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Federal Motor Vehicle Safety Standards; Antilock Brake Systems for Light Vehicles

American Government Special Collections Reference Desk

American Government Topics:  National Highway Traffic Safety Administration

Federal Motor Vehicle Safety Standards; Antilock Brake Systems for Light Vehicles

Barry Felrice
Federal Register
January 4, 1994

[Federal Register: January 4, 1994]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. 93-94; Notice 1]
RIN 2127-AE47

 
Federal Motor Vehicle Safety Standards; Antilock Brake Systems 
for Light Vehicles

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

ACTION: Advance notice of proposed rulemaking.

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SUMMARY: The National Highway Traffic Safety Administration 
Authorization Act of 1991 directs this agency to initiate rulemaking to 
consider the need for any additional brake performance standards for 
passenger cars, including antilock brake standards. Pursuant to this 
mandate, the agency is issuing this notice to obtain responses to 
questions regarding the braking performance of passenger cars and other 
light vehicles and the need to require antilock brake systems on these 
vehicles. This notice poses questions about the desirability of a 
requirement that light vehicles be equipped with antilock brake systems 
(ABS), including questions about such a requirement's anticipated 
safety benefits, potential regulatory approaches and anticipated 
performance requirements and test procedures, the requirement's 
applicability, its schedule for implementation, and the anticipated 
costs.

DATES: Comments on this notice must be received on or before March 7, 
1994.

ADDRESSES: All comments on this notice should refer to the docket and 
notice number and be submitted to the following: Docket Section, room 
5109, National Highway Traffic Safety Administration, 400 Seventh 
Street, SW., Washington, DC 20590 (Docket hours 9:30 a.m. to 4 p.m.)

FOR FURTHER INFORMATION CONTACT:
Mr. George Soodoo, Office of Crash Avoidance, National Highway Traffic 
Safety Administration, 400 Seventh Street, SW., Washington, DC 20590 
(202) 366-5892.

SUPPLEMENTARY INFORMATION: 

Table of Contents

I. Background
    A. Existing and Proposed Standards
    B. Statutory Mandates
    C. Antilock Brake Systems
    D. Current Size of ABS Market
II. NHTSA Activities Related to Braking Performance
III. Issues for Possible Agency Action
    A. Overview of the Issues
    B. Safety Need
    C. Regulatory Approaches to Improving the Lateral Stability and 
Control of Light Vehicles
    D. Test Procedures
    E. Test Conditions
    F. Varieties of ABSs Permissible Under Potential Proposals
    G. Implementation
    H. Costs Associated with Potential Proposals
IV. Rulemaking Analyses and Notices
    A. DOT Regulatory Policies and Procedures
    B. Executive Order 12612 (Federalism)

I. Background

A. Existing and Proposed Standards

    Federal Motor Vehicle Safety Standard No. 105, Hydraulic Brake 
Systems, specifies requirements for vehicles equipped with hydraulic 
brake systems. (49 CFR 571.105). Standard No. 105 applies to all 
vehicles except motorcycles that are equipped with hydraulic brakes. It 
has specific requirements which apply to passenger cars and to vehicles 
other than passenger cars with a gross vehicle weight rating (GVWR) (1) 
equal to or less than 10,000 pounds and (2) greater than 10,000 
pounds.\1\ The Standard's purpose is to ensure safe braking performance 
under normal and emergency conditions. The Standard includes a variety 
of performance requirements that evaluate a vehicle's service brake 
system in terms of stopping distance, partial failure, fade and 
recovery, water recovery, and spike stops. It also sets forth 
requirements related to a vehicle's parking brake performance.
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    \1\This document will refer to passenger cars and other vehicles 
with a GVWR of 10,000 pounds or less (e.g., light trucks and vans 
and multipurpose passenger vehicles) as ``light vehicles.'' Where 
necessary to refer to passenger cars, ``passenger cars'' will be 
used, and where necessary to refer to vehicles with a GVWR of 10,000 
pounds or less other than passenger cars, ``other light vehicles'' 
will be used.
---------------------------------------------------------------------------

    None of NHTSA's safety standards currently mandates the 
installation of antilock braking systems (ABS) on light vehicles or 
specifies performance requirements intended to ensure the proper 
functioning of an ABS voluntarily installed on a light vehicle. A light 
vehicle equipped with an ABS is required to meet the same stopping 
distance requirements as a non-ABS-equipped light vehicle. In addition, 
a light vehicle with a failed ABS must be capable of meeting the 
stopping distance requirements for partial failure of the service brake 
system, as follows: passenger cars are required to stop within 456 feet 
and other light vehicles must stop within 517 feet when traveling at 60 
mph on a high coefficient of friction surface. (See section S5.5 of 
Standard No. 105).
    NHTSA has proposed requirements for functioning and failed ABSs. 
NHTSA is currently reviewing comments to a supplemental notice of 
proposed rulemaking (SNPRM) that proposes to establish a new standard, 
Standard No. 135, Passenger Car Brake Systems, which would replace 
Standard No. 105 as it applies to passenger cars. (56 FR 30528, July 3, 
1991). The rulemaking to establish the new standard resulted from 
NHTSA's efforts to harmonize its safety standards with international 
standards. The agency anticipates the next regulatory action related to 
Standard No. 135 will be issued in early 1994.
    In the SNPRM, NHTSA proposed requirements for functioning antilock 
systems, which include straight line stops on high and low coefficient 
of friction surfaces, a high coefficient of friction to low coefficient 
of friction surface transition test, and a low coefficient of friction 
to high coefficient of friction surface transition test. A high 
coefficient of friction surface, such as dry asphalt, is one that is 
relatively sticky and thus provides higher levels of braking force and 
better lateral stability and control during braking. Conversely, a low 
coefficient of friction surface, such as wet or icy pavement, is one 
that is relatively slippery and thus provides lower levels of braking 
force and poorer lateral stability and control during braking. These 
surfaces are referred to as high mu and low mu surfaces, respectively.
    The agency also proposed requirements for failed antilock systems, 
which are more stringent than Standard No. 105's antilock failure 
requirements. For an antilock functional failure, the agency proposed a 
stopping distance of 85 meters (279 feet) from 100 kilometers per hour 
(62 mph).

