manufactured during the period 
from September 1, 2008 to August 31, 2009 would be required to comply 
with the standard; 60 percent of those manufactured during the period 
from September 1, 2009 to August 31, 2010; 90 percent of those 
manufactured during the period from September 1, 2010 to August 31, 
2011, and all light vehicles thereafter.
    In general, we believe that it would be practicable for vehicle 
manufacturers to meet the requirements of the phase-in discussed above. 
We anticipate that vehicle manufacturers would be able to meet the 
requirements of the proposed standard by installing ESC systems 
currently in production, and most vehicle lines would likely experience 
some level of redesign over the next four to five years, which would 
provide an opportunity to incorporate an ESC system during the course 
of the manufacturer's normal production cycle (see section VI for a 
more complete discussion).
    However, NHTSA is proposing to exclude multi-stage manufacturers 
and alterers from the requirements of the phase-in and to extend by one 
year the time for compliance by those manufacturers (i.e., until 
September 1, 2012). This NPRM also proposes to exclude small volume 
manufacturers

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(i.e., manufacturers producing less than 5,000 vehicles for sale in the 
U.S. market in one year) from the phase-in, instead requiring such 
manufacturers to fully comply with the standard on September 1, 2011.
    Under our proposal, vehicle manufacturers would be permitted to 
earn carry-forward credits for compliant vehicles, produced in excess 
of the phase-in requirements, which are manufactured between the 
effective date of the final rule and the conclusion of the phase-in 
period.\6\
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    \6\ We note that carry-forward credits would not be permitted to 
be used to defer the mandatory compliance date of September 1, 2011 
for all covered vehicles.
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C. Anticipated Impacts of the Proposal

    As noted above, we believe that ESC has among the highest life-
saving potential of any vehicle safety device developed in the past 
three decades, ranking with seatbelts and air bags in terms of 
importance. NHTSA estimates that ESC would save 5,300 to 10,300 lives 
and prevent 168,000 to 252,000 injuries in all types of crashes annuvly 
if all light vehicles on the road were equipped with ESC systems. A 
large portion of these savings would come from rollover crashes. ESC 
systems would substantially reduce (by 4,200 to 5,400) of the more than 
10,000 deaths each year on American roads resulting from rollover 
crashes.
    About 29 percent of model year (MY) 2006 light vehicles sold in the 
U.S. were equipped with ESC, and manufacturers intend to increase the 
number of ESC installations in light vehicles to 71 percent by MY 
2011.\7\ This rule would require a 100 percent installation rate for 
ESC by MY 2012 (with exceptions for some vehicles manufactured in 
stages or by small volume manufacturers). As the discussion below 
demonstrates, ESC has very significant life-saving and injury-
preventing potential in absolute terms, but it does so in a very cost-
effective manner vis-a-vis other agency rulemakings. ESC offers 
consistently strong benefits and cost-effectiveness across all types of 
light vehicles, including passenger cars, SUVs, vans, and pick-up 
trucks.
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    \7\ In April 2006, NHTSA sent letters to seven vehicle 
manufacturers requesting voluntary submission of information 
regarding their planned production of ESC-equipped vehicles for 
model years 2007 to 2012. Manufacturers responded with product plans 
containing confidential information. These agency letters and 
manufacturer responses (with confidential information redacted) may 
be found in the docket for this rulemaking.
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    Of the 5,300 to 10,300 highway deaths and 168,000 to 252,000 MAIS 
1-5 injuries which we project will be prevented annually for all types 
of crashes once all light vehicles on the road are equipped with ESC, 
we would attribute 1,536 to 2,211 prevented fatalities (including 1,161 
to 1,445 involving rollover) to this proposed rulemaking, in addition 
to the prevention of 50,594 to 69,630 injuries. This compares favorably 
with the Regulatory Impact Analyses for other important rulemakings 
such as FMVSS No. 208 mandatory air bags (1,964 to 3,670 lives saved), 
FMVSS No. 214 side impact protection (690 to 1,030 lives saved), and 
FMVSS No. 201 upper interior head impact protection (870 to 1,050 lives 
saved). (See section VII, Benefits and Costs of this notice and the 
Preliminary Regulatory Impact Analysis submitted to the docket for this 
rulemaking). In addition, the agency estimates that property damage and 
travel delay costs would be reduced by $260 to $453 million annually.
    The agency estimates that the production-weighted, average cost per 
vehicle to meet the proposed standard's requirements would be $58 
($90.3 per passenger car and $29.2 per light truck). These are 
incremental costs over the MY 2011 installation of ABS, which is 
expected to be installed in almost 93 percent of the light vehicle 
fleet, and ESC, which is expected to be installed in 71 percent of the 
light vehicle fleet. Vehicle costs are estimated to be $368 (in 2005$) 
for anti-lock brakes (ABS) and an additional $111 for ESC, for a total 
system cost of $479 per vehicle. Currently, every vehicle that is 
equipped with ESC, is also equipped with ABS and traction control. 
However, the agency believes that traction control is a convenience 
feature. Accordingly, it is not required by this proposal. We also 
assumed an annual production of 17 million light vehicles (9 million 
light trucks and 8 million passenger cars). Thus, the total annual 
vehicle cost of this regulation, corresponding to ESC installation 
beyond manufacturers' planned production, is expected to be 
approximately $985 million.
    In terms of cost-effectiveness, this proposal for passenger cars 
and light trucks would save 1,536 to 2,211 lives and prevent 50,594 to 
69,630 injuries at a cost of $0.19 to $0.32 million per equivalent life 
saved at a 3 percent discount rate and $0.27 to $0.43 at a 7 percent 
discount rate. Again, the cost-effectiveness for ESC compares favorably 
with the Regulatory Impact Analyses for other important rulemakings 
such as FMVSS No. 202 head restraints safety improvement ($2.61 million 
per life saved), FMVSS No. 208 center seat shoulder belts ($3.39 to 
$5.92 million per life saved), FMVSS No. 208 advanced air bags ($1.9 to 
$9.0 million per life saved), and FMVSS No. 301 fuel system integrity 
upgrade ($1.96 to $5.13 million per life saved).
    We note that the costs for passenger cars are higher because a 
greater portion of those vehicles require installation of ABS in 
addition to ESC. Nevertheless, the proposal remains highly cost-
effective even when passenger cars are considered alone. The passenger 
car portion of the proposal would save 956 lives and prevent 34,902 
injuries at a cost of $0.35 million per equivalent life saved at a 3 
percent discount rate and $0.47 at a 7 percent discount rate. 
Therefore, the agency deemed it appropriate to make the proposed 
standard applicable to all light vehicles, because such approach makes 
sense from both a safety and cost standpoint.

