Federal Motor Vehicle Safety Standards; Stability and Control of Medium and Heavy Vehicles During Braking

DEPARTMENT OF TRANSPORTATION

49 CFR Part 571

[Docket No. 92-29; Notice 4]

RIN 2127-AA00

Federal Motor Vehicle Safety Standards; Stability and Control of

Medium and Heavy Vehicles During Braking

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

ACTION: Supplemental notice of proposed rulemaking (SNPRM).

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SUMMARY: This notice proposes to modify the implementation schedule for

and certain requirements in the agency's September 1993 notice

proposing to improve the stability and control of medium and heavy

vehicles during braking. In response to the Intermodal Surface

Transportation Efficiency Act (ISTEA) of 1991, the agency proposed in

the September notice that medium and heavy vehicles be equipped with an

antilock brake system (ABS) and be able to comply with a 30 mph

braking-in-a-curve test on a low coefficient of friction surface using

a full brake application.

In this supplemental notice, NHTSA is proposing to amend the

implementation schedule for the rule and to require independent wheel

control on at least one axle. The agency's decision to issue this

notice was prompted by comments on the NPRM favoring such changes.

DATES: Comments on this notice must be received on or before May 12,

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: On September 28, 1993, NHTSA published a

notice of proposed rulemaking (NPRM) in which the agency proposed

amending Standard No. 105, Hydraulic Brake Systems and Standard No.

121, Air Brake Systems, to require medium and heavy vehicles1 to

be equipped with an antilock brake system (ABS) to improve the lateral

stability and control of these vehicles during braking. (58 FR 50739).

The NPRM proposed supplementing the ABS requirement by including a 30

mph braking-in-a-curve test on a low coefficient of friction surface

using a full brake application. The agency believed that the proposed

requirements would improve heavy vehicle stability and control during

braking and thus significantly reduce the deaths and injuries caused

when these vehicles jackknife or otherwise lose control. The notice

also proposed requiring an in-cab ABS malfunction lamp and, during a

transition period of eight years, an external trailer lamp to warn

drivers of non-ABS tractors of trailer ABS malfunction. The agency

believed that the proposed malfunction indicators would provide

valuable information about ABS malfunctioning to the driver and to

maintenance and inspection personnel. The proposal was based on

comments received in response to an advance notice of proposed

rulemaking (ANPRM) published on June 8, 1992 and other available

information (57 FR 24212).

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\1\ Such vehicles will be referred to as ``heavy vehicles''

throughout the remainder of this notice.

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NHTSA received over 50 comments in response to the NPRM. These

commenters included heavy vehicle manufacturers, brake manufacturers,

safety advocacy groups, heavy vehicle users, trade associations, State

entities, and other individuals. The majority of commenters agreed that

the agency should take measures to improve the stability and control of

heavy vehicles during braking to reduce the number of loss-of-control

crashes. Commenters addressed specific issues raised in the NPRM,

including the decision proposing to require vehicles to be equipped

with ABS, the type of ABS, the braking-in-a-curve test procedure, the

implementation schedule for the requirements, the malfunction indicator

requirement, the power requirement, and the rulemaking's cost.

This SNPRM focuses on two issues raised in the NPRM and addressed

by the commenters: (1) The implementation schedule and (2) the wheels

to be controlled by an antilock brake system.

Implementation Schedule

In the NPRM, NHTSA stated that its goal is to achieve significant

improvements in braking performance at a reasonable cost to

manufacturers and consumers. Based on the available information, NHTSA

decided to propose the following implementation schedule:

Truck Tractors

2 years after final rule (1996)

Trailers, including converter dollies

3 years after final rule (1997)

Single unit trucks

4 years after final rule (1998)

Buses

5 years after final rule (1999)

NHTSA believed that this implementation schedule is appropriate

given the current state of ABS technology. The agency believed that it

would provide the industry, ABS manufacturers, and maintenance

personnel sufficient leadtime to prepare for the changes that will be

required to accommodate the new technology.

With respect to truck tractors, NHTSA stated that it was confident

that ABS for this type of vehicle would be fully developed, performance

tested, and field tested within two years after the final rule since

ABS manufacturers have focused their initial efforts on developing ABS

for truck tractors. The agency noted that ABS for truck tractors is

currently available on a commercial basis in this country and

throughout Europe. Nevertheless, a two year leadtime appeared to be

necessary to ensure a smooth transition before the agency mandated this

technology given the technical complexities and costs associated with

ABS.

