[Federal Register Volume 61, Number 106 (Friday, May 31, 1996)]
[Rules and Regulations]
[Pages 27288-27304]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-13557]



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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. 96-050; Notice 1]
RIN 2127-AG31


Federal Motor Vehicle Safety Standards; Air Brake Systems

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

ACTION: Final rule; technical amendment.

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SUMMARY: This document revises Standard No. 121, Air brake systems to 
remove obsolete provisions and to update and reorganize the standard. 
This revision substantially clarifies and simplifies this safety 
standard without changing any of its substantive requirements.

EFFECTIVE DATE: This rule is effective March 1, 1997.

FOR FURTHER INFORMATION CONTACT: Mr. Richard Carter, Office of Vehicle 
Safety Standards, NPS-11, National Highway Traffic Safety 
Administration, 400 Seventh Street, SW., Washington, DC

[[Page 27289]]

20590. Telephone: (202) 366-5274. Fax: (202) 366-4329. For legal 
issues: Mr. Marvin L. Shaw, Office of Chief Counsel, NCC-20, National 
Highway Traffic Safety Administration, 400 Seventh Street, SW., 
Washington, DC 20590. Telephone: (202) 366-2992.

SUPPLEMENTARY INFORMATION: Pursuant to the March 4, 1995, directive, 
``Regulatory Reinvention Initiative,'' from the President to the heads 
of departments and agencies, the National Highway Traffic Safety 
Administration (NHTSA) has undertaken a review of all its regulations 
and directives. During the course of this review, the agency identified 
several regulations that are potential candidates for amendment.
    One of these regulations is Standard No. 121, Air brake systems. 
There are two major types of changes. The first type of change involves 
deleting obsolete provisions. For example, S5.3.3.2 of current Standard 
No. 121 sets forth optional requirements about brake actuation time for 
systems manufactured before May 3, 1991. Similarly, S6.1.8.1(a) sets 
forth an optional burnish procedure for vehicles manufactured before 
September 1, 1994. The second type of change involves updating the Code 
of Federal Regulations to include the agency's recent amendments to 
Standard No. 121. For instance, on March 10, 1995, NHTSA amended 
Standard No. 121 to require air braked vehicles to be equipped with 
antilock brake systems and to reinstate stopping distance requirements. 
(60 FR 13216). Portions of these amendments were subsequently revised 
on December 13, 1995, (60 FR 63965) and February 15, 1996, (61 FR 
2412). Today's notice contains the agency's most recent amendments of 
these provisions. In removing obsolete provisions and updating the 
standard, the agency's goal is to clarify and simplify Standard No. 
121, without changing any of its substantive requirements.
    This rulemaking action responds to petitions for reconsideration 
addressing the agency's antilock brake system rulemaking in which the 
Heavy Duty Brake Manufacturers Council (HDBMC), the American Automobile 
Manufacturers Association (AAMA), and Midland-Grau requested that the 
agency publish a complete and updated version of Standard No. 121.
    In rewriting Standard No. 121, a significant issue was what 
effective date to select. A number of new requirements for Standard No. 
121 will take effect in the next few years. Of particular note, the 
requirements for antilock brake systems and for stopping distance tests 
are being phased in for various vehicle types (e.g., truck tractors, 
trailers, and single unit vehicles) between March 1, 1997, and March 1, 
1998. As a result of these new amendments, the standard's requirements 
vary significantly for different dates over the next two years.
    After examining the current standard, NHTSA has concluded that 
clarifying and simplifying Standard No. 121 can best be accomplished by 
selecting an effective date of March 1, 1997, the date when truck 
tractors must first comply with the new antilock brake system and 
stopping distance requirements. Most of the changes in the regulatory 
text delete obsolete requirements and provisions which are, or will be, 
irrelevant by March 1, 1997.
    This rulemaking action results in a more straightforward Standard 
No. 121 that will take mandatory effect on March 1, 1997, with optional 
compliance for vehicles manufactured before that date. Manufacturers 
and other interested persons should continue to consult the current 
Standard No. 121 concerning the additional compliance options that are 
available before that date. While the existing standard is longer and 
more complex than desirable, it is well understood by the industry. 
Moreover, it is not clear that any effort to rewrite Standard No. 121 
for an earlier effective date could be successful in achieving the goal 
of a substantially clarified and simpler standard, given the many 
additional complex provisions that would have to be retained.
    The rewritten Standard No. 121 is organized as follows:

S1. Scope.
S2. Purpose.
S3. Application.
S4. Definitions.
S5.  Requirements.
S5.1  Required equipment for trucks and buses.
S5.2  Required equipment for trailers.
S5.3  Service brakes--road tests.
S5.4  Service brakes--dynamometer tests.
S5.5  Service brakes--antilock systems.
S5.6  Parking brakes.
S5.7  Emergency brakes for trucks and buses.
S5.8  Emergency brakes for trailers.
S5.9  Final inspection.
S6.  Conditions.
S6.1  Road test conditions.
S6.2  Dynamometer test conditions.

Rulemaking Analyses and Notices

Executive Order 12866 and DOT Regulatory Policies and Procedures

    NHTSA has considered the impact of this rulemaking action under 
E.O. 12866 and the Department of Transportation's regulatory policies 
and procedures. This rulemaking document was not reviewed under E.O. 
12866, ``Regulatory Planning and Review.'' This action has been 
determined to be not ``significant'' under the Department of 
Transportation's regulatory policies and procedures.
    The purpose of this rewrite is to clarify and simplify the 
requirements of Standard No. 121. This rewrite does not substantively 
change the requirements of the standard. This means that the rulemaking 
will not have any impacts on safety or the compliance costs for 
manufacturers. Accordingly, a full regulatory evaluation has not been 
prepared for this rulemaking.

Regulatory Flexibility Act

    NHTSA has also considered the effects of this regulatory action 
under the Regulatory Flexibility Act. I hereby certify that this 
rulemaking will not have a significant economic impact on a substantial 
number of small entities. For the reasons stated above, simplifying and 
clarifying Standard No. 121 will not result in any economic impacts on 
those vehicle manufacturers that are small entities. Further, since no 
cost changes are associated with this rulemaking, small organizations 
and small governmental entities should not be affected in their 
capacity as purchasers of new vehicles.

National Environmental Policy Act

    NHTSA has analyzed this rulemaking for the purposes of the National 
Environmental Policy Act and determined that it has no significant 
impact on the quality of human life.

Executive Order 12612 (Federalism)

    NHTSA has analyzed this rulemaking in accordance with the 
principles and criteria set forth in Executive Order 12612. NHTSA has 
determined that this rulemaking does not have sufficient federalism 
implications to warrant the preparation of a Federalism Assessment.

Civil Justice Reform

    This rule will 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

[[Page 27290]]

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, NHTSA amends 49 CFR Part 571 as 
follows:

PART 571 --FEDERAL MOTOR VEHICLE SAFETY STANDARDS

    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 571.121 is revised to read as follows:


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

    S1. Scope. This standard establishes performance and equipment 
requirements for braking systems on vehicles equipped with air brake 
systems.
    S2. Purpose. The purpose of this standard is to insure safe braking 
performance under normal and emergency conditions.
    S3. Application. This standard applies to trucks, buses, and 
trailers equipped with air brake systems. However, it does not apply 
to:
    (a) Any trailer that has a width of more than 102.36 inches with 
extendable equipment in the fully retracted position and is equipped 
with two short track axles in a line across the width of the trailer.
    (b) Any vehicle equipped with an axle that has a gross axle weight 
rating (GAWR) of 29,000 pounds or more;
    (c) Any truck or bus that has a speed attainable in 2 miles of not 
more than 33 mph;
    (d) Any truck that has a speed attainable in 2 miles of not more 
than 45 mph, an unloaded vehicle weight that is not less than 95 
percent of its gross vehicle weight rating (GVWR), and no capacity to 
carry occupants other than the driver and operating crew;
    (e) Any trailer that has a GVWR of more than 120,000 pounds and 
whose body conforms to that described in the definition of heavy hauler 
trailer set forth in S4;
    (f) Any trailer that has an unloaded vehicle weight which is not 
less than 95 percent of its GVWR; and
    (g) Any load divider dolly.
    S4. Definitions.
    Agricultural commodity trailer means a trailer that is designed to 
transport bulk agricultural commodities in off-road harvesting sites 
and to a processing plant or storage location, as evidenced by skeletal 
construction that accommodates harvest containers, a maximum length of 
28 feet, and an arrangement of air control lines and reservoirs that 
minimizes damage in field operations.
    Air brake system means a system that uses air as a medium for 
transmitting pressure or force from the driver control to the service 
brake, including an air-over-hydraulic brake subsystem, but does not 
include a system that uses compressed air or vacuum only to assist the 
driver in applying muscular force to hydraulic or mechanical 
components.
    Air-over-hydraulic brake subsystem means a subsystem of the air 
brake system that uses compressed air to transmit a force from the 
driver control to a hydraulic brake system to actuate the service 
brakes.
    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 
modulators which adjust brake actuating forces in response to those 
signals.
    Auto transporter means a truck and a trailer designed for use in 
combination to transport motor vehicles, in that the towing vehicle is 
designed to carry cargo at a location other than the fifth wheel and to 
load this cargo only by means of the towed vehicle.
    Common diaphragm means a single brake chamber diaphragm which is a 
component of the parking, emergency, and service brake systems.
    Container chassis trailer means a semitrailer of skeleton 
construction limited to a bottom frame, one or more axles, specially 
built and fitted with locking devices for the transport of intermodal 
shipping containers, so that when the chassis and container are 
assembled, the units serve the same function as an over the road 
trailer.
    Directly controlled wheel means a wheel for which the degree of 
rotational wheel slip is sensed, either at that wheel or on the axle 
shaft for that wheel and corresponding signals are transmitted to one 
or more modulators that adjust the brake actuating forces at that 
wheel. Each modulator may also adjust the brake actuating forces at 
other wheels that are on the same axle or in the same axle set in 
response to the same signal or signals.
    Full-treadle brake application means a brake application in which 
the treadle valve pressure in any of the valve's output circuits 
reaches 85 pounds per square inch (psi) within 0.2 seconds after the 
application is initiated, or in which maximum treadle travel is 
achieved within 0.2 seconds after the application is initiated.
    Heavy hauler trailer means a trailer which has one or more of the 
following characteristics, but which is not a container chassis 
trailer:
    (1) Its brake lines are designed to adapt to separation or 
extension of the vehicle frame; or
    (2) Its body consists only of a platform whose primary cargo-
carrying surface is not more than 40 inches above the ground in an 
unloaded condition, except that it may include sides that are designed 
to be easily removable and a permanent ``front end structure'' as that 
term is used in Sec. 393.106 of this title.
    Independently controlled wheel means a directly controlled wheel 
for which the modulator does not adjust the brake actuating forces at 
any other wheel on the same axle.
    Indirectly controlled wheel means a wheel at which the degree of 
rotational wheel slip is not sensed, but at which the modulator of an 
antilock braking system adjusts its brake actuating forces in response 
to signals from one or more sensed wheel(s).
    Initial brake temperature means the average temperature of the 
service brakes on the hottest axle of the vehicle 0.2 mile before any 
brake application in the case of road tests, or 18 seconds before any 
brake application in the case of dynamometer testing.
    Intermodal shipping container means a reusable, transportable 
enclosure that is especially designed with integral locking devices for 
securing the container to the trailer to facilitate the efficient and 
bulk shipping and transfer of goods by, or between various modes of 
transport, such as highway, rail, sea and air.
    Load divider dolly means a trailer composed of a trailer chassis 
and one or more axles, with no solid bed, body, or container attached, 
and which is designed exclusively to support a portion of the load on a 
trailer or truck excluded from all the requirements of this standard.
    Maximum drive-through speed means the highest possible constant 
speed at which the vehicle can be driven through 200 feet of a 500-foot 
radius curve arc without leaving the 12-foot lane.

[[Page 27291]]

    Maximum treadle travel means the distance that the treadle moves 
from its position when no force is applied to its position when the 
treadle reaches a full stop.
    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.
    Pulpwood trailer means a trailer that is designed exclusively for 
harvesting logs or pulpwood and constructed with a skeletal frame with 
no means for attachment of a solid bed, body, or container, and with an 
arrangement of air control lines and reservoirs designed to minimize 
damage in off-road operations.
    Straddle trailer means a trailer that is designed to transport bulk 
agricultural commodities from the harvesting location as evidenced by a 
framework that is driven over the cargo and lifting arms that suspend 
the cargo for transit.
    Wheel lockup means 100 percent wheel slip.
    S5. Requirements. Each vehicle shall meet the following 
requirements under the conditions specified in S6.
    S5.1  Required equipment for trucks and buses. Each truck and bus 
shall have the following equipment:
    S5.1.1  Air compressor. An air compressor of sufficient capacity to 
increase air pressure in the supply and service reservoirs from 85 psi 
to 100 psi when the engine is operating at the vehicle manufacturer's 
maximum recommended r.p.m. within a time, in seconds, determined by the 
quotient (Actual reservoir capacity x 25) / Required reservoir 
capacity.
    S5.1.1.1  Air compressor cut-in pressure. The air compressor 
governor cut-in pressure shall be 100 psi or greater.
    S5.1.2  Reservoirs. One or more service reservoir systems, from 
which air is delivered to the brake chambers, and either an automatic 
condensate drain valve for each service reservoir or a supply reservoir 
between the service reservoir system and the source of air pressure.
    S5.1.2.1  The combined volume of all service reservoirs and supply 
reservoirs shall be at least 12 times the combined volume of all 
service brake chambers. For each brake chamber type having a full 
stroke at least as great as the first number in Column 1 of Table V, 
but no more than the second number in Column 1 of Table V, the volume 
of each brake chamber for purposes of calculating the required combined 
service and supply reservoir volume shall be either that specified in 
Column 2 of Table V or the actual volume of the brake chamber at 
maximum travel of the brake piston or pushrod, whichever is lower. The 
volume of a brake chamber not listed in Table V is the volume of the 
brake chamber at maximum travel of the brake piston or pushrod. The 
reservoirs of the truck portion of an auto transporter need not meet 
this requirement for reservoir volume.
    S5.1.2.2  Each reservoir shall be capable of withstanding an 
internal hydrostatic pressure of five times the compressor cutout 
pressure or 500 psi, whichever is greater, for 10 minutes.
    S5.1.2.3  Each service reservoir system shall be protected against 
loss of air pressure due to failure or leakage in the system between 
the service reservoir and the source of air pressure, by check valves 
or equivalent devices whose proper functioning can be checked without 
disconnecting any air line or fitting.
    S5.1.2.4  Each reservoir shall have a condensate drain valve that 
can be manually operated.
    S5.1.3  Towing vehicle protection system. If the vehicle is 
intended to tow another vehicle equipped with air brakes, a system to 
protect the air pressure in the towing vehicle from the effects of a 
loss of air pressure in the towed vehicle.
    S5.1.4  Pressure gauge. A pressure gauge in each service brake 
system, readily visible to a person seated in the normal driving 
position, that indicates the service reservoir system air pressure. The 
accuracy of the gauge shall be within plus or minus 7 percent of the 
compressor cut-out pressure.
    S5.1.5  Warning signal. A signal, other than a pressure gauge, that 
gives a continuous warning to a person in the normal driving position 
when the ignition is in the ``on'' (``run'') position and the air 
pressure in the service reservoir system is below 60 psi. The signal 
shall be either visible within the driver's forward field of view, or 
both audible and visible.
    S5.1.6  Antilock brake system.
    S5.1.6.1(a) Each single-unit vehicle manufactured on or after March 
1, 1998, shall be equipped with an antilock brake system that directly 
controls the wheels of at least one front axle and the wheels of at 
least one rear axle of the vehicle. Wheels on other axles of the 
vehicle may be indirectly controlled by the antilock brake system.
    (b) Each truck tractor manufactured on or after March 1, 1997, 
shall be equipped with an antilock brake system that directly controls 
the wheels of at least one front axle and the wheels of at least one 
rear axle of the vehicle, with the wheels of at least one axle being 
independently controlled. Wheels on other axles of the vehicle may be 
indirectly controlled by the antilock brake system. A truck tractor 
shall have no more than three wheels controlled by one modulator.
    S5.1.6.2  Antilock malfunction signal and circuit.
    (a) Each truck tractor manufactured on or after March 1, 1997, and 
each single unit vehicle manufactured on or after March 1, 1998, shall 
be equipped with an indicator lamp, mounted in front of and in clear 
view of the driver, which is activated whenever there is a malfunction 
that affects the generation or transmission of response or control 
signals in the vehicle's antilock brake system. The indicator lamp 
shall remain activated as long as such a malfunction exists, whenever 
the ignition (start) switch is in the ``on'' (``run'') position, 
whether or not the engine is running. Each message about the existence 
of such a malfunction shall be stored in the antilock brake system 
after the ignition switch is turned to the ``off'' position and 
automatically reactivated when the ignition switch is again turned to 
the ``on'' (``run'') position. The indicator lamp shall also be 
activated as a check of lamp function whenever the ignition is turned 
to the ``on'' (``run'') position. The indicator lamp shall be 
deactivated at the end of the check of lamp function unless there is a 
malfunction or a message about a malfunction that existed when the key 
switch was last turned to the ``off'' position.
    (b) Each truck tractor manufactured on or after March 1, 2001, and 
each single unit vehicle manufactured on or after March 1, 2001, that 
is equipped to tow another air-braked vehicle, shall be equipped with 
an electrical circuit that is capable of transmitting a malfunction 
signal from the antilock brake system(s) on one or more towed 
vehicle(s) (e.g., trailer(s) and dolly(ies)) to the trailer ABS 
malfunction lamp in the cab of the towing vehicle, and shall have the 
means for connection of this electrical circuit to the towed vehicle. 
Each such truck tractor and single unit vehicle shall also be equipped 
with an indicator lamp, separate from the lamp required in S5.1.6.2(a), 
mounted in front of and in clear view of the driver, which is activated 
whenever the malfunction signal circuit described above receives a 
signal indicating an ABS malfunction on one or more towed vehicle(s). 
The indicator lamp shall remain activated as long as an ABS malfunction 
signal from one or more towed vehicle(s) is present, whenever the 
ignition (start) switch is in the ``on'' (``run'') position, whether or