II. Safety Problems Addressed by the Proposed Standard

    Crash data studies conducted in the U.S., Europe and Japan indicate 
that ESC is very effective in reducing single-vehicle crashes. Studies 
of the behavior of ordinary drivers in critical situations using the 
National Advanced Driving Simulator also show a very large reduction in 
instances of loss of control when the vehicle is equipped with ESC. 
Based on its crash data studies, NHTSA estimates that ESC will reduce 
single vehicle crashes of passenger cars by 34 percent and single 
vehicle crashes of SUVs by 59 percent. NHTSA's latest crash data study 
also shows that ESC is most effective in reducing single-vehicle 
crashes that result in rollover. ESC is estimated to prevent 71 percent 
of passenger car rollovers and 84 percent of SUV rollovers in single 
vehicle crashes. It is also estimated to reduce some multi-vehicle 
crashes but at a much lower rate than its effect on single vehicle 
crashes.

A. Single-Vehicle Crash and Rollover Statistics

    About one in seven light vehicles involved in police-reported 
crashes collide with something other than another vehicle. However, the 
proportion of these single-vehicle crashes increases steadily with 
increasing crash severity, and almost half of serious and fatal 
injuries occur in single-vehicle crashes. We can describe the 
relationship between crash severity and the number of vehicles involved 
in the crash using information from the agency's crash data programs. 
We limit our discussion here to light vehicles, which consist of (1) 
passenger cars and (2) multipurpose passenger vehicles, trucks and 
buses under 4,536

[[Page 54716]]