With respect to trailers, NHTSA noted that ABS manufacturers are

currently marketing ABS for these vehicles. NHTSA stated that it

expected its fleet evaluation on 50 ABS-equipped trailers to be

completed in 1993. (This evaluation, titled ``An In-Service Evaluation

of the Performance, Reliability, Maintainability, and Durability of

Antilock Braking Systems (ABSs) for Semitrailers'' has been completed

and is available for review in the agency's public docket room. The

agency welcomes comments about the report.)

With respect to single-unit trucks and buses, NHTSA proposed

leadtime of four years and five years, respectively, after the final

rule's publication, resulting in an effective date in 1998 and 1999.

NHTSA proposed effective dates that it believed would give the industry

sufficient leadtime to develop, field test, and performance test ABS on

straight trucks and buses. The agency also explained that ABS for such

vehicles is still being developed, so these leadtimes appeared to be

necessary to ensure that the technology would be reliable when it is

required.

The American Automobile Manufacturers Association (AAMA), which

represents the eight major domestic truck manufacturers,2

recommended that the effective dates for the proposed heavy vehicle

stability and control requirements and the previously proposed stopping

distance requirements be ``synchronized for the various vehicle

types.'' (58 FR 11009, February 23, 1993).3

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\2\ Chrysler, Ford, Freightliner, General Motors, Mack,

Navistar, PACCAR, and Volvo-GM.

\3\ The February NPRM proposed that the stopping distance

requirements take effect two years after the final rule for all

applicable vehicles.

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AAMA recommended that the agency adopt the following effective

dates for both the stability and control requirements and the stopping

distance requirements, assuming that the two rules are issued before

September 1994:

Truck tractors

2 years after final rule (1996)

Trailers, including converter dollies

3 years after final rule (1997)

Air-braked single unit trucks and buses

3 years after final rule (1997)

Hydraulic-braked single unit trucks and buses

4 years after final rule (1998)

Similarly, manufacturers of brake components and antilock brake

systems recommended that the implementation schedule for the lateral

stability and control requirements be accelerated. Rockwell requested

that the leadtime for air-braked single unit trucks and buses be

shortened to three years after the final rule. The Heavy Duty Brake

Manufacturers Council requested that the effective dates of the

stopping distance rulemaking and the stability rulemaking be ``made

coincident to allow the industry to maximize its efforts by effectively

utilizing its limited resources.''

The American Trucking Association (ATA) recommended effective dates

of December 31, 1999 for tractors and December 31, 2001 for trailers,

claiming that this schedule would permit each fleet, through its own

tests, to determine which ABS is best suited to its operations and to

phase ABS in accordingly. In contrast, Advocates for Highway Safety

(Advocates) favored the proposed implementation schedule and opposed

any schedule that moved the compliance calendar to the next century. It

believed that a delayed schedule would unreasonably postpone safety

benefits for the public because ABS technology is both reliable and

available.

After reviewing the comments, NHTSA has tentatively determined that

it may be appropriate to make the effective dates for the heavy vehicle

stability and control requirements concurrent with the stopping

distance requirements. This could facilitate a more orderly

implementation process, avoid the need for manufacturers to redesign

the brakes on individual vehicles twice, and reduce the development and

compliance costs that manufacturers would face as a result of these

regulations. Specifically, the agency is considering to adopt the

following implementation schedule for both sets of requirements:

Truck tractors

2 years after final rule (1996)

Trailers

3 years after final rule (1997)

Air-braked single unit trucks and buses

3 years after final rule (1997)

Hydraulic-braked single unit trucks and buses

4 years after final rule (1998)

This proposed implementation schedule, which would accelerate

compliance for air-braked single unit trucks and buses and hydraulic-

braked buses, is consistent with the recommendation of the heavy

vehicle manufacturers, brake manufacturers, and the safety advocacy

groups. The agency agrees with the manufacturers that reliable antilock

systems can be developed within this time-frame. NHTSA tentatively

concludes that the implementation schedule recommended by ATA is too

protracted, especially in light of the widespread use of ABS in Europe,

increased use of ABS in this country, and the comments by the brake and

vehicle manufacturers.

NHTSA requests comments about the implementation schedule being

proposed in this supplemental notice. Specifically, commenters should

respond to the following questions:

1. Is it appropriate to make the effective dates concurrent for the

stopping distance and stability requirements for heavy vehicles?

2. Is it appropriate to accelerate the stability and control

effective dates for air braked trucks and buses and hydraulic braked

buses, and to delay the effective date for the proposed stopping

distance requirements for some classes of vehicles?

