Air Brake Systems; Denial of Petition for Rulemaking

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 552

Air Brake Systems; Denial of Petition for Rulemaking

AGENCY: National Highway Traffic Safety Administration, Transportation.

ACTION: Denial of petition for rulemaking.

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SUMMARY: This notice denies a petition for rulemaking, submitted by the

California Highway Patrol, that requests the agency to amend the air

pressure warning signal requirements in Federal Motor Vehicle Safety

Standard No. 121, Air Brake Systems. After conducting its review, the

agency has determined that the petition should not be granted because

the situation described by the petition does not raise a significant

safety problem. The agency further notes that establishing an upper

limit to the operating range of the low pressure warning signal would

not correct the problem of the signal's failure to warn a driver of low

pressure in the trailer brake system. Since there is no reasonable

possibility that the requested amendment would be issued at the

conclusion of a rulemaking proceeding, the agency is denying the

petition.

FOR FURTHER INFORMATION CONTACT: Mr. Chris Tinto, Office of Vehicle

Safety Standards, National Highway Traffic Safety Administration, 400

Seventh Street SW., Washington, DC 20590, (202) 366-5229.

SUPPLEMENTARY INFORMATION: Federal Motor Vehicle Safety Standard No.

121, Air Brake Systems, establishes performance requirements for

braking systems on vehicles equipped with air brakes. The purpose of

the standard is to ensure safe braking performance under normal and

emergency braking conditions.

The standard requires vehicles equipped with air brakes to have

certain equipment. Section S5.1.5 requires that each vehicle equipped

with an air brake system be equipped with a ``signal, other than a

pressure gage, that gives a continuous warning to a person in the

normal driving position when the ignition is in the ``on'' or ``run''

position and the air pressure in the service reservoir system is below

60 p.s.i.'' The purpose of this requirement is to inform the driver of

situations in which there may be low, potentially unsafe levels of air

pressure in the service brake system.

On June 7, 1993, the California Highway Patrol (CHP), submitted a

petition for rulemaking that requested the agency to amend the low air

pressure warning signal requirements in S5.1.5 of Standard No. 121. The

petitioner contended that:

this subsection permits a warning signal that is activated at any

pressure above 60 psi as long as it also produces the signal at

pressures below 60 psi. This would permit a device that activates a

warning in the normal operating range of the system, approximately

85-115 psi. This could result in a false signal where the driver

would not be warned of a true low air pressure situation. Though

unlikely, a warning device that was activated whenever the ignition

key was in the ``on'' or ``run'' position would comply with the

existing regulation, while fulfilling neither the intent of the

regulation nor any useful purpose.

Based on its concern, CHP requested that the agency initiate

rulemaking to specify an upper limit to the warning signal operating

range, so that it would give a ``true warning'' of a low air pressure

condition. CHP recommended that the upper cutoff be 75 p.s.i.

After reviewing the petition, NHTSA has decided not to establish an

upper limit to the low pressure warning signal requirement. The agency

disagrees with CHP's claims that establishing such an upper limit would

improve safety. The agency notes that under the current requirement,

some valves may activate at slightly higher air pressures than 60

p.s.i. since the valves are typically designed with a tolerance of

about 6 p.s.i. Nevertheless, activation at 65 p.s.i.

rather than 60 p.s.i. also indicates a relatively low pressure level

about which the driver should be concerned. The agency believes that

the modification requested by the petition is not warranted, since the

agency is aware of no safety problems related to this requirement which

has been in effect since 1971. The agency further notes that setting an

upper limit might unreasonably restrict the potential for designing new

air brake systems, since the valve manufacturers would be faced with

the unnecessary task of redesigning the valves, even though such a

modification would not provide any safety benefits.

Based on the above considerations, NHTSA has determined that CHP's

petition should not be granted. In accordance with 49 CFR Part 552, the

agency has completed its technical review of the petition and

determined that there is no reasonable possibility that the requested

amendment would be issued at the conclusion of a rulemaking proceeding.

Accordingly, the agency is denying the petition.

Notwithstanding NHTSA's decision to deny the petition, the agency

is reviewing the pressure setting requirements for the low pressure

warning switch in light of possible problems with a recent amendment to

Standard No. 121. On October 8, 1991, NHTSA issued a final rule that

eliminated the requirements for a separate protected reservoir capable

of releasing the parking brakes. (56 FR 50666) Among other things, that

amendment added a requirement for 70 p.s.i. supply line pressure

retention and established the air pressure at which automatic

application of the parking brakes would commence during loss of air

pressure.

In comments on a separate rulemaking on the parking brake

requirements applicable to air-applied, mechanically held systems (58

FR 13437, March 11, 1993), the American Trucking Associations (ATA) and

Allied Signal contended that the 70 p.s.i. requirement prevents tractor

low air pressure warning systems from warning drivers of the loss of

service air pressure and thus loss of service brakes on trailers.

Allied requested that the agency raise the governor cut-in pressure to

100 p.s.i., which it believed would enable manufacturers to provide low

pressure warnings. It stated that the pressure switch is currently

limited by the 85 p.s.i. minimum governor cut-in pressure requirement.

In addition, ATA has informed the agency that it is conducting tests to

determine whether it should petition the agency to raise the cut-in

requirements from the present 85 p.s.i. minimum and the low pressure

warning limits from 60 p.s.i. to 75 p.s.i. or 80 p.s.i. Based on these

test results, NHTSA may consider initiating rulemaking to raise the

lower limit for the low pressure warning signal.

Authority: 49 U.S.C. 30103 and 30162; delegations of authority

at 49 CFR 1.50 and 501.8.

Issued on: July 14, 1994.

Stanley R. Scheiner,

Acting Associate Administrator for Rulemaking.

[FR Doc. 94-17589 Filed 7-19-94; 8:45 am]

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