kilograms (10,000 pounds) gross vehicle weight rating (GVWR).\8\
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    \8\ For brevity, we use the term light trucks in this document 
to refer to multipurpose passenger vehicles, such as vans, minivans, 
and SUVs, trucks and buses under 4,536 kilograms (10,000 pounds) 
GVWR.
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    The 2000-2004 data from the National Automotive Sampling System 
(NASS) Crashworthiness Data System (CDS) and 2004 data from the 
Fatality Analysis Reporting System (FARS) were combined to estimate the 
current target population for this rulemaking. It includes 28,252 
people who were killed as occupants of light vehicles. Over half of 
these (15,007) occurred in single-vehicle crashes. Of these, 8,460 
occurred in rollovers. About 1.1 million injuries (AIS 1-5) occurred in 
crashes that could be affected by ESC, almost 500,000 in single vehicle 
crashes (of which almost half were in rollovers). Multi-vehicle crashes 
that could be affected by ESC accounted for 13,245 fatalities and 
almost 600,000 injuries.
    Rollover crashes are complex events that reflect the interaction of 
driver, road, vehicle, and environmental factors. We can describe the 
relationship between these factors and the risk of rollover using 
information from the agency's crash data programs.
    According to 2004 data from FARS, 10,555 people were killed as 
occupants in light vehicle rollover crashes, which represents 33 
percent of all occupants killed that year in crashes. Of those, 8,567 
were killed in single-vehicle rollover crashes. Seventy-four percent of 
the people who died in single-vehicle rollover crashes were not using a 
seat belt, and 61 percent were partially or completely ejected from the 
vehicle (including 50 percent who were completely ejected). FARS shows 
that 55 percent of light vehicle occupant fatalities in single-vehicle 
crashes involved a rollover event.
    Using data from the 2000-2004 NASS CDS files, we estimate that 
280,000 light vehicles were towed from a police-reported rollover crash 
each year (on average), and that 29,000 occupants of these vehicles 
were seriously injured. Of these 280,000 light vehicle rollover 
crashes, 230,000 were single-vehicle crashes. Sixty-two percent of 
those people who suffered a serious injury in a single-vehicle tow-away 
rollover crash were not using a seat belt, and 52 percent were 
partially or completely ejected (including 41 percent who were 
completely ejected). Estimates from NASS CDS indicate that 82 percent 
of tow-away rollovers were single-vehicle crashes, and that 88 percent 
(202,000) of the single-vehicle rollover crashes occurred after the 
vehicle left the roadway. An audit of 1992-96 NASS CDS data showed that 
about 95 percent of rollovers in single-vehicle crashes were tripped by 
mechanisms such as curbs, soft soil, pot holes, guard rails, and wheel 
rims digging into the pavement, rather than by tire/road interface 
friction as in the case of untripped rollover events.

B. The Agency's Comprehensive Response to Rollover

    As mentioned above, this proposal for ESC is part of the agency's 
comprehensive plan to address the issue of vehicle rollover. The 
following provides background on NHTSA's comprehensive plan to reduce 
rollover crashes. In 2002, the agency formed an Integrated Project Team 
(IPT) to examine the rollover problem and make recommendations on how 
to reduce rollovers and improve safety when rollovers nevertheless 
occur. In June 2003, based on the work of the team, the agency 
published a report entitled, ``Initiatives to Address the Mitigation of 
Vehicle Rollover.'' \9\ The report recommended improving vehicle 
stability, ejection mitigation, roof crush resistance, as well as road 
improvement and behavioral strategies aimed at consumer education.
---------------------------------------------------------------------------

    \9\ See Docket Number NHTSA 2003-14622-1.
---------------------------------------------------------------------------

    Since then, the agency has been working to implement these 
recommendations as part of it comprehensive agency plan for reducing 
the serious risk of rollover crashes and the risk of death and serious 
injury when rollover crashes do occur. It is evident that the most 
effective way to reduce deaths and injuries in rollover crashes is to 
prevent the rollover crash from occurring. This proposal to adopt a new 
Federal motor vehicle safety standard for electronic stability control 
systems is one part of that comprehensive agency plan.
    Moreover, we note that the agency also published a notice of 
proposed rulemaking in the Federal Register in August 2005, seeking to 
upgrade our safety standard on roof crush resistance (FMVSS No. 216); 
that notice, like the present one, contains an in-depth discussion of 
the rollover problem and the countermeasures which the agency intends 
to pursue as part of its comprehensive response to the rollover problem 
(see 70 FR 49223 (August 23, 2005)).

III. Electronic Stability Control Systems

    Although Electronic Stability Control (ESC) systems are known by 
many different trade names such as Vehicle Stability Control (VSC), 
Electronic Stability Program (ESP), StabiliTrak and Vehicle Stability 
Enhancement (VSE), their function and performance are similar. They are 
systems that uses computer control of individual wheel brakes to help 
the driver maintain control of the vehicle during extreme maneuvers by 
keeping the vehicle headed in the direction the driver is steering even 
when the vehicle nears or reaches the limits of road traction.
    When a driver attempts an ``extreme maneuver'' (e.g., one initiated 
to avoid a crash or due to misjudgment of the severity of a curve), the 
driver may lose control if the vehicle responds differently as it nears 
the limits of road traction than it does during ordinary driving. The 
driver's loss of control can result in either the rear of the vehicle 
``spinning out'' or the front of the vehicle ``plowing out.'' As long 
as there is sufficient road traction, a highly skilled driver may be 
able to maintain control in many extreme maneuvers using 
countersteering (i.e., momentarily turning away from the intended 
direction) and other techniques. However, average drivers in a panic 
situation in which the vehicle beginning to spin out would be unlikely 
to countersteer to regain control.
    ESC uses automatic braking of individual wheels to adjust the 
vehicle's heading if it departs from the direction the driver is 
steering. Thus, it prevents the heading from changing too quickly 
(spinning out) or not quickly enough (plowing out). Although it cannot 
increase the available traction, ESC affords the driver the maximum 
possibility of keeping the vehicle under control and on the road in an 
emergency maneuver using just the natural reaction of steering in the 
intended direction.
    Keeping the vehicle on the road prevents single-vehicle crashes, 
which are the circumstances that lead to most rollovers. However, if 
the speed is simply too great for the available road traction, even a 
vehicle with ESC will unavoidably drift off the road (but not spin 
out). Furthermore, ESC cannot prevent road departures due to driver 
inattention or drowsiness rather than loss of control.