B. Statutory Mandate

    Sections 2500 through 2509 of the ``Intermodal Surface 
Transportation Efficiency Act of 1991'' are called the ``National 
Highway Traffice Safety Administration Authorization Act of 1991'' 
(``Authorization Act''). Among other things, the Authorization Act 
directs NHTSA to initiate rulemaking on a number of safety matters, 
including brake performance standards for passenger cars.
    Today's ANPRM initiates the rulemaking required by section 2507 of 
the Authorization Act. That section provides that, not later than 
December 31, 1993, an advance notice of proposed rulemaking be 
published, in accordance with the National Traffic and Motor Vehicle 
Safety Act of 1966, to consider the need for any additional brake 
performance standards for passenger cars, including ABS standards. The 
Act also directs the agency to ``consider any such [antilock brake 
system] adopted by a manufacturer'' to facilitate and encourage 
innovation and early application of economical and effective antilock 
brake systems for all such vehicles.
    Section 2507 requires the rulemaking action to be completed not 
later than 36 months from issuance of the ANPRM. Under sections 2507 
and 2052(b)(2)(B)(ii), the action will be considered completed when the 
agency either promulgates a final rule or decides not to promulgate a 
rule.

C. Antilock Brake Systems

    The primary benefit of an ABS is its ability to prevent loss-of-
control accidents caused by wheel lockup during braking. This allows 
the driver to maintain steering control and lateral stability even in 
panic braking situations. In addition, vehicles equipped with an ABS 
typically have enhanced braking efficiency and as a consequence usually 
have shorter stopping distances, particularly on low mu surfaces, 
compared to the same vehicle without an ABS.
    ABSs help prevent braking induced loss-of-control situations by 
automatically controlling the amount of braking pressure applied to a 
wheel. Current antilock braking systems include wheel speed sensors 
that measure wheel speeds and transmit signals to an Electronic Control 
Unit (ECU). The ECU monitors wheel speeds, and changes in wheel speeds, 
based on electrical signals transmitted from sensors located at the 
wheels or within the axle housings. If the wheels start to lock, the 
ECU signals a modulator control valve to actuate, thereby holding 
constant or reducing the amount of braking pressure applied to the 
wheel or axle that is nearing lockup. This continuous feedback cycle of 
sensing, controlling, modulating, and sensing prevents wheel lockup, 
and results in improved vehicle stability and steering control during 
braking on all types of road surface conditions.
    There are two primary types of ABS configurations that are 
currently available for most light vehicles: all-wheel systems and 
rear-wheel-only systems. An all-wheel ABS directly controls all the 
wheels on the vehicle, typically by using individual wheel control for 
the front axle wheels and either individual wheel control or select low 
control for the rear axle wheels. (Select low control provides the same 
brake pressure modulation to both wheels of an axle whenever either 
wheel on that axle approaches lockup.) A vehicle equipped with an all-
wheel ABS is able to maintain steering control, even during hard 
braking on wet surfaces. Because maintaining steering control can be a 
key factor in accident avoidance, a vehicle equipped with an all-wheel 
ABS would be expected to experience better lateral stability and 
control during hard braking, particularly on wet or slippery road 
surface conditions.
    Rear-wheel-only ABSs directly control only the rear wheels of the 
vehicle, using the select low method of control. A vehicle equipped 
with a rear-wheel-only ABS may still experience front wheel lockup 
during braking, since the front wheels are not controlled by the ABS. 
Rear-wheel-only systems have relatively less accident reduction 
potential than all-wheel systems, because front wheel lockup could 
result in a vehicle losing steering control. In a crash-threatening 
situation, maintaining steering control can be a critical factor in 
accident avoidance.

D. Current Size of ABS Market

    ABSs are currently available on over 130 models of passenger cars 
and other light vehicles (light trucks and vans (LTVs), and sport 
utility vehicles). ABSs are offered as standard equipment on almost all 
top-of-the line models and as standard equipment or an option on an 
increasing number of mid-priced and low-priced models. For instance, 
the Chevrolet Cavalier with a manufacturer's suggested retail price of 
under $10,000 offers an ABS as standard equipment. Manufacturers of 
ABSs currently available on vehicles sold in the United States include 
Bendix, Bosch, Dewandre-WABCO, GM-Delco, Honda, Kelsey-Hayes, 
Nippondenso, Sumitomo, and Teves.
    In 1992, 2,682,218 of the passenger cars sold in the United States 
were equipped with an ABS. This represented approximately 32 percent of 
all passenger cars sold in this country during that year. Passenger 
cars that are equipped with an ABS typically have an all-wheel ABS that 
permits steering control since the system modulates the brake force at 
each wheel. That same year, approximately 3,600,000 of the other light 
vehicles sold in the United States were equipped with an ABS, and 
approximately 3,100,000 of those vehicles were equipped with a rear-
wheel-only ABS. While rear-wheel-only systems provide benefits (e.g., 
improved stability during braking) for light trucks that frequently 
experience a wide range of loading levels, a rear-wheel-only ABS 
provides no ABS control to the front wheels.
    These nearly 6,300,000 ABS-equipped passenger cars and light trucks 
represented 49 percent of the 12.8 million light vehicles sold in the 
United States in 1992. Based on reports from industry, NHTSA estimates 
that over 75 percent of all new passenger cars and other light vehicles 
will be equipped with an ABS by 1996.

