[Federal Register Volume 60, Number 47 (Friday, March 10, 1995)]
[Rules and Regulations]
[Pages 13285-13297]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-5413]



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[[Page 13286]]

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 57l

[Docket No. 93-06; Notice 3]
RIN 2127-AD07


Federal Motor Vehicle Safety Standards; Stopping Distance 
Requirements for Vehicles Equipped With Air Brake Systems

AGENCY: National Highway Traffic Safety Administration (NHTSA), 
Department of Transportation.

ACTION: Final rule.

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SUMMARY: This notice reinstates stopping distance performance 
requirements in Standard No. 121, Air Brake Systems, for medium and 
heavy vehicles that are equipped with air brake systems. The 
requirements specify distances in which different types of medium and 
heavy vehicle configurations must come to a complete stop from 60 mph 
on a high coefficient of friction surface. The requirements are 
designed to reduce the number and severity of crashes.
    This notice is one part of the agency's comprehensive effort to 
improve the braking ability of heavy vehicles. In another final rule 
published elsewhere in today's Federal Register, the agency is adopting 
identical stopping distance requirements for medium and heavy vehicles 
that are equipped with hydraulic brake systems. In a third final rule 
that responds to the Intermodal Surface Transportation Efficiency Act 
(ISTEA) of 1991, the agency is requiring medium and heavy vehicles to 
be equipped with an antilock brake system (ABS) to improve the lateral 
stability and control of these vehicles during braking.

DATES: Effective Dates: The amendments become effective on March 1, 
1997. Compliance to Sec. 571.121 with respect to trailers and single 
unit trucks and buses will be required as of March 1, 1998.
    Petitions for Reconsideration: Any petitions for reconsideration of 
this rule must be received by NHTSA no later than April 10, 1995.

ADDRESSES: Petitions for reconsideration of this rule should refer to 
Docket 93-06; Notice 3 and should be submitted to: Administrator, 
National Highway Traffic Safety Administration, 400 Seventh Street SW., 
Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Mr. George Soodoo, Office of Vehicle 
Safety Standards, National Highway Traffic Safety Administration, 400 
Seventh Street SW., Washington, DC 20590 (202-366-5892).

SUPPLEMENTARY INFORMATION:

I. Background
    A. Brake Related Crashes
    B. Braking Devices
II. NHTSA Activities
    A. Regulatory History
    B. Agency Research
    C. Heavy Vehicle Safety Report to Congress
III. Agency Proposal
IV. Comments on the Proposal
V. Agency Decision
    A. Overview
    B. Stopping Distance Performance
    1. Stopping Distance Requirements
    2. Stopping Distance Test Conditions
    a. Test Surface Specification
    b. Wheel Lockup Restrictions
    c. Control Trailer
    d. Vehicle Loading
    e. Initial Brake Temperature
    f. Emergency Stopping Distance Requirements
    g. Burnish Procedure
    h. Parking Brake Test
    C. Threshold Pressure Requirement
    D. Requirements for Brake Linings
    E. Implementation Schedule
    F. Intermediate and Final Stage Manufacturers/Trailer 
Manufacturers
    G. Costs
VI. Rulemaking Analyses and Notices
    A. Executive Order 12866 and DOT Regulatory Policies and 
Procedures
    B. Regulatory Flexibility Act
    C. Paperwork Reduction Act
    D. National Environmental Policy Act
    E. Executive Order 12612 (Federalism)
    F. Civil Justice Reform

I. Background

A. Brake Related Crashes

    Medium and heavy vehicles<SUP>1 are involved in thousands of motor 
vehicle crashes each year. One of the most important factors that 
contributes to these crashes is brake system performance. Crashes in 
which braking is a contributory factor can be further subdivided into 
(1) crashes due to brake failures or defective brakes, (2) runaways on 
downgrades, due to maladjusted or overheated brakes, (3) crashes in 
which vehicles are unable to stop in time, and (4) skidding, 
jackknifing, or loss-of-control crashes due primarily to locked wheels 
during braking.

    \1\Hereafter, referred to as heavy vehicles.
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    This final rule, reinstating stopping distance requirements for 
air-braked vehicles and the companion final rule specifying stopping 
distance requirements for hydraulically braked heavy vehicles will 
reduce the severity of or prevent crashes attributable to a heavy 
vehicle's inability to stop in time.<SUP>2 In these crashes, the heavy 
vehicle's brakes function, but do not stop the vehicle quickly enough 
to avoid a crash. One way to reduce the severity or number of such 
crashes is to improve heavy vehicle braking performance by reducing the 
distance needed to stop a vehicle. Even if crashes of this type were 
not totally prevented by such improvements in performance, the 
improvements would reduce collision impact speeds, and thus reduce 
crash severity.

    \2\Today's companion final rule to require heavy vehicles to be 
equipped with antilock brake systems (ABS) will prevent braking-
induced loss-of-control crashes.
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    The following estimates regarding heavy vehicle crashes are from 
NHTSA's 1992 General Estimates System (GES) which is based on data 
transcribed from a nationally representative sample of state police 
accident reports (PARs) and the Fatal Accident Reporting System (FARS). 
NHTSA estimates that in 1992 there were about 168,000 crashes involving 
heavy combination vehicles (excluding truck tractors when operating 
bobtail, i.e., without a trailer). These crashes resulted in about 
13,600 injuries and 387 fatalities to truck occupants and about 51,500 
injuries and 2,452 fatalities to occupants of other involved vehicles. 
For bobtail truck tractors alone, the agency estimates that there were 
about 8,400 crashes resulting in about 1,200 injuries and 39 fatalities 
to truck occupants and about 2,600 injuries and 178 fatalities to 
occupants of other involved vehicles. For heavy single-unit trucks, the 
agency estimates that there were about 192,600 crashes resulting in 
about 15,700 injuries and 165 fatalities to truck occupants and about 
48,300 injuries and 891 fatalities to occupants of other involved 
vehicles. In addition, crashes involving heavy vehicles result in more 
expensive and severe property damage than crashes involving light 
vehicles.
    It is very difficult to quantify the number of crashes in which a 
vehicle's brakes are unable to stop the vehicle in time. NHTSA 
estimates that in 1992 there were about 18,000 crashes involving heavy 
combination vehicles (excluding bobtail truck tractors). These crashes 
resulted in about 1,800 injuries and 57 fatalities to truck occupants 
and about 8,400 injuries and 754 fatalities to occupants of other 
involved vehicles. For bobtail truck tractors alone, the agency 
estimates that there were about 260 crashes resulting in about 100 
injuries and 7 fatalities to truck occupants and about 240 injuries and 
48 fatalities to occupants of other involved [[Page 13287]] vehicles. 
For heavy single-unit trucks, the agency estimates that there were 
about 30,100 crashes resulting in about 4,200 injuries and 17 
fatalities to truck occupants and about 15,000 injuries and 276 
fatalities to occupants of other involved vehicles. The Final Economic 
Analysis (FEA) provides greater detail about how today's final rules 
will reduce injuries and fatalities resulting from such crashes.
    The agency emphasizes that not all inability-to-stop-in-time 
crashes are preventable. Nevertheless, improvements to heavy vehicle 
brake systems should prevent or reduce the severity of a significant 
number of these crashes.

B. Braking Devices

    In order to understand the discussion of braking in this preamble, 
it is necessary to be familiar with several devices used in braking 
systems. Therefore, the agency provides a brief explanation of those 
devices below.
    Automatic front axle limiting valves (ALVs) automatically limit the 
amount of braking pressure applied at steering axle brakes. ALVs are 
typically installed to allay the concern of some drivers about loss of 
steering control due to front wheel lockup during hard braking and to 
reduce steering pull due to unequal brake adjustment on the front wheel 
brakes. However, these devices can actually increase the likelihood of 
drive axle and trailer lockup because the brakes on the front axle do 
less than their proportional share of the braking. Therefore, drivers 
must apply brakes harder to stop the vehicle. Accordingly, stopping 
distance performance could, in most cases, be improved by eliminating 
the use of ALVs.
    Bobtail proportioning valves (BPVs) automatically reduce brake 
application pressure to the drive axles of a bobtail truck tractor, 
thereby allowing greater use of the vehicle's steering-axle braking 
power. Bobtail tractors demonstrate the worst stopping capability of 
all vehicle types, primarily because the braking systems of tractors 
are designed to optimize their stopping distance when they are towing a 
loaded trailer. Without the trailer, the lack of load on the tractor 
drive axles can cause premature wheel lockup and reduced stopping 
capability. An agency study found that, on average, the stopping 
distance of bobtail tractors is approximately 122 feet longer than that 
of tractors when connected to loaded trailers.<SUP>3 However, 
significantly shorter stops have been obtained when bobtails are 
equipped with BPVs.

    \3\``NHTSA Heavy Duty Vehicle Brake Research Program Report No. 
1, ``Stopping Capability of Air Braked Vehicles,'' (DOT HS 806 738, 
April 1985) and Report No. 9, ``Stopping Distances of 1988 Heavy 
Vehicles.''
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    Load-Sensing Proportioning Valves (LSVs) reduce the likelihood of 
premature wheel lockup by mechanically sensing drive-axle suspension 
deflection that results from weight transfer during braking, and 
adjusting brake proportioning based on different loading conditions. 
However, LSVs cannot prevent lockup of a vehicle's brakes if they are 
applied too hard, particularly on a low coefficient of friction 
surface.
    Antilock brake systems (ABSs) automatically control the amount of 
braking pressure applied to a wheel so as to prevent wheel lock, thus 
increasing stability and control in emergency stops by preventing 
skidding, spinning, and jackknifing. Today's stability and control 
final rule provides a detailed discussion of these devices.