3. Since hydraulic braked trucks and buses would have to be

equipped with ABS one year later than air braked trucks and buses,

would truck and bus fleets specify hydraulic brake systems for their

new vehicles for that one year to avoid the additional cost of ABS on

air braked trucks and buses?

4. The agency received comments to the stability and control NPRM

from only one bus manufacturer. Do bus manufacturers have any specific

concerns about the revised implementation dates proposed in this

notice?

5. Do the heavy vehicle ABS suppliers have the manufacturing

capacity to meet the demand for air braked antilock systems in 1996 and

1997?

Antilock Brake System Wheel Control

In the NPRM, NHTSA proposed to require that the antilock brake

system monitor and control the wheels of the front axle and of at least

one rear axle. NHTSA believed that this would ensure that the wheels on

the steering axle are directly controlled by the antilock braking

device. By ``directly controlled,'' the agency meant that the signal

provided at the wheel or on the axle of the wheel directly modulates

the braking forces of that wheel. The agency tentatively concluded that

it is necessary to specify that the ABS directly control the steering

axle because some ABS control only a vehicle's drive-axle, a situation

which could result in the loss of steering control if the front wheels

locked during braking.

Several commenters addressed the need for front wheel control. ATA

strongly opposed mandating ABS for the steering axle of single-unit

trucks and suggested the agency reconsider mandating them on all

tractors. In contrast, Rockwell, WABCO, Freightliner, AAMA, Advocates,

and the Insurance Institute for Highway Safety (IIHS) favored requiring

that ABS be equipped on front axles. AAMA favored equipping each

vehicle with ABS that has at least one independent channel of control

for the wheels on a front axle and at least one independent channel of

control for the wheels on a rear axle, but objected to mandating more

than two independent channels of control. Because Rockwell,

Freightliner, Advocates, and the Insurance Institute for Highway Safety

(IIHS) were concerned that the current proposal would allow ``select

low''4 antilock systems on any axle, they recommended that the

equipment requirement include language that would require ``independent

control of each wheel'' of the axles that are required to be ABS-

controlled. They believed such a requirement would prevent significant

degradation in the stopping performance, particularly on a split mu

surface.5 Rockwell WABCO recommended a minimum standard of at

least one rear axle having independent wheel brake control. It opposed

allowing select low ABS which it believed would experience

significantly longer stopping distances on split mu surfaces. Allied

Signal recommended requiring independent control of the brakes on the

steering axle. Bosch recommended a minimum requirement of a 4S/3M ABS.

Freightliner favored requiring at least four independent channels of

control, two for each axle, allowing independent control of each wheel

on the forward and rear axle. Similarly, IIHS favored requiring that

the brakes/wheels of the front axle be independently controlled by an

antilock system and that the brakes/wheels of at least one rear axle

have similar independent antilock control. Advocates recommended that

ABS be functional on all axles, not just one axle in each multiple axle

set on a heavy vehicle. Because commenters differed on which axle the

antilock system should provide independent wheel control, NHTSA has

decided to propose requiring that the wheels on at least one axle be

independently controlled, without specifying the axle on which it

should be installed. This would allow manufacturers the flexibility to

determine on which axle the wheels would be independently controlled by

the antilock system.

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\4\While some ABS are equipped with modulators that

independently control each wheel, a select low ABS controls both

wheels on each axle with one modulator while having a wheel speed

sensor at each wheel location. As such, both brakes on the

controlled axle are applied and released simultaneously by the ABS.

Such a system affords vehicle and directional stability, and shorter

stopping distances on surfaces with uniform friction, but increases

stopping distances if road-surface friction on one side of the

vehicle differs from that on the other.

\5\With such a surface, the road is split along its length so

that the wheels on one side of the vehicle are on a high friction

surface and the wheels on the other side are on a low friction

surface; the term ``mu'' concerns the surface's coefficient of

friction.

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After reviewing the comments, NHTSA has decided to propose

modifications to the proposal to require heavy vehicles to be equipped

with systems that independently control each wheel on at least one axle

of a truck, a truck tractor, or a bus. Based on the comments and other

available information, the agency believes that a minimum requirement

that includes an antilock braking system that controls the wheels on at

least one front and one rear axle where the wheels on at least one of

these axles are independently controlled would provide an acceptable

level of stopping distance performance on low mu and split mu surfaces.

