Federal Motor Vehicle Safety Standards No. 121; Air Brake Systems, 12354-12357 [E8-4460]
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12354
Federal Register / Vol. 73, No. 46 / Friday, March 7, 2008 / Proposed Rules
(b) Waiver approvals. The Secretary
may grant a State a waiver if the State
demonstrates that it has an alternative
approach to a requirement in this
chapter that will safeguard the State and
Federal governments’ interest and that
enables the State to be in substantial
compliance with the other requirements
of this chapter.
(c) Contents of waiver request. The
State’s request for approval of an
alternative approach or waiver of a
requirement in this chapter must
demonstrate why meeting the condition
is unnecessary, diminishes the State’s
ability to meet program requirements, or
that the alternative approach leads to a
more efficient, economical, and effective
administration of the programs for
which federal financial participation is
provided, benefiting both the State and
Federal Governments.
(d) Review of waiver requests. The
Secretary, or his or her designee, will
review waiver requests to assure that all
necessary information is provided, that
all processes provide for effective
economical and effective program
operation, and that the conditions for
waiver in this section are met.
(e) Agency’s response to a waiver
request. When a waiver is approved by
an agency, it becomes part of the State’s
approved ITD and is applicable to the
approving agency. A waiver is subject to
the ITD suspension provisions in
§ 95.611(c)(3). When a waiver is
disapproved, the entire ITD will be
disapproved. The ITD disapproval is a
final administrative decision and is not
subject to administrative appeal.
17. Amend § 95.631 by removing
‘‘APD’’ and adding in its place ‘‘ITD’’ in
the introductory text, and by revising
paragraph (a) to read as follows:
§ 95.631 Cost identification for purpose of
FFP claims.
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(a) Development costs. (1) Using its
normal departmental accounting system
to the extent consistent with the cost
principles set forth in OMB Circular
A–87, the State agency shall specifically
identify what items of costs constitute
development costs, assign these costs to
specific project cost centers, and
distribute these costs to funding sources
based on the specific identification,
assignment and distribution outlined in
the approved ITD;
(2) The methods for distributing costs
set forth in the ITD should provide for
assigning identifiable costs, to the extent
practicable, directly to program/
functions. The State agency shall amend
the cost allocation plan required by
subpart E of this part to include the
approved ITD methodology for the
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identification, assignment and
distribution of the development costs.
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18. Add new § 95.635 to read as
follows:
§ 95.635 Disallowance of Federal financial
participation automated systems that failed
to comply substantially with requirements.
(a) Federal financial participation at
the applicable matching rate is available
for automated data processing (ADP)
system expenditures that meet the
requirements specified under the
approved ITD including the approved
cost allocation plan.
(b) All or part of any costs for system
projects that fail to comply substantially
with an ITD approved under applicable
regulation at 45 CFR part 95.611, or for
the Title IV–D program contained in 45
CFR part 307, the applicable regulations
for the Title IV–E and Title IV–B
programs contained in Chapter 13,
subchapter G, 45 CFR 1355.55, or the
applicable regulations for the Title XIX
program contained in 42 CFR chapter 4
subchapter C, part 433, are subject to
disallowance by the Department.
19. Amend § 95.641 by removing
‘‘APD’’ and adding in its place ‘‘ITD’’
wherever it appears.
Subpart G—Equipment Acquired
Under Public Assistance Programs
20. Revise paragraph (a) of § 95.705 to
read as follows:
§ 95.705 Equipment costs—Federal
financial participation.
(a) General rule. In computing claims
for Federal financial participation,
equipment having a unit acquisition
cost of $25,000 or less may be claimed
in the period acquired or depreciated, at
the option of the State agency.
Equipment having a unit acquisition
cost of more than $25,000 shall be
depreciated. For purposes of this
section, the term depreciate also
includes use allowances computed in
accordance with the cost principles
prescribed in 45 CFR part 92.
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21. Revise paragraph (a) and the
introductory text of paragraph (b) of
§ 95.707 to read as follows:
§ 95.707 Equipment management and
disposition.
(a) Once equipment, whose costs are
claimed for Federal financial
participation (i.e., equipment that is
capitalized and depreciated or is
claimed in the period acquired), has
reached the end of its useful life (as
defined in an approved ITD), the
equipment shall be subject to the
property disposal rules in 45 CFR 92.32.
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(b) The State agency is responsible for
adequately managing the equipment,
maintaining records on the equipment,
and taking periodic physical
inventories. Physical inventories may be
made on the basis of statistical
sampling.
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[FR Doc. E8–4009 Filed 3–6–08; 8:45 am]
BILLING CODE 4184–01–P
DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety
Administration
49 CFR Part 571
Federal Motor Vehicle Safety
Standards No. 121; Air Brake Systems
National Highway Traffic
Safety Administration (NHTSA), DOT.
ACTION: Denial of petition for
rulemaking.
AGENCY:
SUMMARY: This Notice denies a petition
by Mr. Wayne Walch of TP Trucking in
which the petitioner requested three
changes to Federal Motor Vehicle Safety
Standard (FMVSS) No. 121, Air brake
systems, related to the air compressor
operation and low air pressure warning
system. After reviewing the petition and
the available real world data, the agency
has decided to deny it in its entirety
because one of the suggested changes is
already in the standard, the second
would not result in any measurable
safety benefit, and the third was, among
other things, not described in sufficient
detail for the agency to evaluate its
function or purpose.
