Federal Motor Vehicle Safety Standards; Hydraulic Brake Systems; Passenger Car Brake Systems

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. 85-06; Notice 8]

RIN 2127-AA13

Federal Motor Vehicle Safety Standards; Hydraulic Brake Systems;

Passenger Car Brake Systems

AGENCY: National Highway Traffic Safety Administration (NHTSA),

Department of Transportation.

ACTION: Final rule.

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SUMMARY: This rule establishes a new Federal motor vehicle safety

standard, FMVSS No. 135, Passenger Car Brake Systems, and replaces

Standard FMVSS No. 105, Hydraulic Brake Systems, as it applies to

passenger cars. NHTSA's decision to establish the new standard results

from the agency's efforts to harmonize its standards with international

standards. The agency has determined that this new standard will

achieve the goal of international harmonization while remaining

consistent with the statutory mandate to ensure motor vehicle safety.

DATES: Effective Date: The amendments made by this rule are effective

March 6, 1995. As of this date, manufacturers have the option of

complying with either FMVSS No. 105 or with FMVSS No. 135. Compliance

with FMVSS No. 135 becomes mandatory on September 1, 2000.

Petitions for Reconsideration: Any petition for reconsideration of

this rule must be received by NHTSA no later than March 6, 1995.

[[Page 6412]]

ADDRESSES: Petitions for reconsideration should be submitted to:

Administrator, National Highway Traffic Safety Administration, 400

Seventh Street SW., Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Ms. Terri Droneburg, Office of Vehicle

Safety Standards, National Highway Traffic Safety Administration, 400

Seventh Street SW., Washington, DC 20590 (202) 366-6617.

SUPPLEMENTARY INFORMATION:

TABLE OF CONTENTS

I. Background

A. Federal Motor Vehicle Safety Standards

B. European Braking Requirements

C. Harmonizing US and European Braking Requirements

D. Antilock Brake Systems

II. Summary of comments on the 1991 SNPRM (Notice 5)

III. NHTSA Decision

A. Overview

B. Application

C. Definitions

D. Equipment Requirements

1. Lining Wear Indicator

2. ABS Disabling Control Switch

3. Vehicle and Reservoir Labeling

4. Brake System Warning Indicator

E. General Test Conditions

1. Ambient Temperature

2. Road Test Surface

3. Instrumentation

F. Road Test Procedures and Performance Requirements

1. Permissible Wheel Lockup

2. Road Test Sequence

3. Pre-Burnish

4. Burnish

5. Adhesion Utilization

a. General

b. Wheel Lock Sequence Test

c. Torque Wheel Test

6. Cold effectiveness

7. High speed effectiveness

8. System failure

a. Stops with Engine Off

b. Antilock Functional Failure

c. Variable Proportioning Functional Failure

d. Hydraulic Circuit Failure

e. Power Assist Unit Inoperative

9. Parking brake requirements

a. Dynamic

b. Static

10. Fade and Recovery

a. Heating Snubs

b. Hot Performance

c. Recovery Performance

G. Miscellaneous Issues

IV. Regulatory analysis

A. Executive Order 12866 and DOT Regulatory Policies and

Procedures

B. Regulatory Flexibility Act

C. Executive Order 12612 (Federalism)

D. Executive Order 12778 (Civil Justice Reform)

E. National Environmental Policy Act

I. Background

A. Federal Motor Vehicle Safety Standards

The National Traffic and Motor Vehicle Safety Act (``the Safety

Act''), recently revised and codified ``without substantive change'' at

49 U.S.C. Chapter 301, authorizes the National Highway Traffic Safety

Administration (NHTSA) to issue Federal motor vehicle safety standards

(FMVSS) to ensure motor vehicle safety. The Safety Act requires that

each FMVSS be objective and practicable so that a manufacturer can

certify that each of its vehicles meets all applicable standards. Each

FMVSS specifies the performance requirements and any necessary test

conditions and procedures that NHTSA uses in its periodic tests of

motor vehicles and motor vehicle equipment. Each tested vehicle must

meet the objective requirements contained within the applicable FMVSS.

Under this self-certification system, the government does not

subjectively approve or disapprove a type of vehicle or a type of

braking system.

B. European Braking Requirements

Unlike the self-certification system used in the United States, the

European community has established a ``type approval'' system in which

the government approves each type of motor vehicle or item of motor

vehicle equipment, based on whether it can meet the safety

requirements. For example, the current United Nations Economic

Commission for Europe (ECE) braking regulation, Regulation 13 (R13) and

its proposed harmonized regulation, R13H, use a calculation method to

determine the adhesion utilization of a vehicle as designed.

Manufacturers submit their calculations (or the input parameters

necessary to make the calculations) to governmental authorities along

with a prototype vehicle, and the governments then approve or

disapprove the vehicle type based on a review of those calculations and

testing of actual vehicles.

C. Harmonizing US and European Braking Regulations

In order to eliminate any unnecessary non-tariff barriers to trade

in accordance with the General Agreement on Tariffs and Trade (GATT),

the United States has participated in discussions held within the

Meeting of Experts on Brakes and Running Gear (GRRF) of the ECE. As a

result of these discussions, NHTSA has issued a series of rulemaking

notices proposing to establish a new FMVSS, FMVSS No. 135, Passenger

Car Brake Systems. Likewise, the GRRF has also developed a proposed new

Regulation 13-H, which would be compatible with FMVSS No. 135.

Throughout the rulemaking, NHTSA has emphasized that any requirements

it adopts must be consistent with the need for safety and the Safety

Act. The agency emphasizes that safety cannot be sacrificed in its

efforts to harmonize the FMVSS with the ECE regulations.

On May 10, 1985, NHTSA published in the Federal Register (50 FR

19744) a notice of proposed rulemaking (NPRM; Docket 85-06, Notice 1)

to establish FMVSS No. 135, which would replace FMVSS No. 105 as it

applies to passenger cars. On January 14, 1987, NHTSA published in the

Federal Register (52 FR 1474) a supplemental notice of proposed

rulemaking (SNPRM; Docket 85-06, Notice 4), to improve and refine the

proposed Standard. On July 3, 1991, NHTSA published in the Federal

Register (56 FR 30528) a second SNPRM (Docket 85-06, Notice 5) as a

result of comments on the SNPRM and vehicle testing by NHTSA.

In these previous notices, NHTSA set out its overall approach to

developing the proposed harmonized standard. The agency stated that the

new standard would differ from the existing one primarily in containing

a revised test procedure based on harmonized international procedures

developed during discussions held between NHTSA and GRRF. NHTSA stated

its belief that the new FMVSS would ensure the same level of safety for

the aspects of performance covered by FMVSS No. 105, while improving

safety by addressing some additional safety issues. The agency proposed

establishing new adhesion utilization requirements that it believes

would ensure stability during braking under all friction conditions.

In this final rule, after considering the public comments on all of

the notices, NHTSA has made several minor revisions to the requirements

proposed in the July 1991 SNPRM. This document explains the changes

incorporated in the final rule and the reasons for the agency's

decision.

D. Antilock Brake Systems

One issue that NHTSA considered during the process of developing a

harmonized standard was what requirements are appropriate for vehicles

equipped with antilock brake systems. While NHTSA was evaluating

comments to the July 1991 SNPRM, Congress enacted the Highway Safety

Act of 1991, which directs NHTSA to publish an advance notice of

proposed rulemaking (ANPRM) to consider the need for additional brake

performance

[[Page 6413]]

standards for passenger cars, including ABS standards. (59 FR 281,

January 4, 1994.) Vehicles included in this evaluation effort are

passenger cars, light trucks, and multi-purpose vehicles (MPV's).

Given that NHTSA is reviewing the need for antilock systems

separately, the agency has decided not to include requirements

addressing ABS performance in this final rule to establish FMVSS No.

135. The previously proposed section on ABS will be reserved until all

the issues in the research program have been evaluated. At that time,

the agency will consider how best to proceed with requirements

applicable to ABS on light vehicles and may initiate a separate

rulemaking for that purpose.

II. Summary of Comments on the July 1991 SNPRM (Notice 5)

Over 30 commenters responded to the July 1991 SNPRM. Commenters

included vehicle manufacturers, brake manufacturers, international

organizations, safety advocacy groups, and individuals. The commenters

addressed a wide range of topics, including adhesion utilization, the

various effectiveness requirements, equipment requirements such as the

failure warning indicators, and test conditions such as the road test

surface, lockup conditions, burnish procedures, and the

instrumentation.

Advocates for Highway and Auto Safety (Advocates) and the Center

for Auto Safety (CAS) generally opposed the supplemental proposal,

believing that the proposed FMVSS No. 135 was less stringent than FMVSS

No. 105 and the previous harmonization proposals. Advocates and CAS

opposed several specific proposals in the 1991 SNPRM, including the

increase in certain stopping distances, eliminating automatic brake

warning indicators, specifying certain aspects of the new adhesion

utilization test, eliminating the pre-burnish test, changing the

burnish testing procedure and the fade and recovery sequence, allowing

momentary wheel lockup, and introducing peak friction coefficient (PFC)

values as a substitute for skid numbers in defining the adequacy of

testing surfaces.

In contrast, the former Motor Vehicle Manufacturers Association

(MVMA),1 General Motors (GM), Ford, Chrysler, and manufacturers

from Europe and Japan have strongly supported harmonized safety

standards in general and a harmonized passenger car brake standard in

particular. For instance, GM stated that the payoff for successfully

harmonizing brake regulations is significant. When the U.S. and

European regulations are commonized, it is most probable that this

uniform set of requirements will be recognized and accepted throughout

all vehicle importing and exporting countries. This will enable

manufacturers to build vehicles with standardized brake systems

acceptable throughout the world, thereby providing significant cost

savings to vehicle buyers. It continued that harmonization of brake

regulations will also represent an important milestone in the ongoing

efforts to commonize motor vehicle safety regulations, and thereby

dismantle one of the most significant non-tariff barriers to

international motor vehicle trade.

\1\ The MVMA became the American Automobile Manufacturers

Association in early 1993. This notice will refer to the group by

its former name, MVMA. The membership of the new group is slightly

different than that of the MVMA, and to refer to the group by its

new name would lead to imprecision in indicating which manufacturers

were represented by its comments.

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Notwithstanding their general support for harmonization, vehicle

manufacturers expressed concern about what they perceive as the

increased stringency of portions of FMVSS No. 135 in relation to FMVSS

No. 105.

III. NHTSA Decision

A. Overview

After reviewing the comments, NHTSA has decided to establish FMVSS

No. 135, with respect to hydraulic brake systems on passenger cars. The

new standard includes equipment requirements, dynamic road test

requirements, system failure requirements, and parking brake

requirements, as well as test conditions and procedures related to

these requirements. With respect to the equipment requirements, FMVSS

No. 135 includes provisions addressing the brake lining wear indicator,

an ABS disabling switch, reservoir labeling, and a brake system warning

indicator. With respect to the test conditions, FMVSS No. 135 includes

provisions addressing the ambient temperature, the road test surface,

instrumentation, and the initial brake temperature. With respect to the

dynamic road tests, FMVSS No. 135 includes provisions addressing

permissible wheel lockup, the test sequence, burnish, the wheel lock

sequence test, the torque wheel test, the cold effectiveness test, the

high speed effectiveness test, the hot performance test, and the fade

and recovery test. FMVSS No. 135 also includes requirements for a

static parking brake test and several types of system failure tests,

including stops with the engine off, ABS functional failure,

proportional valve functional failure, hydraulic circuit failure, and

power assist failure.

The following discussion follows the order set forth in the

regulatory text for FMVSS No. 135 to facilitate the reader's

understanding of the issues.

B. Application

In each previous proposal, NHTSA proposed that FMVSS No. 135 would

apply to passenger cars. Kelsey-Hayes asked whether this definition

included all purpose vehicles, mini-vans, and light trucks.

NHTSA notes that 49 CFR 571.3 defines passenger car, multipurpose

passenger vehicle, and truck. All purpose vehicles and mini-vans

ordinarily come within the definition of multipurpose passenger

vehicle. At this time, FMVSS No. 135 will apply only to passenger cars

and not to multipurpose passenger vehicles or trucks, although

application to other types of vehicles may be considered at a later

date.

C. Definitions

In the 1991 SNPRM (Notice 5), NHTSA proposed definitions for

certain terms, including directly controlled wheel and antilock brake

system.

Bendix and Mercedes Benz requested a clarification of the

definition of an ABS ``directly controlled wheel.'' Bendix recommended

that the definition include a select average or drive shaft sensor

control of an axle, which it believed would provide sufficient accuracy

to control individual wheel slip, thereby avoiding adhesion utilization

testing. GM commented that the definition in the 1991 SNPRM would

prohibit a type of ABS control known as ``select low'' that uses a

single, centrally located sensor on the rear axle to partially control

the systems operation.

Given that NHTSA is considering whether to equip vehicles with ABS

in a separate rulemaking, the agency has decided that it is not

necessary at this time to define ``directly controlled wheel.''

Accordingly, this term is not included in the definition section of the

regulatory text. The agency may revisit this issue if the agency

decides to propose requirements for antilock brakes on passenger cars.

The agency has included a new definition for ``antilock brake system.''

The GRRF and Fiat requested that the definition of initial brake

temperature be based on the temperature of the hottest service brake

rather than the average of both brakes on an axle, claiming that there

should be little difference in the ``cold'' temperature across each

axle.

[[Page 6414]]

After reviewing the comments, NHTSA has determined that there is no

reason to modify the proposed initial brake temperatures. Commenters

provided no convincing data or arguments to support their requested

changes to initial brake temperatures that have been proposed in the

NPRM and the two SNPRMs.

D. Equipment Requirements

1. Lining Wear Indicator

In the 1991 SNPRM (Notice 5), NHTSA proposed that the harmonized

standard include requirements to warn the driver about excessive brake

wear. Specifically, this warning could be done either by a device that

warns a driver that lining replacement is necessary or by a device that

provides a visual means of checking brake lining wear from outside the

vehicle. The agency believed that this proposal would reduce the

likelihood that cars would be driven with excessively worn brake

linings.

Advocates recommended that all cars have an in-cab visual or

audible alarm, stating that an outside visual check would be

ineffective, therefore resulting in many owners being unaware of brake

lining deterioration. Advocates further stated that the increasing

intervals between maintenance checks required of newer cars means that

repair personnel would not have an opportunity to discover brake lining

wear before it reaches dangerous levels. Honda commented that, for drum

brakes, inspection holes on drums may be insufficient to spot the areas

of worst brake wear, and recommended allowing removal of the brake

drum.

After reviewing the comments, NHTSA continues to believe that the

proposed requirements for warning drivers about excessive brake wear

are appropriate. Section S5.1.2 of FMVSS No. 135 requires a

manufacturer to warn of worn brake linings in one of two ways: (1) An

acoustic or optical device warning the driver at his or her driving

position, or (2) a visual means of checking brake lining wear from the

outside or underside of the vehicle, using tools or equipment normally

supplied with the vehicle. The agency notes that FMVSS No. 105 does not

require an in-cab warning indicator. Based on this fact, the agency

disagrees with Advocates about the need to mandate an in-cab visual or

audible alarm.

NHTSA has decided not to adopt Honda's request to allow the removal

of the drum brake to identify the wear status. The agency believes that

it has provided appropriate ways to determine excessive brake wear. The

agency is concerned that adopting Honda's request might be detrimental

to safety.

VW, Fiat, Mercedes Benz, GRRF, and Toyota requested that the agency

permit the use of the International Organization for Standardization

(ISO) brake symbol, a circle with two arcs outside the circle on

opposite sides, for the brake wear indicator in lieu of the proposed

words. The commenters stated that symbols are more appropriate for a

harmonized standard.

NHTSA has decided to permit use of the ISO symbol as a supplement

to the words ``brake wear.'' Nevertheless, the agency believes that it

would be inappropriate to allow only the ISO symbol as an alternative

to the required words. The agency believes that the symbol's meaning

would be unclear or ambiguous to a driver, since in this country they

are not generally understood to represent the concept of brake wear.

2. ABS Disabling Control Switch

In the 1991 SNPRM (Notice 5), NHTSA proposed (S5.3.2) to prohibit,

for vehicles equipped with ABS, a manual control that would fully or

partially disable the ABS. Previous notices did not address an

automatic disabling switch. The subject was discussed within GRRF,

however, and it was decided that R13H would not allow a disabling

switch.