II. NHTSA Activities Related to Braking Performance

    Over the years, NHTSA has studied the effectiveness of ABSs in 
avoiding crashes and reducing their severity. The agency conducted the 
Tri-Level Study of the Causes of Traffic Accidents, (DOT HS 801-631, 
Final Report, June 1975) to determine the effectiveness of ABSs. While 
this is not a recent study, its conclusions might still be relevant. 
Among these conclusions are that (1) rear-wheel-only ABSs had an 
accident reduction potential of one to four percent, (2) four wheel 
ABSs provide the greatest safety benefits and could reduce accidents by 
eight to 15 percent, (3) an ABS's ability to maintain control was found 
to be a more important safety attribute than its ability to improve 
stopping distance performance.
    NHTSA has also conducted test track evaluations of ABS equipped 
light vehicles. (Hiltner, Arehart, and Radlinski, ``Light Vehicle ABS 
Performance Evaluation,'' DOT HS 807 813, December 1991; and ``Light 
Vehicle ABS Performance Evaluation--Phase II,'' DOT HS 807 924, May 
1992.) The December 1991 report describes tests conducted on ten light 
vehicles to evaluate the improvement in braking performance and vehicle 
stability and control resulting from each vehicle's ABS. The test 
program's purpose was to show the degree to which an ABS improves a 
given vehicle's brake performance, not to compare vehicles or similar 
ABSs to one another. Therefore, each vehicle was tested with the ABS 
``on'' and with the ABS ``off'' or disabled. Eight of the ten vehicles 
were equipped with an all-wheel ABS. Each vehicle was run through a set 
of eighteen separate test conditions, using both panic stops and 
driver-best-effort stops in both the empty and loaded condition at 
speeds of 35 mph and 60 mph. Braking maneuvers consisted of straight 
line stops on a uniform surface, straight line stops on a split mu 
surface, stops in a 500 foot curve, and stops involving lane changes. 
The tests were conducted at 35, 45, 50, and 60 mph, at both the empty 
and loaded weight conditions. The tests were conducted on a variety of 
surfaces, including wet Jennite, gravel, and dry concrete.
    Among the findings in the December 1991 report were that (1) each 
ABS, and especially the all-wheel systems, improved the vehicle's 
lateral stability during panic braking; (2) the all-wheel systems 
shortened stopping distances on most hard paved surfaces, with 
improvements of up to 25 percent on wet concrete and up to 50 percent 
on wet Jennite; (3) each ABS lengthened the vehicle's stopping 
distances in panic stops on gravel, with increases exceeding 25 percent 
in some cases; and (4) the rear-wheel system enhanced the vehicle's 
lateral stability but did not reduce stopping distances in most panic 
brake applications.
    The May 1992 report describes tests conducted on eight light 
vehicles to evaluate how the ABS influenced vehicle stopping distance 
and lateral stability and control on various surfaces. This evaluation 
supplements the December 1991 program by testing different vehicles on 
more slippery test surfaces, although it only used straight line 
maneuvers. Among the report's findings were that (1) with one 
exception, the seven vehicles with all-wheel systems were under 
complete directional control during the tests with the ABS ``on,'' (2) 
the vehicle with a rear-wheel-only ABS generally provided improved, but 
not complete, lateral stability and control, (3) ABSs improved stopping 
performance on all surfaces, except that stopping distance worsened on 
dry gravel surfaces, and (4) no vehicle experienced problems in the 
high to low mu transition testing with the ABS operational.
    NHTSA has recently published two proposals related to the braking 
performance of medium and heavy vehicles (hereinafter referred to as 
``heavy vehicles''). On February 23, 1993, the agency proposed 
reinstating stopping distance requirements for these vehicles. (58 FR 
11003). In addition, on September 28, 1993, the agency published a 
proposal that would require heavy vehicles to be equipped with an ABS 
to improve the lateral stability and control of these vehicles during 
braking. (58 FR 50738). The ABS requirement would be supplemented by a 
30 mph braking-in-a-curve ``check'' test conducted on a low coefficient 
of friction surface using a full, panic brake application. Some of the 
issues raised in these rulemakings, such as the test surface and the 
proposed definition of ``ABS,'' are relevant to this rulemaking.

III. Issues for Possible Agency Action

A. Overview of the issues

    This ANPRM discusses whether the agency should propose to require 
ABS for light vehicles, pursuant to the mandate in ISTEA. While 
manufacturers are equipping an increasingly large number of light 
vehicles with ABS, it appears that it would be quite a few years, if 
ever, before all light vehicles would voluntarily be equipped with such 
devices. Based on the agency's review of comments to this notice and 
its review of additional accident data and other information, NHTSA 
will determine whether it should propose to require that all light 
vehicles be equipped with ABSs.
    This ANPRM also makes a number of requests for data and 
information. The agency wishes to emphasize that since this is an 
ANPRM, no rule will be issued on this specific subject without first 
issuing an ANPRM to provide further opportunity to comment. In 
commenting on a particular matter on responding to a particular 
question, interested persons are requested to provide any relevant 
factual information to support their conclusions or opinions, including 
but not limited to, testing, statistical, and cost data, and the source 
of such information.
    The agency seeks comments about the following topics:
    (a) The anticipated safety benefits from requiring light vehicles 
to be equipped with ABSs;
    (b) Potential regulatory approaches to improve the lateral 
stability and control of light vehicles during braking, including a 
requirement for an ABS and any anticipated performance requirements and 
test procedures;
    (c) The types of light vehicles to which these requirements would 
apply and whether all vehicles should be required to be equipped with 
an all-wheel ABS;
    (d) A schedule for implementing the ABS requirements to maximize 
their benefits at reasonable costs; and
    (e) The costs of requiring light vehicles to be equipped with 
antilock braking systems that would comply with the anticipated 
requirements.
    For ease of reference, the questions below are numbered 
consecutively. The agency requests that commenters identify each answer 
they give by the number of each question being answered.