FOR FURTHER INFORMATION CONTACT: For
non-legal issues, you may contact Mr.
Jeff Woods, Office of Crash Avoidance
Standards, NHTSA, 1200 New Jersey
Avenue, SE., Washington, DC 20590
(Telephone: 202–366–6206) (FAX: 202–
366–7002). For legal issues, you may
contact Mr. Ari Scott, Office of the Chief
Counsel, NHTSA, 1200 New Jersey
Avenue, SE., Washington, DC 20590
(Telephone: 202–366–2992) (FAX: 202–
366–3820).
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Background
II. General Description of Air Brake Systems
and FMVSS No. 121 Requirements
III. Function of Low Air Pressure Warning
and Gauges in Normal and Emergency
Braking Conditions
IV. Real World Data
V. Agency Analysis and Decision
VI. Conclusion
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I. Background
The agency received a petition for
rulemaking dated October 20, 2006,
from Mr. Wayne Walch of TP Trucking,
located in Eagle Point, Oregon. The
petitioner suggested three
improvements related to the air
compressor operation and low air
pressure warning system, which he
believed would make air brake systems
safer, and requested that Federal Motor
Vehicle Safety Standard (FMVSS) No.
121, Air brake systems, be changed
accordingly. These suggestions include:
• A warning device that would
activate when the air compressor begins
a new cycle.
• A warning device that would
activate if the air compressor exceeds a
predetermined amount of time to reach
the cut-out pressure.
• A warning device that would
activate just before the beginning of the
air compressor cycle.
In his petition, Mr. Walch describes
the typical operation of a low pressure
warning system in which an audible
warning signal is activated when the
reservoir pressure is at 55 pounds per
square inch (psi) or below, or one half
of the compressor governor cutout
pressure, whichever is less. The
petitioner states that he believes this
system is not robust as it provides no
indication of continual air loss or when
the compressor is constantly running
and this can result in a dangerous
situation.
In arguing the merits of the petition,
the petitioner describes several
scenarios in which the recommended
systems would operate. First, the
petitioner describes a scenario in which
a system has an air leak and the
compressor keeps running
continuously. As the driver applies the
brakes, the compressor cannot maintain
the needed pressure, and the driver
loses his brakes. If the truck is traveling
down hill, the driver could have a
serious crash in this situation. The
petitioner states that even if the springoperated parking brakes activate, they
do not have the stopping efficiency as
the normal service brakes. The
petitioner further states that if the
parking brakes activate due to that
condition, the vehicle could stop in an
unsafe area, and that most drivers will
not know how to release the spring
parking brakes. As such, the petition
asks for the above three changes to
FMVSS No. 121 to make air brakes safer.
They are as follows:
1. Provide an indication to the driver
upon air compressor cut-in. Thus if the
driver is aware that the air compressor
is cycling but the brakes aren’t being
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used, the driver would be alerted to air
system leakage.
2. Set the time on new vehicles for the
air compressor to increase system
pressure from cut-in to cut-out pressure.
If the system is taking too long to build
pressure, then a warning needs to be
displayed to the driver.
3. Require a low air pressure warning
device that activates just before the start
of the air compressor cycle. Items 1 and
2 above will prevent this.
II. General Description of Air Brake
Systems and FMVSS No. 121
Requirements
The operation of an air brake system
relies on compressed air stored in
reservoirs (tanks) mounted on the
vehicle (truck, bus, or trailer). By storing
compressed air in the reservoirs, the air
is readily available to make rapid
application of the brakes possible. When
the driver applies the service brakes, the
compressed air flows from the reservoirs
into the service brake chambers that
actuate the brake mechanism at each
wheel. The air in the reservoirs is
replenished by an air compressor on the
engine of the truck or bus, which is
controlled by a governor that activates
the air compressor (cut-in pressure) and
then turns off the air compressor once
the reservoirs are fully charged (cut-out
pressure). Trailers are also equipped
with reservoirs, which receive their air
supply from a towing vehicle that is
typically a truck or truck tractor. In the
case of multiple trailer combination
vehicles, the tractor supplies air to all of
the trailers in the combination.
As the driver applies the brakes, the
air flows from the reservoirs into the
service brake chambers at a pressure
corresponding to the position of the
brake pedal (treadle valve). Therefore, a
light brake application would typically
result in 10 to 20 psi of compressed air
in the brake chambers, and a hard brake
application would typically result in 40
psi or higher pressures in the brake
chambers. Since the brake chambers are
filled with compressed air taken from
the reservoirs and upon releasing the
service brakes the air is vented to the
atmosphere, the air pressure in the
reservoirs becomes slightly depleted
whenever the brakes are applied. When
the reservoir pressure drops to cut-in
pressure, the governor activates the air
compressor to build the system pressure
back up to the cut-out pressure.
The process of the air compressor
activating at reservoir cut-in pressure,
then building to reservoir cut-out
pressure, is known as compressor
cycling, and the time between cycles
can vary greatly among vehicle types
and the type of driving that is
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experienced. The most frequent
compressor cycling occurs in stop-andgo operations, such as experienced by
transit buses and refuse trucks, whereas
the least frequent compressor cycling
would typically be on a tractor trailer
combination vehicle being operated at
highway speeds with infrequent brake
applications.