A. How ESC Prevents Loss of Vehicle Control

    The following explanation of ESC operation illustrates the basic 
principle of yaw stability control, but it does not attempt to explain 
advanced refinements of the yaw control strategy described below that 
use vehicle sideslip (lateral sliding that may not alter yaw rate) to 
optimize performance on slippery pavements.

[[Page 54717]]

    An ESC system maintains what is known as ``yaw'' (or heading) 
control by determining the driver's intended heading, measuring the 
vehicle's actual response, and automatically turning the vehicle if its 
response does not match the driver's intention. However, with ESC, 
turning is accomplished by applying counter torques from the braking 
system rather than from steering input.
    Speed and steering angle measurements are used to determine the 
driver's intended heading. The vehicle response is measured in terms of 
lateral acceleration and yaw rate by onboard sensors. If the vehicle is 
responding in a manner corresponding to driver input, the yaw rate will 
be in balance with the speed and lateral acceleration.
    The concept of ``yaw rate'' can be illustrated by imaging the view 
from above of a car following a large circle painted on a parking lot. 
One is looking at the top of the roof of the vehicle and seeing the 
circle. If the car starts in a heading pointed north and drives half 
way around circle, its new heading is south. Its yaw angle has changed 
180 degrees. If it takes 10 seconds to go half way around the circle, 
the ``yaw rate'' is 180 degrees per 10 seconds or 18 deg/sec. If the 
speed stays the same, the car is constantly rotating at a rate of 18 
deg/sec around a vertical axis that can be imagined as piercing its 
roof. If the speed is doubled, the yaw rate increases to 36 deg/sec.
    While driving in a circle, the driver notices that he must hold the 
steering wheel tightly to avoid sliding toward the passenger seat. The 
bracing force is necessary to overcome the lateral acceleration that is 
caused by the car following the curve. The lateral acceleration is also 
measured by the ESC system. When the speed is doubled the lateral 
acceleration increases by a factor of four if the vehicle follows the 
same circle. There is a fixed physical relationship between the car's 
speed, the radius of its circular path, and its lateral acceleration.
    The ESC system uses this information as follows: Since the ESC 
system measures the car's speed and its lateral acceleration, it can 
compute the radius of the circle. Since it then has the radius of the 
circle and the car's speed, the ESC system can compute the correct yaw 
rate for a car following the path. Of course, the system includes a yaw 
rate sensor, and it compares the actual measured yaw rate of the car to 
that computed for the path the car is following. If the computed and 
measured yaw rates begin to diverge as the car that is trying to follow 
the circle speeds up, it means the driver is beginning to lose control, 
even if the driver cannot yet sense it. Soon, an unassisted vehicle 
would have a heading significantly different from the desired path and 
would be out of control either by oversteering (spinning out) or 
understeering.
    When the ESC system detects an imbalance between the measured yaw 
rate of a vehicle and the path defined by the vehicle's speed and 
lateral acceleration, the ESC system automatically intervenes to turn 
the vehicle. The automatic turning of the vehicle is accomplished by 
uneven brake application rather than by steering wheel movement. If 
only one wheel is braked, the uneven brake force will cause the 
vehicle's heading to change. Figure 1 shows the action of ESC using 
single wheel braking to correct the onset of oversteering or 
understeering. (Please note that all Figures discussed in this preamble 
may be found at the end of the preamble, immediately preceding the 
proposed regulatory text.)
     Oversteering. In Figure 1 (bottom panel), the vehicle has 
entered a left curve that is extreme for the speed it is traveling. The 
rear of the vehicle begins to slide which would lead to a vehicle 
without ESC turning sideways (or ``spinning out'') unless the driver 
expertly countersteers. In a vehicle equipped with ESC, the system 
immediately detects that the vehicle's heading is changing more quickly 
than appropriate for the driver's intended path (i.e., the yaw rate is 
too high). It momentarily applies the right front brake to turn the 
heading of the vehicle back to the correct path. The action happens 
quickly so that the driver does not perceive the need for steering 
corrections. Even if the driver brakes because the curve is sharper 
than anticipated, the system is still capable of generating uneven 
braking if necessary to correct the heading.
     Understeering. Figure 1 (top panel) shows a similar 
situation faced by a vehicle whose response as it nears the limits of 
road traction is to slide at the front (``plowing out'' or 
understeering) rather than oversteering. In this situation, the ESC 
system rapidly detects that the vehicle's heading is changing less 
quickly than appropriate for the driver's intended path (i.e., the yaw 
rate is too low). It momentarily applies the left rear brake to turn 
the heading of the vehicle back to the correct path.
    While Figure 1 may suggest that particular vehicles go out of 
control as either vehicles prone to oversteer or vehicles prone to 
understeer, it is just as likely that a given vehicle could require 
both understeer and oversteer interventions during progressive phases 
of a complex avoidance maneuver such as a double lane change.
    Although ESC cannot change the tire/road friction conditions the 
driver is confronted with in a critical situation, there are clear 
reasons to expect it to reduce loss-of-control crashes, as discussed 
below.
    In vehicles without ESC, the response of the vehicle to steering 
inputs changes as the vehicle nears the limits of road traction. All of 
the experience of the average driver is in operating the vehicle in its 
``linear range'', i.e., the range of lateral acceleration in which a 
given steering wheel movement produces a proportional change in the 
vehicle's heading. The driver merely turns the wheel the expected 
amount to produce the desired heading. Adjustments in heading are easy 
to achieve because the vehicle's response is proportional to the 
driver's steering input, and there is very little lag time between 
input and response. The car is traveling in the direction it is 
pointed, and the driver feels in control. However, at lateral 
accelerations above about one-half ``g'' on dry pavement for ordinary 
vehicles, the relationship between the driver's steering input and the 
vehicle's response changes (toward oversteer or understeer), and the 
lag time of the vehicle response can lengthen. When a driver encounters 
these changes during a panic situation, it adds to the likelihood that 
the driver will loose control and crash because the familiar actions 
learned by driving in the linear range would not be the correct 
steering actions.
    However, ordinary linear range driving skills are much more likely 
to be adequate for a driver of a vehicle with ESC to avoid loss of 
control in a panic situation. By monitoring yaw rate and sideslip, ESC 
can intervene early in the impending loss-of-control situation with the 
appropriate brake forces necessary to restore yaw stability before the 
driver would attempt an over correction or other error. The net effect 
of ESC is that the driver's ordinary driving actions learned in linear 
range driving are the correct actions to control the vehicle in an 
emergency. Also, the vehicle will not change its heading from the 
desired path in a way that would induce further panic in a driver 
facing a critical situation. Studies using a driving simulator, 
discussed in Section IV, demonstrate that ordinary drivers are much 
less likely to lose control of a vehicle with ESC when faced with a 
critical situation.
    Besides allowing drivers to cope with emergency maneuvers and 
slippery pavement using only ``linear range'' skills, ESC provides more 
powerful