B. Safety Need

    The threshold issue in deciding whether to amend an existing safety 
standard concerns the requirement's safety need. NHTSA is reviewing 
accident data, including information from the Fatal Accident Reporting 
System (FARS), NHTSA's General Estimates System (GES), the National 
Accident Sampling System (NASS), and State accident data files. This 
review focuses on the benefits achieved by equipping light vehicles 
with an ABS in a variety of different crash modes. Among the crash 
modes being studied are (1) single vehicle run-off-the-road crashes in 
which skidding or spinning was the vehicle's pre-crash stability 
condition, (2) multi-vehicle crashes resulting from a vehicle's loss-
of-control or inability-to-stop-in-time, and (3) crashes in which a 
vehicle strikes pedestrians, animals, or road objects.
    Initial data from these sources indicate that braking induced loss-
of-control crashes and inability-to-stop-in-time crashes are frequent 
types of crashes that warrant further study. Such crashes are 
especially prevalent on wet or slippery roads, a condition in which 
ABSs would be effective. Eleven percent of all fatal crashes in 1991 
occurred on wet or slippery roads, and 18 percent of property-damage-
only crashes occurred under such conditions.
    NHTSA's research test findings indicate that equipping light 
vehicles with an ABS would be beneficial to safety. The primary benefit 
with equipping light vehicles with an ABS is that a driver is better 
able to maintain vehicle stability and steering control during crash-
threatening braking situations. A secondary, but still important 
benefit with an ABS, is that a vehicle's stopping ability is improved 
on some surfaces.
    NHTSA's preliminary evaluation of rear-wheel antilock brake systems 
indicates that such ABSs on light trucks are particularly effective in 
reducing the number of run-off-road crashes. Analyses of State accident 
files found that rear-wheel ABS was effective in reducing the risk of 
such nonfatal rollovers (and side and frontal impacts with fixed 
objects) for almost every type of truck, under any type of road 
condition. Reductions of rollovers were typically in the 30-40 percent 
range, reductions of side impacts with fixed objects in the 15-30 
percent range, and reductions in frontal impacts with fixed objects in 
the 5-20 percent range. The risk of collisions with pedestrians, 
animals, bicycles, trains, or on-road objects was also significantly 
reduced, by about 5-15 percent. A copy of this preliminary evaluation 
is available in the public docket.
    NHTSA is continuing to analyze the data and a comprehensive report 
of the findings will be published at a later date. In the meantime, the 
agency requests additional information on braking induced loss-of-
control crashes and inability-to-stop-in-time crashes from rental 
fleets, corporate fleets, insurance companies, police officers, and 
others. This information would assist the agency in its efforts to 
quantify the benefits from ABSs. Accordingly, the agency requests 
comments from these organizations and others about their experiences in 
which drivers of light vehicles have lost control during braking or 
been unable to stop before a crash.
    With these considerations in mind, the agency poses the following 
questions.
    1. Based on the available data, what safety benefits would result 
from the issuance of requirements to prevent or minimize the effect of 
braking induced loss-of-control crashes or inability-to-stop-in-time 
crashes? In what types of crashes would these benefits occur? Please 
provide estimates in terms of accidents, injuries, and fatalities 
prevented. The agency also requests quantitative estimates of 
reductions in property damage.
    2. What additional injury and non-injury data and other information 
exist about real-world crashes and near crashes involving drivers of 
light vehicles who skidded or otherwise lost control?
    3. At the time of loss-of-control or inability-to-stop-in-time 
crashes, what were the driving conditions and weather environment? At 
what speed was the vehicle traveling? Was the roadway dry, wet, or icy? 
To what degree did these adverse driving conditions contribute to the 
crash and its severity? Did the crash occur on an interstate, secondary 
highway, or residential road? What, if any, crash avoidance maneuver 
precipitated the crash?
    4. With respect to loss-of-control or inability-to-stop-in-time 
crashes known to the commenter, would equipping the vehicle with an ABS 
or a more effective ABS (e.g., an all-wheel system instead of a rear-
wheel-only system) have helped in avoiding any of the crashes or 
reducing their severity?
    5. With respect to fleets that have switched or begun switching to 
ABS-equipped light vehicles, have the ABS-equipped light vehicles had a 
lower crash rate than the non-ABS-equipped light vehicles? If there has 
been a reduction in crashes, please quantify the reduction in terms of 
lives saved, injuries prevented, and property damage reduced.

C. Regulatory Approaches to Improve the Lateral Stability and Control 
of Light Vehicles

    If NHTSA were to propose amending its braking safety standards to 
improve the lateral stability and control of light vehicles during 
braking, the amendment would have to meet the Vehicle Safety Act's 
criteria that the requirement be practicable and be stated in objective 
terms (section 103(a)). Any rulemaking addressing antilock would also 
be guided by the findings in PACCAR v. NHTSA, 573 F.2d 632 (9th Cir. 
1978) cert. denied 439 U.S. 862 (1978). Even though PACCAR concerned 
air braked vehicles subject to a different safety standard, some of 
that decision's concerns about testing brake systems are relevant to 
proposing to require ABSs on light vehicles. PACCAR held that at the 
time of their implementation, parts of Standard No. 121 were not 
reasonable nor practicable. The court held that objective test methods 
and more probative and convincing data evidencing the reliability and 
safety of vehicles that are equipped with antilock and in use must be 
available before the agency can enforce a standard requiring its 
installation.
    6. In the NPRM addressing lateral stability and control for heavy 
vehicles, NHTSA proposed that each heavy vehicle be equipped with an 
antilock braking system that satisfies the agency's proposed definition 
of ``ABS.'' In addition, as a ``check'' on the performance of the ABS, 
the agency proposed that a heavy vehicle would have to comply with a 
braking-in-a-curve test. The agency tentatively concluded that this 
approach would ensure that heavy vehicles would be able to 
significantly improve their lateral stability and control during 
braking.
    NHTSA is considering applying this approach to light vehicles by 
proposing both a requirement mandating the installation of ABSs on 
light vehicles and road tests that serve as a check on the performance 
of the ABS. The agency requests comments about the possible benefits 
and shortcomings of using this approach for light vehicles.
    7. In developing the proposed definition for ``ABS'' in the heavy 
vehicle rulemaking, NHTSA referred to the definitions of ``ABS'' 
adopted by the Society of Automotive Engineers (SAE) and the Economic 
Commission for Europe's (ECE) Regulation 13, Annex 13 (1988). Based on 
these definitions and other considerations, the agency proposed the 
following definition of ``antilock brake system'' in the heavy vehicle 
rulemaking:

a portion of a service brake system that automatically controls the 
degree of rotational wheel slip during braking by:
    (1) sensing the rate of angular rotation of the wheels;
    (2) transmitting signals regarding the rate of wheel angular 
rotation to one or more devices which interpret those signals and 
generate responsive controlling output signals; and
    (3) transmitting those controlling signals to one or more 
devices which adjust brake actuating forces in response to those 
signals.