The service brake system on air
braked vehicles is typically split into a
primary and a secondary air system. The
primary system usually controls the
brakes on the drive axle(s) and the
secondary system controls the brakes on
the steer axle. Both systems have their
own reservoirs that are typically fed by
a supply reservoir that receives air
directly from the air compressor. The
primary and secondary air reservoirs are
equipped with check valves for isolation
so that a loss of pressure in one system
does not cause a loss of pressure in the
other system. In case one system loses
pressure, the remaining system still
provides an emergency braking
capability on the vehicle, as well as
continuing to operate any trailer service
brakes, and keeps the parking brakes in
the released position. Most parking
brakes on heavy vehicles are of the
spring brake design that require
adequate brake system air pressure in
order to release them so the vehicle can
be moved.
FMVSS No. 121 has several
requirements relating to the reservoirs
and air compressor systems on trucks,
buses, and trailers. The minimum size
of the reservoirs is specified in FMVSS
No. 121 so that an adequate reserve of
air is available to repeatedly apply the
brakes without an excessive loss of
system air pressure. For trucks and
buses, S5.1.2.1 requires that the total
reservoir volume (combined volume of
primary, secondary, and supply
reservoirs) is at least 12 times the
combined volume of all of the service
brake chambers on the vehicle. Slight
exceptions are provided in Table V—
Brake Chamber Rated Volumes, so that
vehicle manufacturers can install longstroke brake chambers in place of
standard-stroke brake chambers without
having to increase the size of the
reservoirs. For trailers, S5.2.1.1 requires
that trailers have a reservoir capacity
that is at least eight times the combined
volume of the brake chambers, and
again an exception is provided via Table
V for the use of long-stroke brake
chambers.
S5.1.1 Air compressor requires that
an air compressor has sufficient
capacity to increase the pressure in the
reservoirs from 85 psi to 100 psi within
the time, in seconds, expressed by the
equation: [Actual reservoir capacity ×
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25] ÷ [required reservoir capacity], with
the engine at maximum recommended
r.p.m. Thus if a truck had minimumsized air reservoirs, the compressor
must be able to reach 100 psi from 85
psi within 25 seconds with the engine
at maximum recommended rated speed.
S5.1.1.1 Air compressor cut-in pressure
requires that the governor cut-in
pressure is at least 85 psi for a bus and
at least 100 psi for a truck.
S5.1.4 Pressure gauge requires a
pressure gauge that is visible to the
driver for each service brake system. In
a typical split air brake system there are
two independent air subsystems
(primary and secondary) that each have
a reservoir or series of reservoirs. The
air pressure gauge has two pressure
indicators (pointers)—one for the
primary system, and one for the
secondary system, or, two separate
gauges can be used with one gauge
provided for each system.
S5.1.5 Warning signal requires a low
air pressure warning signal that is either
visible to the driver, or if it is not
directly in front of the driver, is both
visible and audible. The warning signal
must activate when the pressure in any
reservoir system is below 60 psi and the
vehicle’s ignition is in the ‘‘on’’
position.
III. Function of Low Air Pressure
Warning and Gauges in Normal and
Emergency Braking Conditions
During normal driving, the reservoir
systems are automatically recharged by
the air compressor, and the driver can
monitor the air pressure gauges to see
that the air pressure in the reservoirs is
staying between the cut-in and cut-out
pressure limits. Most drivers of airbraked vehicles are aware of the
function of the low air pressure warning
signal and air pressure gauges on heavy
vehicles. The vast majority of drivers of
air-braked vehicles have commercial
drivers licenses (CDL’s). In order to
obtain a CDL with an endorsement to
drive vehicles with air brakes, drivers
are required to demonstrate that they
possess the knowledge and skills to
operate a vehicle equipped with air
brakes. After starting the engine, the air
brake system builds pressure in the
primary and secondary systems as
indicated by the gauges, and the low
pressure warning turns off indicating
normal system operation. However, the
minimum pressure for the low air
pressure warning system activation as
required in FMVSS No. 121 is ‘‘below
60 psi’’ which is slightly higher than
stated by the petitioner (55 psi, or onehalf the compressor governor cut-out
pressure, whichever is less). The
petitioner cited the North American
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Standard Out-of-Service Criteria for the
low pressure warning device published
by the Commercial Vehicle Safety
Alliance and these air pressure values
are slightly lower than required by
FMVSS No. 121 that applies to the
manufacturers of new vehicles. To
ensure compliance with the ‘‘below 60
psi’’ requirement in FMVSS No. 121, the
actual low pressure warning typically
activates slightly above 60 psi when
measured on vehicles.
There are several common types of
brake system failures that can cause the
low pressure warning signal to activate.
To begin, minor leaks in the system can
often be overcome by the capacity of the
air compressor to re-supply air to the
brake system. However, this discussion
focuses on substantial leaks and failures
that the air compressor cannot
overcome, as well as failures of the air
compressor itself.
A substantial leak in a brake hose
supplying a service brake chamber, or in
a service brake chamber (e.g., due to a
failed diaphragm), will result in leakage
whenever the brake pedal is applied. If
the leak is sufficiently large and the
brake pedal is applied for a long
duration, the pressure in either the
primary or secondary reservoir may
become sufficiently low to activate the
warning signal, which is required to
activate when the air pressure in the
service reservoir system is below 60 psi.
However, the remaining service brake
system (secondary or primary) will
remain intact and provide for an
emergency braking capability, and will
continue to keep the parking brakes
released. The driver would be able to
determine by viewing the air pressure
gauges the rate of pressure loss and
whether the loss was in the primary or
secondary system.
