Federal Motor Vehicle Safety Standards; Air Brake Systems; Air Compressor Cut-In

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. 90-3; Notice 7]

RIN 2127-AF63

Federal Motor Vehicle Safety Standards; Air Brake Systems; Air

Compressor Cut-In

AGENCY: National Highway Traffic Safety Administration (NHTSA),

Department of Transportation.

ACTION: Final rule, petitions for reconsideration.

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SUMMARY: In response to a petition for reconsideration submitted by

Flxible Corporation, this document amends Standard No. 121, Air Brake

Systems, with respect to the air pressure at which a bus's air

compressor must automatically activate. A bus manufacturer will be

allowed to set the air compressor governor cut-in pressure at 85 psi or

greater. The agency believes that allowing the air pressure to fall to

85 psi or greater, instead of 100 psi or greater, before the air

compressor is required to cut in, provides a more appropriate

activation pressure that accounts for the severe duty cycle experienced

by some buses. By reducing the frequency of compressor operation, this

modification will reduce potential safety problems caused by the air

compressor introducing engine oil into the vehicle's air system.

DATES: Effective date. The amendment becomes effective January 28,

1997.

Compliance date. Compliance with the amendment will be required on

and after March 1, 1997.

Petitions for reconsideration. Any petitions for reconsideration of

this rule must be received by NHTSA no later than January 13, 1997.

ADDRESSES: Petitions for reconsideration of this rule should refer to

the above referenced docket numbers and should be submitted to:

Administrator, National Highway Traffic Safety Administration, 400

Seventh Street, S.W., Washington, D.C. 20590.

FOR FURTHER INFORMATION CONTACT:

For non-legal issues: Mr. Richard Carter, Office of Crash

Avoidance, National Highway Traffic Safety Administration, 400 Seventh

Street, SW., Washington, D.C. 20590 (202) 366-5274.

For legal issues: Mr. Marvin L. Shaw, NCC-20, Rulemaking Division,

Office of Chief Counsel, National Highway Traffic Safety

Administration, 400 Seventh Street, SW., Washington, D.C. 20590 (202-

366-2992).

SUPPLEMENTARY INFORMATION:

I. Background

Standard No. 121, Air Brake Systems, specifies performance and

equipment requirements for braking systems on vehicles equipped with

air brakes, including a requirement specifying the minimum air pressure

at which a vehicle's air compressor governor must automatically

activate the compressor, thereby increasing air pressure in the air

brake system. (See S5.1.1.1) The governor maintains reservoir air

pressure between predetermined minimum and maximum pressures.

II. February 1996 Final Rule

In response to a petition for rulemaking submitted by the Truck

Trailer Manufacturers Association (TTMA), NHTSA amended S5.1.1.1 to

require the automatic activation of the air compressor on a powered

vehicle whenever the pressure in the air brake system falls below 100

pounds per square inch (psi) (61 FR 6173, February 16, 1996). Prior to

the February 1996 final rule, the air compressor was required to

automatically activate whenever the air pressure in the reservoir fell

below 85 psi. Manufacturers of air braked vehicles are required to

comply with this amendment on and after March 1, 1997.

Enhanced truck tractor performance is the primary goal of the

February 1996 amendment, which ensures that new air braked truck

tractors are capable both of providing trailers with sufficient

pressure for release of the trailer parking brakes and of providing

adequate service braking. By raising the cut-in pressure, an additional

quantity of stored compressed air will be available for an air brake

system. In addition, requiring an overall higher system air pressure

will allow a better balance between protection valve settings between

the tractors and trailers.

Because NHTSA determined that the change in compressor cut-in

pressure will benefit single-unit trucks and buses as well as truck

tractors, the agency applied the change to all powered vehicles. A

higher cut-in pressure provides a margin of safety for vehicles

equipped with long-stroke chambers and antilock brake systems which

consume more air than conventional brake systems. NHTSA anticipated no

safety problems as the result of the February 1996 amendment. The

agency further anticipated that the amendment would not result in an

undue burden for manufacturers, since most vehicles already complied

with the cut-in requirement.

III. Petition for Reconsideration

On March 4, 1996, Flxible Corporation (Flxible), a manufacturer of

air-braked transit buses, petitioned NHTSA to amend the air compressor

cut-in requirements in Standard No. 121 with respect to buses. It

stated that while the amended requirements were appropriate for truck

tractors, the automatic cut-in pressure requirements should not have

been raised from 85 psi to 100 psi for city transit buses. The

petitioner stated that the air brakes on buses do not experience the

same conditions as those on tractors. Therefore, it stated that the

rule should not be applied to vehicles other than truck tractors,

without a full understanding of the potential problems and consequences

associated with that decision.

Flxible stated that transit buses have a unique duty cycle that

requires more frequent brake applications than other vehicles. It

further stated that the air brake systems on transit buses are

connected to unique air consuming devices and systems that almost

continuously consume air. These devices and systems include air

operated door systems, air operated kneeling systems, air consuming

brake interlocks, and air throttles on mechanical engines.

