[Federal Register Volume 60, Number 22 (Thursday, February 2, 1995)]
[Rules and Regulations]
[Pages 6411-6446]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-2324]



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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 < 100  deg.C (212  deg.F) to ``ambient 
temperature plus 100  deg.C.'' They believed that this would normalize 
the actual amount of brake burnish achieved and thus could reduce the 
amount of time required to run the burnish.
    NHTSA notes that the burnish IBT is set at an upper limit to avoid 
overheating. Since the friction coefficient of the brake linings varies 
with the IBT, allowing a ``range of IBT upper limits'' is not an 
objective test condition.
    NHTSA continues to believe that the burnish procedures being 
adopted in this final rule represents an efficient, representative 
burnish procedure that is consistent with the GRRF proposal.
    Honda requested the agency clarify that the road surface condition 
specified 

[[Page 6420]]
in S6.2 not apply to S7.1.3(j) (i.e., that the road surface with a PFC 
of 0.9 not apply to burnish procedures).
    NHTSA agrees with Honda that this provision needs to be clarified 
since burnish is merely a conditioning procedure for brakes and does 
not actually test for a specified stopping distance on a road of a 
particular adhesion quality. The PFC of the road surface has no effect 
on the burnish. Accordingly, S7.1.3 is modified to include a sentence 
stating that ``The road test surface conditions specified in S6.2 do 
not apply to the burnish procedure.''
5. Adhesion Utilization
    a. General. In the NPRM (Notice 1) and both SNPRMs (Notices 4 and 
5), NHTSA proposed adhesion utilization requirements to ensure that a 
vehicle's brake system is able to utilize the available adhesion at the 
tire-road interface to ensure stable stops within a specified distance. 
Adhesion utilization is addressed to some extent by FMVSS No. 105's 
(and the proposed standard's) service brake effectiveness requirements, 
since stops must be made within specified distances without leaving a 
lane of specified width. Under both standards, however, all of those 
stops are made on a high friction surface. The existing standard does 
not include any requirements concerning stops made on lower friction 
surfaces, such as wet roads. Therefore, unlike most of the proposed 
requirements for FMVSS No. 135, the adhesion utilization requirements 
do not have any corresponding requirement in FMVSS No. 105.
    NHTSA notes that the proposed adhesion utilization requirements 
evolved considerably over the course of the NPRM and two SNPRM's. 
Persons interested in the reasons for that evolution, leading up to the 
proposal set forth in the 1991 SNPRM, are referred to those three 
notices.
    In the 1991 SNPRM, NHTSA proposed a two-step procedure for 
assessing adhesion utilization based on a determination of the 
vehicle's brake balance: a wheel lock sequence test and then, for those 
vehicles that did not pass the wheel lock sequence test, a torque wheel 
test. The purpose of the wheel lock sequence test is to identify those 
vehicles that are heavily front biased, since such vehicles would be 
considered to have inherently good stability characteristics. The 
purpose of the torque wheel test is to evaluate more precisely those 
vehicles that fail the wheel lock sequence test, since torque wheels 
directly measure braking forces. The agency believed that this 
approach, which is based on a suggestion from the Organization 
Internationale des Constructeurs d'Automobiles (OICA), would 
accommodate vehicles that are heavily front biased in their brake 
balance and those that are closer to neutral balance. The agency 
believed that this proposal would ensure an appropriate level of safety 
as well as facilitate harmonization since GRRF agreed to adopt this 
approach as part of its harmonized adhesion utilization procedures.
    CAS opposed the adhesion utilization tests proposed in the 1991 
SNPRM. It requested that the agency specify other methods of adhesion 
utilization to produce objective results for all passenger cars. CAS 
was concerned that vehicles that marginally pass the wheel lock 
sequence test would undergo no further testing of front-to-rear brake 
balance. Instead of the proposed adhesion utilization tests, CAS 
suggested the use of Hunter Manufacturing's low-speed plate brake 
tester.
    NHTSA believes that the adhesion utilization tests being adopted in 
today's final rule provide the most practicable and appropriate methods 
to evaluate a vehicle's adhesion utilization. The wheel lock sequence 
test screens out vehicles with front bias, which have inherently 
superior stability.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. Each vehicle shall have one 
or more visual brake system warning indicators, mounted in front of and 
in clear view of the driver, which meet the requirements of S5.5.1 
through S5.5.5. In addition, a vehicle manufactured without a split 
service brake system shall be equipped with an audible warning signal 
that activates under the conditions specified in S5.5.1(a).
    S5.5.1. Activation. An indicator shall be activated when the 
ignition (start) switch is in the ``on'' (``run'') position and 
whenever any of conditions (a), (b), (c) or (d) occur:
    (a) A gross loss of fluid or fluid pressure (such as caused by 
rupture of a brake line but not by a structural failure of a housing 
that is common to two or more subsystems) as indicated by one of the 
following conditions (chosen at the option of the manufacturer):
    (1) A drop in the level of the brake fluid in any master cylinder 
reservoir compartment to less than the recommended safe level specified 
by the manufacturer or to one-fourth of the fluid capacity of that 
reservoir compartment, whichever is greater.
    (2) For vehicles equipped with a split service brake system, a 
differential pressure of 1.5 MPa (218 psi) between the intact and 
failed brake subsystems measured at a master cylinder outlet or a slave 
cylinder outlet.
    (3) A drop in the supply pressure in a brake power unit to one-half 
of the normal system pressure.
    (b) Any electrical functional failure in an antilock or variable 
brake proportioning system.
    (c) Application of the parking brake.
    (d) Brake lining wear-out, if the manufacturer has elected to use 
an electrical device to provide an optical warning to meet the 
requirements of S5.1.2(a).
    S5.5.2. Function check.
    (a) All indicators shall be activated as a check function by 
either:
    (1) Automatic activation when the ignition (start) switch is turned 
to the ``on'' (``run'') position when the engine is not running, or 
when the ignition (``start'') switch is in a position between ``on'' 
(``run'') and ``start'' that is designated by the manufacturer as a 
check position, or
    (2) A single manual action by the driver, such as momentary 
activation of a test button or switch mounted on the instrument panel 
in front of and in clear view of the driver, or, in the case of an 
indicator for application of the parking brake, by applying the parking 
brake when the ignition is in the ``on'' (``run'') position.
    (b) In the case of a vehicle that has an interlock device that 
prevents the engine from being started under one or more conditions, 
check functions meeting the requirements of S5.5.2(a) need not be 
operational under any condition in which the engine cannot be started.
    (c) The manufacturer shall explain the brake check function test 
procedure in the owner's manual.
    S5.5.3. Duration. Each indicator activated due to a condition 
specified in S5.5.1 shall remain activated as long as the condition 
exists, whenever the ignition (``start'') switch is in the ``on'' 
(``run'') position, whether or not the engine is running.
    S5.5.4. Function. When a visual warning indicator is activated, it 
may be continuous or flashing, except that the visual warning indicator 
on a vehicle not equipped with a split service brake system shall be 
flashing. The audible warning required for a vehicle manufactured 
without a split service brake system may be continuous or intermittent.
    S5.5.5. Labeling.
    (a) Each visual indicator shall display a word or words in 
accordance with the requirements of Standard No. 101 (49 CFR 571.101) 
and this section, which shall be legible to the driver under all 
daytime and nighttime conditions when activated. Unless otherwise 
specified, the words shall have letters not less than 3.2 mm (\1/8\ 
inch) high and the letters and background shall be of contrasting 
colors, one of which is red. Words or symbols in addition to those 
required by Standard No. 101 and this section may be provided for 
purposes of clarity.
    (b) Vehicles manufactured with a split service brake system may use 
a common brake warning indicator to indicate two or more of the 
functions described in S5.5.1(a) through S5.5.1(d). If a common 
indicator is used, it shall display the word ``Brake.''
    (c) A vehicle manufactured without a split service brake system 
shall use a separate indicator to indicate the failure condition in 
S5.5.1(a). This indicator shall display the words ``STOP--BRAKE 
FAILURE'' in block capital letters not less than 6.4 mm (\1/4\ inch) in 
height. 