Failures or leaks can also occur in the
air supply portion of the system,
including the governor, air compressor,
compressor discharge hose, and the air
dryer located between the air
compressor and the service reservoirs.
Whether the compressor does not cut-in,
or its discharge air is vented to
atmosphere because of a hose failure
downstream of the compressor, the
result is that as the driver depletes air
in both reservoir systems during the
application of the service brakes, the
pressure in both the primary and
secondary systems continues to drop
until the low-pressure warning system
activates. Typically, the primary system
will activate the low pressure warning
signal first while the secondary system
will have a higher pressure. At this
point the vehicle is in emergency
braking mode and the driver has the
ability to pull off the roadway. If for
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some reason the brakes were repeatedly
applied, the pressure in both the
primary and secondary systems would
become further depleted and the spring
brakes would eventually apply
automatically which would also bring
the vehicle to a stop. Truck drivers with
CDLs are generally knowledgeable about
these aspects of air brake system failures
and the importance and meaning of low
pressure warning signals.
IV. Real World Data
The petitioner cites two scenarios for
truck crashes that it states are related to
the inadequacy of the currently required
low air pressure warning system. The
first is runaway trucks on downgrades
that the petitioner claims is caused by
air leaks. The petitioner provided no
data to support this conclusion.
Similarly, the agency is not aware that
this is a prevalent crash mode. Our
experience indicates that runaway truck
crashes are most often due to brake fade
from overheated and/or out-ofadjustment S-cam drum brakes that
result in a loss of brake effectiveness,
often exacerbated by excessive speed on
a downgrade. We have no indications
that runaway truck crashes are being
caused by air leaks or contributed to by
inadequate low pressure warning
systems.
The other crash scenario presented by
the petitioner was a truck stopping in an
unsafe area because of an air leak that
caused the parking brakes to apply and
most drivers would not know how to
move the vehicle. While it is true that
this can happen, the agency has no
indications of widespread problems
with trucks being stranded on roadways
or in unsafe areas due to loss of air
pressure in the brake system and being
involved in crashes. The petitioner also
did not provide such data. Additionally,
as we have previously stated, the
current low-pressure warning system
already alerts the driver of a substantial
loss of air pressure and the truck’s
braking system can be operating in the
emergency braking mode. As such, the
driver can still make several brake
applications to safely bring the truck to
a stop off of a travel lane.
V. Agency Analysis and Decision
The first requested change made by
the petitioner is:
There needs to be a way to make the driver
aware of when the air compressor is starting
a new cycle. This lets the driver know there
is a loss of air in the system. If he is not using
the brakes and the air compressor is cycling
he should stop the vehicle and do an
inspection for an air leak or call for repairs
to the air system before continuing on or
before a possible accident on a downhill
grade.
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The agency believes that this change
would mean that a lamp on the
instrument panel would illuminate (or
some other type of indicator would
signal) every time that the air
compressor cycled on at cut-in pressure.
Since cycling of the compressor occurs
during normal operation of a vehicle
equipped with an air brake system, the
agency believes that most truck drivers
would find this to be a nuisance,
particularly when driving at night. The
agency’s fleet evaluation experience in
the early 1990’s with antilock brake
systems (ABS) warning lamps was that
drivers would sometimes remove the
bulb or cover it with opaque tape
because of a perceived nuisance (when
in fact it was indicating a malfunction
in the ABS that, under hard braking,
could result in a loss-of-control crash).
A warning system that activates during
normal operation may have a limited
safety benefit, and activations are more
effective when they only occur when
there is a condition that warrants some
type of intervention by the driver.
Therefore, we do not believe it would be
appropriate to adopt the petitioner’s
first request. However, we note that
neither FMVSS No. 101, Controls and
Displays, nor FMVSS No. 121 prohibits
the addition of a compressor cycling
lamp, if a truck operator chooses to have
such a system installed.
The second requested change is:
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They need to set the time on new vehicles
at the factory on how long it takes the air
compressor at the start of its cycle to meet
the cut off pressure. If it is taking to[o] long
or continuous running occurs there needs to
be something to warn the driver there is a
major problem. This is a very unsafe
situation and should have a priority warning
to the driver.
Regarding the requested change by the
petitioner to set the required time for air
pressure build time, we note that this
facet of air brake systems is addressed
in the previously discussed section
S5.1.1 in FMVSS No. 121, which
requires the air compressor to have
sufficient capacity to increase the air
system pressure from 85 to 100 psi in
the specified amount of time. However,
this requirement allows for some
variation in the amount of time needed
to charge the air system. Under FMVSS
No. 121, the time for charging the air
system is measured with the engine at
maximum rated speed, so the actual
charging time during normal driving can
vary based upon actual engine speed
and gear selection. Compared to
charging time with the engine at
maximum rated speed, the charging
time would be longer when the truck is
sitting at idle. Other factors, such as the
frequency of brake application, number
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of towed units, air being supplied to
increase air suspension pressure, etc.,
would cause air to be depleted at the
same time the air compressor is
charging the system. Therefore, these
would also affect the charging time, and
we believe that requiring a warning to
activate when a constant time period
has elapsed is an impracticable
requirement, given the variable nature
of the charging period under the current
regulatory scheme. We note that our
safety standard already regulates
performance in the area of air pressure
charging time, but we believe that it
does so more appropriately than the
proposed change. For this reason, we
are not adopting the petitioner’s second
request.
The final requested change is:
It would be some help to have a low air
pressure warning device that comes on just
before the start of the air compressor cycle.
