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

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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