[[Page 6436]]

    (d) If separate indicators are used for one or more than one of the 
functions described in S5.5.1(a) to S5.5.1(d), the indicators shall 
display the following wording:
    (1) If a separate indicator is provided for the low brake fluid 
condition in S5.5.1(a)(1), the words ``Brake Fluid'' shall be used 
except for vehicles using hydraulic system mineral oil.
    (2) If a separate indicator is provided for the gross loss of 
pressure condition in S5.5.1(a)(2), the words ``Brake Pressure'' shall 
be used.
    (3) If a separate indicator is provided for the condition specified 
in S5.5.1(b), the letters and background shall be of contrasting 
colors, one of which is yellow. The indicator shall be labeled with the 
words ``Antilock'' or ``Anti-lock'' or ``ABS''; or ``Brake 
Proportioning,'' in accordance with Table 2 of Standard No. 101.
    (4) If a separate indicator is provided for application of the 
parking brake as specified for S5.5.1(c), the single word ``Park'' or 
the words ``Parking Brake'' may be used.
    (5) If a separate indicator is provided to indicate brake lining 
wear-out as specified in S5.5.1(d), the words ``Brake Wear'' shall be 
used.
    (6) If a separate indicator is provided for any other function, the 
display shall include the word ``Brake'' and appropriate additional 
labeling.
    S5.6. Brake system integrity. Each vehicle shall meet the complete 
performance requirements of this standard without:
    (a) Detachment or fracture of any component of the braking system, 
such as brake springs and brake shoes or disc pad facings other than 
minor cracks that do not impair attachment of the friction facings. All 
mechanical components of the braking system shall be intact and 
functional. Friction facing tearout (complete detachment of lining) 
shall not exceed 10 percent of the lining on any single frictional 
element.
    (b) Any visible brake fluid or lubricant on the friction surface of 
the brake, or leakage at the master cylinder or brake power unit 
reservoir cover, seal, and filler openings.
    S6. General test conditions. Each vehicle must meet the performance 
requirements specified in S7 under the following test conditions and in 
accordance with the test procedures and test sequence specified. Where 
a range of conditions is specified, the vehicle must meet the 
requirements at all points within the range.
    S6.1. Ambient conditions.
    S6.1.1. Ambient temperature. The ambient temperature is any 
temperature between O  deg.C (32  deg.F) and 40  deg.C (104  deg.F).
    S6.1.2. Wind speed. The wind speed is not greater than 5 m/s (11.2 
mph).
    S6.2. Road test surface.
    S6.2.1. Pavement friction. Unless otherwise specified, the road 
test surface produces a peak friction coefficient (PFC) of 0.9 when 
measured using an American Society for Testing and Materials (ASTM) 
E1136 standard reference test tire, in accordance with ASTM Method E 
1337-90, at a speed of 64.4 km/h (40 mph), without water delivery.
    S6.2.2. Gradient. Except for the parking brake gradient holding 
test, the test surface has no more than a 1% gradient in the direction 
of testing and no more than a 2% gradient perpendicular to the 
direction of testing.
    S6.2.3. Lane width. Road tests are conducted on a test lane 3.5 m 
(11.5 ft) wide.
    S6.3. Vehicle conditions.
    S6.3.1. Vehicle weight.
    S6.3.1.1. For the tests at GVWR, the vehicle is loaded to its GVWR 
such that the weight on each axle as measured at the tire-ground 
interface is in proportion to its GAWR, with the fuel tank filled to 
100% of capacity. However, if the weight on any axle of a vehicle at 
LLVW exceeds the axle's proportional share of the GVWR, the load 
required to reach GVWR is placed so that the weight on that axle 
remains the same as at LLVW.
    S6.3.1.2. For the test at LLVW, the vehicle is loaded to its LLVW 
such that the added weight is distributed in the front passenger seat 
area.
    S6.3.2. Fuel tank loading. The fuel tank is filled to 100% of 
capacity at the beginning of testing and may not be less than 75% of 
capacity during any part of the testing.
    S6.3.3. Lining preparation. At the beginning of preparation for the 
road tests, the brakes of the vehicle are in the same condition as when 
the vehicle was manufactured. No burnishing or other special 
preparation is allowed, unless all vehicles sold to the public are 
similarly prepared as a part of the manufacturing process.
     S6.3.4. Adjustments and repairs. These requirements must be met 
without replacing any brake system parts or making any adjustments to 
the brake system except as specified in this standard. Where brake 
adjustments are specified (S7.1.3), adjust the brakes, including the 
parking brakes, in accordance with the manufacturer's recommendation. 
No brake adjustments are allowed during or between subsequent tests in 
the test sequence.
    S6.3.5. Automatic brake adjusters. Automatic adjusters are 
operational throughout the entire test sequence. They may be adjusted 
either manually or by other means, as recommended by the manufacturer, 
only prior to the beginning of the road test sequence.
    S6.3.6. Antilock brake system (ABS). If a car is equipped with an 
ABS, the ABS is fully operational for all tests, except where specified 
in the following sections.
    S6.3.7. Variable brake proportioning valve. If a car is equipped 
with a variable brake proportioning system, the proportioning valve is 
fully operational for all tests except the test for failed variable 
brake proportioning system.
    S6.3.8. Tire inflation pressure. Tires are inflated to the pressure 
recommended by the vehicle manufacturer for the GVWR of the vehicle.
    S6.3.9. Engine. Engine idle speed and ignition timing are set 
according to the manufacturer's recommendations. If the vehicle is 
equipped with an adjustable engine speed governor, it is adjusted 
according to the manufacturer's recommendations.
    S6.3.10. Vehicle openings. All vehicle openings (doors, windows, 
hood, trunk, convertible top, cargo doors, etc.) are closed except as 
required for instrumentation purposes.
    S6.4. Instrumentation.
    S6.4.1. Brake temperature measurement. The brake temperature is 
measured by plug-type thermocouples installed in the approximate center 
of the facing length and width of the most heavily loaded shoe or disc 
pad, one per brake, as shown in Figure 1. A second thermocouple may be 
installed at the beginning of the test sequence if the lining wear is 
expected to reach a point causing the first thermocouple to contact the 
metal rubbing surface of a drum or rotor. For center-grooved shoes or 
pads, thermocouples are installed within 3 mm (.12 in) to 6 mm (.24 in) 
of the groove and as close to the center as possible.
    S6.4.2. Brake line pressure measurement for the torque wheel test. 
The vehicle shall be fitted with pressure transducers in each hydraulic 
circuit. On hydraulically proportioned circuits, the pressure 
transducer shall be downstream of the operative proportioning valve.
    S6.4.3. Brake torque measurement for the torque wheel test. The 
vehicle shall be fitted with torque wheels at each wheel position, 
including slip ring assemblies and wheel speed indicators to permit 
wheel lock to be detected.