When this low air warning comes on the
vehicle is in a dangerous situation. Number
1 and 2 will prevent this.
The third requested change in the
petition is not clearly defined for the
agency to fully evaluate. The statement
‘‘just before the start of the air
compressor cycle’’ has two meanings.
The first meaning is a pressure slightly
above the cut-in pressure, e.g.,
approximately 105 to 110 psi. The
second meaning is a pressure slightly
below the cut-in pressure, e.g.,
approximately 90 to 95 psi. Based upon
the information in the petition, the
agency does not understand the concept
of this warning lamp, and how its
operation differs from the currentlyrequired low pressure warning signal
required in FMVSS No. 121, other than
being set to activate at a higher air
pressure. It also seems nearly identical
to/redundant with the petitioner’s first
requested change, as this warning
would activate just before the start of a
new air compressor cycle, and then the
warning from the first request would
activate when the compressor began that
new cycle. Furthermore, we note that
activation of a warning signal at either
of these pressures would result in the
warning being activated extremely
frequently, including during normal
driving operations. Given these reasons,
we are denying the petitioner’s third
requested change.
VI. Conclusion
Based upon this review of the
petition, the agency is denying it. In
summary, it appears that one or two
warning lamps would be required to
activate upon each cut-in of the
compressor cycle, and this would not
provide additional information to the
driver beyond the information that is
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already available from the existing air
pressure gauges. In addition, we believe
that warning systems that activate
frequently during normal driving
conditions can be perceived as a
nuisance, and may have limited safety
effect. Finally, we are not aware of any
known safety problems not addressed
by the existing low pressure warning
signal requirements in FMVSS No. 121.
Issued: March 3, 2008.
Stephen R. Kratzke,
Associate Administrator for Rulemaking.
[FR Doc. E8–4460 Filed 3–6–08; 8:45 am]
BILLING CODE 4910–59–P
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric
Administration
50 CFR Part 679
[Docket No. 070917520–8258–02]
RIN 0648–AW06
Fisheries of the Exclusive Economic
Zone Off Alaska; Groundfish Fisheries
of the Bering Sea and Aleutian Islands
Management Area
National Marine Fisheries
Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA),
Commerce.
ACTION: Proposed rule; request for
comments.
AGENCY:
SUMMARY: NMFS issues a proposed rule
that would implement Amendment 89
to the Fishery Management Plan for
Groundfish of the Bering Sea and
Aleutian Islands Management Area
(FMP) to establish Bering Sea habitat
conservation measures. Amendment 89,
if approved, would prohibit nonpelagic
trawling in certain waters of the Bering
Sea subarea to protect bottom habitat
from the potential adverse effects of
nonpelagic trawling. Amendment 89
also would establish the Northern
Bering Sea Research Area for studying
the impacts of nonpelagic trawling on
bottom habitat. This proposed rule is
necessary to protect Bering Sea subarea
bottom habitat from the potential effects
of nonpelagic trawling and to provide
the opportunity to further study the
effects of nonpelagic trawling on bottom
habitat. This action is intended to
promote the goals and objectives of the
Magnuson-Stevens Fishery
Conservation and Management Act, the
FMP, and other applicable laws.
DATES: Written comments must be
received by April 21, 2008.
ADDRESSES: Send comments to Sue
Salveson, Assistant Regional
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]]>Agencies
[Federal Register Volume 73, Number 46 (Friday, March 7, 2008)]
[Proposed Rules]
[Pages 12354-12357]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-4460]
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DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
Federal Motor Vehicle Safety Standards No. 121; Air Brake Systems
AGENCY: National Highway Traffic Safety Administration (NHTSA), DOT.
ACTION: Denial of petition for rulemaking.
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SUMMARY: This Notice denies a petition by Mr. Wayne Walch of TP
Trucking in which the petitioner requested three changes to Federal
Motor Vehicle Safety Standard (FMVSS) No. 121, Air brake systems,
related to the air compressor operation and low air pressure warning
system. After reviewing the petition and the available real world data,
the agency has decided to deny it in its entirety because one of the
suggested changes is already in the standard, the second would not
result in any measurable safety benefit, and the third was, among other
things, not described in sufficient detail for the agency to evaluate
its function or purpose.
FOR FURTHER INFORMATION CONTACT: For non-legal issues, you may contact
Mr. Jeff Woods, Office of Crash Avoidance Standards, NHTSA, 1200 New
Jersey Avenue, SE., Washington, DC 20590 (Telephone: 202-366-6206)
(FAX: 202-366-7002). For legal issues, you may contact Mr. Ari Scott,
Office of the Chief Counsel, NHTSA, 1200 New Jersey Avenue, SE.,
Washington, DC 20590 (Telephone: 202-366-2992) (FAX: 202-366-3820).
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Background
II. General Description of Air Brake Systems and FMVSS No. 121
Requirements
III. Function of Low Air Pressure Warning and Gauges in Normal and
Emergency Braking Conditions
IV. Real World Data
V. Agency Analysis and Decision
VI. Conclusion
[[Page 12355]]
I. Background
The agency received a petition for rulemaking dated October 20,
2006, from Mr. Wayne Walch of TP Trucking, located in Eagle Point,
Oregon. The petitioner suggested three improvements related to the air
compressor operation and low air pressure warning system, which he
believed would make air brake systems safer, and requested that Federal
Motor Vehicle Safety Standard (FMVSS) No. 121, Air brake systems, be
changed accordingly. These suggestions include:
A warning device that would activate when the air
compressor begins a new cycle.