II. NHTSA Activities

A. Regulatory History

    In the notice of proposed rulemaking (NPRM) to reinstate stopping 
distance requirements for air-braked vehicles, NHTSA provided a 
detailed discussion of the regulatory and judicial history of the 
stopping distance requirements for air braked vehicles. (58 FR 11009, 
February 23, 1993). When last in effect, the stopping distance 
requirements in Standard No. 121 required all heavy vehicles to stop 
within 293 feet from a speed of 60 mph on a high coefficient of 
friction surface (i.e., a nonslippery surface typical of dry concrete). 
(41 FR 8783, March 1, 1976).
    In response to a suit challenging Standard No. 121's stopping 
distance requirements, the United States Court of Appeals for the 9th 
Circuit invalidated the Standard's stopping distance and ``no lockup'' 
requirements for trucks, buses, and trailers in PACCAR v. NHTSA, 573 
F.2d 632, (9th Cir. 1978) cert. denied, 439 U.S. 862 (1978). The court 
held that NHTSA was justified in promulgating a standard requiring 
improved air brake systems and stability mechanisms. However, after 
reviewing the record about reliability problems with antilock brake 
systems then in use, the court held that the standard was ``neither 
reasonable nor practicable at the time it was put into effect.''
    The court further stated that:

    * * * those parts of the Standard requiring heavier axles and 
the antilock device should be suspended. The evidence indicates that 
this can be accomplished if we hold, as we do, that the stopping 
distance requirements from 60 mph are invalid * * * We hold only 
that more probative and convincing data evidencing the reliability 
and safety of vehicles that are equipped with antilock and in use 
must be available before the agency can enforce a standard requiring 
its installation.

    The stability and control final rule contains a detailed discussion 
about the PACCAR decision and how the agency has responded to the 
findings in that decision. The Agency has decided to specify different 
stopping distances for different configurations of heavy vehicles. 
Today's requirements can further be distinguished from those 
invalidated in the 1970s by the fact that manufacturers will not need 
to significantly redesign their brakes or use overly aggressive 
foundation brakes to comply with the requirements being established in 
today's final rule.
    Even though the stopping distance requirements being specified in 
today's final rule are generally less stringent for some configurations 
than those invalidated by the PACCAR decision, the agency believes that 
the braking requirements in today's final rules, taken as a whole, 
significantly enhance the overall braking performance of air-braked 
vehicles given the agency's decision to require these vehicles to be 
equipped with ABS.

B. Agency Research

    As a part of its review of heavy vehicle braking, NHTSA has issued 
two reports on the stopping distance capability of several different 
types of heavy air-braked vehicles in various loading conditions.<SUP>4 
The agency also tested some vehicles equipped with ALVs, BPVs, and ABS, 
thus allowing comparisons of stopping distances with and without these 
devices. The tests were conducted on school buses, transit buses, 
single unit trucks, tractor trailers in the loaded and empty conditions 
and with various equipment (with ABS activated and deactivated, and 
with and without ALVs and BPVs). Among the conclusions reached by the 
agency on the basis of the test data were: (1) ALVs significantly 
degrade straight line stopping performance, especially in the bobtail 
configuration (with stopping distances as long as 531 feet); (2) BPVs 
significantly reduce the stopping distances of bobtail tractors; (3) 
ABSs are effective in providing short, stable stops in all operating 
conditions; (4) ABSs provide the greatest performance gain in the 
bobtail configuration, where stable stops as short as 233 feet were 
obtained; (5) braking performance of bobtail tractors and empty single 
unit [[Page 13288]] trucks could be improved by removing ALVs from both 
vehicle types and installing BPVs on bobtails; and (6) a stopping 
distance performance requirement for truck tractors with empty trailers 
would not provide any additional performance benefits that could not be 
achieved through specifying requirements for either the bobtail or 
loaded condition.

    \4\NHTSA Heavy Duty Vehicle Brake Research Program Report No. 1, 
``Stopping Capability of Air Braked Vehicles,'' (DOT HS 806 738, 
April 1985) and Report No. 9, ``Stopping Distances of 1988 Heavy 
Vehicles.'' DOT HS 807 531, February 1990.
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C. Heavy Vehicle Safety Report to Congress

    In response to section 9107 of the Truck and Bus Regulatory Reform 
Act of 1988, NHTSA submitted a report to Congress titled ``Improved 
Brake Systems for Commercial Vehicles.'' (DOT HS 807 706, April 
1991.)<SUP>5 After discussing crash data concerning heavy vehicle brake 
systems, the report explained the factors that are related to braking 
effectiveness, stability and control during braking, and braking system 
compatibility. The report indicated that stopping distances and vehicle 
stability could be improved by not equipping heavy vehicles with ALVs 
and instead equipping them with BPVs, load-sensing proportioning 
valves, and antilock brake systems.

    \5\This report may be examined at the Agency's Technical 
Reference Office, room 5108, at no charge. It is available from the 
National Technical Information Service (NTIS), Springfield, VA 22161 
for a small charge.
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III. Agency Proposal

    On February 23, 1993, NHTSA proposed to amend Standard No. 121 to 
reinstate stopping distance performance requirements for stops from 60 
mph on a high coefficient of friction surface for trucks, truck 
tractors, and buses that are equipped with air brake systems (58 FR 
11009). Based on testing at VRTC, the Agency proposed different 
stopping distances for different configurations of heavy vehicles. 
Specifically, the Agency proposed that unloaded single unit trucks and 
bobtail tractors stop within 335 feet, loaded single unit trucks stop 
within 310 feet, and all buses stop within 280 feet. The Agency 
proposed two alternatives for testing a truck tractor in the loaded 
condition and stated that one of the alternatives would be chosen for 
the final rule. The first alternative proposed that the truck tractor 
be tested with a braked control trailer and stop within 280 feet, while 
the second alternative proposed that the truck tractor be tested with 
an unbraked control trailer and stop within 355 feet. The Agency 
explained that its long-term objective is to upgrade the braking 
efficiency of heavy vehicles to enable them to make controlled, stable 
stops, under all loading and road surface conditions. The Agency 
believed that the proposed requirements would reduce the disparity in 
braking ability between heavy vehicles and passenger cars. On the same 
day, the Agency proposed identical stopping distance requirements for 
heavy vehicles equipped with hydraulic brakes (58 FR 11003). The Agency 
stated that many vehicles were already able to comply with the proposed 
requirements. The inadequate performance of those vehicles that were 
not able to comply was due to either poor brake torque balance between 
the vehicles' axles resulting in premature lockup of the wheels on the 
vehicles' rear axles or a lack of sufficient total brake torque 
capability. Those vehicles that exhibited poor brake balance could be 
brought into compliance by installing ABS, or by adding BPVs and/or 
eliminating ALVs. Those vehicles that lack sufficient total brake 
torque capability could be brought into compliance by incorporating 
relatively minor changes to their foundation brake components involving 
the substitution of other currently available components.
    NHTSA proposed that air-braked vehicles would have to come to a 
complete stop within a 12-foot-wide lane with restrictions on which 
wheels would be permitted to lockup during the stop. The proposal 
requested comments about whether and to what degree wheel lockup during 
testing would be permitted. Specifically, the Agency proposed to allow 
unlimited lockup below 20 mph and defined two types of wheel lockup 
allowed above 20 mph: ``permissible wheel lockup,'' which is defined as 
100 percent wheel slip of one or more wheels for a duration of one 
second or less<SUP>6 for testing purposes, and ``limited lockup,'' 
which is defined as lockup of not more than one wheel per axle or two 
wheels per tandem. In addition, NHTSA proposed test conditions related 
to the road test surface, the use of a braked or unbraked control 
trailer, and the initial brake temperature. NHTSA also proposed 
specifying a threshold pressure to enhance brake force compatibility 
between tractors and trailers.

    \6\As explained below, the final rule refers to this concept as 
``momentary wheel lockup.''
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IV. Comments on the Proposal

    NHTSA received 49 comments in response to the NPRM. Commenters 
included heavy vehicle manufacturers, brake manufacturers, safety 
advocacy groups, heavy vehicle users, industry trade associations, and 
other individuals. The American Automobile Manufacturers Association 
(AAMA) submitted joint comments on behalf of the eight major domestic 
manufacturers of heavy vehicles: Chrysler, Ford, Freightliner, General 
Motors (GM), Mack Trucks, Navistar, PACCAR, and Volvo-GM.
    All the commenters supported the Agency's decision to reinstate 
stopping distance requirements for heavy vehicles equipped with air 
brakes. However, they offered mixed views about the specific stopping 
distances being proposed. GM, Navistar, Heavy Duty Brake Manufacturers 
Council (HDBMC), and Rockwell WABCO stated that the proposed stopping 
distance requirements are appropriate. In contrast, the Insurance 
Institute for Highway Safety (IIHS), the Coalition for Consumer Health, 
and Advocates for Highway Safety (Advocates) believed that the required 
distances should be much shorter for trucks and buses. Advocates stated 
that the proposal did little more than ``grandfather'' existing braking 
capabilities and therefore would not result in the best available 
braking performance for large trucks.
    The American Trucking Association (ATA), IIHS and several other 
commenters suggested that the Agency should merge the proposed stopping 
distance and stability requirements into a common rulemaking, thereby 
allowing the industry to implement a more effective test program.
    Commenters also addressed specific issues raised in the NPRM, 
including vehicle test speed, the test surface specification, the 
control trailer, wheel lockup restrictions, the initial brake 
temperature, the failed system test, vehicle loading, the threshold 
pressure requirements, the parking brake test, the burnish procedures, 
and the implementation schedule for the requirements. More specific 
discussions of these comments, and the Agency's responses to them, are 
set forth below.