Flxible stated that higher governor cut-in pressures result in

higher compressor pumping pressures. Frequent air depletion by the

various on-vehicle devices causes the compressor to operate on an

almost continuous duty cycle. This severe duty cycle, combined with the

new higher pumping pressures, causes the air compressor to introduce

greater quantities of engine oil into the vehicle's air system, because

the air compressors must run a substantially

[[Page 60636]]

longer period of time. This condition occurs even on newer mileage

vehicles, and worsens with vehicle and component age. According to the

petitioner, oil carry-over can affect elastomeric seals, diaphragms and

other items in the vehicle air system. Such contamination may cause

components to stick or otherwise function in a manner that may

adversely affect brake timing. The result is costly system maintenance

and repair at more frequent than normally recommended service periods.

Flxible requested that the governor cut-in pressure setting be set

at 85 psi. Flxible stated that although it uses governors with higher

cut-in and cut-out pressures to meet specific vehicle in-service

conditions and requirements, it would like the option to use lower cut-

in pressures.

IV. Agency Determination

After reviewing Flxibles petition, NHTSA has decided to amend

Standard No. 121 with respect to the air pressure at which a bus's air

compressor must automatically activate. A bus manufacturer is allowed

to set the air compressor governor cut-in pressure at 85 psi or

greater. The agency believes that reducing the required automatic cut-

in pressure from 100 psi or greater to 85 psi or greater provides buses

with a more appropriate activation pressure that accounts for the

severe duty cycle experienced by some buses. This modification will

avoid potential safety problems caused by the air compressor

introducing engine oil into the vehicle's air system.

NHTSA believes that today's modification in the cut-in pressure

will not adversely affect the use of long-stroke brake chambers. After

reviewing the issue of air pressure depletion starting at 85 psi, 100

psi, and higher levels, the agency concludes that changing the

requirements to 85 psi will not interfere with the safe introduction of

long-stroke chambers.1 Therefore, the rationale for raising the

minimum cut-in pressure for single unit vehicles, i.e., to facilitate

the introduction of long-stroke chambers, is not undermined.

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\1\ Those data have been placed in the public docket.

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NHTSA anticipates that the practical affect of today's amendment

will be limited, because most air compressor governor settings are

preset by the air compressor manufacturers and not by the vehicle

manufacturers. NHTSA estimates that over 95 percent of air compressor

governors are set at 100 psi or greater. Flxible stated that it would

readjust only those units where it was determined to be necessary.

Accordingly, as a practical matter, in only a few special situations

will the air compressor cut-in pressure actually be activated at 85

psi.

V. Rulemaking Analyses and Notices

1. Executive Order 12866 (Federal Regulatory Planning and Review) and

DOT Regulatory Policies and Procedures

This rulemaking was not reviewed under E.O. 12866. NHTSA has

analyzed this rulemaking and determined that it is not ``significant''

within the meaning of the Department of Transportation's regulatory

policies and procedures. A full regulatory evaluation is not required

because the rule will have a minimal effect on the costs or performance

of the existing air brake systems. Today's amendment merely affords

greater flexibility to manufacturers of air-braked buses.

2. Regulatory Flexibility Act

In accordance with the Regulatory Flexibility Act, NHTSA evaluated

the effects of this action on small entities as part of the February

1996 final rule. Based upon that evaluation which remains valid, I

certify that the amendment will not have a significant economic impact

on a substantial number of small entities. Vehicle and brake

manufacturers typically do not qualify as small entities. Vehicle

manufacturers, small businesses, small organizations, and small

governmental units which purchase motor vehicles will not be

significantly affected by the requirements since the cost of new

vehicles will not change. Accordingly, no regulatory flexibility

analysis has been prepared.

3. Executive Order 12612 (Federalism)

This action has been analyzed in accordance with the principles and

criteria contained in Executive Order 12612, and it has been determined

that the rule will not have sufficient Federalism implications to

warrant preparation of a Federalism Assessment. No State laws will be

affected.

4. National Environmental Policy Act

Finally, the agency has considered the environmental implications

of this rule in accordance with the National Environmental Policy Act

of 1969 and determined that the rule will not significantly affect the

human environment.

5. Civil Justice Reform

This rule will not have any retroactive effect. Under section

103(d) of the National Traffic and Motor Vehicle Safety Act (49 U.S.C.

30111), 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. Section 105 of the Act (49 U.S.C. 30161) sets forth a

procedure for judicial review of final rules establishing, amending or

revoking Federal motor vehicle safety standards. That section does not

require submission of a petition for reconsideration or other

administrative proceedings before parties may file suit in court.

List of Subjects in 49 CFR Part 571

Imports, Motor vehicle safety, Motor vehicles, Rubber and rubber

products, Tires.

In consideration of the foregoing, the agency is amending Standard

No. 121, Air Brake Systems, in part 571 of title 49 of the Code of

Federal Regulations as follows:

PART 571--[AMENDED]

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

follows:

Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166;

delegation of authority at 49 CFR 1.50

2. In Sec. 571.121, S5.1.1.1 is revised to read as follows:

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

* * * * *

S5.1.1.1 Air compressor cut-in pressure. The air compressor

governor cut-in pressure for each bus shall be 85 p.s.i. or greater.

The air compressor governor cut-in pressure for each truck shall be 100

p.s.i. or greater.

* * * * *

Issued on: November 19, 1996.

Ricardo Martinez,

Administrator.

[FR Doc. 96-30055 Filed 11-27-96; 8:45 am]

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