    Under this definition describing fundamental and necessary 
performance aspects that any braking system must have to be considered 
an ABS, the agency believes that any ABS would be permitted, provided 
that it is a ``closed loop'' system that ensures feedback between what 
is actually happening at the tire-road surface interface and what the 
device is doing to respond to impending wheel lockup.
    The agency requests comments about whether to apply to light 
vehicles the approach proposed to improve the lateral stability and 
control of heavy vehicles. Is it necessary and appropriate to 
supplement the combination of a definition of ``ABS'' and an equipment 
requirement with one or more ``check'' tests to ensure the lateral 
stability and control of light vehicles? Is the definition of ``ABS,'' 
as proposed in the heavy vehicle NPRM, appropriate for light vehicles? 
What are the advantages or disadvantages of a requirement expressly 
mandating an ABS instead of taking the more indirect approach of 
adopting dynamic tests? Notwithstanding the agency's tentative 
conclusion that the proposed definition for heavy vehicle ``ABS'' is 
sufficiently broad to allow a variety of ABSs, the agency welcomes 
comment about the use of this definition for light vehicles. Would it 
ensure suitable stopping distances and cover all appropriate brake 
designs, while not unnecessarily prohibiting brake systems that 
effectively prevent wheel lockup in a sufficiently wide variety of 
circumstances?

D. Test Procedures

    8. In the heavy vehicle ABS rulemaking, NHTSA proposed that such 
vehicles would have to comply with a braking-in-a-curve test, but 
decided not to propose additional tests such as a split mu test or a 
lane change test. The agency believed that such additional tests would 
be impracticable for heavy vehicles given the criteria set forth in 
PACCAR. Notwithstanding the agency's tentative decision in the heavy 
vehicle ABS rulemaking to propose only a braking-in-a-curve test, the 
agency is seeking comment on whether to require that light vehicles be 
capable of stopping without loss-of-control in the following test 
maneuvers:
    (a) While turning on a low mu surface;
    (b) While stopping on a straight line split mu surface;
    (c) While in transition from a high mu surface to a low mu surface; 
and
    (d) While in transition from a low mu surface to a high mu surface.
    NHTSA is considering additional tests for light vehicle antilock 
systems for three reasons. First, ABS requirements on passenger cars 
were originally developed in proposals for Standard No. 135, Passenger 
Car Brake Systems, which are based on the effort to harmonize braking 
standards with EEC and ECE requirements. These proposals included split 
mu tests and surface transition tests. Second, the agency believes that 
light vehicle ABS may need to have a higher level of capability for 
some aspects of performance than heavy vehicle ABS. For instance, the 
antilock systems on heavy vehicles do not have to be as quick as the 
systems on light vehicles in responding to impending wheel lock. The 
wheel lockup allowed by light vehicle antilock systems available today 
is about 0.2 seconds, compared with a lockup duration closer to one 
second for heavy vehicle systems. This is so because heavy vehicles 
typically have a longer wheel base than light vehicles, and a high 
vehicle moment of inertia about the vertical axis. On these vehicles, 
yaw movement during braking with ABS on a split mu surface or during a 
braking-in-a-curve maneuver takes place at a relatively slower rate 
than on light vehicles, primarily because of the higher vehicle moment 
of inertia. Third, in contrast to testing light vehicles, the 
availability of test facilities and the safety of the tests would make 
more extensive testing impracticable for heavy vehicles because such 
vehicles are larger and more prone to rollover than light vehicles. For 
the above reasons, the split mu and surface transition tests might be 
appropriate additions to the braking-in-a-curve test for light 
vehicles.
    The agency anticipates that each of these tests would be conducted 
at 30 mph using a full pedal application (200 pounds pedal force 
applied within 0.2 seconds) and that the vehicle would be required to 
stay within a 12-foot lane. There would be no stopping distance 
requirement as part of these tests. (The issue of separate tests for 
stopping distance is discussed below in connection with question 13.)
    9. As mentioned above, NHTSA is considering whether to propose a 
``braking-in-a-curve test'' in which a light vehicle's braking would be 
evaluated at a relatively slow speed on a slippery surface. This test 
is designed to evaluate the capability of a vehicle to be controlled 
while braking in a curve. The test could be conducted on a 500-foot 
radius curve on a surface with a peak friction coefficient (PFC) of 0.5 
or less. What benefits would be obtained from such a braking-in-a-curve 
test? What problems, if any, would be associated with this maneuver? 
Would this testing approach be a sufficient indicator of the lateral 
control and stability expected from an ABS equipped light vehicle? How 
would rear-wheel-only antilock systems perform under this test 
procedure?
    10. NHTSA is considering whether to propose another type of test, 
possibly as an alternative to the braking-in-a-curve test. This test is 
known as a ``split coefficient of friction test'' (or split mu test) 
and is designed to evaluate a vehicle's ability to be controlled when 
one side of a road is slick and the other side is much stickier. If 
NHTSA were to propose such a test, it probably would be conducted on a 
straight lane surface with the high mu part of the surface having a PFC 
equal to or greater than 0.5 and the low mu part of the surface having 
a PFC of less than or equal to one-half the PFC of the high mu surface. 
An alternative way to describe the test surface would be to specify the 
PFCs for both parts of the surface (e.g., the high mu part would be 0.9 
or greater and the low mu part would be 0.45 or less). The test lane 
would be split down the centerline along its length, so that the wheels 
on one side of the vehicle are on the high friction surface and the 
wheels on the other side of the vehicle are on the slick surface. What 
benefits would be obtained from testing on such a split mu surface? 
What problems, if any, would result from such a surface? Would this 
test be a sufficient indicator of the lateral stability and control 
expected from an ABS-equipped vehicle? How would rear-wheel-only 
antilock systems perform under this test procedure? What is the best 
way to specify the test surface?
    11. NHTSA is also considering whether to propose a ``low to high mu 
surface transition test.'' This test is designed to evaluate the 
capability of an antilock system to modulate brake pressure to achieve 
a high level of deceleration after the vehicle makes a transition to 
the high mu surface. NHTSA anticipates that if it proposes such a test, 
the high mu surface would have a PFC equal to or greater than 0.5, and 
the low mu surface would have a PFC of less than or equal to one half 
the PFC of the high mu surface. The agency is considering whether to 
propose requiring that the vehicle achieve at least 95 percent of the 
deceleration of the uniform coefficient deceleration on the high mu 
surface within one second. What benefits would be obtained from such a 
transition test? What problems, if any, would be associated with this 
test maneuver? Would this test be a sufficient indicator of the 
modulation capability expected from an ABS-equipped light vehicle? 
Would the suggested way of specifying test surfaces be appropriate? The 
agency requests comments about whether to specify the time needed to 
achieve a specific deceleration and to specify a maximum lockup 
duration during the transition. How would rear-wheel only antilock 
systems perform under this test procedure?
    12. NHTSA is considering whether to propose a ``high to low mu 
surface transaction test.'' This test is designed to evaluate the 
response for the ABS when the vehicle begins braking on a high mu 
surface then experiences a change to a low mu surface. This type of 
surface is discussed in the previous question. The agency is 
considering whether to require that the vehicle's wheels not lock for 
more than 0.2 seconds, with wheel lock defined as 100 percent slip. 
What benefits would be obtained from such a surface transition test? 
What problems, if any, would be associated with this test maneuver? 
Would this test be a sufficient indicator of the modulation control and 
the response to impending wheel lock expected from an ABS-equipped 
light vehicle? How would rear-wheel only antilock systems perform under 
this test procedure?
    13. The efficiency of an ABS affects a vehicle's stopping distance 
performance with the ABS cycling. Consistent with the agency's decision 
in the heavy vehicle ABS rulemaking not to propose stopping distance 
requirements with tests involving low mu surfaces, NHTSA does not 
anticipate proposing, at this stage of this rulemaking, stopping 
distance requirements with the curve, split mu, or transaction tests 
because of the variability of vehicle stopping distance performance on 
low mu surfaces. Do commenters agree with the agency's tentative 
decision not to propose stopping distance requirements with tests 
involving low mu surfaces?
    Notwithstanding this tentative decision, NHTSA believes that a 
measurement of efficiency might provide consumers with information to 
compare the relative overall performance of various ABSs. In its 
evaluations, the agency has calculated ABS efficiency by dividing 
vehicle decelerations (g's) by the peak friction coefficient measured 
with the vehicle's tire. The agency notes that an ABS efficiency value 
could provide consumers with a means of comparing the ABS performance 
capability since no stopping distance requirements are being considered 
for the tests mentioned in this notice to evaluate ABS performance. 
Each antilock system achieves a certain level of efficiency based on 
design factors such as the wheel deceleration rate threshold at which 
ABS cycling begins, the control algorithm, and the modulator valves. In 
general, the higher the ABS efficiency, the shorter the stopping 
distance should be with the ABS operational. NHTSA's light vehicle ABS 
testing has shown that the improvements in braking performance provided 
by an ABS varies, in some cases considerably, from system to system and 
from vehicle to vehicle. Hence, simply setting a standard that requires 
all-wheel ABS would not necessarily mean that the performance of these 
systems would be similar. The agency therefore request comments on what 
would be an appropriate method for measuring ABS efficiency, and 
whether ABS efficiency would be a meaningful indicator of a system's 
overall performance.
    14. The current requirements in Standard No. 105 for vehicles with 
failed antilock systems including stopping distance requirements from 
60 mph of 456 feet for passenger cars and 517 feet for other light 
vehicles with a GVWR of not more than 10,000 pounds. This test is 
designed to ensure that the vehicle has adequate braking if the ABS 
fails. These distances may be overly generous for an ABS failure on 
some vehicles, given that the service brake system is generally still 
intact. NHTSA anticipates proposing ABS failure requirements for 
Standard No. 105 similar to those proposed for Standard No. 135. In 
that rulemaking, the agency proposed a stopping distance of 279 feet 
from a test speed of 62 mph on a surface with a PFC of 0.9. What 
problems, if any, would be associated with such a requirement? Should 
the standard allow an ABS that experiences a large degradation of 
stopping performance if the ABS fails? What is the best method for 
disabling an ABS for a failed system test? Should performance 
requirements for integrated ABSs be any different from the requirements 
for add-on ABSs, in the failed condition? If so, why? Should the failed 
ABS stopping distance be one absolute value for all vehicles, or should 
it be based on the performance relative to the stopping distance 
performance when each vehicle's ABS is in the ``on'' position?