A warning device that would activate if the air compressor
exceeds a predetermined amount of time to reach the cut-out pressure.
A warning device that would activate just before the
beginning of the air compressor cycle.
In his petition, Mr. Walch describes the typical operation of a low
pressure warning system in which an audible warning signal is activated
when the reservoir pressure is at 55 pounds per square inch (psi) or
below, or one half of the compressor governor cutout pressure,
whichever is less. The petitioner states that he believes this system
is not robust as it provides no indication of continual air loss or
when the compressor is constantly running and this can result in a
dangerous situation.
In arguing the merits of the petition, the petitioner describes
several scenarios in which the recommended systems would operate.
First, the petitioner describes a scenario in which a system has an air
leak and the compressor keeps running continuously. As the driver
applies the brakes, the compressor cannot maintain the needed pressure,
and the driver loses his brakes. If the truck is traveling down hill,
the driver could have a serious crash in this situation. The petitioner
states that even if the spring-operated parking brakes activate, they
do not have the stopping efficiency as the normal service brakes. The
petitioner further states that if the parking brakes activate due to
that condition, the vehicle could stop in an unsafe area, and that most
drivers will not know how to release the spring parking brakes. As
such, the petition asks for the above three changes to FMVSS No. 121 to
make air brakes safer. They are as follows:
1. Provide an indication to the driver upon air compressor cut-in.
Thus if the driver is aware that the air compressor is cycling but the
brakes aren't being used, the driver would be alerted to air system
leakage.
2. Set the time on new vehicles for the air compressor to increase
system pressure from cut-in to cut-out pressure. If the system is
taking too long to build pressure, then a warning needs to be displayed
to the driver.
3. Require a low air pressure warning device that activates just
before the start of the air compressor cycle. Items 1 and 2 above will
prevent this.
II. General Description of Air Brake Systems and FMVSS No. 121
Requirements
The operation of an air brake system relies on compressed air
stored in reservoirs (tanks) mounted on the vehicle (truck, bus, or
trailer). By storing compressed air in the reservoirs, the air is
readily available to make rapid application of the brakes possible.
When the driver applies the service brakes, the compressed air flows
from the reservoirs into the service brake chambers that actuate the
brake mechanism at each wheel. The air in the reservoirs is replenished
by an air compressor on the engine of the truck or bus, which is
controlled by a governor that activates the air compressor (cut-in
pressure) and then turns off the air compressor once the reservoirs are
fully charged (cut-out pressure). Trailers are also equipped with
reservoirs, which receive their air supply from a towing vehicle that
is typically a truck or truck tractor. In the case of multiple trailer
combination vehicles, the tractor supplies air to all of the trailers
in the combination.
As the driver applies the brakes, the air flows from the reservoirs
into the service brake chambers at a pressure corresponding to the
position of the brake pedal (treadle valve). Therefore, a light brake
application would typically result in 10 to 20 psi of compressed air in
the brake chambers, and a hard brake application would typically result
in 40 psi or higher pressures in the brake chambers. Since the brake
chambers are filled with compressed air taken from the reservoirs and
upon releasing the service brakes the air is vented to the atmosphere,
the air pressure in the reservoirs becomes slightly depleted whenever
the brakes are applied. When the reservoir pressure drops to cut-in
pressure, the governor activates the air compressor to build the system
pressure back up to the cut-out pressure.
The process of the air compressor activating at reservoir cut-in
pressure, then building to reservoir cut-out pressure, is known as
compressor cycling, and the time between cycles can vary greatly among
vehicle types and the type of driving that is experienced. The most
frequent compressor cycling occurs in stop-and-go operations, such as
experienced by transit buses and refuse trucks, whereas the least
frequent compressor cycling would typically be on a tractor trailer
combination vehicle being operated at highway speeds with infrequent
brake applications.
The service brake system on air braked vehicles is typically split
into a primary and a secondary air system. The primary system usually
controls the brakes on the drive axle(s) and the secondary system
controls the brakes on the steer axle. Both systems have their own
reservoirs that are typically fed by a supply reservoir that receives
air directly from the air compressor. The primary and secondary air
reservoirs are equipped with check valves for isolation so that a loss
of pressure in one system does not cause a loss of pressure in the
other system. In case one system loses pressure, the remaining system
still provides an emergency braking capability on the vehicle, as well
as continuing to operate any trailer service brakes, and keeps the
parking brakes in the released position. Most parking brakes on heavy
vehicles are of the spring brake design that require adequate brake
system air pressure in order to release them so the vehicle can be
moved.
FMVSS No. 121 has several requirements relating to the reservoirs
and air compressor systems on trucks, buses, and trailers. The minimum
size of the reservoirs is specified in FMVSS No. 121 so that an
adequate reserve of air is available to repeatedly apply the brakes
without an excessive loss of system air pressure. For trucks and buses,
S5.1.2.1 requires that the total reservoir volume (combined volume of
primary, secondary, and supply reservoirs) is at least 12 times the
combined volume of all of the service brake chambers on the vehicle.
Slight exceptions are provided in Table V--Brake Chamber Rated Volumes,
so that vehicle manufacturers can install long-stroke brake chambers in
place of standard-stroke brake chambers without having to increase the
size of the reservoirs. For trailers, S5.2.1.1 requires that trailers
have a reservoir capacity that is at least eight times the combined
volume of the brake chambers, and again an exception is provided via
Table V for the use of long-stroke brake chambers.