[[Page 27292]]

not the engine is running. The indicator lamp shall also be activated 
as a check of lamp function whenever the ignition is turned to the 
``on'' (``run'') position. The indicator lamp shall be deactivated at 
the end of the check of lamp function unless a trailer ABS malfunction 
signal is present.
    S5.1.6.3  Antilock power circuit for towed vehicles. Each truck 
tractor manufactured on or after March 1, 1997, and each single unit 
vehicle manufactured on or after March 1, 1998, that is equipped to tow 
another air-braked vehicle shall be equipped with one or more 
electrical circuits that provide continuous power to the antilock 
system on the towed vehicle or vehicles whenever the ignition (start) 
switch is in the ``on'' (``run'') position. Such a circuit shall be 
adequate to enable the antilock system on each towed vehicle to be 
fully operable.
    S5.1.7  Service brake stop lamp switch. A switch that lights the 
stop lamps when the service brake control is statically depressed to a 
point that produces a pressure of 6 psi or less in the service brake 
chambers.
    S5.1.8  Brake distribution and automatic adjustment. Each vehicle 
shall be equipped with a service brake system acting on all wheels.
    (a) Brake adjuster. Wear of the service brakes shall be compensated 
for by means of a system of automatic adjustment. When inspected 
pursuant to S5.9, the adjustment of the service brakes shall be within 
the limits recommended by the vehicle manufacturer.
    (b) Brake indicator. For each brake equipped with an external 
automatic adjustment mechanism and having an exposed pushrod, the 
condition of service brake under-adjustment shall be displayed by a 
brake adjustment indicator that is discernible when viewed with 20/40 
vision from a location adjacent to or underneath the vehicle, when 
inspected pursuant to S5.9.
    S5.2  Required equipment for trailers. Each trailer shall have the 
following equipment:
    S5.2.1  Reservoirs. One or more reservoirs to which the air is 
delivered from the towing vehicle.
    S5.2.1.1  The total volume of each service reservoir shall be at 
least eight times the combined volume of all service brake chambers 
serviced by that reservoir. For each brake chamber type having a full 
stroke at least as great as the first number in Column 1 of Table V, 
but no more than the second number in column 1, the volume of each 
brake chamber for purposes of calculating the required total service 
reservoir volume shall be either the number specified in Column 2 of 
Table V or the actual volume of the brake chamber at maximum travel of 
the brake piston or pushrod, whichever is lower. The volume of a brake 
chamber not listed in Table V is the volume of the brake chamber at 
maximum travel of the brake piston or pushrod. The reservoirs on a 
heavy hauler trailer and the trailer portion of an auto transporter 
need not meet this requirement for reservoir volume.
    S5.2.1.2  Each reservoir shall be capable of withstanding an 
internal hydrostatic pressure of 500 psi for 10 minutes.
    S5.2.1.3  Each reservoir shall have a condensate drain valve that 
can be manually operated.
    S5.2.1.4  Each service reservoir shall be protected against loss of 
air pressure due to failure or leakage in the system between the 
service reservoir and its source of air pressure by check valves or 
equivalent devices.
    S5.2.2  Brake distribution and automatic adjustment. Each vehicle 
shall be equipped with a service brake system acting on all wheels.
    (a) Brake adjuster. Wear of the service brakes shall be compensated 
for by means of a system of automatic adjustment. When inspected 
pursuant to S5.9, the adjustment of the service brakes shall be within 
the limits recommended by the vehicle manufacturer.
    (b) Brake indicator. For each brake equipped with an external 
automatic adjustment mechanism and having an exposed pushrod, the 
condition of service brake under-adjustment shall be displayed by a 
brake adjustment indicator in a manner that is discernible when viewed 
with 20/40 vision from a location adjacent to or underneath the 
vehicle, when inspected pursuant to S5.9.
    S5.2.3  Antilock brake system.
    S5.2.3.1(a) Each semitrailer (including a trailer converter dolly) 
manufactured on or after March 1, 1998, shall be equipped with an 
antilock brake system that directly controls the wheels of at least one 
axle of the vehicle. Wheels on other axles of the vehicle may be 
indirectly controlled by the antilock brake system.
    (b) Each full trailer manufactured on or after March 1, 1998, shall 
be equipped with an antilock brake system that directly controls the 
wheels of at least one front axle of the vehicle and at least one rear 
axle of the vehicle. Wheels on other axles of the vehicle may be 
indirectly controlled by the antilock brake system.
    S5.2.3.2  Antilock malfunction signal. Each trailer (including a 
trailer converter dolly) manufactured on or after March 1, 2001, that 
is equipped with an antilock brake system shall be equipped with an 
electrical circuit that is capable of signaling a malfunction in the 
trailer's antilock brake system, and shall have the means for 
connection of this antilock brake system malfunction signal circuit to 
the towing vehicle. The electrical circuit need not be separate or 
dedicated exclusively to this malfunction signaling function. The 
signal shall be present whenever there is a malfunction that affects 
the generation or transmission of response or control signals in the 
trailer's antilock brake system. The signal shall remain present as 
long as the malfunction exists, whenever power is supplied to the 
antilock brake system. Each message about the existence of such a 
malfunction shall be stored in the antilock brake system whenever power 
is no longer supplied to the system, and the malfunction signal shall 
be automatically reactivated whenever power is again supplied to the 
trailer's antilock brake system. In addition, each trailer manufactured 
on or after March 1, 2001, that is designed to tow other air-brake 
equipped trailers shall be capable of transmitting a malfunction signal 
from the antilock brake systems of additional trailers it tows to the 
vehicle towing it.
    S5.2.3.3  Antilock malfunction indicator. In addition to the 
requirements of S5.2.3.2, each trailer (including a trailer converter 
dolly) manufactured on or after March 1, 1998, and before March 1, 
2009, shall be equipped with an external indicator lamp that is 
activated whenever there is a malfunction that affects the generation 
or transmission of response or control signals in the trailer's 
antilock brake system. The indicator lamp shall remain activated as 
long as such a malfunction exists, whenever power is supplied to the 
antilock brake system. Each message about the existence of such a 
malfunction shall be stored in the antilock brake system whenever power 
is no longer supplied to the system, and the malfunction signal shall 
be automatically reactivated when power is again supplied to the 
trailer's antilock brake system. The indicator lamp shall also be 
activated as a check of lamp function whenever power is supplied to the 
antilock brake system and the vehicle is stationary. The indicator lamp 
shall be deactivated at the end of the check of lamp function unless 
there is a malfunction or a message about a malfunction that existed 
when power

[[Page 27293]]