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[GRAPHIC][TIFF OMITTED]TR02FE95.001



[[Page 6438]]

    S6.5. Procedural conditions.
    S6.5.1. Brake control. All service brake system performance 
requirements, including the partial system requirements of S7.7, S7.10 
and S7.11, must be met solely by use of the service brake control.
    S6.5.2. Test speeds. If a vehicle is incapable of attaining the 
specified normal test speed, it is tested at a speed that is a multiple 
of 5 km/h (3.1 mph) that is 4 to 8 km/h (2.5 to 5.0 mph) less than its 
maximum speed and its performance must be within a stopping distance 
given by the formula provided for the specific requirement.
    S6.5.3. Stopping distance.
    S6.5.3.1. The braking performance of a vehicle is determined by 
measuring the stopping distance from a given initial speed.
    S6.5.3.2. Unless otherwise specified, the vehicle is stopped in the 
shortest distance achievable (best effort) on all stops. Where more 
than one stop is required for a given set of test conditions, a vehicle 
is deemed to comply with the corresponding stopping distance 
requirements if at least one of the stops is made within the prescribed 
distance.
    S6.5.3.3. In the stopping distance formulas given for each 
applicable test (such as S=0.10V+0.0060V\2\), S is the maximum stopping 
distance in meters, and V is the test speed in km/h.
    S6.5.4. Vehicle position and attitude.
    S6.5.4.3. The vehicle is aligned in the center of the lane at the 
start of each brake application. Steering corrections are permitted 
during each stop.
    S6.5.4.2. Stops are made without any part of the vehicle leaving 
the lane and without rotation of the vehicle about its vertical axis of 
more than 15 deg. from the center line of the test lane at 
any time during any stop.
    S6.5.5. Transmission selector control.
    S6.5.5.1. For tests in neutral, a stop or snub is made in 
accordance with the following procedures:
    (a) Exceed the test speed by 6 to 12 km/h (3.7 to 7.5 mph);
    (b) Close the throttle and coast in gear to approximately 3 km/h 
(1.9 mph) above the test speed;
    (c) Shift to neutral; and
    (d) When the test speed is reached, apply the brakes.
    S6.5.5.2. For tests in gear, a stop or snub is made in accordance 
with the following procedures:
    (a) With the transmission selector in the control position 
recommended by the manufacturer for driving on a level surface at the 
applicable test speed, exceed the test speed by 6 to 12 km/h (3.7 to 
7.5 mph);
    (b) Close the throttle and coast in gear; and
    (c) When the test speed is reached apply the brakes.
    (d) To avoid engine stall, a manual transmission may be shifted to 
neutral (or the clutch disengaged) when the vehicle speed is below 30 
km/h (18.6 mph).
    S6.5.6. Initial brake temperature (IBT). If the lower limit of the 
specified IBT for the first stop in a test sequence (other than a 
parking brake grade holding test) has not been reached, the brakes are 
heated to the IBT by making one or more brake applications from a speed 
of 50 km/h (31.1 mph), at a deceleration rate not greater than 3 m/s\2\ 
(9.8 fps\2\).
    S7. Road test procedures and performance requirements. Each vehicle 
shall meet all the applicable requirements of this section, when tested 
according to the conditions and procedures set forth below and in S6, 
in the sequence specified in Table 1.

                      Table 1.--Road Test Schedule                      
------------------------------------------------------------------------
                                                                Section 
                        Testing order                             No.   
------------------------------------------------------------------------
Vehicle loaded to GVWR:                                                 
    1  Burnish...............................................      S7.1 
    2  Wheel lock sequence...................................      S7.2 
Vehicle loaded to LLVW:                                                 
    3  Wheel lock sequence...................................      S7.2 
    4  ABS performance.......................................      S7.3 
    5  Torque wheel..........................................      S7.4 
Vehicle laded to GVWR:                                                  
    6  Torque wheel..........................................      S7.4 
    7  Cold effectiveness....................................      S7.5 
    8  High speed effectiveness..............................      S7.6 
    9  Stops with engine off.................................      S7.7 
Vehicle loaded to LLVW:                                                 
    10  Cold effectiveness...................................      S7.5 
    11  High speed effectiveness.............................      S7.6 
    12  Failed antilock......................................      S7.8 
    13  Failed proportioning valve...........................      S7.9 
    14  Hydraulic circuit failure............................      S7.10
Vehicle loaded to GVWR:                                                 
    15  Hydraulic circuit failure............................      S7.10
    16  Failed antilock......................................      S7.8 
    17  Failed proportioning valve...........................      S7.9 
    18  Power brake unit failure.............................      S7.11
    19  Parking brake--static................................      S7.12
    20  Parking brake--dynamic...............................      S7.13
    21  Heating snubs........................................      S7.14
    22  Hot performance......................................      S7.15
    23  Brake cooling........................................      S7.16
    24  Recovery performance.................................      S7.17
    25  Final inspection.....................................      S7.18
------------------------------------------------------------------------