JAMA, and Toyota requested a change in the regulatory text to

permit ABS disabling switches for off-road vehicles. The commenters

stated this is necessary because ABS tends to lengthen stopping

distances in rough, gravelly, or muddy terrain. MVMA, Chrysler and Ford

opposed permitting a manual ABS disabling switch, but wanted the agency

to allow an intelligent or automatic switch (i.e., one not controlled

by the vehicle occupants) to accommodate off-road conditions.

NHTSA has decided not to permit either a manual or an automatic ABS

disabling switch. The agency notes that no commenter requested any kind

of ABS-disabling switch for passenger cars, which are the subject of

this rulemaking. Moreover, Mercedes, MVMA, Ford, and Chrysler stated

that passenger cars should not have an ABS disabling switch. While

those commenters favoring an ABS disabling switch focused on its use

for off-road vehicles, FMVSS No. 135 applies only to passenger cars as

defined in Sec. 571.3(b). These definitions preclude including MPV's as

passenger cars. The agency therefore believes that there is no reason

to permit an ABS-disabling switch under the new standard.

3. Vehicle and Reservoir Labeling

In the 1991 SNPRM (Notice 5), NHTSA proposed requirements for the

reservoir label in S5.4.3 and the warning indicators in S5.5.5. The

agency tentatively concluded that it would be inappropriate to allow

use of ISO symbols with respect to these devices, except that such

symbols could be used in addition to the required labeling to enhance

clarity. The agency noted that this was consistent with FMVSS No. 101,

Controls and Displays and past agency decisions made in response to

petitions for inconsequential noncompliance based on the use of ISO

symbols in place of words or symbols required by FMVSS No. 101.2

The agency has denied these petitions in cases where it believed that

the symbol's meaning would not be readily apparent to drivers.

\2\NHTSA notes that FMVSS No. 101 allows the use of some ISO

symbols, but not the ones at issue.

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VW, Fiat, Mercedes Benz, and Toyota commented that the agency

should permit use of the ISO brake symbol in FMVSS No. 135 in lieu of

the words ``brake,'' ``park,'' or ``parking brake,'' and in lieu of the

words ``ABS'' or ``anti-lock'' for ABS failure. GRRF stated that

symbols are more appropriate for international use than words in any

single language.

Notice 5 and this final rule (Section S5.5.5(a)) allow the use of

ISO symbols in addition to the required labeling for the purpose of

clarity. However, the agency has decided not to allow the ISO symbol

alone to be used as a substitute for the required words. NHTSA believes

that the ISO symbol can be ambiguous to some drivers since the ISO

symbol, is not universally understood to represent brakes. The agency

notes that the commenters did not provide any data showing that the ISO

brake failure warning indicator is clearly understood by drivers in

countries in which it is currently in use. Moreover, the meaning of the

symbol is not readily apparent from its appearance, in contrast to some

symbols, such as the one for horns, whose meaning is understandable on

its face.

Fiat and the GRRF requested that S5.4.3 be amended to allow the ISO

brake fluid symbol to be used on the brake reservoir instead of DOT

fluid designations.

NHTSA has decided not to allow the ISO symbol instead of the DOT

brake fluid designations (e.g., DOT 3, DOT 4, and DOT 5). The purpose

of this requirement is to inform drivers about what kind of brake fluid

to add to their vehicles and to avoid use of an improper fluid. The

agency notes that

[[Page 6415]]

the ISO has no rating equivalent to DOT 5 fluid and does not

differentiate between DOT 3 and DOT 4 fluids. Even though the agency

has decided not to allow use of the ISO symbol, a manufacturer may use

the ISO symbol as a supplement to the required textual words.

4. Brake System Warning Indicators

In the SNPRMs (Notices 4 and 5), NHTSA proposed to require (S5.5.2)

brake system malfunction indicators to be activated by either an

automatic brake indicator check function or a manual check function.

While FMVSS No. 105 currently requires brake indicator lamps to be

activated automatically when the vehicle is started, in Europe the

check function often requires manual action, such as pressing a button

or applying the parking brake.

Advocates and CAS opposed the use of a manual check function to

check brake system integrity in lieu of an automatic check function.

Advocates argued that the existing requirement for all operating

systems to be automatically monitored for the driver when turning the

ignition key has been ``one of the great advances in American

automobile regulation'' and disagrees that the need for safety will be

met by this approach.

After reviewing the available information, NHTSA has decided to

permit the manual check function in the final rule, as an alternative

to the automatic check function. The agency believes that requiring an

automatic check function is not necessary to ensure safety. Moreover,

the agency has granted several petitions for inconsequential

noncompliance from manufacturers that did not provide an automatic

check function. These decisions to grant the petitions are consistent

with the agency's current belief that allowing use of a manual brake

warning indicator, which is consistent with international

harmonization, will not have any corresponding detriment to safety.

BMW recommended that NHTSA modify S5.5.3 which specifies the

duration during which an indicator is activated. BMW claimed that some

ABS warning indicators can only be detected after a certain minimum

wheel speed is achieved. Accordingly, it requested that the antilock

failure indicator only be required to activate when a road speed of 10

km/h is achieved.

While NHTSA agrees with BMW that the wheel must be rotating to

properly check a wheel sensor, the agency believes that it is important

for the check function to be able to be performed while the vehicle is

stationary. Given the current state of technology, NHTSA believes that

the ABS malfunction warning system can be designed to remember if there

had been an ABS sensor failure the last time the vehicle's speed was

over the threshold, even after the ignition has been turned off.

Accordingly, BMW's request is denied.

VW recommended decreasing the minimum lettering height for the

brake warning indicator letters to 2 mm (5/64-inch), claiming that the

proposed 3.2 mm (1/8-inch) height is larger than necessary.

NHTSA has decided to retain the minimum letter height, based on its

concern that some drivers, especially elderly drivers, would not be

able to distinguish letters under 3.2 mm. The agency further notes that

the 1/8'' dimension is the same as the dimension currently specified in

FMVSS No 105.

Kelsey-Hayes commented that, if a separate indicator is used for

ABS failure, rear-only ABS equipped vehicles should use a failure

indicator specifying ``Rear Anti-lock.''

NHTSA believes that it would be inappropriate to require the words

``Rear Anti-Lock'' to distinguish a rear wheel ABS from a four wheel

ABS. The indicator's purpose is to inform the operator that there is a

malfunction with the vehicle's ABS. The driver should be aware, through

the owner's manual and/or information provided at the time of the

vehicle's purchase, whether it is equipped with a four-wheel or rear-

only ABS. However, even though the agency will not require this

information, adding the word ``rear'' to the ABS failure warning is not

prohibited under the standard.

Kelsey-Hayes stated that both red service brake failure warning

indicators ``Brake'' and yellow ``ABS'' malfunction indicators should

be activated simultaneously in the case of a service brake failure in

cars equipped with separate lights.

NHTSA disagrees with Kelsey-Hayes' recommendation for simultaneous

activation of both lights in case of a service brake failure, unless

the service brake failure is one that also disables or impairs the

operation of the ABS. The two lights signal different types of

failures, with different consequences. There can be failures that

affect both systems, in which case both indicators would activate.

However, automatically activating the ABS indicator in case of any

service brake failure would be misleading, and therefore inappropriate.

E. General Test Conditions

1. Ambient Temperature

In S6.1.1 of the 1991 SNPRM, NHTSA proposed that for all tests

specified in S7, the ambient temperature be between 0 deg.C (32 deg.F)

and 40 deg.C (104 deg.F).

Bendix commented that NHTSA should permit the low adhesion tests to

be conducted at temperatures less than 32 deg.F because the ambient

temperature provision requires testers either to wet the test surface

or artificially make ice.

NHTSA notes that the issue of low temperature testing is moot since

Bendix's comment was made with respect to the ABS performance test in

proposed S7.3, which the agency has decided not to adopt in today's

final rule. Even if this test had been adopted, NHTSA notes that it

would be unnecessary to use ice to represent a low PFC. The agency

further notes that no other commenter suggested the need to use ice for

any test.

2. Road Test Surface

In the 1991 SNPRM, NHTSA proposed that the primary stopping

distance tests be performed on a test surface with a PFC of 0.9. This

road test surface specification differed from FMVSS No. 105, the NPRM,

and the 1987 SNPRM, all of which specified a skid number of 81 to

define the road test surface. In response to comments to Notice 4,

NHTSA decided to propose a PFC for the test surface. The agency noted

that PFC is a more relevant surface adhesion measurement for the non-

locked wheel tests required by FMVSS No. 135, since the maximum

deceleration attained in a non-locked wheel stop is directly related to

PFC, but not skid number.

Fiat, Toyota, and GRRF stated that ECE R13 specifies that the test

surface should be ``a road surface affording good adhesion.'' VW

requested that the standard provide the option of specifying either a

skid number or a PFC.

NHTSA, after reviewing its test data and other available

information, continues to believe that a PFC of 0.9 is an appropriate,

objective value for the test surface. ECE R13's specification that the

road surface should afford ``good adhesion'' is unreasonably subjective

and therefore inappropriate for an FMVSS. Such an imprecise test

condition would lead to unreasonable variability, thereby causing test

results that varied based on the road surface and not the vehicle's

actual braking ability. Similarly, it would be inappropriate to allow

the optional use of skid numbers, which would result in unnecessary

variability, since the same

[[Page 6416]]

vehicle might have different test results based on which method was

used to define the test surface. As explained in the 1991 SNPRM (Notice

5), PFC is more relevant than skid number for the non-locked wheel

tests, since the maximum deceleration that can be attained in a non-

locked wheel stop is directly related to PFC, which represents the

maximum friction available.

GM and MVMA requested that the agency adopt a dry road PFC of 1.0,

since compared with a PFC of 0.9, they believe 1.0 more closely

parallels a skid number of 81 specified in FMVSS No. 105. Ford

requested that the test surface be specified at 0.95 PFC. GM stated

that not raising the PFC to 1.0 would require manufacturers to

compensate for the loss of adhesion by equipping vehicles with higher

rolling resistance tires, which would adversely affect the fuel economy

of GM's car fleet by 1.2 mpg. GM further commented that compared with

FMVSS No. 105, a cold effectiveness stopping distance of 70 m on a PFC

of 0.9 would significantly increase the requirement's stringency.

Based on industry-government cooperative testing to evaluate the

effect of fluctuations of PFC on vehicle stopping performance, NHTSA

has determined that a PFC of 0.9 reasonably represents stopping on a

dry surface and will not be a significant source of variability in the

stopping3 distance tests. While this testing focused on heavy

vehicle stopping performance, the agency believes that the test

findings are applicable to passenger cars subject to FMVSS No. 135,

since the tests addressed the road surface coefficients of friction.

Testing indicates that the expected minor variability of a high

coefficient of friction surface appears to have a negligible impact on

vehicle stopping distance performance. Variation of the average

stopping distances for the six different surfaces was small, with the

deviation from the average being only 5 feet. Accordingly, the agency

believes that any variability in the stopping performance on a high

coefficient of friction surface is more likely due to variation in the

vehicle's performance rather than test surface variability.

\3\``MVMA/NHTSA/SAE Round Robin Brake Test,'' Transportation

Research Center of Ohio, Report No. 091194, August 26, 1991.

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NHTSA has decided that a test road surface specification of PFC 1.0

would result in practicability problems for the agency. It would have

to conduct compliance testing on a surface with a PFC higher than 1.0.

Such a surface is difficult to find. The agency also notes that GM

conducted an extensive survey of actual road surfaces, which indicated

that a PFC of 0.9 is fairly typical.

As explained in detail in NHTSA's decision to require heavy

vehicles to be equipped with antilock brake systems, using PFC values

to express test surfaces is appropriate even though these values may

indicate some fluctuation. Given this fluctuation, the agency has

considered whether the fluctuation significantly affects the

requirement's objectivity. In an earlier rulemaking about FMVSS No.

208, Occupant Crash Protection, the agency explained that since some

variability in any test procedure is inherent, the agency need only be

concerned about preventing ``unreasonable'' or ``excessive''

variability to avoid causing manufacturers to ``overdesign'' vehicles

to exceed the minimum levels of protection specified by the Federal

safety standards. (49 FR 20465, May 14, 1984; 49 FR 28962, July 17,

1984.) With respect to the tests in FMVSS No. 135, variability of the

PFC value of the test surface will have a negligible impact on a

vehicle's ability to comply with the requirements.

Ford stated that it would be impossible to build a track to exactly

a PFC of 0.9, given PFC variability, test tire variability, and

changing track surfaces due to aging and weathering.

In evaluating the requirement's practicability, NHTSA has

considered possible difficulties with respect to building and

maintaining test surfaces with a PFC of 0.9 for the high coefficient

stopping tests. (Those interested in building and maintaining a test

surface should refer to NHTSA's ``Manual for the Construction and

Maintenance of Skid Surfaces,'' (DOT HS 800 814.) Variations in PFC for

high coefficient of friction surfaces do not affect stopping distance

test results appreciably. After reviewing the comments and available

information, NHTSA has concluded that specified test surfaces can be

achieved and maintained. As explained above, recent ``Round Robin''

testing related to research about heavy vehicle braking by the agency

and others on several test tracks indicates that the test surface

specification does not raise practicability or objectivity concerns.

MVMA, GM, and Ford recommended use of a correction factor for

stopping distance to account for testing on surfaces with PFCs that

differed from those prescribed in the standard. They stated that a

manufacturer is fortunate if the tests they conduct are actually

carried out on surfaces with the precise PFC as specified in the

harmonized standard.

NHTSA believes that it would be inappropriate to specify a stopping

distance correction factor, as requested by the comments. The agency

notes that the same variables that will apply to manufacturer testing

in accordance with FMVSS No. 135 also applied to their testing under

FMVSS No. 105, and no correction factor was established or needed at

the time. NHTSA further notes that a manufacturer may test its vehicles

on whatever surface it likes, and may make any corrections it chooses.

The FMVSS specifies requirements with which manufacturers must certify

that their vehicles comply on a given surface under specified test

conditions. Moreover, the agency will follow the procedures specified

in the FMVSS for purposes of compliance testing. If a manufacturer is

confident that its testing on a different surface will yield results

comparable to agency test results under FMVSS No. 135 (by applying a

correction factor), it need not exactly follow every agency

specification.

Advocates opposed the proposal to replace skid numbers with PFC. It

claimed that PFC numbers cannot be correlated to skid numbers because

they do not describe the same event. Advocates further commented that

most state highway authorities use skid numbers to evaluate a roadway's

skid resistance, and that NHTSA would make it impossible for data

comparison by encouraging different authorities to use different

measurement standards. In contrast, Fiat, Ford, ITT-Teves, GRRF, OICA,

Mercedes, and MVMA stated that using PFC rather than skid numbers will

lead to more repeatable road surface adhesion measurements and that PFC

directly correlates to vehicle stopping distance.

PFC and skid number can both be measured simultaneously during

traction tests. However, the two road surface specifications are used

for different purposes. Highway officials use skid numbers to determine

when to resurface a road, not to determine test vehicle performance in

stopping tests. The agency notes that because FMVSS No. 135 evaluates a

vehicle's capability during braking to use the available friction

capability at the interface between the tire and road, PFC is the more

appropriate measure for that purpose. It is not necessary to establish

a correlation between the two numbers, for any given surface.

While ITT-Teves, MVMA, and Ford agreed with the proposed use of the

ASTM test tire and test procedure, the GRRF, VW, Mercedes Benz, Fiat,

and OICA, stated that the ASTM test methods for determining PFC are not

[[Page 6417]]

familiar in Europe. They requested NHTSA to consider other methods of

determining adhesion or PFC, but suggested no specific test method or

procedure.

NHTSA is aware that the ASTM trailer and test method are not widely

used outside of the United States. However, any method of determining

PFC specified in the standard must be objective and repeatable. Those

commenters that requested consideration of other methods did not

provide any evidence that there are other standardized methods in

existence that are as objective, repeatable, and universally accepted

as the ASTM method that has been specified.

NHTSA also notes that the concerns expressed by several European

entities about compliance need not adversely affect them, since the

agency does not insist that any manufacturer use a specific test method

or procedure. Rather, the individual manufacturer must determine

whether to test exactly to the specifications of FMVSS No. 135 or to

use its own methods of determining that its braking systems will meet

the requirements of the standard. NHTSA, as stated earlier, will use

the procedures established in FMVSS No. 135 in its own testing. The

agency has decided to specify the ASTM test procedure for all of its

compliance tests. The agency emphasizes that GRRF's suggested wording

(i.e., ``a surface affording good adhesion'') would be inappropriate

for a Federal safety standard since it is not objective. The two

specifications are not in conflict with each other, however. Because

NHTSA's goal is to define ``good adhesion'' objectively, the agency has

decided to specify a surface measured with a standard test method to a

specific adhesion level.