E. Test Conditions

    15. As explained in the previous section, NHTSA anticipates 
specifying the test surfaces used in the test procedures in terms of 
peak friction coefficient. While the braking-in-a-curve test would have 
a PFC of 0.5, the split mu and transition tests would have the surface 
specified based on the relative PFC of each of the two portions of the 
surface. The braking-in-a-curve test surface represents a wet secondary 
road in poor condition, and the split mu and transition test surface 
represent roads with different coefficients of friction such as those 
with ice patches. What practicability concerns, if any, are raised by 
conducting tests on surfaces with both low and high coefficients of 
friction?
    16. Two different methods of applying brakes can be used when 
testing ABSs (and braking systems in general). One method is a ``full 
pedal'' application typical of how a driver might apply the brake pedal 
in reaction to a crash-threatening situation. This type of brake 
application can precipitate wheel lock-up and loss-of-control if the 
vehicle is operating on a slippery surface. A second method is a 
modulated ``driver-best-effort'' application in which the driver 
modulates the brake in an attempt to maintain stability and lateral 
control. This method enables stops that are as quick and short as 
possible while still maintaining stability and steering control. As 
with the heavy vehicle ABS rulemaking, the agency anticipates proposing 
a full pedal application because it is more representative of a typical 
driver's response to a real world crash-threatening situation. In 
addition, such an application is more objective and repeatable. In 
specifying the amount of brake application force in this test 
procedure, the agency anticipates that a pedal force of 200 pounds in 
0.2 seconds would adequately represent a full pedal application for 
light vehicles. The agency requests comments about the best way to 
specify the brake application provisions.