[[Page 54718]]

control interventions than those available to even expert drivers of 
non-ESC vehicles. For all practical purposes, the yaw control actions 
with non-ESC vehicles are limited to steering. However, as the tires 
approach the maximum lateral force sustainable under the available 
pavement friction, the yaw moment generated by a given increment of 
steering angle is much less than at the low lateral forces occurring in 
regular driving.\10\. This means that as the vehicle approaches its 
maximum cornering capability, the ability of the steering system to 
turn the vehicle is greatly diminished, even in the hands of an expert 
driver. ESC creates the yaw moment to turn the vehicle using braking at 
an individual wheel rather than the steering system. This intervention 
remains powerful even at limits of tire traction because both the 
braking force of the individual tire and the reduction of lateral force 
that accompanies the braking force act to create the desired yaw 
moment. Therefore, ESC can be especially beneficial on slippery 
surfaces. While a vehicle's possibility of staying on the road in a 
critical maneuver ultimately is limited by the tire/pavement friction, 
ESC maximizes an ordinary driver's ability to use the available 
friction.
---------------------------------------------------------------------------

    \10\ Liebemann et al., (2005) Safety and Performance 
Enhancement: The Bosch Electronic Stability Control (ESP), 19th 
International Technical Conference on the Enhanced Safety of 
Vehicles (ESV), Washington, DC.
---------------------------------------------------------------------------