Honda recommended that the test condition state ``PFC shall be

situated between the slip ratio of 10 to 30 percent and the friction

coefficient of the road surface.'' It stated that this slip ratio was

appropriate because most roads are within this range. It stated that

slip ratios can vary even if PFC value remains constant.

NHTSA believes that slip ratios are not appropriate for defining a

pavement surface to be used for stopping distance tests, because the

minimum stopping distance is obtained at the maximum traction value,

which is defined directly by the PFC. The agency believes that it is

most important to provide a surface with the available traction defined

so that all vehicles have an equal chance for achieving the shortest

stop, regardless of the optimum vehicle slip ratio for each vehicle.

For a given PFC, the vehicle slip ratio at which maximum traction is

achieved varies depending on the vehicle characteristics. Accordingly,

slip ratio cannot be used to define a test surface, because it is

vehicle- dependent.

3. Instrumentation

In the 1991 SNPRM (Notice 5), NHTSA specified in S6.4, the

instrumentation to measure brake temperature, brake line pressure, and

brake torque.

The GRRF, Ford, Fiat, and VW recommended that NHTSA allow

alternative methods to measure brake temperature. Ford stated that plug

type thermocouples develop problems as brake pad wear occurs and that

use of rubbing-type thermocouples would reduce cost and time.

NHTSA notes that a standard must include a specific method to

ensure objectivity, so that the requirements are the same for all

vehicles. In addition, a specific method ensures uniformity and thus

facilitates compliance testing. The specification of plug-type

thermocouples is the same as specified in Society of Automotive

Engineers' (SAE) Recommended Practices and is identical to that

specified in FMVSS No. 105, FMVSS No. 121, and FMVSS No. 122. The

agency is not aware of any problems resulting from use of this

procedure. NHTSA further notes that while the agency will use plug type

thermocouples specified in S6.4.1 for its own testing, a manufacturer

may use whatever type of brake temperature measuring device it prefers

for its own testing. Nevertheless, NHTSA does not recommend using

rubbing-type thermocouples in FMVSS No. 135, based on agency testing

that indicates that the two types of thermocouples give different

readings for brake temperature.

Bendix recommended that NHTSA specify whether brake linings can be

heated up to an initial brake temperature (IBT) before the static

parking brake test and that a procedure be specified. The procedure

would be important for vehicles with parking systems not utilizing the

service friction elements.

NHTSA notes that IBT as defined in S4, and S6.5.6, describes the

procedure for establishing IBT, and S7.12.2(a) sets the maximum IBT (no

minimum) for the parking brake test regardless of the type of friction

elements. The non-service brake friction materials should not be heated

because under normal driving circumstances they are never used (heated

up) until the parking brake is applied after the vehicle stops. This is

not necessarily the case with service brake friction materials.

Therefore, it would be unrealistic to describe a heating procedure.

However, the agency has decided to revise section S7.12.2(a) as

follows to clarify the requirements on IBT for both service and non-

service parking brake friction materials. Specifically, the revised

language makes clear that IBT applies to both service and parking brake

friction materials.

``7.12.2(a) IBT.

(1) Parking brake systems utilizing service brake friction

materials shall be tested with the IBT 100 deg.C

(212 deg.F) and shall have no additional burnishing or artificial

heating prior to the start of the parking brake test.

(2) Parking brake systems utilizing non-service brake friction

materials shall be tested with the friction materials at ambient

temperature at the start of the test. The friction materials shall have

no additional burnishing or artificial heating prior to or during the

parking brake test.''

F. Road Test Procedures and Performance Requirements

1. Permissible Wheel Lockup

In the 1991 SNPRM (Notice 5), NHTSA proposed to allow wheel lockup

of 0.1 seconds or less of any wheel during several road tests. This

differed from earlier proposals that prohibited any type of lockup. The

agency concluded that, due to pavement irregularities, it would be

extremely difficult for a test driver to achieve maximum deceleration

without causing momentary lockup of one or more wheels. The agency

believed that the brief lockup time permitted would not result in

vehicle instability, especially considering that, even ABS controlled

brakes occasionally undergo nominal, self-correcting lockup conditions

for very short periods of time.

Advocates and CAS opposed permitting any lockup, stating that it

may result in vehicle instability. Advocates believed that allowing

momentary lockup would result in the sale of more rear-biased vehicles

that are susceptible to skidding. Bendix recommended a revised wheel

lock criteria to increase the permitted lockup time, stating that it

would take longer than 0.1 seconds for a driver to detect and react to

wheel lock up. It believed that this would lead to less aggressive

driver performance in testing to FMVSS No. 135 specifications, as

drivers tried to avoid any type of lockup.

NHTSA has decided to permit a minimal amount of wheel lock up to

facilitate vehicle testing. The agency believes that it will not be

detrimental to safety as alleged by Advocates.

[[Page 6418]]

Allowing momentary wheel lockup during compliance testing will not

affect a vehicle's real world ability to lock or not lock its wheels.

Rather, this provision merely acknowledges that momentary lockup may

inadvertently occur during compliance testing due to road surface

irregularities, as test drivers attempt to achieve the shortest stops

possible. Therefore, this provision ensures that entire test runs are

not invalidated due to such an occasional occurrence.

NHTSA also notes that while Advocates claimed that the proposal to

permit momentary lockup during stops represents ``a significant

modification of the current FMVSS No. 105 test procedure'' whose real-

world safety implications are unknown, FMVSS No. 105 in fact generally

permits lockup of one wheel during stopping distance tests. The

provision being adopted today thus represents a more stringent test

condition, not a less stringent one.

In response to Bendix's comment, the momentary lockup is not a

situation that a driver is supposed to detect and respond to; it is

simply an allowance for a minor, inadvertent occurrence during testing.

Therefore, Bendix's request to permit a longer lockup period is not

necessary or appropriate.

Honda and Ford recommended that S7.2.1(f) be changed to define

wheel lock as an angular velocity of zero, rather than the current

definition of 10 percent of vehicle speed. They reasoned that it would

be difficult to read the definite value with a 10 percent margin,

because speed recorded on the data sheet changes gradually and the data

also includes vehicles vibration.

The wording proposed for S7.2.1(f) was not intended to redefine

wheel lockup as 10 percent of vehicle speed (90 percent wheel slip).

Rather, it was intended to provide a practical criterion for making a

determination that wheel lockup (100 percent wheel slip) exists, given

the limitations of current instrumentation and recording devices. The

proposal was based on the agency's experience at the Vehicle Research &

Test Center (VRTC). Much of the vehicle testing that NHTSA has relied

on to formulate FMVSS No. 135 was conducted at VRTC. This testing

indicated that, with the instrumentation used by VRTC, it would be

difficult to accurately measure zero angular velocity, due to spurious

``signal noise''. Thus, it would be extremely difficult to ascertain

when a wheel reached an angular velocity of zero.

The comments expressed by Ford and Honda indicate that they have

experienced similar problems with ``signal noise'' due to vibration and

``drift'' of the signal when reading the vehicle speed trace, which

make it more difficult to relate the wheel rotational speed measurement

to that variable than to read its absolute value. The difference

between the agency's experience and that of Ford and Honda is probably

due to differences in the instrumentation packages used.

After further reviewing this issue, NHTSA has decided to remove the

proposed S7.2.1(f) entirely, because it was probably biased toward a

particular type of instrumentation, and the agency does not want to

impose unnecessary restrictions on what instrumentation is used to test

for compliance with the standard. In order to clarify the meaning of

wheel lockup, a definition stating that wheel lockup means 100 percent

wheel slip has been added to S4. This definition is the same as has

recently been added to both FMVSS No. 105, Hydraulic Brake Systems, and

FMVSS No. 121, Air Brake Systems.

As a practical matter, NHTSA notes that there is essentially no

difference between the method proposed in Notice 5 and that recommended

by Ford and Honda. Once a wheel reaches 90 percent slip, complete

lockup will be essentially instantaneous. As clarified in this final

rule, there is no question of what is meant by wheel lockup. How that

is measured is left to individual testing organizations, as is true for

other aspects of standard.

2. Road Test Sequence

In the 1991 SNPRM (Notice 5), NHTSA proposed the following road

test sequence: Burnish and wheel lock sequence at gross vehicle weight

rating (GVWR); wheel lock sequence, ABS performance, and the torque

wheel test at lightly loaded vehicle weight (LLVW); the torque wheel,

cold effectiveness, high speed effectiveness, stops with engine off at

GVWR; cold effectiveness, high speed effectiveness, failed ABS, failed

proportional valve, and hydraulic circuit failure at LLVW; and

hydraulic circuit failure, failed ABS, failed proportional valve, power

brake unit failure, the static and dynamic parking brake tests, heating

snubs, hot performance, brake cooling, recovery performance, and final

inspection at GVWR.

JAMA and GRRF supported the proposed road test sequence, even

though R13H does not specify a test sequence. GM recommended modifying

the test sequence by eliminating two of the four ballast changes (i.e.,

reduce the times needed to switch between lightly loaded and fully

loaded). It also recommended not including the full ABS test and the

dynamic parking brake test.

As explained below, NHTSA has decided not to include the full ABS

test and the dynamic parking brake test. Nevertheless, the agency

believes that it would be inappropriate to change the test sequence for

the sake of reducing the test preparation effort. The agency emphasizes

that the test sequence being adopted specifies that the GVW and LLVW

wheel lock sequence tests be conducted first, since their results

determine whether the torque wheel test needs to be conducted. The

agency further notes that the test sequence being adopted permits

removal of the torque wheels as soon as that test is completed. This is

important since the torque wheels might get wet or otherwise adversely

affected if they were not removed. Based on these considerations, the

agency has determined that it would be inappropriate to switch the test

sequence, which would result in fewer ballast changes.

3. Pre-Burnish

FMVSS No. 105 specifies a pre-burnish requirement to evaluate

brakes in the brand new condition. In the initial NPRM (Notice 1),

NHTSA proposed a similar requirement for the harmonized standard.

However, in the 1987 SNPRM (Notice 4), the agency explained that it no

longer believed a pre-burnish test was necessary for safety, given the

relatively short period of time that the vehicle's brakes remain in the

pre-burnished condition.

In comments to both SNPRMs, Advocates and CAS strongly opposed

deleting this test. They stated that it takes hundreds of miles of use

before brakes are properly burnished, especially for vehicles used in

rural areas, in which long distances may be traveled with few brake

applications. Advocates stated that certain brakes, most particularly

disc-type brakes, are highly resistant to burnishing. That organization

argued that the agency acknowledged this high mileage need for proper

burnishing in the 1985 NPRM, but attempted to rationalize this

concession in the first SNPRM. It also argued that stopping distance

performance may be considerably greater before burnish than afterwards.

Advocates stated that deleting a pre-burnish test would allow

manufacturers to produce and sell cars whose pre- burnish, on-the-road

braking capability is unknown. It stated that it does not believe this

is in the best interests of traffic safety, and that it does not

believe the agency can allow cars to be sold and used that have no

regulatory control

[[Page 6419]]

over their stopping distances before burnishing takes place.

NHTSA is not persuaded by the comments from CAS and Advocates

regarding the need for a pre-burnish test, and has decided to not

include this test in the final rule. The arguments by CAS and Advocates

are essentially the same as those made in response to the 1987 SNPRM

(Notice 4). These comments were already addressed in the preamble to

the 1991 SNPRM (Notice 5, 56 FR 30533).

Advocates has made an unsupported statement that disc brakes are

highly resistant to burnishing. No test data or other evidence was

supplied to support this allegation. Regardless, the pertinent question

is not how long or how many miles it takes to burnish brakes in use,

but whether there is a big enough difference in performance before and

after the 200-stop burnish specified in the standard to present a

safety problem. If some types of brakes do take a long time to become

fully burnished, then they would not be fully burnished after the 200-

stop burnish sequence specified in the standard, so they would have to

meet the cold effectiveness stopping requirements in a partially-

burnished state. If that were the case, their eventual, fully-burnished

performance would be even better than that required by the standard.

Advocates also argued that stopping distances before burnish may be

considerably longer than after burnish. This statement was also

unsupported by any test data. Agency testing conducted during the

development of this standard (Harmonization of Braking Regulations--

Report No. 1, Evaluation of First Proposed Test Procedure for Passenger

Cars, Volume 1, May, 1983, DOT HS 806-452) showed that in some cases

stopping distances were somewhat shorter after burnish, and in other

cases stopping distances were shorter in the unburnished state.

However, the overall conclusion was that the burnish had a small effect

on stopping distances. Also, this research was done using the burnish

procedure specified in FMVSS No. 105, which is more severe than that

specified in FMVSS No. 135, and would therefore have a greater effect

on braking performance.

4. Burnish

Burnish procedures serve as a conditioning to permit the braking

system to achieve its full capability. In the 1987 SNPRM (Notice 4),

NHTSA proposed specifying 200 burnish stops. The agency stated that the

burnish procedures would stabilize brake performance and reduce vehicle

and test variability. In the 1991 SNPRM (Notice 5), the agency proposed

almost the same requirements as the earlier SNPRM. The only substantive

change from the earlier notice entailed specifying that the pedal force

would be adjusted as necessary to maintain the specified constant

deceleration rate.

Kelsey-Hayes and Honda recommended that the burnish procedures be

made consistent with the ones in FMVSS No. 105, with respect to the

number of burnishes, the test speed, and the deceleration rate.

Specifically, both commenters recommended that the test speed be 65 km/

h (40.4 mph) and the deceleration rate to be 3.5 m/s (11.5 fps). While

these conditions enabled Kelsey-Hayes to conduct the FMVSS No. 105

burnish on a secluded public road, the proposed burnish requirements

for FMVSS No. 135 would have to be conducted at a commercial test

facility, which may not be readily available. Honda stated that the

cost of the proposed FMVSS No. 135 burnish test was more than the cost

of the FMVSS No. 105 burnish, even though the brake temperatures at the

end of the respective burnish procedures are the same. JAMA and Toyota

recommended that the test speed be reduced from 80 km/h to 70 km/h

because the brake temperature would increase too much under the

proposed burnish speed.

NHTSA has decided to adopt the burnish procedure as proposed in the

1987 and 1991 SNPRMs. As explained in those notices, the agency

purposely changed the burnish procedure from the one in FMVSS No. 105

to provide a more realistic burnish. NHTSA believes that the new

burnish procedure will more closely match real world situations,

including the actual type of burnish most drivers will achieve in the

course of normal driving. The burnish procedure in the harmonized

standard will better reflect the real world capabilities of the brakes

in a passenger car. The new burnish procedure itself will not affect

the time or mileage needed to burnish brakes for the average driver.

NHTSA believes that the burnish procedures adopted by today's final

rule represent an efficient burnish procedure that is consistent with

R13 and the ECE harmonized version of R13H.

NHTSA is not able to determine the meaning of JAMA's comment that

the temperature ``would increase too much'' under the specified burnish

procedure. As previously stated, the agency believes that the specified

burnish is more representative of actual driving experience. Therefore,

any temperature increase during burnish would also be experienced on

the road.

Advocates and CAS stated that the burnish procedure proposed for

FMVSS No. 135 would not ensure that cars are tested with properly

burnished brakes. They stated that decreasing the deceleration rate,

lowering the initial brake temperature, and introducing a variable

pedal force would extend the time and mileage needed to complete a full

burnish. Advocates further believed the proposed burnish procedure

would not evaluate how well the brake system reacts to higher

temperatures, along with the resulting potential for fade during the

initial burnishing.

NHTSA believes that Advocates and CAS misunderstand a fundamental

principle of brake burnish procedures: a less severe burnish results in

a more severe test. The burnish procedure has no bearing whatsoever on

how long it will take a vehicle to achieve full performance in actual

use. More specifically, the agency notes that the changes proposed in

the 1987 SNPRM (Notice 4) about the burnish procedure (e.g., lower

initial brake temperature, lower deceleration rate) would be more

similar to typical driving than those in FMVSS No. 105. Moreover, NHTSA

believes that most vehicles will not be driven for long periods of time

in a significantly less burnished condition than that obtained from the

burnish procedures being adopted.

Advocates also said that it does not agree with NHTSA'S claim that

drivers rarely exceed a deceleration rate of 3.0 m/s(2) except in

emergencies. Advocates claimed that typical stop-and-go braking

deceleration rates, especially in congested urban expressway traffic

with high speed differentials, can exceed this rate. NHTSA acknowledges

that deceleration rates can exceed 3.0 m/s(2), but burnish is meant to

simulate typical use, not these unusual circumstances.