    S7.1. Burnish.
    S7.1.1. General information. Any pretest instrumentation checks are 
conducted as part of the burnish procedure, including any necessary 
rechecks after instrumentation repair, replacement or adjustment. 
Instrumentation check test conditions must be in accordance with the 
burnish test procedure specified in S7.1.2 and S7.1.3.
    S7.1.2. Vehicle conditions.
    (a) Vehicle load: GVWR only.
    (b) Transmission position: In gear.
    S7.1.3. Test conditions and procedures. The road test surface 
conditions specified in S6.2 do not apply to the burnish procedure.
    (a) IBT: 100  deg.C (212  deg.F).
    (b) Test speed: 80 km/h (49.7 mph).
    (c) Pedal force: Adjust as necessary to maintain specified constant 
deceleration rate.
    (d) Deceleration rate: Maintain a constant deceleration rate of 3.0 
m/s\2\ (9.8 fps\2\).
    (e) Wheel lockup: No lockup of any wheel allowed for longer than 
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
    (f) Number of runs: 200 stops.
    (g) Interval between runs: The interval from the start of one 
service brake application to the start of the next is either the time 
necessary to reduce the IBT to 100  deg.C (212  deg.F) or less, or the 
distance of 2 km (1.24 miles), whichever occurs first.
    (h) Accelerate to 80 km/h (49.7 mph) after each stop and maintain 
that speed until making the next stop.
    (i) After burnishing, adjust the brakes as specified in S6.3.4.
    S7.2  Wheel lockup sequence.
    S7.2.1  General information.
    (a) The purpose of this test is to ensure that lockup of both front 
wheels occurs either simultaneously with, or at a lower deceleration 
rate than, the lockup of both rear wheels, when tested on road surfaces 
affording adhesion such that wheel lockup of the first axle occurs at a 
braking ratio of between 0.15 and 0.80, inclusive.
    (b) This test is for vehicles without antilock brake systems.
    (c) This wheel lock sequence test is to be used as a screening test 
to evaluate a vehicle's axle lockup sequence and to determine whether 
the torque wheel test in S7.4 must be conducted.
    (d) For this test, a simultaneous lockup of the front and rear 
wheels refers to the conditions when the time interval between the 
first occurrence of lockup of the last (second) wheel on the rear axle 
and the first occurrence of lockup of the last (second) wheel on the 
front axle is  0.1 second for vehicle speeds > 15 km/h (9.3 
mph).
    (e) A front or rear axle lockup is defined as the point in time 
when the last (second) wheel on an axle locks up.
    (f) Vehicles that lock their front axle simultaneously or at lower 
deceleration rates than their rear axle need not be tested to the 
torque wheel procedure.
    (g) Vehicles which lock their rear axle at deceleration rates lower 
than the front 

[[Page 6439]]
axle shall also be tested in accordance with the torque wheel procedure 
in S7.4.
    (h) Any determination of noncompliance for failing adhesion 
utilization requirements shall be based on torque wheel test results.
    S7.2.2  Vehicle conditions.
    (a) Vehicle load: GVWR and LLVW.
    (b) Transmission position: In neutral.
    S7.2.3  Test conditions and procedures.
    (a) IBT:  50  deg.C. (122  deg.F),  100 
deg.C, (212  deg.F).
    (b) Test speed: 65 km/h (40.4 mph) for a braking ratio  
0.50; 100 km/h (62.1 mph) for a braking ratio > 0.50.
    (c) Pedal force:
    (1) Pedal force is applied and controlled by the vehicle driver or 
by a mechanical brake pedal actuator.
    (2) Pedal force is increased at a linear rate such that the first 
axle lockup occurs no less than one-half (0.5) second and no more than 
one and one-half (1.5) seconds after the initial application of the 
pedal.
    (3) The pedal is released when the second axle locks, or when the 
pedal force reaches 1000 N (225 lbs), or 0.1 seconds after first axle 
lockup, whichever occurs first.
    (d) Wheel lockup: Only wheel lockups above a vehicle speed of 15 
km/h (9.3 mph) are considered in determining the results of this test.
    (e) Test surfaces: This test is conducted, for each loading 
condition, on two different test surfaces that will result in a braking 
ratio of between 0.15 and 0.80, inclusive. NHTSA reserves the right to 
choose the test surfaces to be used based on adhesion utilization 
curves or any other method of determining ``worst case'' conditions.
    (f) The data recording equipment shall have a minimum sampling rate 
of 40 Hz.
    (g) Data to be recorded. The following information must be 
automatically recorded in phase continuously throughout each test run 
such that values of the variables can be cross referenced in real time.
    (1) Vehicle speed.
    (2) Brake pedal force.
    (3) Angular velocity at each wheel.
    (4) Actual instantaneous vehicle deceleration or the deceleration 
calculated by differentiation of the vehicle speed.
    (h) Speed channel filtration. For analog instrumentation, the speed 
channel shall be filtered by using a low-pass filter having a cut-off 
frequency of less than one fourth the sampling rate.
    (i) Test procedure. For each test surface, three runs meeting the 
pedal force application and time for wheel lockup requirements shall be 
made. Up to a total of six runs will be allowed to obtain three valid 
runs. Only the first three valid runs obtained shall be used for data 
analysis purposes.
    S7.2.4. Performance requirements.
    (a) In order to pass this test a vehicle shall be capable of 
meeting the test requirements on all test surfaces that will result in 
a braking ratio of between 0.15 and 0.80, inclusive.
    (b) If all three valid runs on each surface result in the front 
axle locking before or simultaneously with the rear axle, or the front 
axle locks up with only one or no wheels locking on the rear axle, the 
torque wheel procedure need not be run, and the vehicle is considered 
to meet the adhesion utilization requirements of this Standard. This 
performance requirement shall be met for all vehicle braking ratios 
between 0.15 and 0.80.
    (c) If any one of the three valid runs on any surface results in 
the rear axle locking before the front axle or the rear axle locks up 
with only one or no wheels locking on the front axle the torque wheel 
procedure shall be performed. This performance requirement shall be met 
for all vehicle braking ratios between 0.15 and 0.80.
    (d) If any one of the three valid runs on any surface results in 
neither axle locking (i.e., only one or no wheels locked on each axle) 
before a pedal force of 1000 N (225 lbs) is reached, the vehicle shall 
be tested to the torque wheel procedure.
    (e) If the conditions listed in paragraph (c) or (d) of this 
section occur, vehicle compliance shall be determined from the results 
of a torque wheel test performed in accordance with S7.4.
    S7.3. ABS performance. [Reserved.]
    S7.4. Adhesion utilization (Torque Wheel Method).
    S7.4.1. General information. This test is for vehicles without any 
ABS. The purpose of the test is to determine the adhesion utilization 
of a vehicle.
    S7.4.2. Vehicle conditions.
    (a) Vehicle load: GVWR and LLVW.
    (b) Transmission position: In neutral.
    (c) Tires: For this test, a separate set of tires, identical to 
those used for all other tests under Section 7.0, may be used.
    S7.4.3. Test conditions and procedures.
    (a) IBT:  50 deg.C (122 deg.F),  100  deg.C 
(212 deg.F).
    (b) Test speeds: 100 km/h (62.1 mph), and 50 km/h (31.1 mph).
    (c) Pedal force: Pedal force is increased at a linear rate between 
100 and 150 N/sec (22.5 and 33.7 lbs/sec) for the 100 km/h test speed, 
or between 100 and 200 N/sec (22.5 and 45.0 lbs/sec) for the 50 km/h 
test speed, until the first axle locks or until a pedal force of 1 kN 
(225 lbs) is reached, whichever occurs first.
    (d) Cooling: Between brake applications, the vehicle is driven at 
speeds up to 100 km/h (62.1 mph) until the IBT specified in S7.4.3(a) 
is reached.
    (e) Number of runs: With the vehicle at GVWR, run five stops from a 
speed of 100 km/h (62.1 mph) and five stops from a speed of 50 km/h 
(31.1 mph), while alternating between the two test speeds after each 
stop. With the vehicle at LLVW, repeat the five stops at each test 
speed while alternating between the two test speeds.
    (f) Test surface: PFC of at least 0.9.
    (g) Data to be recorded. The following information must be 
automatically recorded in phase continuously throughout each test run 
such that values of the variables can be cross referenced in real time:
    (1) Vehicle speed.
    (2) Brake pedal force.
    (3) Angular velocity at each wheel.
    (4) Brake torque at each wheel.
    (5) Hydraulic brake line pressure in each brake circuit. 
Hydraulically proportioned circuits shall be fitted with transducers on 
at least one front wheel and one rear wheel downstream of the operative 
proportioning or pressure limiting valve(s).
    (6) Vehicle deceleration.
    (h) Sample rate: All data acquisition and recording equipment shall 
support a minimum sample rate of 40 Hz on all channels.
    (i) Determination of front versus rear brake pressure. Determine 
the front versus rear brake pressure relationship over the entire range 
of line pressures. Unless the vehicle has a variable brake 
proportioning system, this determination is made by static test. If the 
vehicle has a variable brake proportioning system, dynamic tests are 
run with the vehicle both empty and loaded. 15 snubs from 50 km/h (31.1 
mph) are made for each of the two load conditions, using the same 
initial conditions specified in this section.
    S7.4.4. Data reduction.
    (a) The data from each brake application under S7.4.3 is filtered 
using a five-point, on-center moving average for each data channel.
    (b) For each brake application under S7.4.3 determine the slope 
(brake factor) and pressure axis intercept (brake hold-off pressure) of 
the linear least squares equation best describing the measured torque 
output at each braked wheel as a function of measured line pressure 
applied at the same wheel. Only torque output values obtained from data 
collected when the vehicle deceleration 