was last supplied to the antilock brake system.
    S5.3  Service brakes--road tests. The service brake system on each 
truck tractor manufactured before March 1, 1997, shall, under the 
conditions of S6, meet the requirements of S5.3.3 and S5.3.4, when 
tested without adjustments other than those specified in this standard. 
The service brake system on each truck tractor manufactured on or after 
March 1, 1997, shall, under the conditions of S6, meet the requirements 
of S5.3.1, S5.3.3, S5.3.4, and S5.3.6, when tested without adjustments 
other than those specified in this standard. The service brake system 
on each bus and truck (other than a truck tractor) manufactured before 
March 1, 1998, shall, under the conditions of S6, meet the requirements 
of S5.3.3, and S5.3.4, when tested without adjustments other than those 
specified in this standard. The service brake system on each bus and 
truck (other than a truck tractor) manufactured on or after March 1, 
1998, shall, under the conditions of S6, meet the requirements of 
S5.3.1, S5.3.3, and S5.3.4 when tested without adjustments other than 
those specified in this standard. The service brake system on each 
trailer shall, under the conditions of S6, meet the requirements of 
S5.3.3, S5.3.4, and S5.3.5 when tested without adjustments other than 
those specified in this standard. However, a heavy hauler trailer and 
the truck and trailer portions of an auto transporter need not meet the 
requirements of S5.3.
    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:
    (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 S5.3.1(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 S5.3.1 (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.
    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 truck tractor only configuration plus up to 500 lbs., 
and
    (c) At its unloaded vehicle weight (except for truck tractors) plus 
up to 500 lbs. (including driver and instrumentation). If the speed 
attainable in two miles is less than 60 mph, vehicle shall stop from a 
speed in Table II that is 4 to 8 mph less than the speed attainable in 
2 miles.
    S5.3.2  [Reserved]
    S5.3.3  Brake actuation time. Each service brake system shall meet 
the requirements of S5.3.3.1 (a) and (b).
    S5.3.3.1(a) With an initial service reservoir system air pressure 
of 100 psi, the air pressure in each brake chamber shall, when measured 
from the first movement of the service brake control, reach 60 psi in 
not more than 0.45 second in the case of trucks and buses, 0.50 second 
in the case of trailers, other than trailer converter dollies, designed 
to tow another vehicle equipped with air brakes, 0.55 second in the 
case of trailer converter dollies, and 0.60 second in the case of 
trailers other than trailers designed to tow another vehicle equipped 
with air brakes. A vehicle designed to tow another vehicle equipped 
with air brakes shall meet the above actuation time requirement with a 
50-cubic-inch test reservoir connected to the control line output 
coupling. A trailer, including a trailer converter dolly, shall meet 
the above actuation time requirement with its control line input 
coupling connected to the test rig shown in Figure 1.
    (b) For a vehicle that is designed to tow another vehicle equipped 
with air brakes, the pressure in the 50-cubic-inch test reservoir 
referred to in S5.3.3.1(a) shall, when measured from the first movement 
of the service brake control, reach 60 psi not later than the time the 
fastest brake chamber on the vehicle reaches 60 psi or, at the option 
of the manufacturer, in not more than 0.35 second in the case of trucks 
and buses, 0.55 second in the case of trailer converter dollies, and 
0.50 second in the case of trailers other than trailer converter 
dollies.
    S5.3.4  Brake release time. Each service brake system shall meet 
the requirements of S5.3.4.1 (a) and (b).
    S5.3.4.1(a) With an initial service brake chamber air pressure of 
95 psi, the air pressure in each brake chamber shall, when measured 
from the first movement of the service brake control, fall to 5 psi in 
not more than 0.55 second in the case of trucks and buses; 1.00 second 
in the case of trailers, other than trailer converter dollies, designed 
to tow another vehicle equipped with air brakes; 1.10 seconds in the 
case of trailer converter dollies; and 1.20 seconds in the case of 
trailers other than trailers designed to tow another vehicle equipped 
with air brakes. A vehicle designated to tow another vehicle equipped 
with air brakes shall meet the above release time requirement with a 
50-cubic-inch test reservoir connected to the control line output 
coupling. A trailer, including a trailer converter dolly, shall meet 
the above release time requirement with its control line input coupling 
connected to the test rig shown in Figure 1.
    (b) For vehicles designed to tow another vehicle equipped with air 
brakes, the pressure in the 50-cubic-inch test reservoir referred to in 
S5.3.4.1(a) shall, when measured from the first movement of the service 
brake control, fall to 5 psi in not more than 0.75 seconds in the case 
of trucks and buses, 1.10 seconds in the case of trailer converter 
dollies, and 1.00 seconds in the case of trailers other than trailer 
converter dollies.
    S5.3.5  Control signal pressure differential--converter dollies and 
trailers designed to tow another vehicle equipped with air brakes.
    (a) For a trailer designed to tow another vehicle equipped with air 
brakes, the pressure differential between the control line input 
coupling and a 50-cubic-inch test reservoir attached to the control 
line output coupling shall not exceed the values specified in S5.3.5(a) 
(1), (2), and (3) under the conditions specified in S5.3.5(b) (1) 
through (4):
    (1) 1 psi at all input pressures equal to or greater than 5 psi, 
but not greater than 20 psi;
    (2) 2 psi at all input pressures equal to or greater than 20 psi 
but not greater than 40 psi; and
    (3) Not more than a 5-percent differential at any input pressure 
equal to or greater than 40 psi.
    (b) The requirements in S5.3.5(a) shall be met--
    (1) When the pressure at the input coupling is steady, increasing 
or decreasing;
    (2) When air is applied to or released from the control line input 
coupling using the trailer test rig shown in Figure 1;
    (3) With a fixed orifice consisting of a 0.0180 inch diameter hole 
(no. 77 drill bit) in a 0.032 inch thick disc installed

[[Page 27294]]

in the control line between the trailer test rig coupling and the 
vehicle's control line input coupling; and
    (4) Operating the trailer test rig in the same manner and under the 
same conditions as it is operated during testing to measure brake 
actuation and release times, as specified in S5.3.3 and S5.3.4, except 
for the installation of the orifice in the control line to restrict 
airflow rate.
    S5.3.6  Stability and control during braking--truck tractors. When 
stopped four consecutive times for each combination of weight, speed, 
and road conditions specified in S5.3.6.1 and S5.3.6.2, each truck 
tractor manufactured on or after March 1, 1997, shall stop at least 
three times within the 12-foot lane, without any part of the vehicle 
leaving the roadway.
    S5.3.6.1  Using a full-treadle brake application for the duration 
of the stop, stop the vehicle from 30 mph or 75 percent of the maximum 
drive-through speed, whichever is less, on a 500-foot radius curved 
roadway with a wet level surface having a peak friction coefficient of 
0.5 when measured on a straight or curved section of the curved roadway 
using an American Society for Testing and Materials (ASTM) E1136 
standard reference tire, in accordance with ASTM Method E1337-90, at a 
speed of 40 mph, with water delivery.
    S5.3.6.2  Stop the vehicle with the vehicle
    (a) Loaded to its GVWR, and
    (b) At its unloaded weight plus up to 500 pounds (including driver 
and instrumentation), or at the manufacturer's option, at its unloaded 
weight plus up to 500 pounds (including driver and instrumentation) and 
plus not more than an additional 1000 pounds for a roll bar structure 
on the vehicle.
    S5.4  Service brake system--dynamometer tests. When tested without 
prior road testing, under the conditions of S6.2, each brake assembly 
shall meet the requirements of S5.4.1, S5.4.2, and S5.4.3 when tested 
in sequence and without adjustments other than those specified in the 
standard. For purposes of the requirements of S5.4.2 and S5.4.3, an 
average deceleration rate is the change in velocity divided by the 
deceleration time measured from the onset of deceleration.
    S5.4.1  Brake retardation force. The sum of the retardation forces 
exerted by the brakes on each vehicle designed to be towed by another 
vehicle equipped with air brakes shall be such that the quotient sum of 
the brake retardation forces / sum of GAWR's relative to brake chamber 
air pressure, and shall have values not less than those shown in Column 
1 of Table III. Retardation force shall be determined as follows:
    S5.4.1.1  After burnishing the brake pursuant to S6.2.6, retain the 
brake assembly on the inertia dynamometer. With an initial brake 
temperature between 125 deg.F. and 200 deg.F., conduct a stop from 50 
m.p.h., maintaining brake chamber air pressure at a constant 20 psi. 
Measure the average torque exerted by the brake from the time the 
specified air pressure is reached until the brake stops and divide by 
the static loaded tire radius specified by the tire manufacturer to 
determine the retardation force. Repeat the procedure six times, 
increasing the brake chamber air pressure by 10 psi each time. After 
each stop, rotate the brake drum or disc until the temperature of the 
brake falls to between 125 deg.F. And 200 deg.F.
    S5.4.2  Brake power. When mounted on an inertia dynamometer, each 
brake shall be capable of making 10 consecutive decelerations at an 
average rate of 9 f.p.s.p.s. from 50 m.p.h. to 15 m.p.h., at equal 
intervals of 72 seconds, and shall be capable of decelerating to a stop 
from 20 m.p.h. at an average deceleration rate of 14 f.p.s.p.s. 1 
minute after the 10th deceleration. The series of decelerations shall 
be conducted as follows:
    S5.4.2.1  With an initial brake temperature between 150 deg.F. and 
200 deg.F. for the first brake application, and the drum or disc 
rotating at a speed equivalent to 50 m.p.h., apply the brake and 
decelerate at an average deceleration rate of 9 f.p.s.p.s. to 15 m.p.h. 
Upon reaching 15 m.p.h., accelerate to 50 m.p.h. and apply the brake 
for a second time 72 seconds after the start of the first application. 
Repeat the cycle until 10 decelerations have been made. The service 
line air pressure shall not exceed 100 psi during any deceleration.
    S5.4.2.2  One minute after the end of the last deceleration 
required by S5.4.2.1 and with the drum or disc rotating at a speed of 
20 m.p.h., decelerate to a stop at an average deceleration rate of 14 
f.p.s.p.s.
    S5.4.3  Brake recovery. Except as provided in S5.4.3(a) and (b), 
starting two minutes after completing the tests required by S5.4.2, a 
vehicle's brake shall be capable of making 20 consecutive stops from 30 
mph at an average deceleration rate of 12 f.p.s.p.s., at equal 
intervals of one minute measured from the start of each brake 
application. The service line air pressure needed to attain a rate of 
12 f.p.s.p.s. shall be not more than 85 lb/in\2\, and not less than 
20lb/in2 for a brake not subject to the control of an antilock 
system, or 12 lb/in2 for a brake subject to the control of an 
antilock system.
    (a) Notwithstanding S5.4.3, neither front axle brake of a truck-
tractor is subject to the requirements set forth in S5.4.3.
    (b) Notwithstanding S5.4.3, neither front axle brake of a bus or a 
truck other than a truck-tractor is subject to the requirement set 
forth in S5.4.3 prohibiting the service line air pressure from being 
less than 20 lb/in2 for a brake not subject to the control of an 
antilock system or 12 lb/in2 for a brake subject to the control of 
an antilock system.
    S5.5  Antilock system.
    S5.5.1  Antilock system malfunction. On a truck tractor 
manufactured on or after March 1, 1997, that is equipped with an 
antilock brake system and a single unit vehicle manufactured on or 
after March 1, 1998, that is equipped with an antilock brake system, a 
malfunction that affects the generation or transmission of response or 
control signals of any part of the antilock system shall not increase 
the actuation and release times of the service brakes.
    S5.5.2  Antilock system power--trailers. On a trailer (including a 
trailer converter dolly) manufactured on or after March 1, 1998, that 
is equipped with an antilock system that requires electrical power for 
operation, the power shall be obtained from the towing vehicle through 
one or more electrical circuits which provide continuous power whenever 
the powered vehicle's ignition (start) switch is in the ``on'' 
(``run'') position. The antilock system shall automatically receive 
power from the stoplamp circuit, if the primary circuit or circuits are 
not functioning. Each trailer (including a trailer converter dolly) 
manufactured on or after March 1, 1998, that is equipped to tow another 
air-braked vehicle shall be equipped with one or more circuits which 
provide continuous power to the antilock system on the vehicle(s) it 
tows. Such circuits shall be adequate to enable the antilock system on 
each towed vehicle to be fully operable.
    S5.6  Parking brakes. 
    (a) Except as provided in S5.6(b) and S5.6(c), each vehicle other 
than a trailer converter dolly shall have a parking brake system that 
under the conditions of S6.1 meets the requirements of:
    (1) S5.6.1 or S5.6.2, at the manufacturer's option, and
    (2) S5.6.3, S5.6.4, S5.6.5, and S5.6.6.
    (b) At the option of the manufacturer, for vehicles equipped with 
brake systems which incorporate a common diaphragm, the performance 
requirements specified in S5.6(a) which must be met with any single 
leakage-type failure in a common diaphragm