MVMA, Ford, Chrysler, and GM requested a modification of initial

brake temperature from 4 CAS appears to misunderstand the agency's

regulatory framework, since a vehicle either passes or fails a

requirement in a FMVSS; there is no provision for a marginal pass. For

instance, a vehicle that ``marginally passes'' FMVSS No. 105 still

complies with the standard. Therefore, the agency believes CAS's

argument is not relevant to the regulatory framework set forth by

statute and incorporated in the Federal motor vehicle safety standards.

The agency further notes that the Hunter test apparatus is a simplified

version of the road transducer pad that the NHTSA in light of comments

by the industry considered prior to selecting torque wheels as the most

acceptable method of measuring adhesion utilization. Therefore, the

agency believes that it would be inappropriate to require this method

of evaluating compliance.

\4\A heavily front biased vehicle will skid but remain stable

heading forward, since the front wheels will lock first. In

contrast, a rear biased vehicle will spin out, since the rear wheels

will lock first and those wheels would tend to lead.

Advocates stated that the real-world effects of the adhesion

utilization test are uncertain and that NHTSA has not demonstrated a

connection between real-world situations and the wheel lock sequence

results. Advocates further commented that there is more to braking

stability than front-axle bias and that plow-out skids will result in

lane departures and stopping distances that are too long for safety

purposes, even for vehicles with front axle bias and ABS.

Advocates further stated that

Real-world crash results for cars tested under the two-part Adhesion

Utilization protocol may not be favorable for significant numbers of

production cars. The truncation of the testing protocol that has

accompanied the proposed two-stage system of the current SNPRM

comprising the Wheel-lock Sequence and Torque Wheel (especially due

to adoption of the 90% efficiency rationale) creates a ``window'' of

allowable production variability that can permit a significant, but

unquantifiable, percentage of assembly-line vehicles to be rear-

brake biased. Under certain operating conditions, especially those

uncontrolled by the reduced performance specifications of the

current proposed rule, such as the elimination of a low-coefficient

surface test, many cars may experience serious instability under

severe braking. The plain fact is that even if both parts of the

two-stage test as proposed are used for a given car model, this

still will not ensure that all cars will have appropriate front-

brake bias and does not foreswear the potential for an unknown

number of production units to be susceptible of serious spin-out

crashes in panic braking situations. Despite advocating the two-

stage test in this SNPRM, the agency itself obviously still harbors

doubts over its adequacy to detect cars with rear-brake bias.

Advocates has expressed two concerns. Their first concern is that,

by having a simple wheel lock sequence test, manufacturers would

produce cars that have too much front axle bias in their brake systems,

because such a vehicle would always pass the wheel lock sequence test.

The extreme example of this would be a car with no brakes at all on the

rear wheels. Such a vehicle would always be dynamically stable, but if

braked to the point of wheel lockup would provide no ability to steer.

This concern by Advocates ignores the adhesion utilization requirement

is only one of many requirements in the standard, and therefore is not

the sole factor in determining brake system design. If a manufacturer

were to produce a car with too much front bias, it would compromise the

vehicle's ability to satisfy other requirements of the standard, such

as service brake stopping distances, partial failure, failed power

assist, and parking brake requirements.

Advocates' second concern is that, because of the 10% allowance for

test variability, a vehicle could pass the torque wheel test and still

be rear-biased, and therefore ``susceptible of serious spin-out

crashes.'' While it is theoretically possible for a vehicle to be

slightly rear-biased and still pass the torque wheel test, NHTSA

believes this

[[Page 6421]]

possibility is extremely remote. If a manufacturer were to design a

vehicle to exhibit slight rear bias, production and test variability

would create too great a risk that the vehicle would not comply with

either the wheel lock sequence test or the torque wheel test. Rather,

the 10% allowance is meant to allow cars to be designed with brake

balance that is still front-biased, but closer to ideal than could be

achieved if the manufacturer had to worry about a failure of the torque

wheel test due to test variability. Also, for a vehicle to exhibit a

tendency to spin out, it must experience a condition where the rear

wheels are locked and the front wheels are not. Any vehicle falling in

the 10% ``window'' would be so close to ideally balanced that the point

of wheel lockup would be essentially simultaneous for both axles, and a

condition of rear axle lockup without front axle lockup would be almost

impossible to maintain.

b. Wheel Lock Sequence Test. NHTSA explained its tentative

determination in the SNPRM (Notice 5) that the wheel lock sequence test

would identify those vehicles that are heavily front biased. Such

vehicles have good stability characteristics because their front brakes

always lock first during braking, regardless of test surface.

Accordingly, a heavily front biased vehicle would not need to be

subject to the torque wheel test, since it would be considered to have

inherently good stability characteristics. Under the proposal, a

vehicle would need to meet the wheel lock sequence test requirements on

all test surfaces that would result in a braking ratio of between 0.15

and 0.80, inclusive, at each of two vehicle loading conditions: GVWR

and LLVW.\5\ The wheel lock sequence test would require a brake

application at a linear, increasing rate such that lockup of the first

axle is achieved between 0.5 and 1.0 second.

\5\This is defined in Section S4 as the unloaded vehicle weight

plus the weight of a mass of 180 kg, including driver and

instrumentation.

---------------------------------------------------------------------------

GRRF agreed to the proposed wheel lock sequence test and planned to

add it to R13 and R13H. Ford and Chrysler stated that there were

insufficient data to establish whether the wheel lock sequence test

could be consistently repeated. Ford believed that there is potential

for discrepancies between manufacturer testing and NHTSA testing.

NHTSA believes that Ford and Chrysler are incorrect in their

assessment of the wheel lock sequence test. The agency notes that the

available test data indicate that the wheel lock sequence test is

objective and can be consistently repeated.\6\ As explained above, the

wheel lock sequence test is the first part of the adhesion utilization

test procedure, and evaluates whether there is sufficient front axle

bias to ensure stability in a lock up situation. If a car has

insufficient front axle bias to consistently meet the wheel lock

sequence test, it does not automatically fail to comply with FMVSS No.

135. Rather, it would be tested under the torque wheel method. If the

vehicle passes the torque wheel test, the wheel lock sequence test

results are irrelevant.

\6\``Harmonization of Braking Regulations, Report Number 7,

Testing to Evaluate Wheel Lock Sequence and Torque Transducer

Procedures,'' DOT HS 807611, February 1990.

---------------------------------------------------------------------------

NHTSA expects that 90 to 95 percent of cars will pass the wheel

lock sequence test, meaning only 5 to 10 percent of the cars will have

to be tested with the torque wheel method. This will reduce potential

testing expenses by a greater amount than the agency could have

foreseen at the time it published the 1991 SNPRM.\7\

\7\When the 1991 SNPRM was published, the percentage of cars

that may have been required to be torque wheel tested was already

small, given that the agency expected that 95 percent of all cars

would pass the wheel lock sequence test. Thus, only five percent of

all cars were expected to be torque wheel tested. As a result of the

increased use of antilock brake systems that do not need to be

torque wheel tested, the agency anticipates that in model year 1999,

the number of cars that might need torque wheel testing will be less

than one percent.

---------------------------------------------------------------------------

Ford requested that the agency specify a braking ratio of 0.15 to

0.70 instead of the proposed ratio of 0.15 to 0.80. It believed that

this change would help avoid degradation and flat spotting of tires,

since under its recommended ratios only wet surfaces would be required.

NHTSA has determined that it would be inappropriate to lower the

upper limit in the braking ratios. If Ford's recommendation were

adopted, there would be no assurance of stability on typical dry road

surfaces. Therefore, the agency has decided to require the wheel lock

sequence test be performed at any ratio between 0.15 to 0.80.

More generally, NHTSA has considered whether the range of possible

test surfaces for the wheel lock sequence test raises practicability

concerns. The agency notes that a manufacturer will not need to test a

vehicle on every possible surface but could instead make predictions

based on testing at several points and brake design characteristics.

Moreover, instead of using the wheel lock sequence test to screen out

vehicles, a manufacturer could conduct only the torque wheel tests,

which do not involve a wide range of test surfaces, if a manufacturer

doubted that its vehicle could pass the wheel lock sequence test on all

applicable test surfaces. Given the availability of the torque wheel

test, NHTSA believes that there are no practicability concerns

presented by the wide range of test surfaces in the wheel lock sequence

test.

Bendix requested that NHTSA clarify whether the definition of wheel

lock in S7.2.1(f) is applicable to all testing situations or just those

in S7.2. After reviewing this comment, NHTSA has modified the

description of wheel lock in S7.2.1(f) to clarify that it only applies

for purposes of the adhesion utilization test.

MVMA and Ford noted that the proposed wheel lock sequence test

permits wheel lockups of ``less than 0.1 second;'' however, the balance

of the SNPRM permits lockup ``for not longer than 0.1 second.'' The

agency has decided to standardize this factor so all references to

wheel lockup will read -'' 0.1 second.''

MVMA, Chrysler, Ford, Toyota, and the Japanese Automobile

Manufacturers Association (JAMA) commented that it would be difficult

to comply with the proposed test condition for lockup to be achieved

between 0.5 and 1.0 seconds after initial brake application. Several

commenters suggested an upper limit of 1.5 seconds, which they believed

would still preclude spike stops. Ford suggested that the requirement

specify no maximum time, provided the vehicle's speed was greater than

15 kilometers per second (km/s) at the time lock up occurred.

After reviewing the available information including agency testing,

NHTSA has determined that it is appropriate to raise the ceiling to 1.5

seconds. The agency has decided not to remove the ceiling altogether,

given the need to have a specification that is independent of the

actual pedal force rate since the pedal force rate required to achieve

lock up within a specified time will vary among vehicles.

Suzuki, Toyota, and JAMA recommended that S7.2.3(c)(3) be amended

to allow braking force to be terminated 0.1 seconds after the first

axle locks or when the front axle locks. Suzuki stated that there is no

need to require continued braking beyond the first axle lock, since the

test is designed to determine which axle locks first. Toyota and JAMA

stated that if the rear axle locks first, then the pedal must be

immediately released to prevent accidents.

After reviewing the comments, NHTSA has decided to modify

S7.2.3(c)(3) to state the following: ``The pedal is released when the

second axle

[[Page 6422]]

locks, or when the pedal force reaches 1000 N (225 lbs), or 0.1 seconds

after first axle lockup, whichever occurs first.'' This modification of

the language should avoid the problems cited by the commenters.

BMW requested that the wheel lock sequence test be run at speeds of

50 km/h, claiming that the conditions proposed in the 1991 SNPRM demand

a higher initial speed and brake pedal application rate than the OICA

proposal. NHTSA believes that the proposed test speed of 65 km is

appropriate for safety and consistent with ECE R13H. BMW neither raised

a safety concern nor provided any documentation to support its request

to lower the test speed. Accordingly, the test speed for the wheel lock

sequence test is adopted as proposed.

Ford, Chrysler, and MVMA requested deleting the speed channel

filtering test condition or clarifying it so that it applies only to

analog instrumentation methods. They stated that a low pass filter,

having a low cut-off frequency is applicable to analog data recording

but not digital data recording.

NHTSA has decided to clarify S7.2.3(g) and (h) so that it refers

only to analog instrumentation. These sections address the automatic

recording of data and speed channel filtration and are unnecessary for

digital data recording.

In the 1991 SNPRM (Notice 5), NHTSA proposed a modified wheel lock

sequence test for a vehicle equipped with an antilock brake system on

one or both axles. Under this proposal, an ABS equipped vehicle would

have to be capable of stopping on a surface with a transition from a

high PFC to a low PFC without wheel lockup exceeding 0.1 seconds, after

decelerating in a hard braking from 100 km/g to a stop. The agency

believed that this would test the ABS's ability to compensate for

changes in surface quality and conditions encountered in everyday

driving. The agency requested comment about the need to adopt other

aspects of Annex 13 addressing braking efficiency and split coefficient

of friction surfaces, as more advanced ABS are sold in the United

States.

MVMA and Ford requested that vehicles with axles not directly

controlled by ABS be allowed to be certified as complying with the

wheel lock sequence test. They incorrectly stated that while the 1991

SNPRM only applied the wheel lock sequence test to non-ABS vehicles, a

vehicle with rear wheel only ABS should also be permitted to

demonstrate brake balance by the wheel lock sequence test. They stated

that the use of the wheel lock sequence test is unrelated to whether

the vehicle is equipped with ABS and should be allowed for either

design as an alternative to the torque wheel test.

After reviewing the comments, NHTSA has decided that only vehicles

without any ABS should be required to run the wheel lock sequence test.

The agency notes that differentiating between all-wheel and rear-wheel

ABS as it relates to brake balance is not appropriate since in either

case rear wheel lockup will not occur if the ABS is operational.

c. Torque Wheel Test. Under the 1991 SNPRM (Notice 5), a vehicle

that failed any single test run of the wheel lock sequence test would

be subjected to the torque wheel\8\ test to directly measure braking

forces under a wide range of deceleration conditions and provide data

needed to generate detailed adhesion utilization calculations. Under

the proposal, to pass the torque wheel test, a vehicle would need to

demonstrate that the plots of its adhesion utilization performance fell

within a specified range. Section S7.4.3 sets forth the test conditions

for the torque wheel procedure, including initial brake temperature,

test speed, pedal force, cooling, number of test runs, test surface,

and the data to be recorded.

\8\Torque wheels are strain gauge instrumented devices that fit

between the brake rotor or drum and the wheel assembly, and which

directly measure the reaction torque that is developed by the

friction between the tire and road surface during braking.

---------------------------------------------------------------------------

NHTSA tentatively concluded that the torque wheel test represented

an objective and repeatable method for gathering data for the

construction of adhesion utilization curves. The agency noted that the

torque wheel procedure requires more expensive test equipment and more

time to administer than the wheel lock sequence test.

After reviewing the available information, NHTSA has decided to

modify the section on torque wheel testing in S7.4 to exclude from

testing any car equipped with ABS. The agency has determined that

adhesion utilization testing is only relevant for brake balance in the

event of lock up, which will either not occur, or occur for negligible

amounts of time, on wheels controlled by ABS. Assuming the ABS is

operating, this is true for vehicles in which all wheels are directly

controlled by ABS, or on rear wheel-only ABS vehicles. In rear wheel-

only ABS vehicles, the front wheels would always lock before the rear

wheels, which would not lock at all, or lock for negligible amounts of

time. Accordingly, the number of cars that will have to undergo

adhesion utilization testing will drop to a small percentage of the

overall fleet as ABS becomes more prevalent over the next few years.\9\

\9\The agency estimates that by model year 1999, when FMVSS No.

135 will come into full force, approximately 85-90 percent of

passenger cars will be ABS-equipped.

---------------------------------------------------------------------------

GM, Ford, MVMA, and Chrysler requested that S7.4.3 be changed to

require stops from 50 km/h at both GVWR and LLVW, in addition to the

proposal for stops from 100 km/h. They stated that the additional test

runs would increase the database's statistical accuracy and provide

stopping data at the speed at which the wheel lock sequence test is

conducted. They state that specifying an additional test speed will

reduce the standard error in the estimate by 30 percent. In addition,

GM stated that by specifying two test speeds, a manufacturer would no

longer be able to design speed sensitive brake systems specifically

designed to handle stops from 100 km/h. Similarly, Ford commented that

alternating between the test speeds would avoid speed conditioning of

the brakes.

After reviewing the comments and other available information, NHTSA

has decided to modify S7.4.3 to require five stops from 100 km/h, and

five stops from 50 km/h, at each of the test weights, LLVW and GVW, for

a total of 20 stops. The agency agrees with the commenters that stops

from both speeds will prevent speed conditioning and ensure that

manufacturers design brakes that will be effective over a wide range of

initial speeds. NHTSA has decided to increase the maximum pedal force

rate to 200 N/second (45.0 lbs./sec.) for the stops from 50 km/h in

order to achieve sufficient deceleration levels.

Ford stated that the paired torque and force values generated for

S7.4.4 may not be uniformly distributed when plotted against each

other, a situation that may affect the overall outcome. Ford stated

that data point distribution will not be uniform if the pedal force and

the vehicle deceleration are not changing linearly. It recommended

using a linear regression analysis after dividing the input force into

several increments and averaging all data points within the respective

increments to yield a single average value for that increment.

NHTSA has determined that the modification recommended by Ford is

not necessary. The agency believes that there will be no ``constant

pedal force'' increments at all, if the rates of pedal force

application are held within the limits prescribed in S7.4.3(c). The

agency notes that in evaluating this phenomenon in the context of worst

case scenarios, VRTC determined that

[[Page 6423]]

there was no significant change in the results.\10\

\10\``Harmonization of Braking Regulations, Report Number 7,

Testing to Evaluate Wheel Lock Sequence and Torque Transducer

Procedures,'' DOT HS 807611, February 1990.