F. Varieties of ABS Permissible under Potential Proposals

    17. Agency testing indicates that all-wheel antilock systems 
provide full steering control and lateral stability during braking. 
Real-wheel-only antilock systems do not ensure steering control during 
braking, but provide some measure of vehicle stability during braking. 
Should the proposed requirements be drafted so that light vehicles must 
be equipped with systems that provide ABS control on all wheels, or 
should the requirements be drafted to allow rear-wheel-only systems as 
well? What are the differences in benefits between rear-wheel-only and 
all-wheel systems?
    18. If NHTSA were to propose its braking standards to improve the 
lateral stability and control of light vehicles during braking, all 
light vehicles would have to be equipped with lateral stability and 
control devices to achieve the new performance requirements. As 
mentioned above, all-wheel ABSs were installed on 2,700,000 passenger 
cars and on 470,000 other light vehicles in 1992. While another 3.1 
million light vehicles were equipped with rear-wheel-only ABSs, 
vehicles are increasingly being equipped with all-wheel systems rather 
than rear-wheel-only systems. How many vehicles would need to be 
equipped with ABSs to comply with the requirements discussed in this 
notice? Would it be necessary to equip a vehicle with an all-wheel ABS 
to comply with the requirements discussed in this notice or would rear-
wheel-only systems be adequate?
    19. The ECE currently uses three categories to classify antilock 
systems by their performance capabilities. While the ECE mandates the 
most sophisticated Category I systems for heavy vehicles, ABS 
installation remains voluntary for light vehicles. Nevertheless, if a 
manufacturer decides to equip a light vehicle with ABS, then it must 
inform the government approving body about the Category of ABS being 
installed on a given light vehicle. After being reviewed by the 
government, the manufacturer may market its system to consumers as that 
category of ABS.
    NHTSA is considering whether to propose a classification system 
like the ECE's in which there would be categories of increasingly 
stringent performance criteria instead of a minimum requirement for all 
antilock systems. The performance criteria, if proposed, might include 
the following factors:

Category I--

     Braking efficiency of the vehicle equal to or greater than 
75 percent on all road surfaces, including split mu.
     Meets braking-in-a-curve or split mu test requirements for 
stability.
     Meets low mu to high mu surface transition requirement of 
achieving 95 percent of the uniform coefficient deceleration within a 
specified time period.
     Meets high mu to low mu surface transition requirements 
for lockup duration.
     Wheels on all axles must be directly controlled by ABS.

Category II--

     Braking efficiency of the vehicle equal to or greater than 
75 percent on all road surfaces except split mu.
     Meets braking-in-a-curve or split mu test requirements for 
stability.
     Meets low mu to high mu surface transition requirements of 
achieving 95 percent of the uniform coefficient deceleration within a 
specified time period.
     Meets high mu to low mu surface transition requirements 
for lockup duration.
     Wheels on each axle must be directly controlled by ABS.

Category III--

     Braking efficiency of each axle having at least one 
directly controlled wheel equal to or greater than 75 percent, on all 
road surfaces except split mu.
     Meets low mu to high mu surface transition requirements of 
achieving 95 percent of the uniform coefficient deceleration within a 
specified time period.
     Meets high mu to low mu surface transition requirements 
for lockup duration.
The agency anticipates that most, but not all, of the all-wheel ABSs 
would satisfy the criteria for Category I systems and that poorer 
performing all-wheel ABSs and rear-wheel only ABSs would satisfy the 
less stringent criteria of either Category II and Category III.
    Specifying categories would permit simpler antilock braking systems 
to comply with the standard, without lowering the requirements for the 
higher capability systems. It would also serve to inform consumers that 
not all ABSs have the same performance capabilities. However, the 
agency notes that there might be significant drawbacks to specifying 
categories, since such an approach might result in unnecessary 
complexity and permit the manufacture and installation of poorer 
performing systems that do not provide steering control and other 
significant safety benefits. The agency invites comments about whether 
the standard should specify categories of ABSs.

G. Implementation

    NHTSA's goal in initiating rulemaking to require light vehicles to 
be equipped with an ABS is to determine whether significant 
improvements in braking performance can be achieved at a reasonable 
cost to manufacturers and consumers. There are a number of different 
approaches that the agency could take in scheduling the implementation 
of the potential proposals. One approach would be to apply the 
requirements to passenger cars first and then to all other light 
vehicles. A second approach would be for the agency to apply the ABS 
standards to all light vehicles at the same time.
    20. While the Authorization Act requires NHTSA to initiate 
rulemaking on brake performance for passenger cars, NHTSA is 
contemplating using its general authority under the Vehicle Safety Act 
to broaden this mandate to include trucks, vans, sport utility 
vehicles, and buses under 10,000 pounds GVWR. The agency is considering 
this approach because it believes that ABS has more potential benefits 
for vehicles which have a greater disparity between their unloaded and 
fully loaded weights. These latter type vehicles fall into this 
category. The agency notes that the market appears to agree with this 
position as ABS is more prevalent in light trucks than passenger cars. 
NHTSA seeks comment on its tentative decision to include these 
vehicles.
    21. At this stage in the rulemaking, NHTSA is inclined to propose 
an effective date of two years after the final rule, for passenger 
cars, and three years after the final rule for light vehicles other 
than passenger cars (i.e., trucks). The agency believes that this would 
give the industry sufficient leadtime to develop the production 
capacity needed to supply the market with antilock systems. The agency 
expects that an increasing number of light trucks will be offered with 
all-wheel antilock systems, particularly if the proposed requirements 
cannot be met with rear-wheel-only systems. If this is the case, then 
manufacturers of light trucks with these systems might need more 
leadtime than manufacturers of passenger cars to comply with the 
proposed requirements. Would this implementation schedule be 
appropriate? Would it be reasonable to accelerate or delay any portion 
of it? Should the agency apply requirements for ABSs to some light 
vehicles but not others?