[[Page 27295]]

may instead be met with the level of leakage-type failure determined in 
S5.6.7. The election of this option does not affect the performance 
requirements specified in S5.6(a) which apply with single leakage-type 
failures other than failures in a common diaphragm.
    (c) At the option of the manufacturer, the trailer portion of any 
agricultural commodity trailer, heavy hauler trailer, or pulpwood 
trailer may meet the requirements of Sec. 393.43 of this title instead 
of the requirements of S5.6(a).
    S5.6.1  Static retardation force. With all other brakes made 
inoperative, during a static drawbar pull in a forward or rearward 
direction, the static retardation force produced by the application of 
the parking brakes shall be:
    (a) In the case of a vehicle other than a truck-tractor that is 
equipped with more than two axles, such that the quotient static 
retardation force/GAWR is not less than 0.28 for any axle other than a 
steerable front axle; and
    (b) In the case of a truck-tractor that is equipped with more than 
two axles, such that the quotient static retardation force/GVWR is not 
less than 0.14.
    S5.6.2  Grade holding. With all parking brakes applied, the vehicle 
shall remain stationary facing uphill and facing downhill on a smooth, 
dry portland cement concrete roadway with a 20-percent grade, both
    (a) When loaded to its GVWR, and
    (b) At its unloaded vehicle weight plus 500 pounds (including 
driver and instrumentation).
    S5.6.3  Application and holding. Each parking brake system shall 
meet the requirements of S5.6.3.1 through S5.6.3.4.
    S5.6.3.1  The parking brake system shall be capable of achieving 
the minimum performance specified either in S5.6.1 or S5.6.2 with any 
single leakage-type failure, in any other brake system, of a part 
designed to contain compressed air or brake fluid (excluding failure of 
a component of a brake chamber housing but including failure of any 
brake chamber diaphragm that is part of any other brake system 
including a diaphragm which is common to the parking brake system and 
any other brake system), when the pressures in the vehicle's parking 
brake chambers are at the levels determined in S5.6.3.4.
    S5.6.3.2  A mechanical means shall be provided that, after a 
parking brake application is made with the pressures in the vehicle's 
parking brake chambers at the levels determined in S5.6.3.4, and all 
air and fluid pressures in the vehicle's braking systems are then bled 
down to zero, and without using electrical power, holds the parking 
brake application with sufficient parking retardation force to meet the 
minimum performance specified in S5.6.3.1 and in either S5.6.1 or 
S5.6.2.
    S5.6.3.3  For trucks and buses, with an initial reservoir system 
pressure of 100 psi and, if designed to tow a vehicle equipped with air 
brakes, with a 50 cubic inch test reservoir connected to the supply 
line coupling, no later than three seconds from the time of actuation 
of the parking brake control, the mechanical means referred to in 
S5.6.3.2 shall be actuated. For trailers, with the supply line 
initially pressurized to 100 psi using the supply line portion of the 
trailer test rig (Figure 1) and, if designed to tow a vehicle equipped 
with air brakes, with a 50 cubic inch test reservoir connected to the 
rear supply line coupling, no later than three seconds from the time 
venting to the atmosphere of the front supply line coupling is 
initiated, the mechanical means referred to in S5.6.3.2 shall be 
actuated. This requirement shall be met for trucks, buses and trailers 
both with and without any single leakage-type failure, in any other 
brake system, of a part designed to contain compressed air or brake 
fluid (consistent with the parenthetical phrase specified in S5.6.3.1).
    S5.6.3.4  The parking brake chamber pressures for S5.6.3.1 and 
S5.6.3.2 are determined as follows. For trucks and buses, with an 
initial reservoir system pressure of 100 psi and, if designed to tow a 
vehicle equipped with air brakes, with a 50 cubic inch test reservoir 
connected to the supply line coupling, any single leakage type failure, 
in any other brake system, of a part designed to contain compressed air 
or brake fluid (consistent with the parenthetical phrase specified in 
S5.6.3.1), is introduced in the brake system. The parking brake control 
is actuated and the pressures in the vehicle's parking brake chambers 
are measured three seconds after that actuation is initiated. For 
trailers, with the supply line initially pressurized to 100 psi using 
the supply line portion of the trailer test rig (Figure 1) and, if 
designed to tow a vehicle equipped with air brakes, with a 50 cubic 
inch test reservoir connected to the rear supply line coupling, any 
single leakage type failure, in any other brake system, of a part 
designed to contain compressed air or brake fluid (consistent with the 
parenthetical phrase specified in S5.6.3.1), is introduced in the brake 
system. The front supply line coupling is vented to the atmosphere and 
the pressures in the vehicle's parking brake chambers are measured 
three seconds after that venting is initiated.
    S5.6.4  Parking brake control--trucks and buses. The parking brake 
control shall be separate from the service brake control. It shall be 
operable by a person seated in the normal driving position. The control 
shall be identified in a manner that specifies the method of control 
operation. The parking brake control shall control the parking brakes 
of the vehicle and of any air braked vehicle that it is designed to 
tow.
    S5.6.5  Release Performance. Each parking brake system shall meet 
the requirements specified in S5.6.5.1 through S5.6.5.4.
    S5.6.5.1  For trucks and buses, with initial conditions as 
specified in S5.6.5.2, at all times after an application actuation of 
the parking brake control, and with any subsequent level of pressure, 
or combination of levels of pressure, in the reservoirs of any of the 
vehicle's brake systems, no reduction in parking brake retardation 
force shall result from a release actuation of the parking brake 
control unless the parking brakes are capable, after such release, of 
being reapplied at a level meeting the minimum performance specified 
either in S5.6.1 or S5.6.2. This requirement shall be met both with and 
without the engine on, and with and without single leakage-type 
failure, in any other brake system, of a part designed to contain 
compressed air or brake fluid (consistent with the parenthetical phrase 
specified in S5.6.3.1).
    S5.6.5.2  The initial conditions for S5.6.5.1 are as follows: The 
reservoir system pressure is 100 psi. If the vehicle is designed to tow 
a vehicle equipped with air brakes, a 50 cubic inch test reservoir is 
connected to the supply line coupling.
    S5.6.5.3  For trailers, with initial conditions as specified in 
S5.6.5.4, at all times after actuation of the parking brakes by venting 
the front supply line coupling to the atmosphere, and with any 
subsequent level of pressure, or combination of levels of pressure, in 
the reservoirs of any of the vehicle's brake systems, the parking 
brakes shall not be releasable by repressurizing the supply line using 
the supply line portion of the trailer test rig (Figure 1) to any 
pressure above 70 psi, unless the parking brakes are capable, after 
such release, of reapplication by subsequent venting of the front 
supply line coupling to the atmosphere, at a level meeting the minimum 
performance specified either in S5.6.1 or S5.6.2. This requirement 
shall be met both with and without any single leakage-type failure, in 
any other brake system, of a part designed to contain compressed air or 
brake fluid (consistent with the parenthetical phrase specified in 
S5.6.3.1).