[[Page 6440]]
is within the range of 0.15g at 0.80g are used in the regression 
analysis.
    (c) Average the results of paragraph (b) of this section to 
calculate the average brake factor and brake hold-off pressure for all 
brake applications for the front axle.
    (d) Average the results of paragraph (b) of this section to 
calculate the average brake factor and brake hold-off pressure for all 
brake applications for the rear axle.
    (e) Using the relationship between front and rear brake line 
pressure determined in S7.4.3(i) and the tire rolling radius, calculate 
the braking force at each axle as a function of front brake line 
pressure.
    (f) Calculate the braking ratio of the vehicle as a function of the 
front brake line pressure using the following equation:
[GRAPHIC][TIFF OMITTED]TR02FE95.013

where z = braking ratio at a given front line pressure;
T1, T2 = Braking forces at the front and rear axles, 
respectively, corresponding to the same front brake line pressure, and
P = total vehicle weight.

    (g) Calculate the adhesion utilized at each axle as a function of 
braking ratio using the following equations:
[GRAPHIC][TIFF OMITTED]TR02FE95.014

where fi = adhesion utilized by axle i
Ti = braking force at axle i (from (e))
Pi = static weight on axle i
i = 1 for the front axle, or 2 for the rear axle
z = braking ratio (from (f))
h = height of center of gravity of the vehicle
P = total vehicle weight
E = wheelbase

    (h) plot f1 and f2 obtained in (g) as a function of z, 
for both GVWR and LLVW load conditions. These are the adhesion 
utilization curves for the vehicles, which are compared to the 
performance requirements in S7.4.5, shown graphically in Figure 2.
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[[Page 6441]]
[GRAPHIC][TIFF OMITTED]TR02FE95.002



BILLING CODE 4910-59-C

[[Page 6442]]