Ford and MVMA commented that the test condition in S7.4.3(i), which

specifies 20 to 25 snubs from 50 km/h at each of the two loading

conditions, is excessive. They state that one or two stops from each

loading condition would be sufficient for determining variable

proportioning valve (VPV) performance. Alternatively, Ford and MVMA

stated that the digital data obtained for each of the torque wheel test

stops would provide another source of data for determining variable

proportioning valve performance. They requested that if the agency

decides to require 20 to 25 snubs, then the snubs be performed at the

end of the test sequence to avoid any non-repeatable conditioning of

the brake lining.

NHTSA has determined that 20 to 25 snubs to determine the variable

proportioning valve performance may be unnecessary, but that the

suggested 1 to 2 stops would be inadequate to cover the entire range of

brake pressures. The agency has decided to modify S7.4.3(i) to specify

15 snubs. The agency believes that this test procedure will be

sufficient to appropriately evaluate variable proportioning valve

performance without introducing unnecessary conditioning of brake

linings. The agency notes that these extra snubs are only needed when

the vehicle is equipped with a variable proportioning valve. With fixed

proportioning, the test is a static test, which will have no effect on

conditioning of the brake linings.

Ford stated that the linear regression data should only include

torque data collected when the vehicle deceleration is within the range

of 0.15g to 0.80g rather than when torque output values are > 34 N/

minute.

NHTSA agrees with Ford's comment and has modified S7.4.4(b) to

reflect this change. The agency believes that it would be inappropriate

to use data compiled outside the required performance range of the

torque wheel test, since such data may not be relevant to the actual

performance requirements.

GRRF, GM, Ford, the MVMA, Suzuki, JAMA, Toyota, Honda, and OICA

commented that the upper limit line in Figure 2 in S7.4.4(h)

(represented in S7.4.5.1 by the equation z = 0.1 + 0.7 (k-0.2)) is

unnecessary and should be eliminated. Ford and GM stated that the line

is unnecessary because, even though the wheel lock sequence test has no

check for excessive front bias, the cold effectiveness test does.

Suzuki, JAMA, Toyota, and OICA stated that the adhesion utilization

requirement in S7.4.5.2 for a rear axle is more stringent than the

requirement than S7.4.5.1, making S7.4.5.1 redundant.

NHTSA agrees with the commenters that a vehicle that is so front-

biased that it would not satisfy the efficiency requirement proposed in

Notice 5 would in all probability not be able to meet the cold

effectiveness and/or other stopping performance requirements in the

standard. Therefore, the efficiency requirement proposed in S7.4.5.1 of

Notice 5 is essentially redundant. Accordingly, the agency has decided

not to include the upper line in Figure 2. In addition to deleting the

area of Figure 2 defined by the equation z = 0.1 + 0.7 (k-0.2), NHTSA

is modifying S7.4.5 by deleting the text of S7.4.5 and S7.4.5.1, and

renumbering S7.4.5.2 as S7.4.5.

Chrysler recommended using deep dish wheels and changing tires on

the torque wheels, claiming that use of torque wheels will deform

normal road wheels by pushing them further out than their normal

position. Ford and MVMA requested that the agency modify the

requirement to permit use of a separate set of tires in the torque

wheel test, based on its concern that lockup situations in other tests

under FMVSS No. 135 could flatten or wear spots on tires.

NHTSA has decided to permit manufacturers to use a separate set of

tires for the torque wheel test, even though the agency believes that

it is unlikely that the tires will be worn down prior to the adhesion

utilization test which comes at the beginning of FMVSS No. 135's test

sequence. The agency notes that new tires will not alter the adhesion

utilization curve for the vehicle. The agency agrees with Chrysler that

manufacturers using deep dish rims can avoid tire demounting and thus

simplify testing, if they can use such rims with tires already mounted.

Based on these considerations, the agency has modified S7.4.2(d) to

permit optional use of a separate set of tires for the torque wheel

test.

Suzuki commented that for purposes of the torque wheel test, the

definition of LLVW should be changed to unloaded weight plus 200 kg,

rather than the present 180 kg. It stated that 180 kg may be

insufficient to cover the total weight of the driver and required

instrumentation.

NHTSA believes that most instrumentation packages fall within the

180 kg specified in the Standard. Moreover, the agency is not aware of

any instrumentation packages that exceed the weight allowed for LLVW

testing. Based on these considerations, the agency has decided not to

change S7.4.2.

Hunter, a manufacturer of a brake balance tester, stated that its

device can provide results similar to a road transducer pad. It further

stated that its device can be used without the need to modify the

vehicle.

NHTSA is aware of Hunter's brake balance tester, which is a

simplified version of the road transducer pad. While the Hunter device

can provide a rough measure of adhesion utilization, NHTSA believes

that the methods of measuring adhesion utilization adopted by the

agency are superior to the Hunter device, since the torque wheels

evaluate adhesion utilization more precisely. The agency notes that the

automotive industry and foreign governments interested in harmonization

have stated that the proposed methods of measuring AU are appropriate.

In the 1991 SNPRM, the agency stated that assuming one torque wheel

equipment package will service the needs for five years of typical

yearly production runs of 30,000 to 100,000 vehicles, the torque wheel

would result in a unit cost increase of $0.15 to $0.50 per vehicle.

Kelsey-Hayes stated that NHTSA underestimated the expense of torque

wheel equipment. It stated that the agency's discussion of the economic

burden associated with the cost of one set of torque wheels over a test

run is misleading and incomplete, since numerous sets of torque wheel

instrumentation will be required.

NHTSA believes that its estimates in the 1991 SNPRM were reasonably

accurate, with the following minor modifications. The agency expects

that the cost for a set of four torque wheels (including adapters to

accommodate varying wheel mounting bolt patterns) to be approximately

$40,000 and $15,000 for the on-board digital data acquisition system

that will record the testing results. The equipment should last five

production years, which correlates to an annual expense of $11,000 per

year. This figure is further reduced when amortized on a per vehicle

basis. The agency estimates that direct labor costs for each test to be

approximately $50 (including costs for instrumentation technicians, and

drivers). The agency estimates that the marginal cost increase per car

attributed to the torque wheel test will be between $0.10 and $0.16,

depending on the size of the vehicle's production run and the number of

vehicles in the run that the manufacturer wants to test, since the

manufacturer need not test every vehicle in a vehicle run. The agency

[[Page 6424]]

further notes that less than 1.0 percent of vehicles will actually have

to undergo the test by model year 1999, given that most vehicles will

be equipped with antilock systems and even most of those non-ABS

equipped vehicles will pass the wheel lock sequence test. Based on the

above considerations, NHTSA has concluded that the expense and time

required to administer the torque wheel test will not pose an

unreasonable burden on manufacturers.

The agency notes that torque wheels have been in use at least for

the last 50 years for evaluating vehicle characteristics other than

adhesion utilization. Most of the major vehicle manufacturers already

have torque wheels and use them extensively. Therefore, the cost of

torque wheels for FMVSS No. 135 needs to be amortized over more than

just its use in evaluating adhesion utilization.

No costs associated with the test surface are expected for torque

wheel testing because a high coefficient of friction test surface is

already required for testing under the existing standard. No costs are

expected for the wheel lock sequence test because, if enough surfaces

are not already available to potential users, they could use the torque

wheel test, given that it would be cheaper to use than constructing and

maintaining new test surfaces. In other words, costs associated with

the wheel lock sequence test might be so high that manufacturers would

go directly to the torque wheel test to incur lesser costs.

6. Cold Effectiveness

The cold effectiveness test evaluates the ability of a vehicle's

brake system to bring a vehicle to a quick and controlled stop in an

emergency situation. In the 1991 SNPRM, NHTSA proposed the same cold

effectiveness test as proposed in the 1987 SNPRM, with some minor

modifications. Specifically, the agency proposed that vehicles would

have to stop within 70 m in both the fully loaded and lightly loaded

conditions. Based on testing and information supplied by the

commenters, the agency believed that this stopping distance requirement

for a cold effectiveness test is equivalent in stringency to the

current requirement in FMVSS No. 105. The agency continues to believe

that the requirements for the cold effectiveness test are of equivalent

stringency, as explained below.

Like the other effectiveness tests, the proposed stopping distance

requirements for the cold effectiveness test was expressed in the form

of an equation. Specifically, this equation provides that stopping

distance must be less than or equal to 0.10V + 0.0060V, where V refers

to velocity in km/h. The first part of the equation, the 0.10V term,

accounts for brake system reaction time of 0.36 second. The second part

of the equation, 0.0060V, represents an assumed mean fully developed

deceleration rate. The specified performance criterion is not the

deceleration rate or the system reaction time, but the stopping

distance.

Commenters disagreed about the stringency of the proposed stopping

distance tests. While GRRF agreed to the proposed 70 m requirement in

the interest of harmonization, GM, Ford, MVMA, Advocates, and the CAS

disagreed with the proposed stopping distances. GM stated that the

reduction in maximum allowable pedal force increased stringency by 27

percent. It further stated that of nine cars it tested, three failed to

meet the proposed 70 m and an additional four failed to meet the 70 m

within 10 percent compliance margin. Based on this information, GM

argued that a significant number of its vehicles would fail the

proposed cold effectiveness test, even though they would comply with

FMVSS No. 105. Ford and MVMA stated that the stopping distance was

appropriate if the PFC were raised to 1.0.

In contrast, Advocates and CAS commented that the proposed stopping

distances were not sufficiently stringent. Advocates stated that the

stopping distance should be reduced from 70 m in order to force more

original equipment manufacturers to include ABS and brake power assist

units as standard equipment. CAS objected to increasing the reaction

time component in the stopping distance formula.

After reviewing the available information, NHTSA has determined

that requiring a passenger car to come to a complete stop within 70 m

(230 feet) from 100 km/h (62.1 mph) provides an appropriate level of

braking performance. The agency has decided to require the cold

effectiveness test to be conducted at both LLVW and GVWR, with the

pedal force being between 65 and 500 N (14.6 to 112.4 lbs).

As it has emphasized in earlier notices, NHTSA notes that it is

inappropriate to look only at the raw numbers in FMVSS No. 105 and

FMVSS No. 135 and state that one standard is more or less stringent

than the other. Agency tests conducted on identical vehicles to the

performance requirements in FMVSS No. 105 and FMVSS No. 135 indicate

that the average margin of compliance for the cold effectiveness tests

at GVWR in the two standards were almost identical (11.5 percent for

FMVSS No. 135, and 11.9 percent for FMVSS No. 105). Therefore, NHTSA

does not agree with GM's assertions that FMVSS No. 135 is more

stringent than FMVSS No. 105.

NHTSA notes that the stopping distances specified in FMVSS No. 135

are slightly longer than the distances specified in FMVSS No. 105.

Nevertheless, the agency is confident that the two FMVSSs provide a

comparable level of safety, for the following reasons. First, the new

burnish procedure in FMVSS No. 135, which is closer to real world

practice, is not as severe as that in FMVSS No. 105. As a result, the

longer stopping distances in the new standard are mostly attributable

to the less severe, but more realistic, burnish procedures, not to an

inherent weakening of brake efficiency requirements. Second, the

maximum allowable pedal force has been reduced from 150 lbs in FMVSS

No. 105 to 112.4 lbs in FMVSS No. 135. Along with lengthening the

stopping distances slightly, the lower pedal force will more closely

reflect the pedal forces likely to be applied by real world drivers, as

opposed to those on a test track.

NHTSA notes that CAS incorrectly assumes that increasing the brake

reaction time component in the stopping distance equation, by itself,

decreases the test's stringency. Brake reaction time is merely part of

a formula by which stopping distances are gauged, but it is the

stopping distance, and not the formula, which determines the stringency

of the rule. To illustrate, in the 1991 SNPRM, the agency increased the

reaction time component of the cold effectiveness test equation from

0.07V to 0.10V. However, the stopping distance remained at 70 m. To

compensate for this change in the system reaction time, the

deceleration term was modified slightly. Accordingly, a vehicle must

still stop in 70 m, so there is no actual increase or decrease in

stringency from the first SNPRM.

NHTSA believes that Advocates' concern about the installation of

power assist units is moot. According to Ward's Automotive Reports

(December 30, 1993 and April 18, 1994 Reports), all current U.S. cars

and import cars are equipped with power brakes. Moreover, antilock

brake systems are quickly becoming a feature available on many cars. As

stated above, by MY 1999 the agency expects 85 to 90 percent of all new

cars to be ABS-equipped. The market is responding directly to consumer

preference, and therefore Advocates' goal of having more vehicles

equipped with ABS is being achieved without a more stringent stopping

distance requirement.

[[Page 6425]]

NHTSA disagrees with GM's comment that the cold effectiveness

stopping distance requirements are 27 percent more stringent due to

lower allowable pedal force, because cold effectiveness stops are

usually not pedal force limited. In other words, despite the maximum

allowable pedal force of 150 lbs in FMVSS No. 105, vehicles rarely

needed to be braked with such a pedal force to pass the stopping

distance requirement. In fact, pedal forces rarely exceeded the 112.4

lbs (500 N) permitted in FMVSS No. 135. Therefore, the agency does not

believe that the lower maximum pedal force allowed in the new standard

will result in increasing the stringency of the cold effectiveness

requirements in comparison with FMVSS No. 105.

Toyota commented that the minimum initial brake temperature should

be raised from 50 deg.C to 65 deg.C, but did not give any reasons for

the request.

Based on testing conducted at VRTC, NHTSA believes that the present

minimum initial brake temperature, which was proposed in the NPRM and

the two SNPRMs, represents an appropriate temperature at which to begin

the cold effectiveness test runs, and has no information indicating it

should be changed. Therefore, the agency is retaining the initial brake

temperature requirement as proposed.

7. High Speed Effectiveness

In the 1991 SNPRM (Notice 5), NHTSA proposed a high speed

effectiveness test because cars are sometimes driven at higher speeds

than provided for in the cold effectiveness test that is conducted at

100 km/h (62.1 mph). The agency proposed that under the high speed

effectiveness test for vehicles capable of a maximum speed over 125 km/

h, a vehicle would be tested at a speed representing 80 percent of its

maximum speed, with a maximum limit of 160 km/h (99.4 mph). The upper

speed limit was specified due to facility limitations and safety

concerns during testing. The agency proposed that the high speed test

would only be conducted for vehicles with a maximum speed greater than

125 km/h. The agency proposed a new equation to reflect the change in

system reaction time from 0.07V to 0.10V. The agency stated that while

the SNPRM proposal is more stringent than the latest GRRF proposal, the

agency's test data indicated that all test cars would be able to meet

the proposed requirement.

The GRRF generally accepted the high speed effectiveness formula,

and the maximum test speed limit. Nevertheless, it requested that NHTSA

delete the lower speed limit proposed in the 1991 SNPRM, since R13 does

not specify a lower limit. GRRF further stated that the cold

effectiveness test and high speed effectiveness tests are qualitatively

different because the former is run with the engine in neutral, while

the latter is run with the engine in gear.

NHTSA is pleased that the GRRF has agreed to incorporate the

proposed high speed test in R13H. Nevertheless, the agency believes

that it is necessary to include the lower limit test speed.

Accordingly, NHTSA has decided not to conduct the high speed test for

vehicles with a maximum speed under 125 km/h, since it would be

illogical and would provide no safety benefits to conduct a high speed

test at a lower speed than the speed required by the cold effectiveness

test. The agency notes that 80 percent of the lowest maximum speed for

the high speed effectiveness test is 100 km/h. The agency does not

believe that running a high speed test at a speed lower than 100 km/h,

the cold effectiveness test speed, is worthwhile, regardless of engine

drive position.

Ford commented that the test should be run only at GVWR, but gave

no reason for deleting the LLVW run.

NHTSA has decided that it is consistent with the interests of motor

vehicle safety to test at both GVWR and LLVW since vehicles are used at

both weights. Similarly, it is in the interest of international

harmonization to test at both load conditions, since R13 does so.

Accordingly, in FMVSS No. 135's high speed effectiveness test, a

vehicle will be tested at both LLVW and GVWR. The test will be

conducted at a pedal force between 65 and 500 N (14.6 to 112.4 lbs).

JAMA and Toyota recommended specifying only four runs at high

speeds instead of the six proposed in the 1991 SNPRM.

NHTSA previously addressed this issue in the 1987 SNPRM in which

the agency proposed increasing the number of test runs from four to

six. In that notice, NHTSA explained that such a change would minimize

driver effects and decrease test variability, because the prescribed

performance would have to be achieved on only one stop in the six runs.