H. Costs Associated with Potential Proposals

    22. NHTSA estimates that this rulemaking's potential cost would be 
approximately $1.04 billion per year. This cost consists of ABS costs 
of $920 million, installation costs of about $80 million, and increased 
fuel costs of about $40 million due to a small increase in vehicle 
weight. The average retail price of an ABS system to the consumer would 
be about $450. This price is based on a cost study of seven ABS systems 
entitled ``Evaluation of Costs of Antilock Brake Systems'' and a markup 
factor of 1.51. The agency's cost estimate assumes that all-wheel ABS 
would be required on all light vehicles. It projects that all-wheel ABS 
would be voluntarily installed as standard equipment in 85 percent of 
model year 1999 passenger cars, the first model year that would be 
affected if a final rule were issued in 1996 and a 2-year leadtime for 
compliance were provided. The remaining 15 percent or about 1.4 million 
vehicles would be equipped only as a result of a requirement. The cost 
estimate also projects that all light trucks would be voluntarily 
equipped with ABS by model year 1999/2000, 75 percent of them having 
all-wheel systems. Thus, 25 percent of new light trucks, or about 1.5 
million vehicles, would be involuntarily equipped with all-wheel ABS if 
the agency issued a final rule requiring this. In this case, all-wheel 
ABS hardware and installation costs would be incrementally higher 
(about $200 more), as compared to those for rear-wheel systems.
    How much would it cost per vehicle to equip all light vehicles with 
all-wheel ABSs? How much would it cost per vehicle to equip these 
vehicles with rear-wheel-only ABSs? What would be the likely costs to a 
final purchaser for either of the two types of antilock systems?
    23. Each light vehicle manufacturer is requested to provide, with 
respect to model year 1994, and for each of the following types of 
vehicles, passenger cars, light trucks, and light MPVs: the total 
number of the vehicles it will produce; the vehicles it will equip with 
rear-wheel-only ABSs; and the vehicles it will equip with all-wheel 
ABSs.
    With respect to each of model years 1995-1999, and for each of the 
following types of vehicles, passenger cars, light trucks, and light 
MPVs, what percentages of vehicles do you expect to voluntarily equip 
with a rear-wheel-only ABS? With an all-wheel ABS?
    Do you expect to install all-wheel ABSs on all of your passenger 
cars? If so, when? On all of your light trucks? On all of your light 
MPVs?
    24. NHTSA notes that some insurance companies currently offer 
discounts for antilock equipped passenger cars, light trucks and light 
MPVs. Which insurers provide such a discount? How large is the discount 
offered by each of those insurers? What is the basis for such 
discounts?

IV. Rulemaking Analyses and Notices

A. DOT Regulatory Policies and Procedures and Executive Order 12866

    NHTSA has considered the potential burdens and benefits associated 
with this advance notice. NHTSA has determined that this advance notice 
is a significant rulemaking action under the Department of 
Transportation's Regulatory Policies and Procedures and an economically 
significant notice under Executive Order 12866. The advance notice 
would have an annual effect on the economy of $100 million or more. It 
concerns a matter in which there is substantial public interest. 
Further, there is a potential for significant safety benefits if 
effective requirements can be developed to address braking stability 
and control of light vehicles. The preliminary Assessment of Economic 
Significance for this advance notice addresses preliminary estimates of 
the costs and benefits of potential countermeasures that the agency is 
considering in this action. Those estimates are summarized below.
    NHTSA believes that ABS is effective in preventing, and reducing 
the severity of many inability-to-stop-in-time and loss-of-control 
crashes. The previously mentioned 1975 Tri-Level study found ABS to be 
effective. Also, a preliminary agency evaluation of more current data 
found rear-wheel ABS on light trucks to be effective in preventing 
certain types of crashes. The agency is continuing to analyze the on-
road experience of ABS-equipped vehicles as compared to those with 
standard braking systems. At this time, the agency does not have 
sufficient data to estimate the safety benefits of requiring mandatory 
installation of ABS on all light vehicles types. In this advance 
notice, the agency is requesting information on ABS effectiveness and 
the safety benefits that could be expected from a requirement for 
mandatory installation of the technology. In assessing the cost-
effectiveness of any requirement for mandatory installation of the 
technology, benefits accruing to vehicles on which ABS would not have 
been voluntarily installed would be estimated and compared to the costs 
associated with equipping those vehicles with ABS. In the case of light 
trucks, depending on the extent and type of ABS voluntarily installed 
and the type of ABS required, the benefits at issue might be those that 
would be realized from all-wheel ABS as compared to rear-wheel systems.
    NHTSA estimates that the annual consumer cost of requiring antilock 
brake systems on light vehicles to be $1,040 million: $710 million for 
passenger cars and $330 million for light trucks. This assumes that 
all-wheel systems would be required. Estimated ABS hardware cost would 
be $920 million, installation costs would be $80 million, and increased 
fuel costs (due to a small increase in vehicle weight) about $40 
million.

B. Executive Order 12612 (Federalism)

    NHTSA has analyzed this action under the principles and criteria in 
Executive Order 12612. The agency had determined that this advance 
notice does not have sufficient Federalism implication to warrant the 
preparation of a Federalism Assessment. No State laws would be 
affected. The agency welcomes comment on this issue.

Comments

    NHTSA invites comments from interested persons on the questions 
presented in this advance notice and on other relevant issues. It is 
requested but not required that 10 copies be submitted.
    Comments must not exceed 15 pages in length. (49 CFR 553.21). 
Necessary attachments may be appended to these submissions without 
regard to the 15-page limit. This limitation is intended to encourage 
commenters to detail their primary arguments in a concise fashion.
    If a commenter wishes to submit certain information under a claim 
of confidentiality, three copies of the complete submission, including 
purportedly confidential business information, should be submitted to 
the Chief Counsel, NHTSA, at the street address given above, and seven 
copies from which the purportedly confidential information has been 
deleted should be submitted to the Docket Section. A request for 
confidentiality should be accompanied by a cover letter setting forth 
the information specified in the agency's confidential business 
information regulation. 49 CFR Part 512.
    NHTSA will consider all comments received before the close of 
business on the comment closing date indicated in the ``Dates'' caption 
of this advance notice. To the extent possible, the agency will 
consider comments filed after the closing date. Comments on the advance 
notice will be available for inspection in the docket. After the 
closing date, NHTSA will continue to file relevant information in the 
Docket as this information becomes available, and recommends that 
interested persons continue to examine the Docket for new material.
    Those persons desiring to be notified upon receipt of their 
comments in the rules docket should enclose a self-addressed, stamped 
postcard in the envelope with their comments. Upon receiving the 
comments, the docket supervisor will return the postcard by mail.
    A regulatory information number (RIN) is assigned to each 
regulatory action listed in the Unified Agenda of Federal Regulations. 
The Regulatory Information Service Center publishes their Unified 
Agenda in April and October of each year. The RIN contained in the 
heading of this document can be used to cross reference this action 
with the Unified Agenda.

List of Subjects in 49 CFR Part 571

    Imports, Motor vehicle safety, Motor vehicles, Rubber and rubber 
products, Tires.

(15 U.S.C. 1392, 1401, 1407; delegations of authority at 49 CFR 1.50 
and 501.8)

    Issued on: December 29, 1993.
Barry Felrice.
Associate Administrator for Rulemaking.
[FR Doc. 93-32106 Filed 12-29-93; 3:35 pm]
BILLING CODE 4910-59-M

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