V. Agency Decision

A. Overview

    Based on the Fatal Accident Reporting System (FARS) and other crash 
data, test data from the agency's heavy vehicle brake research program, 
comments on the NPRM, and other available information, NHTSA has 
decided to amend Standard No. 121 to reinstate stopping distance 
performance requirements for heavy vehicles that are equipped with air 
brake systems. Separate requirements for stopping from 60 mph on a high 
coefficient of friction surface are specified for four different heavy 
vehicle configurations. The requirements are designed to reduce the 
[[Page 13289]] distance needed for these vehicles to come to a complete 
stop, thereby reducing the severity and number of crashes.
    As noted above, this notice is one part of the Agency's 
comprehensive effort to improve the braking ability of heavy vehicles. 
In a second final rule published elsewhere in today's Federal Register, 
the Agency is adopting identical stopping distance requirements for 
heavy vehicles that are equipped with hydraulic brake systems. The 
Agency believes that it is appropriate to specify identical stopping 
distance requirements for similar vehicles. In a third final rule, the 
Agency is responding to the Intermodal Surface Transportation 
Efficiency Act (ISTEA) of 1991 by requiring each heavy vehicle to be 
equipped with an antilock brake system to improve its lateral stability 
and control during braking.

B. Stopping Distance Performance

1. Stopping Distance Requirements
    Based on its testing at VRTC, NHTSA proposed different stopping 
distances for various categories of vehicles when tested at a speed of 
60 mph on a surface with a peak friction coefficient (PFC) of 0.9, as 
follows:

Loaded and Unloaded Buses
280 ft.
Loaded Truck Tractors with Braked Control Trailer
280 ft.
Loaded Truck Tractors with Unbraked Control Trailer
355 ft.
Loaded Single-Unit Trucks
310 ft.
Unloaded Single-Unit Trucks & Truck Tractors (Bobtail)
335 ft.

    The agency proposed different requirements, instead of a single 
across-the-board requirement like the one invalidated by the PACCAR 
court, because a single requirement for all heavy vehicles with fully 
operational service brakes would be too stringent for bobtail tractors 
and unloaded single unit trucks, but not stringent enough for buses and 
for tractor trailers in the loaded condition.
    AAMA and most other industry commenters agreed with the stopping 
distance values proposed for the various vehicle configurations. 
AlliedSignal commented that these requirements are compatible with its 
view of using BPVs to achieve increased deceleration on air-braked 
tractors, while maintaining lateral stability in the bobtail mode. 
Nevertheless, it requested that ALVs not be prohibited since it 
believed that these devices are appropriate on some vehicles, 
particularly those with large front brakes. AlliedSignal recommended 
that if an ALV is used on a vehicle, it should be automatically 
deactivated when the tractor is in the bobtail mode. ATA agreed with 
the proposal to specify different stopping distances for different 
types and loadings of vehicles. It also agreed with specifying the same 
stopping distances for air-braked and hydraulically-braked vehicles of 
the same type and with the same loading.
    Other commenters opposed some of the proposed stopping distance 
values on the ground that they were too stringent. HDBMC stated that 
certain vehicles would have difficulty complying with the proposed 
stopping distances because they are over-braked when the rear axles are 
unloaded, and under-braked during emergency system stops. Lucas was 
concerned that the service brake stopping distances obtained during the 
agency's testing do not have a 10 percent margin less than the proposed 
280 feet from 60 mph. In order to obtain an acceptable margin, Lucas 
stated that vehicle manufacturers will have to equip certain vehicles 
with larger front brakes, which would represent a major change on some 
vehicles.
    In contrast, other commenters stated that the proposed stopping 
distances were not sufficiently stringent. Advocates stated that the 
proposed stopping distances simply ratify the braking distances 
currently achieved by manufacturers and do not seek to improve real-
world braking performance. It stated that except for the 280-foot 
requirement for buses and loaded tractors with a braked control 
trailer, all of the other proposed stopping distances are longer than 
the 293 feet established before PACCAR. Similarly, IIHS stated that the 
proposals do not go far enough toward requiring the best available 
braking for heavy vehicles.
    Based on the comments and other available information, NHTSA has 
decided to adopt the stopping distances proposed in the NPRM for the 
following categories of vehicles when tested at a speed of 60 mph on a 
surface with a PFC of 0.9:

Loaded and Unloaded Buses<SUP>7
280 ft.

    \7\The final rule amending Standard No. 105 discusses in detail 
the stopping distances applicable to hydraulic-braked school buses.
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Loaded Truck Tractors with Unbraked Control Trailer<SUP>8
355 ft.

    \8\As explained in the section below titled ``control 
trailers,'' the agency proposed but decided not to adopt a revised 
braked control trailer test condition.
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Loaded Single-Unit Trucks
310 ft.
Unloaded Single-Unit Trucks & Truck Tractors (Bobtail)
335 ft.

    As it stated in the NPRM, NHTSA agrees with HDBMC that a small 
number of vehicles will have to be modified to comply with the 
reinstated stopping distance requirements. The agency notes that the 
companion final rule requiring heavy vehicles to be equipped with 
antilock brake systems will improve the braking of those vehicles whose 
braking performance is limited due to poor brake torque balance, and 
will enable them to comply with the stopping distance requirements. For 
those vehicles that will require changes to their foundation brakes, so 
as to provide greater brake torque capability, the agency believes that 
adequate leadtime is being provided to minimize the task of achieving 
compliance with the requirement.
    NHTSA notes that while the companion final rule requiring heavy 
vehicles to be equipped with ABSs will reduce the need to eliminate 
front axle ALVs on single unit trucks and truck tractors and to install 
rear axle BPVs on truck tractors, the agency would still encourage 
vehicle manufacturers to do so. Vehicles without ALVs and/or with BPVs 
can be braked at higher levels of deceleration before the vehicle's ABS 
is activated, which the agency believes will improve the vehicle's 
driveability. The Agency is aware of at least one manufacturer of ABSs 
that currently recommends the incorporation of BPVs on truck tractors 
equipped with ABS.
2. Stopping Distance Test Conditions
a. Test Surface Specification
    In the NPRM, NHTSA proposed that the 60-mph stopping distance tests 
be performed on a test surface with a PFC of 0.9, which is typical of 
dry concrete. In formulating the proposal, the agency considered 
whether the proposed test surface specification raises practicability 
or objectivity concerns in light of PACCAR. Based on its testing, the 
agency tentatively concluded that specifying a test surface with a high 
PFC would reasonably represent stopping on a dry surface and would not 
be a significant source of variability in the stopping distance tests. 
The Agency requested comments on the proposed test surface 
specification.
    Several commenters addressed the appropriate PFC for the test. AAMA 
and Navistar commented that the test surface should be specified at a 
PFC of 1.0 because that PFC value would remove the influence of test 
road variability from compliance testing. AAMA provided data that 
showed that in the course of six months, the PFC varied between 0.85 
and 0.95, and averaged 0.90 over ten readings taken approximately twice 
each month. According to Navistar, its data showed PFCs that ranged 
from 0.91 to 0.98. [[Page 13290]] AAMA argued that since the majority 
of actual test surfaces nominally exceed PFC 0.9, a specification of 
0.9 would impose a cost burden on manufacturers trying to maintain the 
test surface near, but below, the 0.9 value. AAMA stated that 
``worldwide support'' has been expressed for specifying a test surface 
with a PFC of 1.0. Volvo GM provided results of the Motor Vehicle 
Safety Research Advisory Committee (MVSRAC) Antilock Brake System (ABS) 
Task Force ``Round Robin'' testing, which showed that on high 
coefficient of friction surfaces with PFCs ranging from 0.87 to 1.00, 
the stopping distances of the three test vehicles remained relatively 
constant when tested in the bobtail condition. This indicates stopping 
performance on a dry surface is not significantly affected by 
variability. Strait-Stop requested that a tolerance of <plus-minus> 0.1 
relative to 0.9 should be specified to accommodate real-world 
limitations.
    Based on the industry-government cooperative testing to evaluate 
the effect of fluctuations of PFC on vehicle stopping performance, 
NHTSA reaffirms its belief that a PFC of 0.9 reasonably represents a 
typical dry surface and will not be a significant source of variability 
in the stopping distance tests. (Public Files Docket PF88-01, MVSRAC 
ABS Task Force, Round Robin No. 1). 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 (with PFCs ranging from 0.89 to 0.94) 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. NHTSA has 
decided that a test road surface specification of PFC 1.0 would result 
in practicability problems for the agency, since 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 General 
Motors conducted an extensive survey of actual road surfaces, which 
indicated that a PFC of 0.9 is fairly typical.
    NHTSA notes that AAMA's claim that there is worldwide support for 
specifying a PFC of 1.0 is incorrect. The agency notes that when the 
issue was discussed by the ECE in the context of the international 
harmonization of brake standards, the decision was to specify a PFC of 
0.9<SUP>9. Moreover, when the Organization International des 
Constructeurs d'Automobiles (OICA) proposed adopting a PFC of 1.0, no 
country supported such a requirement.