    S7.4.5. Performance requirements. For all braking ratios between 
0.15 and 0.60, each adhesion utilization curve for a rear axle shall be 
situated below a line defined by z = 0.9k where z is the braking ratio 
and k is the PFC.
    S7.5. Cold effectiveness.
    S7.5.1. Vehicle conditions.
    (a) Vehicle load: GVWR and LLVW.
    (b) Transmission position: In neutral.
    S7.5.2. Test conditions and procedures.
    (a) IBT: > 50 deg.C (122 deg.F), < 100 deg.C (212 deg.F).
    (b) Test speed: 100 km/h (62.1 mph).
    (c) Pedal force: > 65N (14.6 lbs), < 500 N (112.4 lbs).
    (d) Wheel lockup: No lockup of any wheel for longer than 0.1 
seconds allowed at speeds greater than 15 km/h (9.3 mph).
    (e) Number of runs: 6 stops.
    (f) Test surface: PFC of 0.9.
    (g) For each stop, bring the vehicle to test speed and then stop 
the vehicle in the shortest possible distance under the specified 
conditions.
    S7.5.3. Performance requirements.
    (a) Stopping distance for 100 km/h test speed: < 70 m (230 ft).
    (b) Stopping distance for reduced test speed: S < 0.10V + 
0.0060V2.
    S7.6. High speed effectiveness. This test is not run if vehicle 
maximum speed is less than or equal to 125 km/h (77.7 mph).
    S7.6.1. Vehicle conditions.
    (a) Vehicle load: GVWR and LLVW.
    (b) Transmission position: In gear.
    S7.6.2. Test conditions and procedures.
    (a) IBT: > 50 deg.C (122 deg.F), < 100 deg.C (212 deg.F).
    (b) Test speed: 80% of vehicle maximum speed if 125 km/h (77.7 mph) 
< vehicle maximum speed < 200 km/h (124.3 mph), or 160 km/h (99.4 mph) 
if vehicle maximum speed  200 km/h (124.3 mph).
    (c) Pedal force: > 65 N (14.6 lbs), < 500 N (112.4 lbs).
    (d) Wheel lockup: No lockup of any wheel for longer than 0.1 
seconds allowed at speeds greater than 15 km/h (9.3 mph).
    (e) Number of runs: 6 stops.
    (f) Test surface: PFC of 0.9.
    S7.6.3. Performance requirements.
    Stopping distance: S < 0.10V + 0.0067V2.
    S7.7. Stops with Engine Off.
    S7.7.1. General information. This test is for vehicles equipped 
with one or more brake power units or brake power assist units.
    S7.7.2. Vehicle conditions.
    (a) Vehicle load: GVWR only.
    (b) Transmission position: In neutral.
    (c) Vehicle engine: Off (not running).
    (d) Ignition key position: May be returned to ``on'' position after 
turning engine off, or a device may be used to ``kill'' the engine 
while leaving the ignition key in the ``on'' position.
    S7.7.3. Test conditions and procedures.
    (a) IBT:  50 deg.C (122 deg.F),  100 deg.C 
(212 deg.F).
    (b) Test speed: 100 km/h (62.1 mph).
    (c) Pedal force:  65 N (14.6 lbs),  500 N 
(122.4 lbs).
    (d) Wheel lockup: No lockup of any wheel allowed for longer than 
0.1 seconds at speeds greater than 15 km/h (9.3 mph).
    (e) Number of runs: 6 stops.
    (f) Test surface: PFC of 0.9.
    (g) All system reservoirs (brake power and/or assist units) are 
fully charged and the vehicle's engine is off (not running) at the 
beginning of each stop.
    S7.7.4. Performance requirements.
    (a) Stopping distance for 100 km/h test speed: 70m (230 
ft.)
    (b) Stopping distance for reduced test speed: S  0.10V + 
0.0060V\2\.
    S7.8. Antilock functional failure.
    S7.8.1. Vehicle conditions.
    (a) Vehicle loading: LLVW and GVWR.
    (b) Transmission position: In neutral.
    S7.8.2. Test conditions and procedures.
    (a) IBT:  50 deg.C (122 deg.F),  100 deg.C 
(212 deg.F).
    (b) Test speed: 100 km/h (62.1 mph).
    (c) Pedal force:  65 N (14.6 lbs),  500 N 
(112.4 lbs).
    (d) Wheel lockup: No lockup of any wheel for more than 0.1 seconds 
allowed at speeds greater than 15 km/h (9.3 mph).
    (e) Number of runs: 6 stops.
    (f) Test surface: PFC of 0.9.
    (g) Functional failure simulation:
    (1) Disconnect the functional power source, or any other electrical 
connector that creates a functional failure.
    (2) Determine whether the brake system indicator is activated when 
any electrical functional failure of the antilock system is created.
    (3) Restore the system to normal at the completion of this test.
    (h) If more than one antilock brake subsystem is provided, repeat 
test for each subsystem.
    S7.8.3. Performance requirements.
    For service brakes on a vehicle equipped with one or more antilock 
systems, in the event of any single functional failure in any such 
system, the service brake system shall continue to operate and shall 
stop the vehicle as specified in S7.8.3(a) or S7.8.3(b).
    (a) Stopping distance for 100 km/h test speed:  85 m 
(279 ft).
    (b) Stopping distance for reduced test speed: S  0.10V + 
0.0075V\2\.
    S7.9. Variable brake proportioning system functional failure.
    S7.9.1. Vehicle conditions.
    (a) Vehicle load: LLVW and GVWR.
    (b) Transmission position: In neutral.
    S7.9.2. Test conditions and procedures.
    (a) IBT:  50 deg.C (122 deg.F),  100 deg.C 
(212 deg.F).
    (b) Test speed: 100 km/h (62.1 mph).
    (c) Pedal force:  65 N (14.6 lbs),  500 N 
(112.4 lbs).
    (d) Wheel lockup: No lockup of any wheel for longer than 0.1 
seconds allowed at speeds greater than 15 km/h (9.3 mph).
    (e) Number of runs: 6 stops.
    (f) Test surface: PFC of 0.9.
    (g) Functional failure simulation:
    (1) Disconnect the functional power source or mechanical linkage to 
render the variable brake proportioning system inoperative.
    (2) If the system utilizes electrical components, determine whether 
the brake system indicator is activated when any electrical functional 
failure of the variable proportioning system is created.
    (3) Restore the system to normal at the completion of this test.
    (h) If more than one variable brake proportioning subsystem is 
provided, repeat the test for each subsystem.
    S7.9.3. Performance requirements. The service brakes on a vehicle 
equipped with one or more variable brake proportioning systems, in the 
event of any single function failure in any such system, shall continue 
to operate and shall stop the vehicle as specified in S7.9.3(a) and 
S7.9.3(b).
    (a) Stopping distance for 100 km/h test speed:  110 m 
(361 ft).
    (b) Stopping distance for reduced test speed: S 0.10V + 
0.0100V\2\.
    S7.10. Hydraulic circuit failure.
    S7.10.1. General information. This test is for vehicles 
manufactured with our without a split service brake system.
    S7.10.2. Vehicle conditions.
    (a) Vehicle load: LLVW and GVWR.
    (b) Transmission position: In neutral.
    S7.10.3. Test conditions and procedures.
    (a) IBT:  50  deg.C (122  deg.F),  100  deg.C 
(212 deg.F).
    (b) Test speed: 100 km/h (62.1 mph).
    (c) Pedal force:  65 N (14.6 lbs),  500 N 
(122.4 lbs).
    (d) Wheel lockup: No lockup of any wheel for longer than 0.1 
seconds allowed at speeds greater than 15 km/h (9.3 mph).
    (e) Test surface: PFC of 0.9.
    (f) Alter the service brake system to produce any one rupture or 
leakage type of failure other than structural failure of a housing that 
is common to two or more subsystems.

