[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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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