    \9\Eleventh Informal Meeting on Harmonization of Brake 
Standards, August 26-27, 1991 and 29th Meeting of Experts on Brakes 
and Running Gear, August 28-30, 1991.
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    NHTSA has decided not to adopt Strait-Stop's request to specify a 
tolerance for the test surface. The agency notes that in specifying the 
test conditions applicable to the test surface, the agency does not 
provide a range of permissible test surfaces. Instead, the braking 
standards set forth specific, objective criteria for the test surface 
according to which the agency conducts its compliance testing.
b. Wheel Lockup Restrictions
    In the NPRM, NHTSA proposed that the straight line stopping 
distance test be conducted without locking more than one wheel per axle 
or two wheels per tandem at speeds greater than 20 mph. In addition, 
the agency proposed to allow unlimited lockup at 20 mph or below, and 
to allow permissible wheel lockup for testing purposes. NHTSA believed 
that allowing limited wheel lockup combined with permissible wheel 
lockup at speeds above 20 mph would ensure a safe and reasonably 
repeatable test condition, while providing an indication of a vehicle's 
stability up to the vehicle's braking performance limit. These 
provisions addressing wheel lockup were based on the previously 
mentioned stopping distance tests conducted at VRTC. NHTSA requested 
comments about the degree to which lockup should be permitted and under 
what circumstances, including whether to allow unrestricted wheel 
lockup of test vehicles.
    Commenters addressed four distinct issues with respect to the wheel 
lockup restrictions: (1) Specifying various types of lockup that would 
be allowed; (2) applying the wheel lockup restrictions to ABS equipped 
axles; (3) applying the wheel lockup restrictions to certain other 
axles; and (4) applying the wheel lockup restrictions to emergency 
system stops.
    AlliedSignal, ATA, AAMA, and Strait-Stop commented that the wheel 
lockup restrictions were not clear. AlliedSignal suggested that 
``permissible'' and ``limited'' be replaced by one term, and that wheel 
lockup be defined as 100 percent wheel slip at both wheels on an axle 
or more than two wheels on a tandem for a duration greater than one 
continuous second. AAMA requested that ``wheel lock restriction'' be 
defined ``as 100 percent wheel slip of both wheels of an axle, or more 
than two wheels on a tandem, for a duration greater than one continuous 
second.'' Strait-Stop requested that permissible wheel lockup be 
defined as lockup of one or more wheels at 100 percent slip for a 
reasonable time. ATA stated that the proposed regulatory language does 
not clearly indicate whether unlimited wheel lockup is permitted at 
speeds below 20 mph.
    After reviewing these comments, NHTSA has decided to adopt the 
proposed concepts pertaining to wheel lockup restrictions in the 
stopping distance test, with some modifications to enhance the 
provision's clarity. Aside from defining wheel lockup as 100 percent 
slip, and renaming ``permissible wheel lockup'' as ``momentary wheel 
lockup,'' NHTSA has decided that it is clearer to specify the concept 
directly in the stopping distance requirement in S5.3.1 instead of 
defining the various types of lockup (e.g., momentary (permissible) 
lockup, limited lockup, unlimited lockup) and then referencing them in 
S5.3.1. Accordingly, a vehicle is required to stop with wheel lockup 
permitted under the following conditions. At vehicle speeds above 20 
mph, one wheel on any axle or two wheels on any tandem may lock up for 
any duration. At vehicle speeds above 20 mph, wheels on certain axles 
(i.e., nonsteerable axles other than the two rearmost nonliftable, 
nonsteerable axles) may lock up for any duration. At vehicle speeds 
above 20 mph, any wheel not permitted to lock, as described in the two 
conditions above, may lock up repeatedly, with each lockup condition 
having a duration of one second or less. At vehicle speeds of 20 mph or 
less, any wheel may lock up for any duration. These exceptions allowing 
certain types of lockup are based on the above-mentioned tests 
conducted at VRTC.
    In establishing the requirements applicable to wheel lockup 
restrictions, NHTSA examined the commenters' recommended definitions 
for wheel lockup restriction. The Agency believes that these 
definitions achieve only part of the Agency's objective in establishing 
wheel lockup restrictions. The Agency interprets AAMA's definition as 
allowing both wheels on an axle to lock up (100 percent slip) for up to 
one second. However, AAMA's recommended definition is unclear about 
whether one wheel is allowed to remain locked up for the duration of 
the stop. NHTSA believes that it would be necessary to add additional 
wording to AAMA's definition to achieve the same 
[[Page 13291]] objective that is already achieved by the Agency's 
requirements.
    Several commenters stated that the wheels on any axle controlled by 
ABS should be excluded from wheel lockup constraints. Rockwell 
International stated that the proposed stopping distance regulation 
will become obsolete soon, since the references to permissible and 
limited wheel lockup will be superseded by the ABS regulation. Rockwell 
WABCO stated that the proposed stability and control rulemaking will 
resolve problems with respect to the wheel lockup definitions. AAMA 
expressed its concern that imposing wheel lockup constraints on ABS-
equipped vehicles could pose practicability problems during tests. For 
example, AAMA said that the test driver could be required to modulate 
brake pressure in order to prevent wheel lockup on axles not equipped 
with ABS, at the same time the ABS is cycling.
    NHTSA believes that the requirements in S5.3.1 continue to be 
necessary, notwithstanding the Agency's decision to require heavy 
vehicles to be equipped with antilock brake systems. The Agency 
believes that the limited lockup and momentary lockup restrictions will 
not impose any unreasonable or currently unachievable performance 
requirement on antilock systems during the stopping distance test, 
since the amount of lockup allowed by these restrictions is 
considerably greater lockup than allowed by any currently available 
antilock system. The antilock requirement specifies that an ABS on a 
truck tractor must control ``the wheels of at least one front axle of 
the vehicle and the wheels of at least one rear axle * * *'' Therefore, 
if a vehicle is equipped with ABS on only one axle of a rear tandem, 
the limited and momentary lockup requirements ensure that the vehicle 
can be braked without excessive wheel lockup of the wheels, including 
those controlled by ABS. Even if both non-ABS-controlled wheels of the 
tandem lock for the duration of the stop (they meet the limited lockup 
requirement test), the ABS-controlled wheels would then be allowed to 
lock for a duration of one second or less, at speeds above 20 mph. The 
Agency, therefore, does not agree with the claims that the backup 
restrictions would prohibit ABS on some vehicles, or that they would 
pose practicability problems for test drivers.
    NHTSA believes that AAMA's concern about problems with specifying 
wheel lockup restrictions is unrealistic. The Agency is unaware of any 
currently used antilock system that would allow wheel lockups that 
would not comply with the above restrictions.
    Rockwell WABCO further stated that the wheel lock issue can be 
resolved by requiring the vehicle to remain in the 12-foot-wide lane 
during testing to the stopping distance requirements.
    NHTSA believes that Rockwell WABCO's suggestion that the sole 
requirement be that a vehicle stay within a 12-foot-wide lane does not 
adequately take into consideration that on a smooth, flat, and straight 
surface, a vehicle with locked wheels might possibly stay within the 
lane. Accordingly, such a stop would not fully demonstrate the 
capability of a vehicle to provide stable stops at the limit of the 
vehicle's braking performance.
    Several commenters recommended that the wheel lockup restrictions 
not be applicable to emergency system stops. AAMA recommended that 
wheel lockup constraints only apply to full service stops ``to avoid 
compromises to full system performance for the sake of partial system 
wheel lock.''
    NHTSA agrees with these comments. In its present form, the 
restrictions on wheel lockup in Standard No. 121 appear in S5.3.1, and 
thus do not apply to the emergency stops specified in S5.7.1. The NPRM 
did not propose to extend those restrictions to emergency braking, and 
the Agency is not making such a change in this final rule.
c. Control Trailer
    In the NPRM, NHTSA proposed two alternatives for testing a truck 
tractor in the loaded condition. The first alternative proposed the use 
of a braked control trailer, which would be similar to the current 
braked control trailer. The second alternative proposed the use of an 
unbraked control trailer.
    AAMA, ATA, HDBMC and Rockwell WABCO supported the use of an 
unbraked control trailer. They believed that its use would eliminate 
many sources of test result variability and would produce test results 
that are consistent, comparable, and useful. Rockwell WABCO stated that 
a braked control trailer with ABS could lead to test performance 
variations since there are many different trailer antilock systems now 
available. It believed that it would be extremely difficult to define 
the required performance of the control trailer and the antilock system 
necessary to have a consistent ``test fixture'' for the stopping 
distance standard.
    Strait-Stop objected to the use of an unbraked control trailer, 
stating that its use would render the stopping distance performance of 
the combination vehicle meaningless. Trade International Corporation 
(TIC) did not explicitly support either of the two control trailer 
alternatives, but objected to the mandated use of ``electronically 
controlled systems'' to the exclusion of any other type of system, for 
the braked control trailer ABS.
    NHTSA has decided to specify the use of an unbraked control trailer 
to test a truck tractor in the loaded condition. The Agency notes that 
this decision, which is consistent with the views of most commenters, 
will eliminate test variability and produce test results that are 
consistent, comparable, and useful. Contrary to Strait-Stop's 
assertion, the Agency, along with most commenters, believes that the 
test results on unbraked control trailers provide meaningful 
comparative information. This is so because the stopping ability of all 
tractors will be evaluated in the same relative context (i.e., all 
tractors would be mated to a similar unbraked control trailer). An 
unbraked control trailer is easier to standardize than a braked control 
trailer since there is no need to specify the foundation brakes and the 
antilock brake system. The section on control trailers in the stability 
and control final rule provides a more extensive discussion of this 
issue.
d. Vehicle Loading
    In the NPRM, NHTSA proposed that tractors would be loaded with an 
unbraked control trailer, which would be loaded above the kingpin only, 
such that the tractor is at GVWR and the trailer's axle is at 4,500 
pounds, with the tractor's fifth wheel adjusted so that the load on 
each axle is proportional to the axle's respective GAWR. (See 
alternative 2, S6.1.10.4.)
    AAMA requested that the Agency add the phrase ``without exceeding 
the GAWR of any tractor or trailer axle.'' AAMA stated that for some 
vehicles, it is impossible to load the tractor to its GVWR through the 
kingpin without exceeding the drive axle GAWR. Due to limited fifth 
wheel adjustment on some vehicles, virtually all of the ballast added 
at the fifth wheel is borne by the tractor's rear axle, with very 
little transferred to the front axle.
    After reviewing AAMA's comment, NHTSA has decided to amend 
S6.1.10.4 to include the phrase ``without exceeding the GAWR of any 
tractor or trailer axle.'' The Agency believes that this modification 
is consistent with the proposal's intent to have the loading 
proportional to each axle's respective GAWR. The Agency is aware that 
this modification will result in some tractors being tested slightly 
below their GVWR. However, since actual users will be similarly 
incapable of loading the vehicle to its GVWR without exceeding 
[[Page 13292]] GAWR, the reduced amount should not adversely affect 
motor vehicle safety.
e. Initial Brake Temperature
    In the NPRM, NHTSA proposed an initial brake temperature of 250 
deg.F to 300  deg.F. The Agency tentatively concluded that specifying a 
high brake temperature would reduce cooling time between stops and 
therefore allow vehicle testing to proceed faster. All the commenters 
that addressed this issue opposed the proposed adoption of such a high 
initial brake temperature.
    Based on these comments and the available test data, NHTSA has 
concluded that an initial brake temperature of between 150  deg.F to 
200  deg.F range is more appropriate than the proposed temperature 
range. As explained in detail in the stability and control final rule, 
testing using the 150  deg.F to 200  deg.F temperature range is more 
repeatable and results in less variation between runs, compared to 
testing conducted at an initial brake temperature of 250  deg.F to 300 
deg.F, particularly for the emergency brake stops.
f. Emergency Stopping Distance Requirements
    Although the NPRM did not propose to change the current emergency 
stopping distance requirements in Standard No. 121, several commenters 
recommended changes. AMA, ATA, Allied Signal, HDBMC, and Rockwell 
International recommended that the Agency eliminate the stopping 
distance performance requirements for a loaded truck tractor's 
emergency braking system when tested with an unbraked control trailer. 
They stated that a failed primary or a failed secondary brake system 
does not realistically simulate any real-world vehicle situation that 
can occur during a single brake system failure. They further stated 
that this requirement would impose extremely unrealistic loads on the 
functioning truck tractor brakes. AAMA stated that the emergency brake 
systems are not designed to stop a loaded unbraked control trailer, and 
that Standard No. 121 already includes a requirement in S5.7.3(c) 
stating that a loss of primary or secondary tractor brakes should not 
result in a loss of trailer brakes. Test data submitted by AAMA and 
Allied Signal showed stopping distances in excess of 2,000 feet for the 
failed primary (rear) brakes on a tractor with a loaded unbraked 
control trailer. The stopping test distances submitted for failed 
secondary (front) brakes on the tractor with a loaded unbraked control 
trailer were within the current requirement of 613 feet. Based on these 
considerations, the commenters recommended that the tractor's emergency 
brake system be tested in the bobtail configuration only.
    After reviewing the comments and other available information, NHTSA 
has decided to apply the emergency brake system test for truck tractors 
only in the unloaded (bobtail) condition for both the failed primary 
and failed secondary conditions. According to test data obtained 
through the Agency's testing and provided by commenters, emergency 
brake system testing presents a unique problem for a loaded truck 
tractor with an unbraked control trailer. With either a primary or 
secondary failure of the tractor's brakes, the loaded combination would 
be braked only by the front axle or rear axle brakes, since the control 
trailer is unbraked. As a result, the stopping distances would be 
extremely long, particularly in the case of the failed rear brakes 
system. In addition, such a situation does not realistically simulate 
failed truck tractor systems since in real-world situations, the 
trailer brakes are intact.
g. Burnish Procedure
    Even though this rulemaking did not address burnish procedures, 
AAMA and HDBMC requested that the Agency indefinitely allow using the 
old or the new burnish procedure as an option.
    The Agency believes that the effective date for the ``new'' burnish 
procedure should be considered in Docket No. 70-27, Notice 33, and 
Docket No. 83-07, Notice 5, independently from the stopping distance 
effective dates.<SUP>10 Given that the industry has been aware since 
August 1993 that the new burnish procedures would be required after 
September 1994, NHTSA believes that vehicle manufacturers have had 
sufficient time to conduct any additional testing and to make any 
necessary design changes in order to meet the requirements of Standard 
No. 121 with the new burnish procedure. Moreover, since the new 
procedures have been in effect since September 1, 1994, the issue of 
extending the option formerly allowed is moot. Therefore, NHTSA has 
decided to terminate the rulemaking on the burnish issue.