[[Page 6443]]

    (g) Determine the control force pressure level or fluid level (as 
appropriate for the indicator being tested) necessary to activate the 
brake warning indicator.
    (h) Number of runs: After the brake warning indicator has been 
activated, make the following stops depending on the type of brake 
system:
    (1) 4 stops for a split service brake system.
    (2) 10 consecutive stops for a non-split service brake system.
    (i) Each stop is made by a continuous application of the service 
brake control.
    (j) Restore the service brake system to normal at the completion of 
this test.
    (k) Repeat the entire sequence for each of the other subsystems.
    S7.10.4. Performance requirements.
    For vehicles manufactured with a split service brake system, in the 
event of any rupture or leakage type of failure in a single subsystem, 
other than a structural failure of a housing that is common to two or 
more subsystems, and after activation of the brake system indicator as 
specified in S5.5.1, the remaining portions of the service brake system 
shall continue to operate and shall stop the vehicle as specified in 
S7.10.4(a) or S7.10.4(b). For vehicles not manufactured with a split 
service brake system, in the event of any one rupture or leakage type 
of failure in any component of the service brake system and after 
activation of the brake system indicator as specified in S5.5.1, the 
vehicle shall by operation of the service brake control stop 10 times 
consecutively as specified in S7.10.4(a) or S7.10.4(b).
    (a) Stopping distance from 100 km/h test speed:  168 m 
(551 ft).
    (b) Stopping distance for reduced test speed: S  0.10V + 
0.0158V2.
    S7.11. Power brake unit or brake power assist unit inoperative 
(System depleted).
    S7.11.1. General information. This test is for vehicles equipped 
with one or more brake power units or brake power assist units.
    S7.11.2. Vehicle conditions.
    (a) Vehicle load: GVWR only.
    (b) Transmission position: In neutral.
    S7.11.3. Test conditions and procedures.
    (a) IBT:  50 deg.C (122 deg.F),  100 deg.C 
(212 deg.F).
    (b) Test speed: 100 km/h (62.1 mph).
    (c) Pedal force:  65 N (14.6 lbs),  500 N 
(112.4 lbs).
    (d) Wheel lockup: No lockup of any wheel for longer than 0.1 
seconds allowed at speeds greater than 15 km/h (9.3 mph).
    (e) Number of runs: 6 stops.
    (f) Test surface: PFC of 0.9.
    (g) Disconnect the primary source of power for one brake power 
assist unit or brake power unit, or one of the brake power unit or 
brake power assist unit subsystems if two or more subsystems are 
provided.
    (h) If the brake power unit or power assist unit operates in 
conjunction with a backup system and the backup system of a primary 
power service failure, the backup system is operative during this test.
    (i) Exhaust any residual brake power reserve capability of the 
disconnected system.
    (j) Make each of the 6 stops by a continuous application of the 
service brake control.
    (k) Restore the system to normal at completion of this test.
    (l) For vehicles equipped with more than one brake power unit or 
brake power assist unit, conduct tests for each in turn.
    S7.11.4. Performance requirements.
    The service brakes on a vehicle equipped with one or more brake 
power assist units or brake power units, with one such unit inoperative 
and depleted of all reserve capability, shall stop the vehicle as 
specified in S7.11.4(a) or S7.11.4(b).
    (a) Stopping distance from 100 km/h test speed:  168 m 
(551 ft).
    (b) Stopping distance for reduced test speed: S  0.10V + 
0.0158V2.
    S7.12. Parking brake--Static test.
    S7.12.1. Vehicle conditions.
    (a) Vehicle load: GVWR only.
    (b) Transmission position: In neutral.
    (c) Parking brake burnish:
    (1) For vehicles with parking brake systems not utilizing the 
service friction elements, the friction elements of such a system are 
burnished prior to the parking brake test according to the published 
recommendations furnished to the purchaser by the manufacturer.
    (2) If no recommendations are furnished, the vehicle's parking 
brake system is tested in an unburnished condition.
    S7.12.2. Test conditions and procedures.
    (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.
    (b) Parking brake control force: Hand control  400 N 
(89.9 lbs); foot control  500 N (112.4 lbs).
    (c) Hand force measurement locations: The force required for 
actuation of a hand-operated brake system is measured at the center of 
the hand grip area or at a distance of 40 mm (1.57 in) from the end of 
the actuation lever as illustrated in Figure 3.

BILLING CODE 4910-59-P

[[Page 6444]]
[GRAPHIC][TIFF OMITTED]TR02FE95.003



BILLING CODE 4910-59-C

[[Page 6445]]

    (d) Parking brake applications: 1 apply and 2 reapply if necessary.
    (e) Test surface gradient: 20% grade.
    (f) Drive the vehicle onto the grade with the longitudinal axis of 
the vehicle in the direction of the slope of the grade.
    (g) Stop the vehicle and hold it stationary by applying the service 
brake control and place the transmission in neutral.
    (h) With the service brake applied sufficiently to just keep the 
vehicle from rolling, apply the parking brake as specified in 
S7.12.2(i) or S7.12.2(j).
    (i) The parking brake system is actuated by a single application 
not exceeding the limits specified in S7.12.2(b).
    (j) In the case of a parking brake system that does not allow 
application of the specified force in a single application, a series of 
applications may be made to achieve the specified force.
    (k) Following the application of the parking brakes, release all 
force on the service brake control and, if the vehicle remains 
stationary, start the measurement of time.
    (l) If the vehicle does not remain stationary, reapplication of a 
force to the parking brake control at the level specified in S7.12.2(b) 
as appropriate for the vehicle being tested (without release of the 
ratcheting or other holding mechanism of the parking brake) is used up 
to two times to attain a stationary position.
    (m) Verify the operation of the parking brake application 
indicator.
    (n) Following observation of the vehicle in a stationary condition 
for the specified time in one direction, repeat the same test procedure 
with the vehicle orientation in the opposite direction on the same 
grade.
    S7.12.3. Performance requirement. The parking brake system shall 
hold the vehicle stationary for 5 minutes in both a forward and reverse 
direction on the grade.
    S7.13. Heating Snubs.
    S7.13.1. General information. The purpose of the snubs is to heat 
up the brakes in preparation for the hot performance test which follows 
immediately.
    S7.13.2. Vehicle conditions.
    (a) Vehicle load: GVWR only.
    (b) Transmission position: In gear.
    S7.13.3. Test conditions and procedures.
    (a) IBT:
    (l) Establish an IBT before the first brake application (snub) of 
 55 deg.C (131 deg.F),  65 deg.C (149 deg.F).
    (2) IBT before subsequent snubs are those occurring at the distance 
intervals.
    (b) Number of snubs: 15.
    (c) Test speeds: The initial speed for each snub is 120 km/h (74.6 
mph) or 80% of Vmax, whichever is slower. Each snub is terminated at 
one-half the initial speed.
    (d) Deceleration rate:
    (1) Maintain a constant deceleration rate of 3.0 m/s2 (9.6 
fps2).
    (2) Attain the specified deceleration within one second and 
maintain it for the remainder of the snub.
    (e) Pedal force: Adjust as necessary to maintain the specified 
constant deceleration rate.
    (f) Time interval: Maintain an interval of 45 seconds between the 
start of brake applications (snubs).
    (g) Accelerate as rapidly as possible to the initial test speed 
immediately after each snub.
    (h) Immediately after the 15th snub, accelerate to 100 km/h (62.1 
mph) and commence the hot performance test.
    S7.14. Hot performance.
    S7.14.1. General information. The hot performance test is conducted 
immediately after completion of the 15th heating snub.
    S7.14.2. Vehicle conditions.
    (a) Vehicle load: GVWR only.
    (b) Transmission position: In neutral.
    S7.14.3. Test conditions and procedures.
    (a) IBT: Temperature achieved at completion of heating snubs.
    (b) Test speed: 100 km/h (62.1 mph).
    (c) Pedal force: (1) The first stop is done with a pedal force not 
greater than the average pedal force recorded during the shortest GVWR 
cold effectiveness stop.
    (2) The second stop is done with a pedal force not greater than 500 
N (112.4 lbs).
    (d) Wheel lockup: No lockup of any wheel for longer than 0.1 
seconds allowed at speeds greater than 15 km/h (9.3 mph).
    (e) Number of runs: 2 stops.
    (f) Immediately after the 15th heating snub, accelerate to 100 km/h 
(62.1 mph) and commence the first stop of the hot performance test.
    (g) If the vehicle is incapable of attaining 100 km/h, it is tested 
at the same speed used for the GVWR cold effectiveness test.
    (h) Immediately after completion of the first hot performance stop, 
accelerate as rapidly as possible to the specified test speed and 
conduct the second hot performance stop.
    (i) Immediately after completion of second hot performance stop, 
drive 1.5 km (0.98 mi) at 50 km/h (31.1 mph) before the first cooling 
stop.
    S7.14.4. Performance requirements.
    (a) For the first hot stop, the stopping distance must be less than 
or equal to a calculated distance which is based on 60 percent of the 
deceleration actually achieved on the shortest GVWR cold effectiveness 
stop. The following equations shall be used in calculating the 
performance requirement:
[GRAPHIC][TIFF OMITTED]TR02FE95.015