[[Page 27296]]

    S5.6.5.4  The initial conditions for S5.6.5.3 are as follows: The 
reservoir system and supply line are pressurized to 100 psi, using the 
supply line portion of the trailer test rig (Figure 1). If the vehicle 
is designed to tow a vehicle equipped with air brakes, a 50 cubic inch 
test reservoir is connected to the rear supply line coupling.
    S5.6.6  Accumulation of actuation energy. Each parking brake system 
shall meet the requirements specified in S5.6.6.1 through S5.6.6.6.
    S5.6.6.1  For trucks and buses, with initial conditions as 
specified in S5.6.6.2, the parking brake system shall be capable of 
meeting the minimum performance specified either in S5.6.1 or S5.6.2, 
with any single leakage-type failure, in any other brake system, of a 
part designed to contain compressed air or brake fluid (consistent with 
the parenthetical phrase specified in S5.6.3.1) at the conclusion of 
the test sequence specified in S5.6.6.3.
    S5.6.6.2  The initial conditions for S5.6.6.1 are as follows: The 
engine is on. The reservoir system pressure is 100 psi. If the vehicle 
is designed to tow a vehicle equipped with air brakes, a 50 cubic inch 
test reservoir is connected to the supply line coupling.
    S5.6.6.3  The test sequence for S5.6.6.1 is as follows: The engine 
is turned off. Any single leakage type failure, in any other brake 
system, of a part designed to contain compressed air or brake fluid 
(consistent with the parenthetical phrase specified in S5.6.3.1), is 
then introduced in the brake system. An application actuation of the 
parking brake control is then made. Thirty seconds after such 
actuation, a release actuation of the parking brake control is made. 
Thirty seconds after the release actuation, a final application 
actuation of the parking brake control is made.
    S5.6.6.4  For trailers, with initial conditions as specified in 
S5.6.6.5, the parking brake system shall be capable of meeting the 
minimum performance specified either in S5.6.1 or S5.6.2, with any 
single leakage-type failure, in any other brake system, of a part 
designed to contain compressed air or brake fluid (consistent with the 
parenthetical phrase specified in S5.6.3.1), at the conclusion of the 
test sequence specified in S5.6.6.6.
    S5.6.6.5  The initial conditions for S5.6.6.4 are as follows: The 
reservoir system and supply line are pressurized to 100 psi, using the 
supply line portion of the trailer test rig (Figure 1). If the vehicle 
is designed to tow a vehicle equipped with air brakes, a 50 cubic inch 
test reservoir is connected to the rear supply line coupling.
    S5.6.6.6  The test sequence for S5.6.6.4 is as follows. Any single 
leakage type failure, in any other brake system, of a part designed to 
contain compressed air or brake fluid (consistent with the 
parenthetical phrase specified in S5.6.3.1), is introduced in the brake 
system. The front supply line coupling is vented to the atmosphere. 
Thirty seconds after the initiation of such venting, the supply line is 
repressurized with the trailer test rig (Figure 1). Thirty seconds 
after the initiation of such repressurizing of the supply line, the 
front supply line is vented to the atmosphere. This procedure is 
conducted either by connection and disconnection of the supply line 
coupling or by use of a valve installed in the supply line portion of 
the trailer test rig near the supply line coupling.
    S5.6.7  Maximum level of common diaphragm leakage-type failure/ 
Equivalent level of leakage from the air chamber containing that 
diaphragm.
    In the case of vehicles for which the option in S5.6(b) has been 
elected, determine the maximum level of common diaphragm leakage-type 
failure (or equivalent level of leakage from the air chamber containing 
that diaphragm) according to the procedures set forth in S5.6.7.1 
through S5.6.7.2.3.
    S5.6.7.1  Trucks and buses. 
    S5.6.7.1.1  According to the following procedure, determine the 
threshold level of common diaphragm leakage-type failure (or equivalent 
level of leakage from the air chamber containing that diaphragm) at 
which the vehicle's parking brakes become unreleasable. With an initial 
reservoir system pressure of 100 psi, the engine turned off, no 
application of any of the vehicle's brakes, and, if the vehicle is 
designed to tow a vehicle equipped with air brakes, a 50 cubic inch 
test reservoir connected to the supply line coupling, introduce a 
leakage-type failure of the common diaphragm (or equivalent leakage 
from the air chamber containing that diaphragm). Apply the parking 
brakes by making an application actuation of the parking brake control. 
Reduce the pressures in all of the vehicle's reservoirs to zero, turn 
on the engine and allow it to idle, and allow the pressures in the 
vehicle's reservoirs to rise until they stabilize or until the 
compressor shut-off point is reached. At that time, make a release 
actuation of the parking brake control, and determine whether all of 
the mechanical means referred to in S5.6.3.2 continue to be actuated 
and hold the parking brake applications with sufficient parking 
retardation force to meet the minimum performance specified in either 
S5.6.1 or S5.6.2. Repeat this procedure with progressively decreasing 
or increasing levels (whichever is applicable) of leakage-type 
diaphragm failures or equivalent leakages, to determine the minimum 
level of common diaphragm leakage-type failure (or equivalent level of 
leakage from the air chamber containing that diaphragm) at which all of 
the mechanical means referred to in S5.6.3.2 continue to be actuated 
and hold the parking brake applications with sufficient parking 
retardation forces to meet the minimum performance specified in either 
S5.6.1 or S5.6.2.
    S5.6.7.1.2  At the level of common diaphragm leakage-type failure 
(or equivalent level of leakage from the air chamber containing that 
diaphragm) determined in S5.6.7.1.1, and using the following procedure, 
determine the threshold maximum reservoir rate (in psi per minute). 
With an initial reservoir system pressure of 100 psi, the engine turned 
off, no application of any of the vehicle's brakes and, if the vehicle 
is designed to tow a vehicle equipped with air brakes, a 50 cubic inch 
test reservoir connected to the supply line coupling, make an 
application actuation of the parking brake control. Determine the 
maximum reservoir leakage rate (in psi per minute), which is the 
maximum rate of decrease in air pressure of any of the vehicle's 
reservoirs that results after that parking brake application.
    S5.6.7.1.3  Using the following procedure, introduce a leakage-type 
failure of the common diaphragm (or equivalent leakage from the air 
chamber containing that diaphragm) that results in a maximum reservoir 
leakage rate that is three times the threshold maximum reservoir 
leakage rate determined in S5.6.7.1.2. With an initial reservoir system 
pressure of 100 psi, the engine turned off, no application of any of 
the vehicle's brakes and, if the vehicle is designed to tow a vehicle 
equipped with air brakes, a 50 cubic inch test reservoir connected to 
the supply line coupling, make an application actuation of the parking 
brake control. Determine the maximum reservoir leakage rate (in psi per 
minute), which is the maximum rate of decrease in air pressure of any 
of the vehicle's reservoirs that results after that parking brake 
application. The level of common diaphragm leakage-type failure (or 
equivalent level of leakage from the air chamber containing that 
diaphragm) associated with this reservoir leakage rate is the level 
that is to be used under the option set forth in S5.6(b).
    S5.6.7.2  Trailers.
    S5.6.7.2.1  According to the following procedure, determine the

[[Page 27297]]

