Federal Motor Vehicle Safety Standards; Antilock Brake Systems for Light Vehicles |
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Topics: National Highway Traffic Safety Administration
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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.
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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]
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