Even though reducing the number of runs to four might nominally

decrease the expense of the test, such a change could increase the

test's stringency.

8. System Failure

In previous notices, NHTSA proposed stopping distance requirements

for situations involving the engine being off, antilock functional

failure, variable proportioning valve failure, hydraulic circuit

failure, and the power assist unit being inoperative. Aside from the

engine off requirement, FMVSS No. 105 includes similar requirements

which are crucial if part of the service brake system or engine should

fail or become inoperative. These requirements ensure that the

vehicle's brake system will still be able to bring the vehicle to a

controlled stop within a reasonable distance.

a. Stops with engine off.--In the NPRM and two SNPRMs, NHTSA

proposed requirements to address stops with the engine off. The agency

explained that the proposed requirement was reasonable since engine

stalling is a relatively common occurrence, even though FMVSS No. 105

does not include a comparable requirement. The proposal to require

vehicles to stop within 73 m after engine failure was slightly less

stringent than the 1987 SNPRM's proposed requirement for stops within

70 m. The agency stated that the proposal was consistent with the

latest proposal by GRRF and thus will promote harmonization.

Advocates and CAS were concerned that the longer permissible

stopping distance of 73 m in the engine failure condition would

increase crashes. The GRRF recommended that the vehicle be able to stop

after engine failure within 70 m rather than the proposed 73 m. The

GRRF stated that the requirements of R13 and R13H should be easily met,

provided that there is an adequate reservoir in the braking system and

a non-return valve is fitted to the brakes. This equipment should

ensure that the brakes can operate even without the engine running.

NHTSA has decided to adopt the engine failure test with a stopping

distance of 70 m. Throughout the rulemaking, the agency has attempted

to make the engine failure stopping distance consistent with GRRF and

consistent with the stopping distance requirement in the cold

effectiveness test. In the 1991 SNPRM, the agency stated that its

proposal was consistent with the GRRF. This was true when the stopping

distance was 73 m for both the cold effectiveness and engine off tests.

Since the cold effectiveness stopping distance is now 70 m, the agency

is adopting a stopping distance of 70 m for the engine off test. The

engine off test will be performed at GVWR, with six stops from 100 km/

h, using a pedal force between 65 N and 500 N.

b. Antilock functional failure.--In the two SNPRMs, NHTSA proposed

separating the antilock and variable proportioning valve failure

requirements into different sections to

[[Page 6426]]

reflect the differing failure modes. In the 1991 SNPRM, the agency

proposed slightly different stopping distances to reflect the increase

in system reaction time and higher decelerations on the cold

effectiveness test, while maintaining the same percentages as in the

1987 SNPRM.

For Antilock functional failure, NHTSA proposed a stopping distance

of 85 m from a test speed of 100 km/h. The proposed requirement would

apply only to functional failures of the ABS system and not to

structural failures that are covered by the hydraulic circuit failure

requirements. The proposed stopping distance maintains the philosophy

that antilock functional failure performance should be 80 percent of

the cold effectiveness performance requirement, and is consistent with

the requirements adopted for Regulation R13H.

Without explaining what it perceived to be inconsistent, Fiat

requested that the agency make the antilock failure requirements in

FMVSS No. 135 consistent with R13H. Advocates and CAS requested that

NHTSA adopt a stopping distance of 80 meters as proposed in the NPRM.

They commented that the SNPRM's proposed stopping distance of 85

meters, while lower than the distance proposed in the 1987 SNPRM, still

exceeded the NPRM by 5 meters.

NHTSA has decided to adopt the 85 meter stopping distance

requirement for antilock functional failure, as proposed. The agency

believes Fiat's comment must have been based on a mistaken impression

that the requirement in Regulation 13H was some other value. In fact,

the two requirements are harmonized.

The observations of CAS and Advocates that the performance

requirement has changed by 5 meters since the NPRM (Notice 1) is

correct. Due to various changes in the equations, which have been

explained in the two SNPRMs, the proposed requirement went from 80

meters to 86 meters, and then back to 85 meters. Nevertheless, the 80

percent of cold effectiveness performance concept has been maintained

throughout this rulemaking. The value being adopted is in agreement

with that philosophy, is harmonized with the proposed Regulation 13H,

and is considerably more stringent than the corresponding requirement

in FMVSS No. 105. CAS and Advocates have provided no justification for

returning to an 80 meter value.

Ford, ITT-TEVES, GM, BMW, Chrysler, the GRRF, and MVMA requested

that the agency clarify the definition of an ABS ``functional failure

simulation'' to indicate that only the ABS system is covered by this

requirement. GM and Chrysler stated that the ABS failure test should

not be misunderstood to include failures affecting other aspects of the

service brake system. They explained that although ABS have previously

been added on to the service brake system, increasingly ABS is

completely integrated into the service brake system.

Based on the comments, NHTSA believes that it is necessary to

clarify the meaning of the phrase ``any single functional failure in

any such system.'' Since this requirement applies to antilock systems,

only a failure in an antilock system is covered by this requirement.

Nevertheless, if a functional failure of the ABS also affects or

degrades the service brake system, no artificial means are entailed to

keep the service brake system intact when that failure is introduced.

In such a situation, the vehicle with the failed ABS and failed service

brake system resulting from the single failure, will then be subject to

both the ABS failure and partial system failure tests. As the

commenters state, manufacturers are increasingly building integrated

brake systems rather than installing add-on antilock systems. The

agency believes that this requirement is appropriate since it will

prohibit any single ABS failure from degrading the service brake

systems beyond the performance requirements of the ABS failure test. To

ensure clarity, NHTSA has decided to add the following provision to

S7.8.2(g)(1): ``Disconnect the functional power source, or any other

electrical connector that would create a functional failure.''

Ford recommended deleting the ABS functional failure test at LLVW,

stating it was the same as the LLVW cold effectiveness test, if the ABS

functional failure is limited to a non-actuation failure mode. In the

cold effectiveness test, ABS is active and therefore may actuate during

the test. For the ABS functional failure test, the ABS is not working.

If the ABS is of an add-on type design rather than an integrated

system, and if the cold effectiveness test is conducted at a brake

force level that does not result in activation of the ABS, then it is

true that the tests would be redundant. However, in many cases one or

both of those conditions are not met, so the tests would be different.

Therefore, it would be inappropriate to delete the test as requested by

Ford.

Bendix stated that with respect to S7.8.2(g)(2)11, the

electrical function failure induced should be one that makes the system

inoperative in order to activate the warning indicator. Kelsey-Hayes

requested that the agency clarify the meaning in S7.8.2(g)(2) about the

continuing operation of the system.

\11\This section requires a determination of whether an ABS

electrical functional failure activates the brake system warning

indicator.

---------------------------------------------------------------------------

An electrical functional failure that makes the ABS inoperative is

required by S5.5.1(b) to activate the warning indicator. S7.8.2(g)(2)

is the test to determine compliance with S5.5.1(b). In response to

Kelsey-Hayes, the agency notes that an unplugged ABS module should

activate the antilock system warning indicator. The agency has decided

to clarify paragraph S7.8.3 by adding the words ``service brake''

before the word ``system.''

c. Variable brake proportioning functional failure.--In the 1991

SNPRM (Notice 5) NHTSA proposed a stopping distance of 110 meters from

a test speed of 100 km/h to evaluate variable proportioning valve

failure. This was slightly shorter than the distance of 112 meters

proposed in the 1987 SNPRM. In both notices, the proposal was based on

the mean fully developed deceleration rate of 60 percent of that

required for the cold effectiveness test. In the 1991 SNPRM, the agency

revised the proposal to better define how a variable proportioning

valve failure is simulated and to clarify that a warning to the driver

of valve failure is only required where there is an electrical

functional failure in the variable proportioning valve.

Fiat commented that the variable proportioning valve functional

failure test is not necessary given that neither EEC directive 75-524

nor R13 and R13H test for this type of failure, despite years of

experience.

NHTSA believes that the lack of documented variable proportioning

valve passenger car failures in the U.S. is not a sufficient reason

against specifying this requirement. The agency notes that there have

been considerable problems with variable proportioning valves on

trucks, the vehicle type most typically equipped with variable

proportioning valves, both in the U.S. and in Europe. Fiat produced no

data to support its assertion that the test is unnecessary for

passenger cars. NHTSA notes that a corresponding requirement is

included in the proposed Regulation 13H.

ITT-TEVES recommended a stopping distance of 168 m for the variable

proportioning valve failure test. It reasoned that vehicles would not

be able to meet the 110 m stopping distance because of wheel lock

caused by a dynamic load transfer from the rear to the front of the

vehicle during braking.

[[Page 6427]]

NHTSA disagrees with ITT-TEVES recommendation to dramatically

increase the stopping distance requirement for the variable

proportioning valve test. The agency believes that it would be

inconsistent with motor vehicle safety to allow a vehicle that is so

greatly influenced by an operational variable proportioning valve that

when the valve fails the brakes lock up and the vehicle needs 168

meters to stop. The agency further notes that the problem discussed by

the commenter, which might affect trucks in rare cases, is even less

likely to affect passenger cars.

The GRRF stated that the 60% cold effectiveness requirement is more

stringent than the European specification in Regulation 13.

Nevertheless, the GRRF stated that it could accept the proposed

performance requirement for variable proportioning valve functional

failure for purposes of Regulation 13H, provided that its concerns set

forth below with respect to S7.9.2(g)(1) are met.

Chrysler, Ford, MVMA, and the GRRF commented that when a variable

proportioning valve is disconnected or fails for any reason, it reverts

to a default position, functioning at the lowest pressure possible in

its proportioning range. Therefore, they state that S7.9.2(g)(1) should

be changed to reflect this default condition. They believe that to

require the proportioning valve to be operated in any specified

position in its operating range would require equipment that is not

found on current vehicles.

NHTSA agrees with the commenters that S7.9.2(g)(1) should be

revised to allow the variable proportioning valve to return to its

normal, default, position, when disconnected, since this will more

accurately test the vehicle's real world braking ability. Accordingly,

the agency has decided not to require the variable proportioning valve

to be held in any position in its operating range, thus allowing it to

revert to its uncontrolled condition.

NHTSA notes that the stopping distances for variable proportioning

valve functional failure are shorter than those of FMVSS No. 105 (while

the stopping distances for structural failure are longer). The agency

has determined that the stopping distances which are more stringent for

functional failures are appropriate, since functional failures are more

likely to occur.

d. Hydraulic circuit failure. In the 1991 SNPRM (Notice 5), NHTSA

proposed a stopping distance of 168 m (551 feet) from a test speed of

100 km/h. This proposal is identical to that included in the proposed

Regulation 13H. It maintains the same deceleration term as in the 1987

SNPRM (Notice 4), but reflects the proposed reaction time changes in

the equation for the cold effectiveness performance requirement.

Advocates stated that increasing the stopping distance in the

hydraulic circuit failure test by 42 feet from the NPRM (Notice 1)

decreased the Standard's stringency compared to the initial proposal.

It further stated that the 1991 SNPRM (Notice 5) also was less

stringent than the 1987 SNPRM (Notice 4). There were no other comments

regarding the stringency of this requirement.

Based on testing and other available information, NHTSA has decided

to adopt the proposed stopping distance of 168 meters (551 feet) from a

test speed of 100 km/h for both the hydraulic circuit failure tests.

The agency has decided to adopt the stopping distance formula

(0.10V+0.0158V2), as proposed in the 1991 SNPRM. As explained in

previous notices, it is not possible to compare the stringency of FMVSS

No. 105 and FMVSS No. 135 directly when discussing hydraulic circuit

failure requirements. This is primarily because there is a significant

difference in allowable pedal force during the test. FMVSS No. 105

limits pedal force to 150 lbs, whereas the maximum pedal force in FMVSS

No. 135 is 500 N (112.4 lbs). Although as a general matter, the

stopping distance of a vehicle improves as greater pedal force is

applied, it is not possible to quantify a precise relationship between

stopping distance and pedal force. The relationship between these

factors is non-linear; it varies among vehicle models, and depends upon

various parts of the vehicle, including tires and brake system

components. It is broadly true, however, that as pedal force increases,

stopping distance decreases.

In response to Advocates' comment regarding the changes between the

1985 NPRM (Notice 1) and the 1991 SNPRM (Notice 5), the rationale for

those changes was set forth in the two SNPRMs.

Bendix requested that S7.10.3(f) be clarified so that the induced

failure for testing would be limited to the normal braking circuits,

but not as part of the ABS that is not part of the normal braking

circuit.

NHTSA notes that it is not clear exactly what Bendix means by

``normal braking circuits.'' Section S7.10.3(f) states that the failure

is to be induced in the service brake system. The failure could be

anywhere in that system, including any part of an ABS that is common to

the service brake system. Any part of the ABS that is not common to the

service brake system would be subject to testing to the failed ABS

requirements, not the hydraulic circuit failure requirements. The

agency believes the test condition is clear as stated, and further

clarification is unnecessary. Therefore, S7.10.3(f) is adopted as

proposed.

e. Power assist unit inoperative. In the 1991 SNPRM, NHTSA proposed

a stopping distance of 168 m (551 feet) from a test speed of 100 km/h.

This proposal is identical to that included in the proposed Regulation

13H. It maintains the same deceleration term as in the 1987 SNPRM, but

reflects the proposed reaction time changes in the equation for the

cold effectiveness performance requirement.

Advocates opposed the proposed stopping distance of 168 m for stops

with an inoperative power assist, stating that it compared unfavorably

with the 165 m proposed in the 1987 SNPRM and the 155 m proposed in the

NPRM. In contrast, Ford and GM stated that the agency had proposed a

significant increase in stringency from FMVSS No. 105. These commenters

recommended a stopping distance of 177 meters (580 ft), stating that

such a distance would be equivalent to R13, and would still be more

stringent than the 456 foot stopping distance in FMVSS No. 105 because

of the decreased maximum pedal force.

After reviewing the comments, NHTSA has decided to adopt the

proposed stopping distance of 168 meters (551 feet) from a test speed

of 100 km/h for stops when the power assist is inoperative. The agency

has decided to adopt the stopping distance formula,

(0.10V+0.0158V2), as proposed in the 1991 SNPRM.

As explained in the section on hydraulic circuit failure, it is not

possible to compare the stringency of FMVSS No. 105 and FMVSS No. 135

directly when discussing power assist failure requirements, primarily

because there is a significant difference in allowable pedal force

during the test. None of the commenters who asked for a more or less

stringent stopping distance value provided justification for their

requests.

9. Parking Brake Requirements

a. Dynamic test. In the NPRM and 1987 SNPRM, NHTSA proposed a

dynamic parking brake test that it believed was consistent with the

GRRF decisions. The dynamic test was intended to ensure that the driver

could use the parking brake to stop a moving vehicle during emergency

situations. In the 1991 SNPRM, NHTSA proposed requiring that vehicles

utilizing the

[[Page 6428]]

service brake's friction linings for the parking brake be tested at a

speed of 80 km/h and that vehicles utilizing separate friction linings

for the parking brake be tested at 60 km/h. The agency decided that it

was not necessary to include a stopping distance requirement, as was

proposed in the 1987 SNPRM.

Volkswagen, Mercedes Benz, GM, Suzuki, MVMA, Chrysler, Ford, and

OICA objected to the proposed dynamic parking brake test. These

commenters stated that the agency had not identified any safety need

for a dynamic parking brake test and that FMVSS No. 105 has no such

test. These commenters stated that such a test is neither needed nor

appropriate since the primary purpose of the parking brake is to

statically hold a vehicle on a gradient and not to provide deceleration

capabilities for a moving vehicle. They state that it is potentially

dangerous for drivers to apply parking brakes in a dynamic situation

because it is difficult to modulate the application force. Moreover,

such applications could lead to uncontrollable rear wheel lock up and

loss of vehicle control.

Volkswagen, Mercedes Benz, GM, Suzuki, MVMA, Chrysler, Ford, and

OICA stated that the dynamic parking test was adopted in ECE R13 prior

to the almost universal use of dual split service brake systems. Such

brake systems provide extra braking reserves in the event of a partial

failure because an independent part of the split system remains intact

and unaffected by the failure in the other part of the system.

According to the commenters, ECE is no longer working on revising its

dynamic test, and is even discussing eliminating it.

Mercedes commented that a dynamic test penalizes parking brake

designs that are highly self energizing (i.e., that require a

relatively low control force but are highly effective in static

situations) because their static-efficient design makes them more

susceptible to fading. It stated that deleting the dynamic test would

improve the design of parking brakes by permitting the optimization of

their static holding performance.