    \10\ On August 30, 1993, NHTSA issued an interim final rule and 
an NPRM addressing whether the old burnish procedures should be 
allowed indefinitely (58 FR 45459). Optional compliance with the 
``new'' procedures had been permissible since 1988 and was extended 
to September 1994. The Agency also proposed extending optional 
compliance until March 1996. The Agency requested comments about 
whether the new burnish procedures should become the sole specified 
procedures or whether the old burnish procedures should be allowed 
for an additional period of time.
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h. Parking Brake Test
    AAMA requested that the agency modify the parking brake procedure 
in this rulemaking by specifying an initial brake temperature of 150-
200  deg.F, and a ``compounding technique'' for consistency of grade 
holding and drawbar procedures. Compounding is described as a full 
treadle service brake application preceding the application of the 
parking brakes. AAMA claimed that during its testing to respond to the 
stopping distance NPRMs, it realized that different manufacturers use 
different parking brake test procedures. Therefore, its stated reason 
for proposing a change is to avoid having compliance issues arise due 
to alleged test procedure ambiguities.
    NHTSA has neither addressed this issue in the NPRM nor conducted 
research about compounding. Therefore, the Agency has determined that 
it would be inappropriate at this time to modify the Standard to 
specify such a compounding test procedure. If the Agency were to decide 
in the future that it may be desirable to amend the Standard to require 
this test condition, it would issue an NPRM to provide the industry and 
other interested parties an opportunity to comment about such a 
modification.
    As discussed above, NHTSA has agreed to AAMA's request to specify 
an initial brake temperature of between 150-200  deg.F for the service 
brake performance tests. As so modified, the parking brake test 
procedure explicitly specifies that the parking brake test be conducted 
``under the conditions of S6.1,'' which specifies the initial brake 
temperature for the test. Therefore, any ambiguity that allegedly 
results from the higher initial brake temperature is no longer present.

C. Threshold Pressure Requirement

    In the NPRM, NHTSA proposed to establish a requirement for 
threshold pressure<SUP>11 levels of 6.0<plus-minus>0.5 psi for truck 
tractors and trailers equipped with an air brake system. The Agency 
tentatively concluded that such a requirement would improve the brake 
balance on combination vehicles and reduce the potential for vehicle 
instability when lightly loaded. The Agency requested comments about 
the need for establishing threshold pressures and whether the proposed 
threshold pressure and its range were appropriate and feasible.

    \11\ ``Threshold pressure'' is the brake application pressure at 
which the brakes actually begin to generate braking torque.
---------------------------------------------------------------------------

    All commenters recognized the need to improve tractor trailer 
compatibility [[Page 13293]] and supported the intent of the proposed 
threshold pressure requirement. However, AAMA, Midland-Grau, and 
Rockwell opposed establishing a threshold pressure requirement until 
additional research could be conducted.<SUP>12 The commenters requested 
that the Agency not issue such a requirement until a cooperative 
industry and government effort can be conducted to better define the 
performance and safety improvements of a threshold pressure and 
tolerance requirement.