S5.1.1 Air compressor requires that an air compressor has
sufficient capacity to increase the pressure in the reservoirs from 85
psi to 100 psi within the time, in seconds, expressed by the equation:
[Actual reservoir capacity x
[[Page 12356]]
25] / [required reservoir capacity], with the engine at maximum
recommended r.p.m. Thus if a truck had minimum-sized air reservoirs,
the compressor must be able to reach 100 psi from 85 psi within 25
seconds with the engine at maximum recommended rated speed. S5.1.1.1
Air compressor cut-in pressure requires that the governor cut-in
pressure is at least 85 psi for a bus and at least 100 psi for a truck.
S5.1.4 Pressure gauge requires a pressure gauge that is visible to
the driver for each service brake system. In a typical split air brake
system there are two independent air subsystems (primary and secondary)
that each have a reservoir or series of reservoirs. The air pressure
gauge has two pressure indicators (pointers)--one for the primary
system, and one for the secondary system, or, two separate gauges can
be used with one gauge provided for each system.
S5.1.5 Warning signal requires a low air pressure warning signal
that is either visible to the driver, or if it is not directly in front
of the driver, is both visible and audible. The warning signal must
activate when the pressure in any reservoir system is below 60 psi and
the vehicle's ignition is in the ``on'' position.
III. Function of Low Air Pressure Warning and Gauges in Normal and
Emergency Braking Conditions
During normal driving, the reservoir systems are automatically
recharged by the air compressor, and the driver can monitor the air
pressure gauges to see that the air pressure in the reservoirs is
staying between the cut-in and cut-out pressure limits. Most drivers of
air-braked vehicles are aware of the function of the low air pressure
warning signal and air pressure gauges on heavy vehicles. The vast
majority of drivers of air-braked vehicles have commercial drivers
licenses (CDL's). In order to obtain a CDL with an endorsement to drive
vehicles with air brakes, drivers are required to demonstrate that they
possess the knowledge and skills to operate a vehicle equipped with air
brakes. After starting the engine, the air brake system builds pressure
in the primary and secondary systems as indicated by the gauges, and
the low pressure warning turns off indicating normal system operation.
However, the minimum pressure for the low air pressure warning system
activation as required in FMVSS No. 121 is ``below 60 psi'' which is
slightly higher than stated by the petitioner (55 psi, or one-half the
compressor governor cut-out pressure, whichever is less). The
petitioner cited the North American Standard Out-of-Service Criteria
for the low pressure warning device published by the Commercial Vehicle
Safety Alliance and these air pressure values are slightly lower than
required by FMVSS No. 121 that applies to the manufacturers of new
vehicles. To ensure compliance with the ``below 60 psi'' requirement in
FMVSS No. 121, the actual low pressure warning typically activates
slightly above 60 psi when measured on vehicles.
There are several common types of brake system failures that can
cause the low pressure warning signal to activate. To begin, minor
leaks in the system can often be overcome by the capacity of the air
compressor to re-supply air to the brake system. However, this
discussion focuses on substantial leaks and failures that the air
compressor cannot overcome, as well as failures of the air compressor
itself.
A substantial leak in a brake hose supplying a service brake
chamber, or in a service brake chamber (e.g., due to a failed
diaphragm), will result in leakage whenever the brake pedal is applied.
If the leak is sufficiently large and the brake pedal is applied for a
long duration, the pressure in either the primary or secondary
reservoir may become sufficiently low to activate the warning signal,
which is required to activate when the air pressure in the service
reservoir system is below 60 psi. However, the remaining service brake
system (secondary or primary) will remain intact and provide for an
emergency braking capability, and will continue to keep the parking
brakes released. The driver would be able to determine by viewing the
air pressure gauges the rate of pressure loss and whether the loss was
in the primary or secondary system.
Failures or leaks can also occur in the air supply portion of the
system, including the governor, air compressor, compressor discharge
hose, and the air dryer located between the air compressor and the
service reservoirs. Whether the compressor does not cut-in, or its
discharge air is vented to atmosphere because of a hose failure
downstream of the compressor, the result is that as the driver depletes
air in both reservoir systems during the application of the service
brakes, the pressure in both the primary and secondary systems
continues to drop until the low-pressure warning system activates.
Typically, the primary system will activate the low pressure warning
signal first while the secondary system will have a higher pressure. At
this point the vehicle is in emergency braking mode and the driver has
the ability to pull off the roadway. If for some reason the brakes were
repeatedly applied, the pressure in both the primary and secondary
systems would become further depleted and the spring brakes would
eventually apply automatically which would also bring the vehicle to a
stop. Truck drivers with CDLs are generally knowledgeable about these
aspects of air brake system failures and the importance and meaning of
low pressure warning signals.
IV. Real World Data
The petitioner cites two scenarios for truck crashes that it states
are related to the inadequacy of the currently required low air
pressure warning system. The first is runaway trucks on downgrades that
the petitioner claims is caused by air leaks. The petitioner provided
no data to support this conclusion. Similarly, the agency is not aware
that this is a prevalent crash mode. Our experience indicates that
runaway truck crashes are most often due to brake fade from overheated
and/or out-of-adjustment S-cam drum brakes that result in a loss of
brake effectiveness, often exacerbated by excessive speed on a
downgrade. We have no indications that runaway truck crashes are being
caused by air leaks or contributed to by inadequate low pressure
warning systems.