In contrast, Advocates and CAS supported including a dynamic

parking brake test, although they opposed the agency's decision not to

propose stopping distance requirements in the 1991 SNPRM. Advocates

stated that the important function of a dynamic standard for parking

brake performance is the ability to control manufacture of parking

brake systems either with or without separate friction that will

reasonably stop a car from controlling test speeds when there is a

complete failure of service brakes. That organization stated that

without a specific stopping distance requirement, the agency was

essentially conceding its attempt to strengthen .105 in order to ensure

adequate dynamic performance of the parking brakes when all service

brakes fail.

CAS commented that NHTSA's defect files contradict GM's comment

that current brake system designs ``obviate the safety need'' for

emergency brakes and performance standards. It believed that in many

instances drivers have had to use the emergency brake as a last resort

to stop the car.

After reviewing the available information, NHTSA has determined

that a dynamic parking brake test would provide no significant safety

benefits. This decision is based on the fact that FMVSS No. 105 does

not include a dynamic parking brake test and on the current state of

braking technology. As the manufacturers correctly stated, the ECE

requirement pre-dated the widespread use of split service brake

systems, which are now standard on all passenger cars. Therefore, the

justification for using the parking brake in an emergency situation is

no longer relevant. The agency further notes that the partial failure

requirements are sufficient in dynamic emergency situations.

Advocates and CAS argued that these requirements are needed to

address the situation of ``complete failure'' of a service brake

system. The agency has no evidence that complete brake failure

(simultaneous failure of both circuits of a split brake system) occurs

with any significant frequency. Moreover, because the parking brake is

for static situations such as parking and not dynamic ones, the parking

brake is not designed to act in dynamic emergencies. Therefore, the

agency is concerned that applying the parking brake in emergency

situations may cause wheel lockup and instability. The agency further

notes that the initial impetus to harmonize with the ECE with respect

to a dynamic parking brake requirements will likely become moot, given

that the ECE is currently discussing deletion of this requirement from

R13 and R13H.

b. Static test. FMVSS No. 105 requires that a passenger car's

parking brake be able to hold the vehicle when it is parked on a 30

percent grade and a force is applied to the parking brake control not

exceeding 125 pounds for foot operated parking brake systems and 90

pounds for hand operated parking brake systems. In the NPRM, the agency

proposed requiring the brake to hold the vehicle when parked on a 20

percent grade and a force not exceeding 500N (112 pounds) for foot-

operated parking brakes and 320N (72 pounds) for hand operated parking

brakes.

In the 1991 SNPRM (Notice 5), NHTSA proposed that the parking brake

be able to hold the vehicle when it is parked on a 20 percent gradient

and a force is applied to the parking brake control not exceeding 500N

(112 pounds) for foot operated brakes and 400N (90 pounds) for hand

operated brakes. The static parking brake test is a pass/fail type of

test, i.e., the parking brake either holds the vehicle or it does not.

Accordingly, the test's stringency is determined by the gradient and

the allowable control force. The two test conditions are interrelated

since the higher the force that is applied to the control, the steeper

the gradient on which the vehicle can be held in place. In proposing in

the SNPRMs to have the hand control force limit at 400 N, the agency

stated that the static parking brake test would be somewhat less

stringent for manual transmission vehicles, but would be equivalent for

automatic transmission vehicles, which make up the majority of cars

sold in the U.S. today.

Advocates objected to the reinstatement in the 1987 SNPRM (Notice

4) of the 400 N (90 lbs.) allowable control force for hand brakes,

stating that the 320 N (72 lbs.) level proposed in the NPRM clearly

recognized the increasing prevalence of hand-operated parking brakes in

the American car fleet and the simultaneous surge in numbers and

percentage representation of elderly car operators who often cannot

apply high levels of force to hand-operated parking brakes.

Advocates also argued that other aspects of the existing parking

brake requirements of FMVSS No. 105 have been weakened. That

organization noted that the gradient for the parking brake test is 30

percent in FMVSS No. 105, as opposed to 20 percent in the proposed

FMVSS No. 135. Advocates stated that in order to offset this less

stringent test parameter, the agency proposed lower allowable control

forces in the NPRM, 500 N for foot-operated systems and 320 N for hand-

operated systems, but later conceded the proposed improvement for hand-

operated systems.

Advocates stated that in the 1987 SNPRM, NHTSA reasoned that it was

appropriate to specify a less severe gradient and a stronger engagement

force for hand-operated parking brakes, because the ``requirements are

somewhat less stringent than those of FMVSS No. 105, but [the agency]

also believes that the FMVSS No. 105 level of stringency for those

particular requirements is unsupported as

[[Page 6429]]

resulting in any measurable safety benefits over the proposal.''

Advocates argued that the agency's argument represents an

unsupported rationalization of an European standard with much less of a

discernible safety benefit. That commenter stated that on any

reasonable intuitive basis, it is clear that FMVSS No. 105 was aimed at

a higher level of safety and that the agency's original NPRM would have

strengthened FMVSS No. 105 and established improved safety for the

American motorist. That organization argued that NHTSA has made no

effort at any time over the life of FMVSS No. 105 to collect real-world

data on the safety benefits of its parking brake performance

requirements.

In contrast, Kelsey-Hayes commented that manufacturers will have to

make design changes since the 500 N (112 lbs) maximum foot operated

pedal force is a significant difference from the 556N (125 lbs)

permitted in FMVSS No. 105. Fiat stated that the agency should consider

a grade of 18 percent, which would be consistent with R13H.

The comments of Advocates and Kelsey-Hayes relate to proposals made

in the original NPRM (Notice 1) and the 1987 SNPRM (Notice 4). Those

arguments were already addressed by the agency in the second SNPRM

(Notice 5), and no new arguments have been presented by the commenters.

The requirements adopted in this final rule are unchanged from the two

SNPRMs.

Fiat is mistaken in its assertion that the grade should be 18%, to

be consistent with R13H. Although the gradient specified in R13 has

been changed to 18%, a corresponding change has not been made in the

latest proposal for R13H, the ECE's most recent statement about brake

harmonization. Therefore, the gradient and parking brake application

force levels adopted in this final rule are consistent with R13H.

Ford commented that the agency should substitute the phrase ``with

the average pedal force determined from the shortest GVWR cold

effectiveness stop'' for the phrase ``the service brake applied

sufficiently to just keep the vehicle from rolling.'' Ford believes the

actual force applied will vary greatly from driver to driver, and the

language as it presently stands is not an objective measure of the

amount of force.

NHTSA believes such a modification is not necessary. The agency

notes that the requirement is derived from the language in FMVSS No.

105, which has not presented any problem. The minimum force necessary

to keep the vehicle from rolling is a function of the vehicle, tires,

and roadway. The driver just keeps increasing the force until that

point is reached, and it will not vary from driver to driver.

Bendix requested that NHTSA specify whether the brake linings can

be heated up to an initial brake temperature before the static parking

brake test; and if so, to specify a procedure. Bendix stated that the

procedure would be especially important for vehicles with parking

systems that do not utilize the service friction elements.

NHTSA has decided to clarify the initial brake temperature

requirements in S7.12.2(a), because the proposal did not distinguish

the maximum initial brake temperature for the parking brake test by the

type of friction element and did not state how the initial brake

temperature should be achieved for the parking brakes. In the final

rule, the agency has decided to specify that the parking brakes with

service brake friction materials are to be tested with the initial

brake temperature less than or equal to 100 deg.C (212 deg.F), while

parking brakes with non-service brake friction materials are to be

tested at ambient temperature at the start of the test.

10. Fade and Recovery

In the 1985 NPRM (Notice 1), NHTSA proposed a fade and recovery

test to ensure adequate braking capability during and after exposure to

the high brake temperatures caused by prolonged or severe use. Such

temperatures are typically experienced in long, downhill driving.

Specifically, the agency developed a heating sequence for this proposal

based on SAE Recommended Practice J1247 (Apr 80), ``Simulated Mountain

Brake Performance Test Procedure.'' Among its provisions was reducing

the interval between snubs from 45 seconds to 30 seconds.12 The

agency stated that the proposed sequence was similar to those in FMVSS

No. 105, but produced a temperature cycle that more closely

approximates an actual mountain descent than either FMVSS No. 105 or

the ECE draft test procedure. Accordingly, the agency decided not to

propose the ECE's draft proposed heating sequence.

12In the 1987 SNPRM, NHTSA proposed an interval of 40

seconds.

---------------------------------------------------------------------------

In the 1991 SNPRM, NHTSA specified a heating sequence in S7.14, a

hot performance test in S7.15, a cooling sequence in S7.16, and a

recovery requirement in S7.17. The agency proposed that the required

stopping distance during the hot performance test be the shorter of 89

meters from a test speed of 100 km/h or 60 percent of the deceleration

achieved on the shortest fully loaded cold effectiveness stopping

distance. In addition, the agency revised certain test conditions and

procedures in the NPRM and 1987 SNPRM to reflect changes in performance

agreed to by the ECE and EEG. For instance, the agency proposed that

the pedal force be adjusted as necessary during each snub to maintain

the specified constant deceleration rate, rather than applying a

specific pedal force. The 1991 SNPRM also proposed that the interval

between the start of the snubs would be 45 seconds. The proposed

modifications to the fade and recovery test were consistent with

modifications made to other road tests being introduced in FMVSS No.

135. These include permitting momentary wheel lockup and a longer

reaction time in calculating the maximum stopping distance.

a. Heating snubs. In response to the proposal in S7.14 about

heating snubs, JAMA, MVMA, Chrysler, Ford, GM, and the GRRF stated that

the 45 second interval between snubs is appropriate. Chrysler submitted

test data showing that brake temperatures and brake lining temperatures

at 30 second intervals were significantly higher than under test

conditions in FMVSS No. 105, addressing fade.

In contrast, CAS and Advocates favored a 30 second interval, as

proposed in the NPRM. The advocacy groups claimed that by allowing

cooler brakes the stopping distance requirements will be less

stringent. Advocates stated that increasing the time interval between

heating snubs from 30 seconds in the NPRM to 40 seconds in the 1987

SNPRM, to 45 seconds in the 1991 SNPRM contradicted NHTSA's earlier

proposals and would not result in brake temperatures comparable to

those obtained in FMVSS No. 105.

Based on its testing and other available information, NHTSA has

determined that the 45 second interval is appropriate. As a result of

this time interval and other changes, the requirement will be closer in

stringency to ECE R13 and FMVSS No. 105. NHTSA believes that FMVSS No.

135's heating snub procedure is roughly equivalent to the requirements

in FMVSS No. 105. The agency notes that in the 1987 SNPRM, the agency

lengthened the time interval between snubs to 40 seconds, but shortened

the stopping distance on the hot stop test to compensate.

b. Hot performance. In response to the proposal in S7.15 about hot

performance, commenters addressed such issues as the stopping distance

requirement, the pedal force, and the number of stops. In Notice 5, the

agency increased the stopping distance in the

[[Page 6430]]

hot stop test slightly to maintain the same relationship to the cold

effectiveness stop.

JAMA and Toyota recommended that the stopping distance for the hot

performance test be lengthened to 90 meters. Similarly, Ford requested

that the stopping distance be lengthened to 93 meters. In contrast,

Advocates objected to the proposed increase in stopping distance from

80 meters in the NPRM, to 86 meters in the 1987 SNPRM, to 89 meters in

the 1991 SNPRM. It stated that the increased stopping distances will

result in the hot performance test being less likely to evaluate fade

since brakes will remain cooler.

After reviewing the available information, NHTSA has decided to

specify a stopping distance for the hot performance test of 89 meters,

as proposed in the 1991 SNPRM. The agency believes that this stopping

distance requirement will ensure adequate braking capability during and

after exposure to high brake temperatures caused by prolonged or severe

use. The first hot stop is done with a pedal force not greater than the

average pedal force recorded during the shortest GVWR cold

effectiveness test. The stopping distance for the first hot stop must

be less than or equal to the distance corresponding to 60 percent of

the deceleration actually achieved on the shortest GVWR cold

effectiveness stop. The second hot stop is done with a pedal force not

greater than 500N, and the stopping distance on at least one of the two

stops must also be less than or equal to 89 m or 0.10V+0.0079V2.

The agency notes that the results of the second stop may only be used

to satisfy the 89 m stopping distance requirement, and not the 60

percent requirement.

In response to Advocates, JAMA, Toyota, and Ford, NHTSA notes that

throughout this rulemaking, the hot performance stopping distance has

always been determined by a formula based on a constant percentage of

the deceleration rate for the cold effectiveness stop, and as the

latter was changed, so was the former. Accordingly, the stopping

distance proposed in the 1991 SNPRM served to retain the same

relationship to the cold effectiveness test. None of the commenters

presented compelling reasons why that philosophy should be abandoned.

Ford, GM and MVMA expressed concern about the proposed pedal force

test conditions for the hot performance stops. GM stated that the

proposed pedal force levels may make it difficult to comply with the

stopping distance requirement. GM requested that the agency adopt a

pedal force limitation of 500 N (112 lbs.) for both hot stops. Ford

recommended using a constant pedal force corresponding to approximately

90 percent in the cold effectiveness deceleration.

NHTSA has decided not to modify the test conditions with respect to

pedal force for these tests. The purpose of the hot performance test is

to determine how much the stopping performance of the vehicle will be

degraded as the result of the brakes being heated, as might happen

during a mountain descent or severe stop-and-go driving. The hot

performance is measured against two separate criteria. First, the

vehicle must attain a specific minimum level of absolute performance.

Second, it must attain a specified percentage of the performance

actually achieved in the ``cold'' condition, as measured by the cold

effectiveness test, even if that performance was significantly higher

than required. In order to determine compliance with the latter

requirement, the performance in the hot performance test is compared to

the performance of the brakes in the cold effectiveness test. In order

for that comparison to be meaningful, the test conditions for the two

tests should be as close to identical as possible.

For the cold effectiveness test, the test conditions are that the

pedal force must not exceed 500N (112 pounds), and the wheels must not

lock for more than 0.1 second. There are two different methods of

conducting this test. European testers usually use a constant pedal

force throughout any given test run. This constant pedal force is

increased in subsequent runs, until the point of wheel lockup is

reached, or the constant force reaches the 500N limit, whichever occurs

first. In the U.S., testers generally apply an initial ``spike'' of

pedal force, up to the point where the 500N limit is reached or a

``chirp'' is heard, indicating the start of wheel lockup, and then the

driver ``backs off'' on pedal force to the point where the wheels do

not stay locked. The ``U.S.'' method generally produces a slightly

shorter stopping distance, but either method is allowed as long as

neither limitation (500N or wheel lockup) is violated.

For the hot performance test, the ideal situation would be to

exactly duplicate the input (pedal force vs. time curve) from the cold

effectiveness test, so the outputs (stopping distances) from the two

tests can be compared. If the constant pedal force method has been used

for the cold effectiveness test, that is relatively easy to do. If the

``U.S.'' method has been used, however, the input is impossible to

duplicate exactly. In order to accommodate both methods of testing,

FMVSS No. 135 specifies that the pedal force for the first hot stop is

to be not greater than the average pedal force recorded on the best

cold effectiveness test run. The agency is aware that this test

condition does not ensure that the input from the cold effectiveness

test will be duplicated exactly. However, it is an objective test

condition, and government and industry experts who have discussed this

subject in numerous GRRF ad hoc meetings have not been able to come up

with a better approach. Accordingly, unless and until the European and

United States industry can agree on a replacement procedure, NHTSA

believes it would be inappropriate to modify the requirements.

Ford commented that the mean pedal force requirement left a

loophole that would allow ABS equipped vehicles to apply the full 500 N

pedal force in the cold effectiveness test and again in the first hot

stop. It believed that this would mask the hot versus cold performance.

NHTSA notes that although the situation described by Ford is

theoretically possible, it is highly unlikely that a manufacturer would

use this ``loophole'' to build a vehicle with poor hot performance

characteristics. The agency notes that such a brake system design would

create too great a likelihood that the ABS would allow lockup of

greater than 0.1 seconds or that the vehicle would have problems

passing the high speed effectiveness or failed-ABS tests.

Ford and Chrysler recommended that only one of the two stops be

required to meet the performance requirements. Chrysler stated that the

second stop is only run because of test driver uncertainty during the

first stop. It cited problems caused by the need for the test driver to

obtain the maximum performance from the brake system that, at the end

of the heating snubs, has unknown performance requirements. Chrysler

believed that if the first stop is invalidated because of wheel lock or

driver hesitation, the driver should be permitted to use this knowledge

in the second stop.