B. Additional Features of Some ESC Systems

    In addition to the basic operation of ``yaw stability control'', 
many ESC systems include additional features. For example, most systems 
reduce engine power during intervention to slow the vehicle and give it 
a better chance of being able to stay on the intended path after its 
heading has been corrected.
    Other ESC systems may go further by performing high deceleration 
automatic braking at all four wheels. Of course, such braking would be 
performed unevenly side to side so that the same net yaw torque or 
``turning force'' would be applied to the vehicle as in the basic case 
of single-wheel braking.
    ESC systems used on vehicles with a high center of gravity (c.g.), 
such as SUVs, are often programmed to perform an additional function 
known as ``roll stability control.'' Roll stability control (RSC) is a 
direct countermeasure for on-pavement rollover crashes of high c.g. 
vehicles. Some RSC systems measure the roll angle of the vehicle using 
an additional roll rate sensor to determine if the vehicle is in danger 
of tipping up. Other systems rely on the existing ESC sensors for 
steering angle, speed, and lateral acceleration, along with knowledge 
of vehicle-specific characteristics to estimate whether the vehicle is 
in danger of tipping up.
    Regardless of the method used to detect the risk of tip-up, the 
various types of roll stability control intervene in the same way. 
Specifically, they intervene by reducing lateral acceleration which is 
the cause of the roll motion of the vehicle on its suspension, thus 
preventing the possibility of it rolling so much that the inside wheels 
may lift off the pavement. The intervention is performed the same way 
as the oversteer intervention shown in the Figure 1. The outside front 
brake is applied heavily to turn the vehicle toward a path of less 
curvature and, therefore, less lateral acceleration.
    The difference between a roll stability control intervention and an 
oversteer intervention by the ESC system operating in the basic yaw 
stability control mode is the triggering circumstance. The oversteer 
intervention occurs when the vehicle's excessive yaw rate indicates 
that its heading is departing from the driver's intended path, but the 
roll stability control intervention occurs when there is a risk the 
vehicle could roll over. Thus, the roll stability control intervention 
occurs when the vehicle is still following the driver's intended path. 
The obvious trade-off of roll stability control is that the vehicle 
must depart to some extent from the driver's intended path in order to 
reduce the lateral acceleration from the level that could cause tip-up.
    If the determination of impending rollover that triggers the roll 
stability intervention is very certain, then the possibility of the 
vehicle leaving the roadway as a result of the roll stability 
intervention represents a lower relative risk to the driver. Obviously, 
systems that intervene only when absolutely necessary and then with the 
minimum loss of lateral acceleration to prevent rollover are the most 
effective. However, roll stability control is a new technology that is 
still evolving. Roll stability control is not a subject of this 
rulemaking because it is too soon for actual crash statistics to 
illuminate its practical effect on crash reduction.

IV. Effectiveness of ESC

    Electronic stability control can directly reduce a vehicle's 
susceptibility to on-road untripped rollovers as measured by the 
``fishhook'' test that is part of NHTSA's NCAP rollover rating program. 
The direct effect is mostly limited to untripped rollovers on paved 
surfaces. However, untripped on-road rollovers are a relatively 
infrequent type of rollover crash. In contrast, the vast majority of 
rollover crashes occur when a vehicle runs off the road and strikes a 
tripping mechanism such as soft soil, a ditch, a curb or a guardrail.
    We expect that requiring ESC to be installed on light trucks and 
passenger cars would result in a large reduction in the number of 
rollover crashes by greatly reducing the number of single-vehicle 
crashes. As noted previously, over 80 percent of rollovers are the 
result of a single-vehicle crash. The purpose of ESC is to assist the 
driver in keeping the vehicle on the road during impending loss-of-
control situations. In this way, it can prevent the exposure of 
vehicles to off-road tripping mechanisms. We note, however, that this 
yaw stability function of ESC is not direct ``rollover resistance'' and 
cannot be measured by the NCAP rollover resistance rating.
    Although ESC is an indirect countermeasure to prevent rollover 
crashes, we believe it is the most powerful countermeasure available to 
address this serious risk. Effectiveness studies by NHTSA and others 
worldwide \11\ estimate that ESC reduces single vehicle crashes by at 
least a third in passenger cars and perhaps reduces loss-of-control 
crashes (e.g., road departures leading to rollovers) by an even greater 
amount. In fact, NHTSA's latest data study that is discussed in this 
section found a reduction in single-vehicle crashes leading to rollover 
of 71 percent for passenger cars and 84 percent for SUVs. Thus, ESC can 
reduce the numbers of rollovers of all vehicles, including lower center 
of gravity vehicles (e.g., passenger cars, minivans and two-wheel drive 
pickup trucks), as well as of the higher center of gravity vehicle 
types (e.g., SUVs and four-wheel drive pickup trucks). ESC can affect 
both crashes that would have resulted in rollover as well as other 
types of crashes

[[Page 54719]]

(e.g., road departures resulting in impacts) that result in deaths and 
injuries.