threshold level of common diaphragm leakage-type failure (or equivalent 
level of leakage from the air chamber containing that diaphragm) at 
which the vehicle's parking brakes become unreleasable. With an initial 
reservoir system and supply line pressure of 100 psi, no application of 
any of the vehicle's brakes, and, if the vehicle is designed to tow a 
vehicle equipped with air brakes, a 50 cubic inch test reservoir 
connected to the supply line coupling, introduce a leakage-type failure 
of the common diaphragm (or equivalent leakage from the air chamber 
containing that diaphragm). Make a parking brake application by venting 
the front supply line coupling to the atmosphere, and reduce the 
pressures in all of the vehicle's reservoirs to zero. Pressurize the 
supply line by connecting the trailer's front supply line coupling to 
the supply line portion of the trailer test rig (Figure 1) with the 
regulator of the trailer test rig set at 100 psi, and determine whether 
all of the mechanical means referred to in S5.6.3.2 continue to be 
actuated and hold the parking brake applications with sufficient 
parking retardation forces to meet the minimum performance specified in 
either S5.6.1 or S5.6.2. Repeat this procedure with progressively 
decreasing or increasing levels (whichever is applicable) of leakage-
type diaphragm failures or equivalent leakages, to determine the 
minimum level of common diaphragm leakage-type failure (or equivalent 
level of leakage from the air chamber containing that diaphragm) at 
which all of the mechanical means referred to in S5.6.3.2 continue to 
be actuated and hold the parking brake applications with sufficient 
parking retardation forces to meet the minimum performance specified in 
either S5.6.1 or S5.6.2.
    S5.6.7.2.2  At the level of common diaphragm leakage-type failure 
(or equivalent level of leakage from the air chamber containing that 
diaphragm) determined in S5.6.7.2.1, and using the following procedure, 
determine the threshold maximum reservoir leakage rate (in psi per 
minute). With an initial reservoir system and supply line pressure of 
100 psi, no application of any of the vehicle's brakes and, if the 
vehicle is designed to tow a vehicle equipped with air brakes, a 50 
cubic inch test reservoir connected to the rear supply line coupling, 
make a parking brake application by venting the front supply line 
coupling to the atmosphere. Determine the maximum reservoir leakage 
rate (in psi per minute), which is the maximum rate of decrease in air 
pressure of any of the vehicle's reservoirs that results after that 
parking brake application.
    S5.6.7.2.3  Using the following procedure, a leakage-type failure 
of the common diaphragm (or equivalent leakage from the air chamber 
containing that diaphragm) that results in a maximum reservoir leakage 
rate that is three times the threshold maximum reservoir leakage rate 
determined in S5.6.7.2.2. With an initial reservoir system and supply 
line pressure of 100 psi, no application of any of the vehicle's brakes 
and, if the vehicle is designed to tow a vehicle equipped with air 
brakes, a 50 cubic inch test reservoir connected to the rear supply 
line coupling, make a parking brake application by venting the front 
supply line coupling to the atmosphere. Determine the maximum reservoir 
leakage rate (in psi per minute), which is the maximum rate of decrease 
in air pressure of any of the vehicle's reservoirs that results after 
that parking brake application. The level of common diaphragm leakage-
type failure (or equivalent level of leakage from the air chamber 
containing that diaphragm) associated with this reservoir leakage rate 
is the level that is to be used under the option set forth in S5.6(b).
    S5.7  Emergency brake system for trucks and buses. Each vehicle 
shall be equipped with an emergency brake system which, under the 
conditions of S6.1, conforms to the requirements of S5.7.1 through 
S5.7.3. However, the truck portion of an auto transporter need not meet 
the road test requirements of S5.7.1 and S5.7.3.
    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, and with unlimited wheel 
lockup permitted at any speed.
    S5.7.2  Emergency brake system operation. The emergency brake 
system shall be applied and released, and be capable of modulation, by 
means of the service brake control.
    S5.7.3  Towing vehicle emergency brake requirements. In addition to 
meeting the other requirements of S5.7, a vehicle designed to tow 
another vehicle equipped with air brakes shall--
    (a) In the case of a truck-tractor in the unloaded condition and a 
single unit truck which is capable of towing an airbrake equipped 
vehicle and is loaded to GVWR, be capable of meeting the requirements 
of S5.7.1 by operation of the service brake control only, with the 
trailer air supply line and air control line from the towing vehicle 
vented to the atmosphere in accordance with S6.1.14;
    (b) In the case of a truck-tractor loaded to GVWR, be capable of 
meeting S5.7.1 by operation of the service brake control only, with the 
air control line from the towing vehicle vented to the atmosphere in 
accordance with S6.1.14; and
    (c) Be capable of modulating the air in the supply or control line 
to the trailer by means of the service brake control with a single 
failure in the towing vehicle service brake system as specified in 
S5.7.1.
    S5.8  Emergency brakes for trailers. Each trailer shall meet the 
requirements of S5.8.1 through S5.8.3.
    S5.8.1  Emergency braking capability. Each trailer other than a 
trailer converter dolly shall have a parking brake system that conforms 
to S5.6 and that applies with the force specified in S5.6.1 or S5.6.2 
when the air pressure in the supply line is at atmospheric pressure. A 
trailer converter dolly shall have, at the manufacturer's option--
    (a) A parking brake system that conforms to S5.6 and that applies 
with the force specified in S5.6.1 or S5.6.2 when the air pressure in 
the supply line is at atmospheric pressure, or
    (b) An emergency system that automatically applies the service 
brakes when the service reservoir is at any pressure above 20 lb/in\2\ 
and the supply line is at atmospheric pressure. However, any 
agricultural commodity trailer, heavy hauler trailer, or pulpwood 
trailer shall meet the requirements of S5.8.1 or, at the option of the 
manufacturer, the requirements of Sec. 393.43 of this title.
    S5.8.2  Supply line pressure retention. Any single leakage type 
failure in the service brake system (except for a failure of the supply 
line, a valve directly connected to the supply line or a component of a 
brake chamber housing) shall not result in the pressure in the supply 
line falling below 70 psi, measured at the forward trailer supply

[[Page 27298]]

coupling. A trailer shall meet the above supply line pressure retention 
requirement with its brake system connected to the trailer test rig 
shown in Figure 1, with the reservoirs of the trailer and test rig 
initially pressurized to 100 psi and the regulator of the trailer test 
rig set at 100 psi; except that a trailer equipped with an air-applied, 
mechanically-held parking brake system and not designed to tow a 
vehicle equipped with air brakes, at the manufacturer's option, may 
meet the requirements of S5.8.4 rather than those of S5.8.2 and S5.8.3.
    S5.8.3  Automatic application of parking brakes. With an initial 
reservoir system pressure of 100 psi and initial supply line pressure 
of 100 psi, and if designed to tow a vehicle equipped with air brakes, 
with a 50 cubic inch test reservoir connected to the rear supply line 
coupling, and with any subsequent single leakage type failure in any 
other brake system, of a part designed to contain compressed air or 
brake fluid (consistent with the parenthetical phrase specified in 
S5.6.3.1), whenever the air pressure in the supply line is 70 psi or 
higher, the parking brakes shall not provide any brake retardation as a 
result of complete or partial automatic application of the parking 
brakes.
    S5.8.4 Automatic application of air-applied, mechanically held 
parking brakes. With its brake system connected to the supply line 
portion of the trailer test rig (Figure 1) and the regulator of the 
trailer test rig set at 100 psi, and with any single leakage type 
failure in the service brake system (except for a failure of the supply 
line, a valve directly connected to the supply line or a component of a 
brake chamber, but including failure of any common diaphragm), the 
parking brakes shall not provide any brake retardation as a result of 
complete or partial automatic application of the parking brakes.
    S5.9  Final inspection. Inspect the service brake system for the 
condition of adjustment and for the brake indicator display in 
accordance with S5.1.8 and S5.2.2.
    S6.  Conditions. The requirements of S5 shall be met by a vehicle 
when it is tested according to the conditions set in this S6, without 
replacing any brake system part or making any adjustments to the brake 
system except as specified. Unless otherwise specified, where a range 
of conditions is specified, the vehicle must be capable of meeting the 
requirements at all points within the range. On vehicles equipped with 
automatic brake adjusters, the automatic brake adjusters must remain 
activated at all times. 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 vehicle 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.
    S6.1  Road test conditions.
    S6.1.1  Except as otherwise specified, the vehicle is loaded to its 
GVWR, distributed proportionally to its GAWRs. During the burnish 
procedure specified in S6.1.8, truck tractors shall be loaded to their 
GVWR, by coupling them to an unbraked flatbed semitrailer, which 
semitrailer shall be loaded so that the weight of the tractor-trailer 
combination equals the GVWR of the truck tractor. The load on the 
unbraked flatbed semitrailer shall be located so that the truck 
tractor's wheels do not lock during burnish.
    S6.1.2  The inflation pressure is as specified by the vehicle 
manufacturer for the GVWR.
    S6.1.3  Unless otherwise specified, the transmission selector 
control is in neutral or the clutch is disengaged during all 
decelerations and during static parking brake tests.
    S6.1.4  All vehicle openings (doors, windows, hood, trunk, cargo 
doors, etc.) are in a closed position except as required for 
instrumentation purposes.
    S6.1.5  The ambient temperature is between 32 deg. F. and 100 deg. 
F.
    S6.1.6  The wind velocity is zero.
    S6.1.7  Unless otherwise specified, stopping tests are conducted on 
a 12-foot wide level, straight roadway having a peak friction 
coefficient of 0.9. For road tests in S5.3, the vehicle is aligned in 
the center of the roadway at the beginning of a stop. Peak friction 
coefficient is measured using an ASTM E1136 standard reference test 
tire in accordance with ASTM method E1337-90, at a speed of 40 mph, 
without water delivery for the surface with PFC of 0.9, and with water 
delivery for the surface with PFC of 0.5.
    S6.1.8  For vehicles with parking brake systems not utilizing the 
service brake friction elements, burnish the friction elements of such 
systems prior to the parking brake test according to the manufacturer's 
recommendations. For vehicles with parking brake systems utilizing the 
service brake friction elements, burnish the brakes as follows: With 
the transmission in the highest gear appropriate for a speed of 40 mph, 
make 500 snubs between 40 mph and 20 mph at a deceleration rate of 10 
f.p.s.p.s., or at the vehicle's maximum deceleration rate if less than 
10 f.p.s.p.s. Except where an adjustment is specified, after each brake 
application accelerate to 40 mph and maintain that speed until making 
the next brake application at a point 1 mile from the initial point of 
the previous brake application. If the vehicle cannot attain a speed of 
40 mph in 1 mph, continue to accelerate until the vehicle reaches 40 
mph or until the vehicle has traveled 1.5 miles from the initial point 
of the previous brake application, whichever occurs first. Any 
automatic pressure limiting valve is in use to limit pressure as 
designed. The brakes may be adjusted up to three times during the 
burnish procedure, at intervals specified by the vehicle manufacturer, 
and may be adjusted at the conclusion of the burnishing, in accordance 
with the vehicle manufacturer's recommendation.
    S6.1.9  Static parking brake tests for a semitrailer are conducted 
with the front-end supported by an unbraked dolly. The weight of the 
dolly is included as part of the trailer load.
    S6.1.10  In a test other than a static parking test, a truck 
tractor is tested at its GVWR by coupling it to an unbraked flatbed 
semi-trailer (hereafter, control trailer) as specified in S6.1.10.2 to 
S6.1.10.4.
    S6.1.10.1  [Reserved]
    S6.1.10.2  The center of gravity height of the ballast on the 
loaded control trailer shall be less than 24 inches above the top of 
the tractor's fifth wheel.
    S6.1.10.3  The control trailer has a single axle with a GAWR of 
18,000 pounds and a length, measured from the transverse centerline of 
the axle to the centerline of the kingpin, of 258 plus-minus 6 
inches.
    S6.1.10.4  The control trailer is loaded so that its axle is loaded 
at 4,500 pounds and the tractor is loaded to its GVWR, loaded above the 
kingpin only, with the tractor's fifth wheel adjusted so that the load 
on each axle measured at the tire-ground interface is most nearly 
proportional to the axles' respective GAWRs, without exceeding the GAWR 
of the tractor's axle or axles or control trailer's axle.
    S6.1.11  Special drive conditions. A vehicle equipped with an 
interlocking axle system or a front wheel drive system that is engaged 
and disengaged by the driver is tested with the system disengaged.
    S6.1.12  Liftable axles. A vehicle with a liftable axle is tested 
at GVWR with the liftable axle down and at unloaded vehicle weight with 
the liftable axle up.
    S6.1.13  Trailer test rig.
    (a) The trailer test rig shown in Figure 1 is calibrated in 
accordance with the calibration curves shown in Figure 3.