In addition to the data provided by Freightliner and Rockwell WABCO,

the agency's ABS heavy vehicle testing showed that independent wheel

control by an ABS enables a vehicle to stop in a shorter distance

compared with either a vehicle equipped with an axle-by-axle control

antilock system, or with a non-ABS equipped vehicle using a driver

best-effort brake application. (``Improved Brake Systems for Commercial

Vehicles,'' DOT HS 807 706, Final Report, April 1991)

NHTSA is also proposing to prohibit tandem control by an antilock

system, by requiring that no more than two wheels be controlled by one

modulator valve. As part of its performance test program, the agency

tested four different ABS configurations: individual wheel control,

side-by-side control, axle-by-axle control, and tandem control. The

agency found that the tandem control system produced stopping distances

that were significantly longer than those of axle-by-axle control or

side-by-side control, particularly on split coefficient of friction

surfaces. These test results are documented in the report, ``Improved

Brake Systems for Commercial Vehicles.'' The agency is aware that the

proposed requirements would allow a 6 x 4 truck or truck tractor to be

equipped with a 4S/3M antilock system, i.e., independent control of

each front wheel, select low control on one rear axle, and no ABS

control on the other rear axle. The agency's testing has found that

vehicle stability is not significantly degraded if two wheels on a

tandem are locked during braking. Accordingly, the agency has used this

concept in developing the limited lockup requirements for the stopping

distance rulemaking where one wheel per axle or two wheels per tandem

are allowed to lock above 20 mph during the stopping distance test.

The agency requests comments to the following questions about

independent control of each wheel on at least one axle and about

prohibiting tandem control by an antilock system:

1. Is it appropriate to require independent control of each wheel

on at least one axle?

2. Would it be appropriate to adopt the alternative recommendations

presented by Rockwell, Freightliner, or Advocates? Would these

alternative recommendations provide significantly greater benefits?

Would they prevent unreasonably long stopping distances on split mu

surfaces?

3. Compared to the original proposal that would allow select low

systems, what would be the additional marginal benefits and cost of the

requirement proposed in this SNPRM? Of the requirements recommended by

Rockwell, Freightliner, or Advocates?

4. Is it appropriate to prohibit tandem control by an antilock

system?

5. How much stability degradation has testing showed with a vehicle

where one axle of a tandem was not controlled by ABS? Are there other

concerns (e.g., tire flat spotting) about an uncontrolled axle on a

tandem?

6. Would fleet operators be willing to spend an additional $300 per

vehicle to upgrade a 4S/3M system to a 4S/4M system with side-by-side

control or axle-by-axle control with in-axle sensors?

Comments on this notice must be received no later than 30 days

after its publication in the Federal Register. While NHTSA typically

provides a comment period of 60 days, the agency has determined that it

is in the public interest to limit the comment period to 30 days since

the agency is statutorily required to finish rulemaking in mid-1994. In

addition, the agency previously provided an opportunity in the

September 1993 NPRM to comment on these and other issues in this

rulemaking. This notice proposes relatively limited modifications in

the agency's tentative position regarding two of those issues.

Rulemaking Analyses

A. Executive Order 12866 (Federal Regulation) and DOT Regulatory

Policies and Procedures

This notice is ``significant'' within the meaning of Executive

Order 12866. Further, NHTSA has analyzed this supplemental proposal and

determined that it is also significant within the meaning of the

Department of Transportation regulatory policies and procedures. The

agency believes that the proposal to make the lateral stability and

control requirements concurrent with the stopping distance requirements

would reduce the rulemaking's costs, based on comments by the

manufacturers. The agency further believes that the proposal related to

wheel control would reduce cost. The agency's expectations upon issuing

the NPRM were that the ABS on trucks, truck tractors, and buses would

provide individual wheel control on at least one axle. As such, the

safety benefits and cost analyses documented in the Preliminary

Regulatory Impact Analysis were performed assuming that to be the case.

Therefore, the agency believes that no additional impact would result

from the changes proposed in this notice.

B. Regulatory Flexibility Act

NHTSA has also considered the effects of this rulemaking action

under the Regulatory Flexibility Act. Based upon the discussion in the

immediately preceding paragraph, I certify that this proposed rule

would not have a significant economic impact on a substantial number of

small entities.

C. Executive Order 12612 (Federalism)

NHTSA has analyzed this rulemaking action in accordance with the

principles and criteria contained in Executive Order 12612. NHTSA has

determined that the proposed rule would not have sufficient Federalism

implications to warrant the preparation of a Federalism Assessment.

D. National Environmental Policy Act

In accordance with the National Environmental Policy Act of 1969,

NHTSA has considered the environmental impacts of this proposed rule.

The agency has determined that this proposed rule, if adopted as a

final rule, would not have any adverse impact on the quality of the

human environment.

VII. Comments

Interested persons are invited to submit comments on the proposal.

It is requested but not required that 10 copies be submitted.

All 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.