    \12\ Only Mr. Robert Crail, a brake engineer, favored adopting a 
requirement to improve pressure compatibility between tractors and 
trailers.
---------------------------------------------------------------------------

    Most commenters believed that selecting a target threshold pressure 
value of 6.0 psi, which was approved by the SAE Brake Committee in 
1985, would not be realistic for current combination vehicles. In 
addition, HDBMC stated that small differences in threshold pressure are 
irrelevant to whether a tractor trailer combination can achieve the 
prescribed stopping distances. HDBMC noted that SAE Recommended 
Practice J1505, ``Brake Force Distribution Test Code'' (May 1985) was 
developed primarily to reduce maintenance costs by improving brake drum 
and lining life and to enable fleets to standardize threshold 
pressures. It further stated that the testing conducted to establish 
SAE J1505 was limited to S-Cam brakes and vehicles with a GAWR of 
16,000 to 20,000 pounds. S-Cam brakes on larger vehicles, wedge brakes 
(which have higher threshold pressures) and disc brakes were not 
tested.
    Several commenters addressed the threshold pressure level that 
should be established if the Agency decided to adopt a threshold 
pressure requirement. Mr. Crail recommended that the tolerance range be 
increased from 6.0<plus-minus>0.5 psi to 6.0<plus-minus>1.0 psi to 
accommodate the variation in relay valves, brake chamber return springs 
and foundation brake return springs. AAMA stated that a tolerance for 
air brake components of <plus-minus>3.73 psi was appropriate. Lucas 
suggested a tolerance of +3 psi and that the Agency should apply this 
tolerance to only tractor drive axles and trailer axles with 16.5 inch 
S-cam drum brakes. ATA recommended a tolerance of between 2 to 11 psi.
    After reviewing the comments and other available information, NHTSA 
has decided not to establish a pressure threshold requirement at this 
time. The Agency notes that additional research and testing needs to be 
conducted on this matter since there currently is insufficient 
information to set a threshold pressure tolerance for combination 
vehicles. The brake components that affect the threshold pressure, such 
as internal friction in the relay valves and the return springs in the 
brake chamber and foundation brakes, provide a tolerance close to 4 
psi. Therefore, establishing a threshold pressure requirement, even 
with a broad tolerance, could pose compliance problems for the 
industry. In addition, additional research needs to be conducted on 
brakes other than S-cam brakes.
    NHTSA emphasizes that after additional cooperative testing is 
completed, a threshold pressure requirement could be proposed that 
would improve the braking performance of a combination vehicle, 
particularly at low application pressures typical of normal stops.

D. Requirements for Brake Linings

    ATA and Mack Trucks requested that NHTSA issue a rule requiring 
replacement brake linings to be of the same quality and have the same 
friction characteristics as the linings used by original equipment 
manufacturers.
    The issue of aftermarket brake linings is the subject of a separate 
NHTSA rulemaking action, and will not be addressed by this notice. If 
the Agency tentatively concludes that such requirements for aftermarket 
brake linings are in the interest of motor vehicle safety, then it will 
issue a proposal to adopt such requirements.

E. Implementation Schedule

    In the NPRM, NHTSA proposed that the stopping distance requirements 
become effective two years after the final rule's publication.
    AAMA supported the proposed effective date, provided that the 
agency incorporated its recommended modifications in the final rule. 
Rockwell recommended that the stopping distance requirements and the 
stability performance requirements be combined so that the effective 
dates for both rulemakings are concurrent. Several commenters on the 
stability and control NPRM, including AAMA, made the same suggestion. 
AAMA noted that since ABS can directly influence achievable stopping 
distance, it is important to optimize brake system performance by 
taking both stopping distance and stability into account.
    On April 12, 1994, NHTSA published a supplemental notice of 
proposed rulemaking that proposed the following implementation schedule 
for both the stopping distance and lateral stability and control 
requirements:

Truck tractors--2 years after final rule (1996)
Trailers--3 years after final rule (1997)
Air-braked single unit trucks and buses--3 years after final rule 
(1997)
Hydraulic-braked single unit trucks and buses--4 years after final rule 
(1998). (59 FR 17326).

    The Agency reasoned that making the effective dates for the two 
rulemakings concurrent would promote a more orderly implementation 
process, avoid the need for manufacturers to redesign the brakes on 
individual vehicles twice, and reduce the development and compliance 
costs that manufacturers would face as a result of these regulations. 
NHTSA requested comments about the implementation schedule proposed in 
the supplemental notice.
    As the stability and control final rule discusses in detail in the 
section titled ``implementation schedule,'' NHTSA has decided to adopt 
an implementation schedule similar to the one proposed in the SNPRM. 
Specifically, truck tractors manufactured on or after March 1, 1997 
will have to be equipped with ABS and comply with the braking-in-a-
curve test and high coefficient of friction stopping distance 
requirements; trailers and single-unit air-braked trucks and buses 
manufactured on or after March 1, 1998 will have to be equipped with 
ABS, and, except for trailers, comply with the high coefficient of 
friction stopping distance requirements; and hydraulic-braked trucks 
and buses manufactured on or after March 1, 1999 will have to be 
equipped with ABS and comply with the high coefficient of friction 
stopping distance requirements. The Agency has decided that these 
effective dates, which were widely supported by vehicle manufacturers, 
brake manufacturers, and safety advocacy groups, will provide for an 
efficient implementation of the heavy vehicle braking rulemakings.

F. Intermediate and Final Stage Manufacturers/Trailer Manufacturers

    Vehicle manufacturers must certify that each of their vehicles 
complies with all applicable Federal motor vehicle safety standards. 
While this statutory certification requirement is straightforward with 
respect to vehicles produced by a single manufacturer, it is more 
complex for vehicles produced in two or more stages. With such 
multistage vehicles, one or more manufacturers produce an ``incomplete 
vehicle'' which requires further manufacturing operations by another 
manufacturer to become a completed vehicle. As defined in 49 CFR 568.3, 
an incomplete vehicle includes, at a [[Page 13294]] minimum, a frame 
and chassis structure, power train, steering system, suspension system, 
and braking system. Incomplete vehicles may be grouped in two 
categories: (1) Chassis-cabs (which are incomplete vehicles with fully 
completed occupant compartments that require only the addition of 
cargo-carrying, work-performing, or load-bearing components to perform 
their intended functions and become completed vehicles (49 CFR 567.3)) 
which are certified by the chassis-cab manufacturer (49 CFR 567.5), and 
(2) incomplete vehicles other than chassis-cabs (``non chassis-cabs''), 
which are not certified by the incomplete vehicle manufacturer.
    The National Truck Equipment Association (NTEA) commented that 
manufacturers of multi-stage vehicles may not be able to demonstrate 
compliance with the proposed amendments because they may not be able, 
in all cases, to ``pass through'' the incomplete vehicle manufacturer's 
certification. NTEA claims that these manufacturers will not have a 
practicable and objective means of demonstrating compliance, since they 
lack the financial resources and capabilities to sponsor testing to the 
requirements. Therefore, NTEA suggested that the Agency exclude multi-
stage vehicles from the proposed road testing requirements.
    As explained below, NHTSA has concluded that the stopping distance 
requirements do not pose an unreasonable burden for final stage 
manufacturers. NHTSA is aware of the concerns of final stage 
manufacturers about road testing their vehicles. However, the final 
stage manufacturers can avoid the necessity of conducting independent 
testing by staying within the limits (``the envelope'') set by the 
incomplete vehicle manufacturer. In fact, S6 of Standard No. 121 
currently provides that ``Compliance of vehicles manufactured in two or 
more stages may, at the option of the final-stage manufacturer, be 
demonstrated to comply with this standard by adherence to the 
instructions of the incomplete manufacturer provided with the vehicle 
in accordance with Sec. 568.4(a)(7)(ii) and Sec. 568.5 of title 49 of 
the Code of Federal Regulations.''<SUP>13 In the final rule adding this 
provision in response to the 9th Circuit's decision in PACCAR, the 
Agency stated that it provides directly in the regulation ``an 
alternative to road testing * * * that would constitute `due care' in 
certification by any final-stage manufacturer that adopted it, whatever 
its resources and engineering expertise.'' (43 FR 48646, October 19, 
1978.)

    \13\ In today's Federal Register notice amending Standard No. 
105 with respect to stopping distances of hydraulically-braked 
vehicles, the Agency is also modifying that Standard to include 
identical language about compliance by final stage manufacturers so 
that this concept expressly applies to hydraulic-braked vehicles 
manufactured in two or more stages, as well.
---------------------------------------------------------------------------