where dc = the average deceleration actually achieved during the 
shortest cold effectiveness stop at GVWR (m/s2),
Sc = actual stopping distance measured on the shortest cold 
effectiveness stop at GVWR (m), and
V = cold effectiveness test speed (km/h).

    (b) In addition to the requirement in S7.14.4(a), the stopping 
distance for at least one of the two hot stops must be S  89 
m (292 ft) from a test speed of 100 km/h (62.1 mph) or, for reduced 
test speed, S  0.10V + 0.0079V2. The results of the 
second stop may not be used to meet the requirements of S7.14.4(a).
    S7.15. Brake cooling stops.
    S7.15.1. General information. The cooling stops are conducted 
immediately after completion of the hot performance test.
    S7.15.2. Vehicle conditions.
    (a) Vehicle load: GVWR only.
    (b) Transmission position: In gear.
    S7.15.3. Test conditions and procedures.
    (a) IBT: Temperature achieved at completion of hot performance.
    (b) Test speed: 50 km/h (31.1 mph).
    (c) Pedal force: Adjust as necessary to maintain specified constant 
deceleration rate.
    (d) Deceleration rate: Maintain a constant deceleration rate of 3.0 
m/s\2\ (9.9 fps\2\).
    (e) Wheel lockup: No lockup of any wheel for longer than 0.1 
seconds allowed at speeds greater than 15
km/h (9.3 mph).
    (f) Number of runs: 4 stops.
    (g) Immediately after the hot performance stops drive 1.5 km (0.93 
mi) at 50 km/h (31.1 mph) before the first cooling stop.
    (h) For the first through the third cooling stops:
    (1) After each stop, immediately accelerate at the maximum rate to 
50 km/h (31.1 mph).
    (2) Maintain that speed until beginning the next stop at a distance 
of 1.5 km (0.93 mi) from the beginning of the previous stop.
    (i) For the fourth cooling stop:
    (1) Immediately after the fourth stop, accelerate at the maximum 
rate to 100 km/h (62.1 mph). 

[[Page 6446]]

    (2) Maintain that speed until beginning the recovery performance 
stops at a distance of 1.5 km (0.93 mi) after the beginning of the 
fourth cooling stop.
    S7.16. Recovery performance.
    S7.16.1. General information. The recovery performance test is 
conducted immediately after completion of the brake cooling stops.
    S7.16.2. Vehicle conditions.
    (a) Vehicle load: GVWR only.
    (b) Transmission position: In neutral.
    S7.16.3. Test conditions and procedures.
    (a) IBT: Temperature achieved at completion of cooling stops.
    (b) Test speed: 100 km/h (62.1 mph).
    (c) Pedal force: The pedal force shall not be greater than the 
average pedal force recorded during the shortest GVWR cold 
effectiveness stop.
    (d) Wheel lockup: No lockup of any wheel for longer than 0.1 
seconds allowed at speeds greater than 15 km/h (9.3 mph).
    (e) Number of runs: 2 stops.
    (f) Immediately after the fourth cooling stop, accelerate at the 
maximum rate to 100 km/h (62.1 mph).
    (g) Maintain that speed until beginning the first recovery 
performance stop at a distance of 1.5 km (0.93 mi) after the beginning 
of the fourth cooling stop.
    (h) If the vehicle is incapable of attaining 100 km/h, it is tested 
at the same speed used for the GVWR cold effectiveness test.
    (i) Immediately after completion of the first recovery performance 
stop accelerate as rapidly as possible to the specified test speed and 
conduct the second recovery performance stop.
    S7.16.4. Performance requirements.
    The stopping distance, S, for at least one of the two stops must be 
within the following limits:
[GRAPHIC][TIFF OMITTED]TR02FE95.016

where dc and V are defined in S7.14.4(a).

    S7.17. Final Inspection. Inspect:
    (a) The service brake system for detachment or fracture of any 
components, such as brake springs and brake shoes or disc pad facings.
    (b) The friction surface of the brake, the master cylinder or brake 
power unit reservoir cover, and seal and filler openings, for leakage 
of brake fluid or lubricant.
    (c) The master cylinder or brake power unit reservoir for 
compliance with the volume and labeling requirements of S5.4.2 and 
S5.4.3. In determining the fully applied worn condition, assume that 
the lining is worn to (1) rivet or bolt heads on riveted or bolted 
linings or (2) within 0.8 mm (1/32 inch) of shoe or pad mounting 
surface on bonded linings or (3) the limit recommended by the 
manufacturer, whichever is larger relative to the total possible shoe 
or pad movement. Drums or rotors are assumed to be at nominal design 
drum diameter or rotor thickness. Linings are assumed adjusted for 
normal operating clearance in the released position.
    (d) The brake system indicators, for compliance with operation in 
various key positions, lens color, labeling, and location, in 
accordance with S5.5.

    Issued: January 23, 1995.
Ricardo Martinez,
Administrator.
[FR Doc. 95-2324 Filed 2-1-95; 8:45 am]
BILLING CODE 4910-59-P