All comments received before the close of business on the comment

closing date indicated above for the proposal will be considered. To

the extent possible, comments filed after the closing date will also be

considered. Comments received too late for consideration in regard to

the final rule will be considered as suggestions for further rulemaking

action. Comments on the proposal will be available for inspection in

the docket at the above address. NHTSA will continue to file relevant

information as it becomes available in the docket after the closing

date, and NHTSA 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 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.

List of Subjects in 49 CFR Part 571

Imports, Motor vehicle safety, Motor vehicles, Rubber and rubber

products, Tires.

In consideration of the foregoing, the agency proposes to amend

Standard No. 105, Hydraulic Brake Systems and Standard No. 121, Air

Brake Systems, in title 49 of the Code of Federal Regulations at part

571 as follows:

PART 571--[AMENDED]

1. The authority citation for part 571 would continue to read as

follows:

Authority: 15 U.S.C. 1392, 1401, 1403, 1407; delegation of

authority at 49 CFR 1.50.

2. Section 571.105 would be amended by amending S4 by adding the

following definitions, revising S5.5, and by adding S5.5.1 and S5.5.2.

The revised and amended paragraphs would read as follows:

Sec. 571.105 Standard No. 105; Hydraulic brake systems.

* * * * *

S4 Definitions

* * * * *

Directly controlled wheel means the wheel at which the degree of

rotational wheel slip is sensed and corresponding signals are

transmitted to a controlling device that adjusts the brake actuating

forces at that wheel. The control device may also adjust the brake

actuating forces at other wheels in response to those signals.

* * * * *

Independently controlled wheel means a wheel at which the degree of

rotational wheel slip is sensed and corresponding signals are

transmitted to one controlling device that adjusts the brake actuating

forces only at that wheel in response to those signals.

* * * * *

S5.5. Antilock and variable proportioning brake systems.

S5.5.1 Each vehicle with a GVWR greater than 10,000 pounds, except

for any vehicle that has a speed attainable in 2 miles of not more than

33 mph, shall be equipped with an antilock braking system that directly

controls the wheels of at least one front axle and the wheels of at

least one rear axle of the vehicle, with no more than two wheels being

controlled by one controlling output device. The wheels of at least one

axle shall be independently controlled.

S5.5.2 In the event of any failure (structural or functional) in

an antilock or variable proportioning brake system, the vehicle shall

be capable of meeting the stopping distance requirements specified in

S5.1.2 for service brake system partial failure.

* * * * *

3. Section 571.121 would be amended by amending S4 to add the

following definitions, revising S5.1.6, and by adding S5.1.6.1, S5.2.3.

and S5.2.3.1. The revised and added paragraphs would read as follows:

Sec. 571.121 Standard No. 121; Air brake systems.

* * * * *

S4. Definitions.

* * * * *

Directly controlled wheel means the wheel at which the degree of

rotational wheel slip is sensed and corresponding signals are

transmitted to a controlling device that adjusts the brake actuating

forces at that wheel. The control device may also adjust the brake

actuating forces at other wheels in response to those signals.

* * * * *

Full trailer means a trailer, except a pole trailer, that is

equipped with two or more axles that support the entire weight of the

trailers.

* * * * *

Independently controlled wheel means a wheel at which the degree of

rotational wheel slip is sensed and corresponding signals are

transmitted to one controlling device that adjusts the brake actuating

forces only at that wheel in response to those signals.

* * * * *

S5.1.6 Antilock brake system.

S5.1.6.1 Each vehicle shall be equipped with an antilock braking

system that directly controls the wheels of at least one front axle and

the wheels of at least one rear axle of the vehicle, with no more than

two wheels being controlled by one controlling output device. The

wheels of at least one axle shall be independently controlled.

* * * * *

S5.2.3 Antilock brake system.

S5.2.3.1(a) Each single axle trailer (including a trailer

converter dolly) shall be equipped with an antilock braking system that

directly controls the wheels of the axle of the vehicle.

(b) Each trailer with two or more rear axles (including a trailer

converter dolly) shall be equipped with an antilock braking system that

directly controls the wheels on at least 50 percent of the axles of the

vehicle, with no more than two wheels being controlled by one

controlling output device.

(c) Each full trailer shall be equipped with an antilock braking

system that directly controls the wheels of at least one front axle of

the vehicle and at least 50 percent of the rear axles of the vehicle,

with no more than two wheels being controlled by one controlling output

device.

Issued on April 7, 1994.

Barry Felrice,

Associate Administrator for Rulemaking.

[FR Doc. 94-8753 Filed 4-11-94; 8:45 am]

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