    With respect to chassis-cabs, the name of each manufacturer in the 
chain of production is required to appear on one or more certification 
labels that are permanently affixed to the vehicle. (49 CFR Parts 567 
and 568.) Under these regulations, certification of an incomplete 
vehicle that is a chassis-cab can ``pass through'' to the final stage 
manufacturer, provided that the final stage manufacturer takes the 
precautions necessary to ensure it does not invalidate the 
certification. The final stage manufacturer must ensure that it 
completes the vehicle without exceeding the GVWR and GAWRS assigned by 
the chassis-cab manufacturer, altering any brake system component, 
moving the center of gravity of the completed vehicle with the body 
installed outside the ``envelope'' of specifications provided by the 
chassis manufacturer, or otherwise violating that envelope. If the 
final stage manufacturer complies with all of the chassis-cab 
manufacturer's specifications, the final stage manufacturer can base 
its certification of compliance with the braking standard entirely upon 
the statement of the chassis-cab manufacturer and therefore will not 
have to recertify the vehicle.
    The provision in S6 also applies to non-chassis-cabs, since the 
manufacturer of a non-chassis-cab is required to furnish documentation 
that indicates a means of compliance with applicable standards to 
intermediate or final stage manufacturers (49 CFR 568.4), and the final 
stage manufacturer is required to identify the incomplete manufacturer 
on the certification label that the final stage manufacturer places on 
the completed vehicle. As with chassis-cabs, the final stage 
manufacturer can avoid the necessity of conducting independent testing 
by staying within the envelope set by the incomplete manufacturer.
    Based on the above considerations, the final stage manufacturer 
would only be required to certify compliance independently in those 
cases in which the final vehicle violates those specifications. NTEA 
commented that there are situations in which the final stage 
manufacturer ``must exceed the `envelope' of restrictions provided by 
the chassis manufacturer due to customer specifications.'' The Agency 
believes that in virtually all such cases the body or equipment that is 
specified by the customer could be fitted on a different truck chassis 
having a larger ``envelope''. Moreover, when the customer has an 
overriding need to specify a particular truck chassis that cannot be 
completed with the desired body or equipment without exceeding the 
envelope, it is reasonable to expect the customer to bear the 
additional cost burden of assuring that the completed vehicle complies 
with the standard. In such situations, it is reasonable to require the 
final stage manufacturer to accept responsibility for certification, 
given the important safety concerns discussed below. The Agency 
emphasizes, however, that it is not necessary for final stage 
manufacturers to make this choice. They can instead select an 
appropriate incomplete vehicle that can be completed without departing 
from the envelope specified by the incomplete vehicle manufacturer.
    Some of the manufacturers that build multi-stage vehicles and 
choose not to stay within the envelope are small businesses that may be 
unable to conduct their own road tests. While manufacturers must 
certify that their vehicles meet all applicable safety standards, this 
does not mean that every final stage manufacturer must independently 
conduct the specific tests set forth in an applicable standard. A final 
stage manufacturer may also certify compliance to the stopping distance 
standard based on, among other things, engineering analyses and 
computer simulations. Moreover, manufacturers need not conduct these 
operations themselves. They can utilize the services of independent 
engineers and testing laboratories. They can also join together through 
trade associations to sponsor testing or analysis. Finally, they can 
rely on testing and analysis performed by other parties, including 
brake manufacturers. Brake manufacturers typically perform extensive 
analyses and tests of their products and, in order to sell those 
products, have a strong incentive to provide their customers, the 
vehicle manufacturers, with information that can be used to certify the 
vehicle to the applicable brake standards. Some manufacturers of motor 
vehicle components currently provide this type of information to 
vehicle manufacturers. Based on the above considerations, NHTSA has 
concluded that manufacturers can certify compliance with the stopping 
distance requirements by means other than road testing.
    Moreover, road testing to establish compliance with the braking 
requirements does not involve expensive and destructive crash testing, 
which cost $18,000 or more, not [[Page 13295]] including the cost of 
the vehicle which is destroyed as a result of the test. Thus, while 
brake testing does involve some expense (the Agency estimates that a 
complete compliance test series for Standard No. 121 would cost 
$5,000), it should be feasible for manufacturers, including small 
manufacturers (especially in groups or through associations), to 
certify compliance, particularly since the road testing does not 
require destruction of their vehicles.
    Furthermore, NHTSA is not authorized when establishing safety 
standards to differentiate between manufacturers on the basis of their 
size or financial resources. While the agency must ``consider whether 
any such proposed standard is reasonable, practicable and appropriate 
for the particular type of motor vehicle or motor vehicle equipment for 
which it is prescribed,'' (49 U.S.C. 30111(b)(3), formerly section 
103(f)(3) of the Vehicle Safety Act), the legislative history of the 
Vehicle Safety Act reveals that any differences between standards for 
different classes of vehicles ``of course [are to] be based on the type 
of vehicle rather than its place of origin or any special circumstances 
of its manufacturer.'' S. Rept. 1301, 2 U.S. Code, Cong. & Admin. News, 
2714 (1966), cited in Chrysler Corp. v. D.O.T., 472 F.2d 659, 679 (6th 
Cir. 1972).
    Strong policy reasons underlie Congress' refusal to differentiate 
between vehicles on the basis of the manufacturers' ``special 
circumstances.'' To protect unsuspecting members of the public from 
exposure to unreasonable risks posed by unsafe vehicles, there is good 
reason to require that every vehicle meet all ``minimum performance 
standards'' that are prescribed for vehicles of its type.
    Moreover, the statute does not authorize NHTSA to grant permanent 
exemptions from safety standards to small manufacturers who otherwise 
would be covered by those standards. See Nader v. Volpe, 475 F.2d 916, 
918 (D.C. Cir. 1973). While Nader involved a single manufacturer that 
sought to be permanently exempted from safety standards, its reasoning 
applies equally to classes of manufacturers that seek such exemptions. 
Although the Safety Act was amended after the Nader decision to permit 
small manufacturers to seek temporary exemptions from safety standards 
if they can demonstrate that compliance with the standard would cause 
them ``substantial economic hardship'' and that they have made a good 
faith effort to comply (49 U.S.C. 30113, formerly section 123 of the 
Vehicle Safety Act), Congress has severely restricted the agency's 
authority to grant such exemptions to very narrow, limited 
circumstances. NTEA is in effect seeking a permanent exemption from 
Standard No. 121 that the statute does not permit.
    NHTSA emphasizes that there are important safety reasons that 
necessitate having a final stage manufacturer certify the completed 
vehicle if it does not stay within the envelope set by the incomplete 
vehicle manufacturer. For instance, if a final stage manufacturer adds 
additional components so that the completed vehicle's GVWR exceeds the 
recommended maximum GVWR weight specified in the envelope for the 
vehicle, the vehicle's braking performance could be adversely affected. 
As an example, a brake system designed to bring a 15,000 pound vehicle 
to a stable and short stop would obviously not be able to safely stop a 
20,000 pound vehicle. Moreover, the brakes on such an underbraked 
vehicle would be prone to overheating. While it is relatively easy to 
understand the degradation in performance in such a gross example, the 
potential for reduced, safety-related performance also exists in 
situations were the ``violation'' of the envelope is much smaller. 
Similarly, if the center of gravity is made too high, a vehicle would 
likely be overbraked on its rear axle(s) and thus be prone to 
instability caused by wheel lockup.
    NHTSA emphasizes that the kinds of crashes that result when a heavy 
vehicle is unable to stop to avoid another vehicle are very serious. As 
part of the cost effectiveness analysis contained in the Final Economic 
Analysis (FEA) for this final rule, the agency used 1992 GES data to 
identify a group of crashes involving heavy vehicles defined as 
``unable-to-stop-in-time'' crashes. The agency examined these crashes 
and the number and severity of the resulting injuries in evaluating the 
impact of this regulation. One means of comparing the relative severity 
of various types of crashes is to ``convert'' the injuries at different 
levels of severity into ``equivalent fatalities''\14\ and to divide 
that by the number of crashes that resulted in those injuries. The 
resulting ratio, equivalent fatalities per crash, can be calculated for 
various types of crashes and compared to indicate the relative severity 
of different crash types. Using 1992 GES data, estimates were made of 
the equivalent fatalities per crash for multiple-vehicle crashes 
involving all types of vehicles, 0.01402 equivalent fatalities per 
crash, for multiple-vehicle crashes involving heavy vehicles, 0.02089 
equivalent fatalities per crash, and for the ``unable-to-stop-in-time'' 
crashes mentioned above, 0.03634. Comparing the rates of equivalent 
fatalities indicate that not only are multiple-vehicle crashes 
involving heavy vehicles 49% more severe than all multiple-vehicle 
crashes, but the ``unable-to-stop-in-time'' crashes, which are the 
types of crashes affected by this final rule, are 159% more severe than 
all multiple-vehicle crashes in general. Also using 1992 GES data, the 
agency made separate estimates of the rate of equivalent fatalities per 
crash for the heavy vehicle occupants and the occupants of other 
involved vehicles. This was done for both multiple-vehicle crashes 
involving heavy vehicles and for the ``unable-to-stop-in-time'' 
crashes. The comparison of these rates shows that the ``unable-to-stop-
in-time'' crashes are 31% more severe in terms of injuries to the heavy 
vehicle occupant and 79% more severe for the occupants of other 
involved vehicles than multiple-vehicle crashes involving heavy 
vehicles.

    \14\The basic methodology used to convert injuries at various 
levels of severity into equivalent fatalities is outlined in the FEA 
for this final rule.
---------------------------------------------------------------------------

G. Costs

    As explained in detail in the FEA, the costs associated with the 
rulemaking involve additional testing costs and hardware/equipment 
costs. The agency estimates the minimum initial testing costs 
associated with reinstating stopping distance requirements for all 
heavy air-braked vehicles would be about $6 million. As noted in the 
FEA, the estimated annual compliance testing costs in years following 
the effective dates of this final rule are estimated to be about $2 
million. Assuming the industry continues to produce about 208,500 heavy 
Class 5-8 air-braked vehicles per year (which are the largest heavy 
vehicles and tractor trailers), the initial testing cost per vehicle 
would be about $29 and for later years the testing cost per vehicle 
would be about $10.
    The hardware and equipment costs of meeting the proposed stopping 
distance requirements for air braked heavy vehicles are based on the 
anticipated improvements to heavy vehicles. The agency notes that all 
of the changes made to meet these requirements would affect vehicles 
operating in the fully loaded, or nearly fully loaded configurations.
    These improvements in braking performance, which are achieved by 
substituting air chambers, slack adjusters and brake linings, are 
estimated to be necessary on about 104,000 air-braked vehicles, 
including both truck tractors and single-unit trucks. The average cost 
per vehicle of [[Page 13296]] these changes is estimated to be $50, 
resulting in a total cost of $5.21 million, which is the total 
estimated cost for vehicle modifications necessitated by this final 
rule.
    The total estimated initial cost impact of this proposal is $11.21 
million ($6.0 million in compliance test costs plus $5.21 million in 
vehicle modification costs), which for an estimated annual production 
of 208,500 air-braked equipped vehicles, is an average of about $54 per 
vehicle.
    The total estimated outyear cost impact of this proposal is $7.21 
million ($2.0 million in compliance test costs plus $5.21 million in 
vehicle modification costs), which for an estimated annual production 
of 208,500 air braked equipped vehicles, is an average of about $35 per 
vehicle.