A. Human Factors Study on the Effectiveness of ESC
---------------------------------------------------------------------------

    \11\ Aga M, Okada A. (2003) Analysis of Vehicle Stability 
Control (VSC)'s Effectiveness from Accident Data, 18th International 
Technical Conference on the Enhanced Safety of Vehicles (ESV), 
Nagoya.
    Dang, J. (2004) Preliminary Results Analyzing Effectiveness of 
Electronic Stability Control (ESC) Systems, Report No. DOT HS 809 
790. U.S. Dept. of Transportation, Washington, DC.
    Farmer, C. (2004) Effect of Electronic Stability Control on 
Automobile Crash Risk, Traffic Injury Prevention Vol 5:317-325.
    Kreiss J-P, et al. (2005) The Effectiveness of Primary Safety 
Features in Passenger Cars in Germany. 19th International Technical 
Conference on the Enhanced Safety of Vehicles (ESV), Washington, DC
    Lie A., et al. (2005) The Effectiveness of ESC (Electronic 
Stability Control) in Reducing Real Life Crashes and Injuries. 19th 
International Technical Conference on the Enhanced Safety of 
Vehicles (ESV), Washington, DC.
---------------------------------------------------------------------------

    A study by the University of Iowa using the National Advanced 
Driving Simulator demonstrated the effect of ESC on the ability of 
ordinary drivers to maintain control in critical situations.\12\ A 
sample of 120 drivers equally divided between men and women and between 
three age groups (18-25, 30-40, and 55-65) was subjected to the 
following three critical driving scenarios. The ``Incursion Scenario'' 
forced drivers to attempt a double lane change at high speed (65 mph 
speed limit signs) by presenting them first with a vehicle that 
suddenly backs into their lane from a driveway and then with another 
vehicle driving toward them in the left lane. The ``Curve Departure 
Scenario'' presented drivers with a constant radius curve that was 
uneventful at the posted speed limit of 65 mph followed by another 
curve that appeared to be similar but that had a decreasing radius that 
was not evident upon entry. The ``Wind Gust Scenario'' presented 
drivers with a sudden lateral wind gust of short duration that pushed 
the drivers toward a lane of oncoming traffic. The 120 drivers were 
further divided evenly between two vehicles, a SUV and a midsize sedan. 
Half the drivers of each vehicle drove with ESC enabled, and half drove 
with ESC disabled.
---------------------------------------------------------------------------

    \12\ Papelis et al. (2004) Study of ESC Assisted Driver 
Performance Using a Driving Simulator, Report No. N04-003-PR, 
University of Iowa.
---------------------------------------------------------------------------

    In 50 of the 179 test runs performed in a vehicle without ESC, the 
driver lost control. In contrast, in only six of the 179 test runs 
performed in a vehicle with ESC, did the driver lose control. One test 
run in each ESC status had to be aborted. These results demonstrate an 
88 percent reduction in loss-of-control crashes when ESC was engaged. 
The study also concluded that the presence of an ESC system helped 
reduce loss of control regardless of age or gender, and that the 
benefit was substantially the same for the different driver subgroups 
in the study. Because of the obvious danger to participants, an 
experiment like this cannot be performed safely with real vehicles on 
real roads. However, the National Advanced Driver Simulator provides 
extraordinary verisimilitude with the driver sitting in a real vehicle, 
seeing a 360-degree scene and experiencing the linear and angular 
accelerations and sounds that would occur in actual driving of the 
specific vehicle.

B. Crash Data Studies of ESC Effectiveness

    There have been a number of studies of ESC effectiveness in Europe 
and Japan beginning in 2003 \13\. All of them have shown large 
potential reductions in single vehicle crashes as a result of ESC. 
However, the sample sizes of crashes of vehicles new enough to have ESC 
tended to be small in these studies. A preliminary NHTSA study 
published in September 2004 \14\ of crash data from 1997-2003 found ESC 
to be effective in reducing single-vehicle crashes, including rollover. 
Among vehicles in the study, the results suggested that ESC reduced 
single vehicle crashes in passenger cars by 35 percent and in SUVs by 
67 percent. In October 2004, the Insurance Institute for Highway Safety 
(IIHS) released the results of a study of the effectiveness of ESC in 
preventing crashes of cars and SUVs. The IIHS found that ESC is most 
effective in reducing fatal single-vehicle crashes, reducing such 
crashes by 56 percent. NHTSA's later peer-reviewed study \15\ of ESC 
effectiveness found that that ESC reduced single vehicle crashes in 
passenger cars by 34 percent and in SUVs by 59 percent, and that its 
effectiveness was greatest in reducing single vehicle crashes resulting 
in rollover (71 percent reduction for passenger cars and an 84 percent 
reduction for SUVs). It also found reductions in fatal single-vehicle 
crashes and fatal single-vehicle rollover crashes that were 
commensurate with the overall crash reductions cited. ESC reduced fatal 
single-vehicle crashes in passenger cars by 35 percent and in SUVs by 
67 percent and reduced fatal single-vehicle crashes involving rollover 
by 69 percent in passenger cars and 88 percent in SUVs.
---------------------------------------------------------------------------