[[Page 27299]]

For the requirements of S5.3.3.1 and S5.3.4.1, the pressure in the 
trailer test rig reservoir is initially set at 100 psi for actuation 
tests and 95 psi for release tests.
    (b) The trailer test rig shown in Figure 1(a) is capable of 
increasing the pressure in a 50 cubic inch reservoir from atmospheric 
to 60 lb/in\2\ in 0.06 second, measured from the first movement of the 
service brake control to apply service brake pressure and of releasing 
pressure in such a reservoir from 95 to 5 lb/in\2\ in 0.22 second 
measured from the first movement of the service brake control to 
release service brake pressure.
    S6.1.14  In testing the emergency braking system of towing vehicles 
under S5.7.3(a) and S5.7.3(b), the hose(s) is vented to the atmosphere 
at any time not less than 1 second and not more than 1 minute before 
the emergency stop begins, while the vehicle is moving at the speed 
from which the stop is to be made and any manual control for the towing 
vehicle protection system is in the position to supply air and brake 
control signals to the vehicle being towed. No brake application is 
made from the time the line(s) is vented until the emergency stop 
begins and no manual operation of the parking brake system or towing 
vehicle protection system occurs from the time the line(s) is vented 
until the stop is completed.
    S6.1.15  Initial brake temperature. Unless otherwise specified, the 
initial brake temperature is not less than 150 deg. F and not more than 
200 deg. F.
    6.2  Dynamometer test conditions.
    S6.2.1  The dynamometer inertia for each wheel is equivalent to the 
load on the wheel with the axle loaded to its GAWR. For a vehicle 
having additional GAWRs specified for operation at reduced speeds, the 
GAWR used is that specified for a speed of 50 mph, or, at the option of 
the manufacturer, any speed greater than 50 mph.
    S6.2.2  The ambient temperature is between 75 deg. F. and 100 deg. 
F.
    S6.2.3  Air at ambient temperature is directed uniformly and 
continuously over the brake drum or disc at a velocity of 2,200 feet 
per minute.
    S6.2.4  The temperature of each brake is measured by a single plug-
type thermocouple installed in the center of the lining surface of the 
most heavily loaded shoe or pad as shown in Figure 2. The thermocouple 
is outside any center groove.
    S6.2.5  The rate of brake drum or disc rotation on a dynamometer or 
responding to the rate of rotation on a vehicle at a given speed is 
calculated by assuming a tire radius equal to the static loaded radius 
specified by the tire manufacturer.
    S6.2.6  Brakes are burnished before testing as follows: place the 
brake assembly on an inertia dynamometer and adjust the brake as 
recommended by the vehicle manufacturer. Make 200 stops from 40 mph at 
a deceleration of 10 f.p.s.p.s., with an initial brake temperature on 
each stop of not less than 315 deg. F and not more than 385 deg. F. 
Make 200 additional stops from 40 mph at a deceleration of 10 
f.p.s.p.s. with an initial brake temperature on each stop of not less 
than 450 deg. F and not more than 550 deg. F. The brakes may be 
adjusted up to three times during the burnish procedure, at intervals 
specified by the vehicle manufacturer, and may be adjusted at the 
conclusion of the burnishing, in accordance with the vehicle 
manufacturer's recommendation.
    S6.2.7  The brake temperature is increased to a specified level by 
conducting one or more stops from 40 m.p.h. at a deceleration of 10 
f.p.s.p.s. The brake temperature is decreased to a specified level by 
rotating the drum or disc at a constant 30 m.p.h.

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BILLING CODE 4910-59-C

[[Page 27304]]

Table I.--Stopping Sequence

1. Burnish.
2. Stops on a peak friction coefficient surface of 0.5:
    (a) With the vehicle at gross vehicle weight rating (GVWR), stop 
the vehicle from 30 mph using the service brake, for a truck tractor 
with a loaded unbraked control trailer.
    (b) With the vehicle at unloaded weight plus up to 500 lbs., stop 
the vehicle from 30 mph using the service brake, for a truck tractor.
3. Manual adjustment of the service brakes allowed for truck tractors, 
within the limits recommended by the vehicle manufacturer.
4. Other stops with vehicle at GVWR:
    (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) 60 mph emergency brake stops on a peak friction coefficient of 
0.9, for a single-unit vehicle. Truck tractors are not required to be 
tested in the loaded condition.
5. Parking brake test with the vehicle loaded to GVWR.
6. Manual adjustment of the service brakes allowed for truck tractors 
and single-unit vehicles, within the limits recommended by the vehicle 
manufacturer.
7. Other stops with the 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) 60 mph emergency brake stops on a peak friction coefficient of 
0.9, for a truck tractor or for a single-unit vehicle.
8. Parking brake test with the vehicle at unloaded weight plus up to 
500 lbs.
9. Final inspection of service brake system for condition of 
adjustment.

                                      Table II.--Stopping Distance in Feet                                      
----------------------------------------------------------------------------------------------------------------
                                                                       Service brake             Emergency brake
                                                           -----------------------------------------------------
              Vehicle speed in miles per hour                 PFC      PFC      PFC      PFC      PFC      PFC  
                                                              0.9      0.9      0.9      0.9      0.9      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) Unloaded truck tractors.                                                                        


                   Table III.--Brake Retardation Force                  
------------------------------------------------------------------------
                                                               Column 2 
                                                                Brake   
          Column 1  Brake Retardation Force, GAWR              Chamber  
                                                              Pressure, 
                                                                 PSI    
------------------------------------------------------------------------
0.05.......................................................           20
0.12.......................................................           30
0.18.......................................................           40
0.25.......................................................           50
0.31.......................................................           60
0.37.......................................................           70
0.41.......................................................           80
------------------------------------------------------------------------


                          Table IV.--[Reserved]                         
                                                                        
                                                                        


                  Table V.--Brake Chamber Rated Volumes                 
------------------------------------------------------------------------
                                                                Column 2
                                                     Column 1    Rated  
   Brake chamber type (Nominal area of piston or       Full      volume 
            diaphragm in square inches)               stroke     (Cubic 
                                                     (Inches)   Inches) 
------------------------------------------------------------------------
Type 9............................................  1.75/2.10         25
Type 12...........................................  1.75/2.10         30
Type 14...........................................  2.25/2.70         40
Type 16...........................................  2.25/2.70         50
Type 18...........................................  2.25/2.70         55
Type 20...........................................  2.25/2.70         60
Type 24...........................................  2.25/2.70         70
Type 30...........................................  2.50/3.20         95
Type 36...........................................  3.00/3.60        135
------------------------------------------------------------------------

    Issued on: May 23, 1996.
Barry Felrice,
Associate Administrator for Safety Performance Standards.
[FR Doc. 96-13557 Filed 5-30-96; 8:45 am]
BILLING CODE 4910-59-P