VI. Rulemaking Analyses and Notices

A. Executive Order 12866 and DOT Regulatory Policies and Procedures

    This rulemaking document was not reviewed under E.O. 12866. NHTSA 
has considered the impact of this rulemaking action under the 
Department of Transportation's regulatory policies and procedures. This 
action has been determined to be not ``significant'' under those 
policies and procedures.
    A FEA setting forth the agency's detailed analysis of the benefits 
and costs of this rulemaking (along with the other rules issued today) 
has been prepared and been placed in the docket. This rulemaking is 
based on the FEA and all additional data available to the agency. The 
Agency estimates that reinstating the stopping distance requirements 
for Standard No. 121 will result in an average of approximately 3.2 
lives saved per year and 84 injuries prevented per year. As mentioned 
above, the agency estimates that the initial annual costs attributable 
to these requirements are approximately $11.21 million ($6.00 million 
for compliance testing and $5.21 million for net equipment costs) and 
the outyear annual costs attributable to these requirements are 
approximately $7.21 million ($2.00 million for compliance testing and 
$5.21 million for net equipment costs).
    Based on its analysis, the agency concludes that the requirements 
will improve safety by ensuring that all heavy vehicles are capable of 
stopping within a specified, safe distance. Based on information 
detailed in the previous section, the agency believes that implementing 
the stopping distance requirements for heavy vehicles will not result 
in significant costs since most of these vehicles currently comply with 
the reinstated requirements. For those vehicles that do not currently 
comply with the requirements, the agency believes that they could be 
upgraded by substituting other with currently produced braking 
components for those now used on these vehicles.
    Since these components are not significantly more expensive than 
those used in poorer performing brake systems, the net cost of 
substituting these components will not be significant and is estimated 
to be about $50 for each vehicle that requires such changes.

B. Regulatory Flexibility Act

    NHTSA has also considered the impacts of this notice under the 
Regulatory Flexibility Act. I hereby certify that this rule will not 
have a significant economic impact on a substantial number of small 
entities. There may be a small number of intermediate and final stage 
manufacturers that are small businesses that may be impacted by this 
final rule, but as discussed previously, the Agency does not believe 
that that impact is substantial, particularly in comparison to the 
possible crash-related consequences of vehicles produced by such 
manufacturers not complying with the rule.

C. Paperwork Reduction Act

    In accordance with the Paperwork Reduction Act of 1980 (P.L. 96-
511), there are no requirements for information collection associated 
with this rule.

D. National Environmental Policy Act

    NHTSA has also analyzed this rule under the National Environmental 
Policy Act and determined that it will not have a significant impact on 
the human environment. No changes in existing production or disposal 
processes will result, except that there is a reduction in these 
factors resulting from the removal of the ALV. There will be a weight 
increase of a few pounds per tractor with the installation of a BPV on 
tractors, but such a small increase should not have any significant 
effect on fuel consumption. Nor should production and disposal 
processes have a significant adverse affect on the environment.

E. Executive Order 12612 (Federalism)

    NHTSA has analyzed this rule in accordance with the principles and 
criteria contained in E.O. 12612, and has determined that this rule 
will not have significant federalism implications warranting the 
preparation of a Federalism Assessment.

F. 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.

List of Subjects in 49 CFR Part 571

    Imports, Motor vehicle safety, Motor vehicles, Rubber and rubber 
products, Tires.
    In consideration of the foregoing, this notice amends Standard No. 
121, Air Brake Systems, in Title 49 of the Code of Federal Regulations 
at Part 571 as follows:

PART 571--[AMENDED]

    1. The authority citation for Part 571 continues to read as 
follows:

    Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166, 
delegation of authority at 49 CFR 1.50.


Sec. 571.121  [Amended]

    2. Section 571.121, is amended by removing the undesignated text 
following paragraph (g) in S3; in S4 by adding the definition for 
``Wheel lockup;'' by revising S5.3.1, S5.3.1.1, and Table II; by 
deleting S5.3.2, S5.3.2.1, and S5.3.2.2; by reserving S5.3.2, and by 
revising S5.7.1 to read as follows:
* * * * *
    Wheel lockup means 100 percent wheel slip.
* * * * *
    S5.3.1  Stopping distance--trucks and buses. When stopped six times 
for each combination of vehicle type, weight, and speed specified in 
S5.3.1.1, in the sequence specified in Table I, each truck tractor 
manufactured on or after March 1, 1997 and each single unit vehicle 
manufactured on or after March 1, 1998 shall stop at least once in not 
more than the distance specified in Table II, measured from the point 
at which movement of the service brake control begins, without any part 
of the vehicle leaving the roadway, and with wheel lockup permitted 
only as follows: [[Page 13297]] 
    (a) At vehicle speeds above 20 mph, any wheel on a nonsteerable 
axle other than the two rearmost nonliftable, nonsteerable axles may 
lock up, for any duration. The wheels on the two rearmost nonliftable, 
nonsteerable axles may lock up according to (b).
    (b) At vehicle speeds above 20 mph, one wheel on any axle or two 
wheels on any tandem may lock up for any duration.
    (c) At vehicle speeds above 20 mph, any wheel not permitted to lock 
in (a) or (b) may lock up repeatedly, with each lockup occurring for a 
duration of one second or less.
    (d) At vehicle speeds of 20 mph or less, any wheel may lock up for 
any duration.

                       Table I.--Stopping Sequence                      
                                                                        
                                                                        
                                                                         
1. Burnish.                                                             
2. Stops with vehicle at gross vehicle weight rating:                   
  (a) 60 mph service brake stops on a peak friction coefficient surface 
   of 0.9, for a truck tractor with a loaded unbraked control trailer,  
   or for a single-unit vehicle.                                        
  (b) 30 mph service brake stops on a peak friction coefficient surface 
   of 0.5, for a truck tractor with a loaded unbraked control trailer.  
  (c) 60 mph emergency brake stops on a peak friction coefficient       
   surface of 0.9, for a single-unit vehicle. Truck tractors are not    
   required to be tested in the loaded condition.                       
3. Parking brake test with vehicle loaded to GVWR.                      
4. Stops with vehicle at unloaded weight plus up to 500 lbs.            
  (a) 60 mph service brake stops on a peak friction coefficient surface 
   of 0.9, for a truck tractor or for a single-unit vehicle.            
  (b) 30 mph service brake stops on a peak friction coefficient surface 
   of 0.5, for a truck tractor.                                         
  (c) 60 mph emergency brake stops on a peak friction coefficient       
   surface of 0.9, for a truck tractor or for a single-unit vehicle.    
5. Parking brake test with vehicle at unloaded weight plus up to 500    
 lbs.                                                                   
6. Final inspection of service brake system for condition of adjustment.
                                                                        

    S5.3.1.1  Stop the vehicle from 60 mph on a surface with a peak 
friction coefficient of 0.9 with the vehicle loaded as follows: (a) 
loaded to its GVWR, (b) in the Bobtail configuration (truck-tractors 
only) plus up to 500 pounds, and (c) at its unloaded vehicle weight 
(except for a truck tractor) plus up to 500 pounds (including driver 
and instrumentation). If the speed attainable in two miles is less than 
60 mph, the vehicle shall stop from a speed in Table II that is 4 to 8 
mph less than the speed attainable in 2 miles.

                                          Table II.--Stopping Distance                                          
                                                    [In feet]                                                   
                                                                                                                
                                                                       Service brake             Emergency brake
              Vehicle speed in miles per hour              -----------------------------------------------------
                                                            PFC 0.9  PFC 0.9  PFC 0.9  PFC 0.9  PFC 0.9  PFC 0.9
                                                                (1)      (2)      (3)      (4)      (5)      (6)
                                                                                                                
----------------------------------------------------------------------------------------------------------------
20........................................................       32       35       38       40       83       85
25........................................................       49       54       59       62      123      131
30........................................................       70       78       84       89      170      186
35........................................................       96      106      114      121      225      250
40........................................................      125      138      149      158      288      325
45........................................................      158      175      189      200      358      409
50........................................................      195      216      233      247      435      504
55........................................................      236      261      281      299      520      608
60........................................................      280      310      335      355      613      720
Note: (1) Loaded and unloaded buses; (2) Loaded single unit trucks; (3) Unloaded truck tractors and single unit 
  trucks; (4) Loaded truck tractors tested with an unbraked control trailer; (5) All vehicles except truck      
  tractors; (6) Unloaaded truck tractors.                                                                       

* * * * *
    S5.7.1  Emergency brake system performance. When stopped six times 
for each combination of weight and speed specified in S5.3.1.1, except 
for a loaded truck tractor with an unbraked control trailer, on a road 
surface having a PFC of 0.9, with a single failure in the service brake 
system of a part designed to contain compressed air or brake fluid 
(except failure of a common valve, manifold, brake fluid housing, or 
brake chamber housing), the vehicle shall stop at least once in not 
more than the distance specified in Column 5 of Table II, measured from 
the point at which movement of the service brake control begins, except 
that a truck-tractor tested at its unloaded vehicle weight plus up to 
500 pounds shall stop at least once in not more than the distance 
specified in Column 6 of Table II. The stop shall be made without any 
part of the vehicle leaving the roadway.
* * * * *
    Issued on: March 1, 1995.
Ricardo Martinez, M.D.
Administrator.
[FR Doc. 95-5413 Filed 3-7-95; 8:45 am]
BILLING CODE 4910-59-P