    \13\ See Footnote 10.
    \14\ Dang, J. (2004) Preliminary Results Analyzing Effectiveness 
of Electronic Stability Control (ESC) Systems, Report No. DOT HS 809 
790. U.S. Dept. of Transportation, Washington, DC.
    \15\ Dang, J. (2006) Statistical Analysis of The Effectiveness 
of Electronic Stability Control (ESC) Systems, U.S. Dept. of 
Transportation, Washington, DC (publication pending peer review). A 
draft version of this report, as supplied to peer reviewers, has 
been placed in the docket for this rulemaking.
---------------------------------------------------------------------------

(a) NHTSA's Preliminary Study
    In September, 2004, NHTSA issued an evaluation note on the 
Preliminary Results Analyzing the Effectiveness of Electronic Stability 
Control (ESC) Systems. The study evaluated the effectiveness of ESC in 
reducing single vehicle crashes in various domestic and imported cars 
and SUVs. It was based on Fatality Analysis Reporting System (FARS) 
data from calendar years 1997-2003 and crash data from five States that 
reported partial Vehicle Identification Number (VIN) information in 
their data files (Florida, Illinois, Maryland, Missouri, and Utah) from 
calendar years 1997-2002. The data were limited to mostly luxury 
vehicles because ESC first became available in 1997 in luxury vehicles 
such as Mercedes-Benz and BMW. The analysis compared specific make/
models of passenger cars and SUVs with ESC versus earlier versions of 
the same make/models, using multi-vehicle crash involvements as a 
control group.
    The passenger car sample consisted of mainly Mercedes-Benz and BMW 
models (61 percent). Mercedes-Benz installed ESC in certain luxury 
models in 1997 and had made it standard equipment in all their models 
(except one) by 2000. BMW also installed ESC in certain 5, 7, and 8 
series models as early as 1997 and had made it standard equipment in 
all their models by 2001. The passenger car sample also included some 
luxury GM cars, which constituted 23 percent of the sample, and a few 
cars from other manufacturers. GM cars where ESC was offered as 
standard equipment are the Buick Park Avenue Ultra, the Cadillac 
DeVille, Seville STS and SLS, the Oldsmobile Aurora, the Pontiac 
Bonneville SSE and SSEi, and the Chevrolet Corvette. The SUV make/
models in the study with ESC include Mercedes-Benz (ML320, ML350, 
ML430, ML500, G500, G55 AMG), Toyota (4Runner, Landcruiser), and Lexus 
(RX300, LX470).
    The first set of analyses used multi-vehicle crash involvements as 
a control group, essentially assuming that ESC has no effect on multi-
vehicle crashes. Specific make/models with ESC were compared with 
earlier versions of similar make/models using multi-vehicle crash 
involvements as a control group, creating 2x2 contingency tables as 
shown in Tables 1 and 2. The study found that single vehicle crashes 
were reduced by

1 - {(699/1483)/(14090/19444){time}  = 35 percent

for passenger cars and by 67 percent for SUVs (Table 1). Similarly, 
fatal single vehicle crashes were reduced by 30 percent in cars and by 
63 percent in SUVs (Table 2). Reductions of single vehicle crashes in 
passenger cars and SUVs were statistically significant at the .01 
level, as evidenced by chi-square statistics exceeding 6.64 in each 2x2 
contingency table (Table 1). Reductions of fatal single vehicle crashes 
are statistically significant at the .01 level in SUVs and at the .05 
level in passenger

[[Page 54720]]

cars with chi-square statistic greater than 3.84 (Table 2).

  Table 1.--Effectiveness of ESC in Reducing Single Vehicle Crashes in
                         Passenger Cars and SUVs
     [Preliminary Study with 1997-2002 crash data from five States]
------------------------------------------------------------------------
                                                           Multi-Vehicle
                                      Single  Vehicle         Crashes
                                          Crashes            (control
                                                              group)
------------------------------------------------------------------------
Passenger Cars:
    No ESC.......................  1483.................           19444
    ESC..........................  699..................           14090
    Percent reduction in single    35%..................  ..............
     vehicle crashes in passenger
     cars with ESC.
    Approximate 95 percent         29% to 41%...........  ..............
     confidence bounds.
    Chi-square value.............  84.1.................  ..............
SUVs:
    No ESC.......................  512..................            6510
    ESC..........