The other crash scenario presented by the petitioner was a truck
stopping in an unsafe area because of an air leak that caused the
parking brakes to apply and most drivers would not know how to move the
vehicle. While it is true that this can happen, the agency has no
indications of widespread problems with trucks being stranded on
roadways or in unsafe areas due to loss of air pressure in the brake
system and being involved in crashes. The petitioner also did not
provide such data. Additionally, as we have previously stated, the
current low-pressure warning system already alerts the driver of a
substantial loss of air pressure and the truck's braking system can be
operating in the emergency braking mode. As such, the driver can still
make several brake applications to safely bring the truck to a stop off
of a travel lane.
V. Agency Analysis and Decision
The first requested change made by the petitioner is:
There needs to be a way to make the driver aware of when the air
compressor is starting a new cycle. This lets the driver know there
is a loss of air in the system. If he is not using the brakes and
the air compressor is cycling he should stop the vehicle and do an
inspection for an air leak or call for repairs to the air system
before continuing on or before a possible accident on a downhill
grade.
[[Page 12357]]
The agency believes that this change would mean that a lamp on the
instrument panel would illuminate (or some other type of indicator
would signal) every time that the air compressor cycled on at cut-in
pressure. Since cycling of the compressor occurs during normal
operation of a vehicle equipped with an air brake system, the agency
believes that most truck drivers would find this to be a nuisance,
particularly when driving at night. The agency's fleet evaluation
experience in the early 1990's with antilock brake systems (ABS)
warning lamps was that drivers would sometimes remove the bulb or cover
it with opaque tape because of a perceived nuisance (when in fact it
was indicating a malfunction in the ABS that, under hard braking, could
result in a loss-of-control crash). A warning system that activates
during normal operation may have a limited safety benefit, and
activations are more effective when they only occur when there is a
condition that warrants some type of intervention by the driver.
Therefore, we do not believe it would be appropriate to adopt the
petitioner's first request. However, we note that neither FMVSS No.
101, Controls and Displays, nor FMVSS No. 121 prohibits the addition of
a compressor cycling lamp, if a truck operator chooses to have such a
system installed.
The second requested change is:
They need to set the time on new vehicles at the factory on how
long it takes the air compressor at the start of its cycle to meet
the cut off pressure. If it is taking to[o] long or continuous
running occurs there needs to be something to warn the driver there
is a major problem. This is a very unsafe situation and should have
a priority warning to the driver.
Regarding the requested change by the petitioner to set the
required time for air pressure build time, we note that this facet of
air brake systems is addressed in the previously discussed section
S5.1.1 in FMVSS No. 121, which requires the air compressor to have
sufficient capacity to increase the air system pressure from 85 to 100
psi in the specified amount of time. However, this requirement allows
for some variation in the amount of time needed to charge the air
system. Under FMVSS No. 121, the time for charging the air system is
measured with the engine at maximum rated speed, so the actual charging
time during normal driving can vary based upon actual engine speed and
gear selection. Compared to charging time with the engine at maximum
rated speed, the charging time would be longer when the truck is
sitting at idle. Other factors, such as the frequency of brake
application, number of towed units, air being supplied to increase air
suspension pressure, etc., would cause air to be depleted at the same
time the air compressor is charging the system. Therefore, these would
also affect the charging time, and we believe that requiring a warning
to activate when a constant time period has elapsed is an impracticable
requirement, given the variable nature of the charging period under the
current regulatory scheme. We note that our safety standard already
regulates performance in the area of air pressure charging time, but we
believe that it does so more appropriately than the proposed change.
For this reason, we are not adopting the petitioner's second request.
The final requested change is:
It would be some help to have a low air pressure warning device
that comes on just before the start of the air compressor cycle.
When this low air warning comes on the vehicle is in a dangerous
situation. Number 1 and 2 will prevent this.
The third requested change in the petition is not clearly defined
for the agency to fully evaluate. The statement ``just before the start
of the air compressor cycle'' has two meanings. The first meaning is a
pressure slightly above the cut-in pressure, e.g., approximately 105 to
110 psi. The second meaning is a pressure slightly below the cut-in
pressure, e.g., approximately 90 to 95 psi. Based upon the information
in the petition, the agency does not understand the concept of this
warning lamp, and how its operation differs from the currently-required
low pressure warning signal required in FMVSS No. 121, other than being
set to activate at a higher air pressure. It also seems nearly
identical to/redundant with the petitioner's first requested change, as
this warning would activate just before the start of a new air
compressor cycle, and then the warning from the first request would
activate when the compressor began that new cycle. Furthermore, we note
that activation of a warning signal at either of these pressures would
result in the warning being activated extremely frequently, including
during normal driving operations. Given these reasons, we are denying
the petitioner's third requested change.
VI. Conclusion
Based upon this review of the petition, the agency is denying it.
In summary, it appears that one or two warning lamps would be required
to activate upon each cut-in of the compressor cycle, and this would
not provide additional information to the driver beyond the information
that is already available from the existing air pressure gauges. In
addition, we believe that warning systems that activate frequently
during normal driving conditions can be perceived as a nuisance, and
may have limited safety effect. Finally, we are not aware of any known
safety problems not addressed by the existing low pressure warning
signal requirements in FMVSS No. 121.
Issued: March 3, 2008.
Stephen R. Kratzke,
Associate Administrator for Rulemaking.
[FR Doc. E8-4460 Filed 3-6-08; 8:45 am]
BILLING CODE 4910-59-P