Chrysler's assertion that the second stop is only run because of

test driver uncertainty during the first stop is untrue. The reason a

second stop is needed is that there are two separate requirements to be

satisfied: a comparison with cold effectiveness performance and a

minimum level of absolute performance. The first stop provides the

comparison with cold performance, because the pedal force is limited to

the average pedal force applied on the best cold effectiveness stop. In

most cases, stopping

[[Page 6431]]

performance is degraded as a result of heating rather than improved, so

Chrysler's concern over inadvertent wheel lockup shouldn't be a problem

on this stop.

The required level of absolute performance may or may not be met on

this first stop. If it is not, the second stop allows a pedal force up

to 500N. The reasoning for allowing a greater pedal force is that, in

an actual driving situation, a driver will apply increased force to the

brake pedal to compensate somewhat for degraded brake performance.

Multiple attempts are not allowed on the hot stop because it is

important to measure hot performance while the brakes are still hot. If

multiple runs were allowed, the performance measured on subsequent runs

would not necessarily be a true measure of hot brake performance. While

this fact makes the test somewhat more difficult to run, the agency

found in its testing that it did not present problems for experienced

test drivers.

c. Recovery performance. The GRRF and Fiat believed that to

harmonize with R13H, the provision about pedal force needed to be

modified to state that ``a pedal force not greater than the average

pedal force recorded during the shortest GVWR cold effectiveness

stops.'' The GRRF further stated that the fade and recovery and hot

performance tests should be compared with the cold effectiveness test

and that the comparison would only be valid if the input (i.e., pedal

force) is the same in each test and the output (deceleration or

stopping distance) is measured as in R13 and R13H.

The wording in S7.14.3(c) regarding the hot stop is already as

requested by GRRF and Fiat, and NHTSA has decided to make a

corresponding change in S7.16.3(c) to accommodate GRRF's request. The

agency believes that this modification will help harmonize the

standards without any corresponding detriment to safety.

Advocates recommended returning to an over-recovery deceleration

based on 120 percent of the shortest GVWR cold effectiveness stop.

As explained in the 1987 SNPRM when the deceleration rate was

increased to 150 percent, the test is still more stringent than FMVSS

No. 105, even at the higher level. The performance requirement has

remained unchanged since 1987, and Advocates has presented no reason

why it should be changed now. Accordingly, the agency has adopted the

requirement as proposed in the two SNPRMs.

Bendix and Ford requested the agency to define ``average pedal

force'' more fully. Bendix also asked the agency to define the phrase

``not greater than'' for purposes of the hot performance test.

NHTSA believes the terms ``average'' and ``not greater than'' are

used the same way they would be defined in any dictionary, and

therefore no definition is needed in the standard. Nevertheless, to

avoid any misunderstanding, the terms are explained as follows: The

term ``average pedal force'' is defined as the average value taken from

the initiation of the pedal force until completion of the cold

effectiveness stop. It is calculated from the pedal force/time curve of

the shortest GVWR cold effectiveness stop, and includes any overshoot

or spike that may be present at the beginning of the test. The phrase

``not greater than'' means that the maximum pedal force which can be

applied during the first hot stop cannot exceed the average pedal

force.

GM, MVMA, JAMA, Toyota and Ford believe that the response term

(0.10V) of the recovery stop equation (S7.17.4) has been omitted (i.e.,

`` * * * S-0.10V * * * '' instead of `` * * *

S * * * '', thereby resulting in an ``apples-

to-oranges'' comparison of the recovery stopping distance without

adjusting for response time to the cold effectiveness stopping distance

which is adjusted for response time. They believe the intent is to

regulate recovery as a function of cold effectiveness performance after

both are corrected to eliminate the response time distance. They

believe that the equation should read as follows: 0.0386V\2\/

1.50dc S-0.10V 0.0386V\2\/0.70dc

NHTSA agrees that the 0.10V term should be in the stopping distance

for recovery performance and has therefore made the following

correction to the equation in S7.17.4:

[GRAPHIC][TIFF OMITTED]TR02FE95.017

G. Miscellaneous Comments

Advocates argued for inclusion of water recovery, spike stop and

final effectiveness requirements that appear in FMVSS No. 105, but are

not included in FMVSS No. 135. Advocates believes that the absence of

these requirements will result in a degradation of safety.

NHTSA has already addressed the need, or lack of it, for these

requirements in previous notices, and need not be repeated here.

Advocates presented nothing to justify their arguments but unsupported

conjecture. The agency has considered Advocates' comments, and has

decided that there is insufficient justification for inclusion of these

requirements.

Advocates also made general comments opposing this rulemaking as a

whole. They stated that the resulting standard is decidedly inferior in

multiple aspects to the existing FMVSS No. 105. Advocates expressed the

fear that the new standard would allow the importation of cars without

power assist, antilock brakes, automatic brake monitoring, and other

desirable features of superior brake performance, that meet only the

minimum requirements of FMVSS No. 135. It stated that these would

likely be the smallest, cheapest cars on the market, which would also

have the poorest overall crashworthiness.

The agency notes that none of the advanced safety features

mentioned by Advocates are presently required by FMVSS No. 105.

Advocates' assertion that FMVSS No. 135 is inferior to FMVSS No. 105 is

contradicted by previously cited agency and industry test data which

show the new standard to be at least, if not more difficult to meet,

overall, than the existing FMVSS No. 105. Accordingly, the agency is

not convinced by Advocates' arguments in opposition of the new

standard, and has decided to issue this final rule.

IV. Regulatory Analysis

A. Executive Order 12866 (Regulatory Planning and Review) and DOT

Regulatory Policies and Procedures

This rulemaking document was not reviewed under Executive Order

12866. NHTSA has considered the economic implications of this

regulation and determined that it is not significant within the meaning

of the DOT Regulatory Policies and Procedure. A Final Regulatory

Evaluation (FRE) has been prepared setting forth the agency's detailed

analysis of the economic effects of this rule, and has been placed in

the public docket.

Based on its analysis, NHTSA has determined that FMVSS No. 135

ensure an equivalent level of safety for those aspects of performance

covered by FMVSS No. 105 and will also address additional areas of

brake performance which offer safety benefits. It will offer decreased

costs for the production of passenger cars, by reducing non-tariff

barriers to trade. Further, the agency believes that the full test

procedure in the new standard will require approximately the same

amount of time and money to complete as the existing procedure under

FMVSS No. 105.

[[Page 6432]]

B. Regulatory Flexibility Act

In accordance with the Regulatory Flexibility Act, NHTSA has

evaluated the effects of this action on small entities. Based upon this

evaluation, I certify that the final rule will not have a significant

economic impact on a substantial number of small entities. Only

relatively simple changes will generally be needed for all passenger

cars to meet this standard. These changes will not significantly affect

the purchase price of a vehicle. No changes will be needed for many

cars. While some change in compliance costs may occur, the change will

not be of a magnitude which will significantly affect the purchase

price of a vehicle. For these reasons, neither manufacturers of

passenger cars, nor small businesses, small organizations, and small

governmental units which purchase motor vehicles, will be significantly

affected by the proposed standard. Accordingly, no regulatory

flexibility analysis has been prepared.

C. Executive Order 12612 (Federalism)

This action has been analyzed in accordance with the principles and

criteria contained in Executive Order 12612, and it has been determined

that the final rule did not have sufficient Federalism implications to

warrant preparation of a Federalism Assessment. No State laws are

affected.

D. Executive Order 12778 (Civil Justice Reform)

This final rule does not have any retroactive effect. Under 49

U.S.C. 30103, whenever a Federal motor vehicle safety standard is in

effect, a State may not adopt or maintain a safety standard applicable

to the same aspect of performance which is not identical to the Federal

standard, except to the extent that the State requirement imposes a

higher level of performance and applies only to vehicles procured for

the State's use. 49 U.S.C. 30161 sets forth a procedure for judicial

review of final rules establishing, amending or revoking Federal motor

vehicle safety standards. That section does not require submission of a

petition for reconsideration or other administrative proceedings before

parties may file suit in court.

E. National Environmental Policy Act

The agency has considered the environmental implications of this

rule in accordance with the National Environmental Policy Act of 1969

and determined that this rule will not significantly affect the human

environment. No changes in existing production or disposal processes

result.

List of Subjects in 49 CFR Part 571

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

products, Tires.

PART 571--[AMENDED]

In consideration of the foregoing, 49 CFR part 571 is being amended

as follows:

1. The authority citation for part 571 continues to read as

follows:

Authority: 49 U.S.C. 322, 30111, 30115, 30117 and 30166;

delegation of authority at 49 CFR 1.50.

2. Section 571.101 is amended by revising table 2 as follows:

Sec. 571.101 Standard No. 101: Controls and displays.

* * * * *

BILLING CODE 4910-59-P

[[Page 6433]]

[GRAPHIC][TIFF OMITTED]TR02FE95.000

BILLING CODE 4910-59-C

[[Page 6434]]

3. Section 571.105 is amended by revising S3 to read as follows:

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

* * * * *

S3. Application. This standard applies to multipurpose passenger

vehicles, trucks, and buses with hydraulic brake systems, and to

passenger cars manufactured before September 1, 2000, with hydraulic

brake systems. At the option of the manufacturer, passenger cars

manufactured before September 1, 2000 may comply with the requirements

of Federal Motor Vehicle Safety Standard No. 135, Passenger Car Brake

Systems, instead of the requirements of this standard.

4. A new Sec. 571.135 is added to read as follows:

Sec. 571.135 Standard No. 135: Passenger car brake systems.

S1. Scope. This standard specifies requirements for service brake

and associated parking brake systems.

S2. Purpose. The purpose of this standard is to ensure safe braking

performance under normal and emergency driving conditions.

S3. Application. This standard applies to passenger cars

manufactured on or after September 1, 2000. In addition, passenger cars

manufactured before September 1, 2000, may, at the option of the

manufacturer, meet the requirements of this standard instead of Federal

Motor Vehicle Safety Standard No. 105, Hydraulic Brake Systems.

S4. Definitions.

Adhesion utilization curves means curves showing, for specified

load conditions, the adhesion utilized by each axle of a vehicle

plotted against the braking ratio of the vehicle.

Antilock brake system or ABS means 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 controlling devices which interpret those

signals and generate responsive controlling output signals; and

(3) Transmitting those controlling signals to one or more modulator

devices which adjust brake actuating forces in response to those

signals.

Backup system means a portion of a service brake system, such as a

pump, that automatically supplies energy in the event of a primary

brake power source failure.

Brake factor means the slope of the linear least squares regression

equation best representing the measured torque output of a brake as a

function of the measured applied line pressure during a given brake

application for which no wheel lockup occurs.

Brake hold-off pressure means the maximum applied line pressure for

which no brake torque is developed, as predicted by the pressure axis

intercept of the linear least squares regression equation best

representing the measured torque output of a brake as a function of the

measured applied line pressure during a given brake application.

Brake power assist unit means a device installed in a hydraulic

brake system that reduces the amount of muscular force that a driver

must apply to actuate the system, and that, if inoperative, does not

prevent the driver from braking the vehicle by a continued application

of muscular force on the service brake control.

Brake power unit means a device installed in a brake system that

provides the energy required to actuate the brakes, either directly or

indirectly through an auxiliary device, with driver action consisting

only of modulating the energy application level.

Braking ratio means the deceleration of the vehicle divided by the

gravitational acceleration constant.

Functional failure means a failure of a component (either

electrical or mechanical in nature) which renders the system totally or

partially inoperative yet the structural integrity of the system is

maintained.

Hydraulic brake system means a system that uses hydraulic fluid as

a medium for transmitting force from a service brake control to the

service brake and that may incorporate a brake power assist unit, or a

brake power unit.

Initial brake temperature or IBT means the average temperature of

the service brakes on the hottest axle of the vehicle 0.32 km (0.2

miles) before any brake application.

Lightly loaded vehicle weight or LLVW means unloaded vehicle weight

plus the weight of a mass of 180 kg (396 pounds), including driver and

instrumentation.

Maximum speed of a vehicle or Vmax means the highest speed

attainable by accelerating at a maximum rate from a standing start for

a distance of 3.2 km (2 miles) on a level surface, with the vehicle at

its lightly loaded weight.

Objective brake factor means the arithmetic average of all the

brake factors measured over the twenty brake applications defined in

S7.4, for all wheel positions having a given brake configuration.

Peak friction coefficient or PFC means the ratio of the maximum

value of braking test wheel longitudinal force to the simultaneous

vertical force occurring prior to wheel lockup, as the braking torque

is progressively increased.

Pressure component means a brake system component that contains the

brake system fluid and controls or senses the fluid pressure.

Snub means the braking deceleration of a vehicle from a higher

reference speed to a lower reference speed that is greater than zero.

Split service brake system means a brake system consisting of two

or more subsystems actuated by a single control designed so that a

leakage-type failure of a pressure component in a single subsystem

(except structural failure of a housing that is common to two or more

subsystems) does not impair the operation of any other subsystem.

Stopping distance means the distance traveled by a vehicle from the

point of application of force to the brake control to the point at

which the vehicle reaches a full stop.

Variable brake proportioning system means a system that has one or

more proportioning devices which automatically change the brake

pressure ratio between any two or more wheels to compensate for changes

in wheel loading due to static load changes and/or dynamic weight

transfer, or due to deceleration.

Wheel lockup means 100 percent wheel slip.

S5. Equipment requirements.

S5.1. Service brake system. Each vehicle shall be equipped with a

service brake system acting on all wheels.

S5.1.1. Wear adjustment. Wear of the service brakes shall be

compensated for by means of a system of automatic adjustment.

S5.1.2. Wear status. The wear condition of all service brakes shall

be indicated by either:

(a) Acoustic or optical devices warning the driver at his or her

driving position when lining replacement is necessary, or

(b) A means of visually checking the degree of brake lining wear,

from the outside or underside of the vehicle, utilizing only the tools

or equipment normally supplied with the vehicle. The removal of wheels

is permitted for this purpose.

S5.2. Parking brake system. Each vehicle shall be equipped with a

parking brake system of a friction type with solely mechanical means to

retain engagement.

S5.3. Controls.

S5.3.1. The service brakes shall be activated by means of a foot

control. The control of the parking brake shall be independent of the

service brake

[[Page 6435]]

control, and may be either a hand or foot control.

S5.3.2. For vehicles equipped with ABS, a control to manually

disable the ABS, either fully or partially, is prohibited.

S5.4. Reservoirs.

S5.4.1. Master cylinder reservoirs. A master cylinder shall have a

reservoir compartment for each service brake subsystem serviced by the

master cylinder. Loss of fluid from one compartment shall not result in

a complete loss of brake fluid from another compartment.

S5.4.2. Reservoir capacity. Reservoirs, whether for master

cylinders or other type systems, shall have a total minimum capacity

equivalent to the fluid displacement resulting when all the wheel

cylinders or caliper pistons serviced by the reservoirs move from a new

lining, fully retracted position (as adjusted initially to the

manufacturer's recommended setting) to a fully worn, fully applied

position, as determined in accordance with S7.17(c) of this standard.

Reservoirs shall have completely separate compartments for each

subsystem except that in reservoir systems utilizing a portion of the

reservoir for a common supply to two or more subsystems, individual

partial compartments shall each have a minimum volume of fluid equal to

at least the volume displaced by the master cylinder piston servicing

the subsystem, during a full stroke of the piston. Each brake power

unit reservoir servicing only the brake system shall have a minimum

capacity equivalent to the fluid displacement required to charge the

system piston(s) or accumulator(s) to normal operating pressure plus

the displacement resulting when all the wheel cylinders or caliper

pistons serviced by the reservoir or accumulator(s) move from a new

lining, fully retracted position (as adjusted initially to the

manufacturer's recommended setting) to a fully worn, fully applied

position.

S5.4.3. Reservoir labeling. Each vehicle shall have a brake fluid

warning statement that reads as follows, in letters at least 3.2 mm

(\1/8\ inch) high: ``WARNING: Clean filler cap before removing. Use

only ________ fluid from a sealed container.'' (Inserting the

recommended type of brake fluid as specified in 49 CFR 571.116,

e.g.,``DOT 3.'') The lettering shall be:

(a) Permanently affixed, engraved or embossed;

(b) Located so as to be visible by direct view, either on or within

100 mm (3.94 inches) of the brake fluid reservoir filler plug or cap;

and

(c) Of a color that contrasts with its background, if it is not

engraved or embossed.

S5.4.4. Fluid level indication. Brake fluid reservoirs shall be so

constructed that the level of fluid can be checked without need for the

reservoir to be opened. This requirement is deemed to have been met if

the vehicle is equipped with a transparent brake fluid reservoir or a

brake fluid level indicator meeting the requirements of S5.5.1(a)(1).

S5.5. Brake system warning indicator.

This text is long and has been trimmed here. Open the source document for the complete record.