Federal Motor Vehicle Safety Standards; Air Brake Systems Control Line Pressure Balance

DEPARTMENT OF TRANSPORTATION

49 CFR Part 571

[Docket No. 85-07; Notice 9]

RIN 2127-AF23

Federal Motor Vehicle Safety Standards; Air Brake Systems Control

Line Pressure Balance

AGENCY: National Highway Traffic Safety Administration (NHTSA),

Department of Transportation.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: In response to a petition for rulemaking submitted by Sealco

Air Controls, Inc., this notice proposes to amend the control line

pressure differential requirements in Standard No. 121, Air Brake

Systems, for converter dollies and trailers designed to tow another

vehicle equipped with air brakes. The agency has tentatively concluded

that the proposed amendments would improve the braking compatibility of

such vehicles by allowing the use of a relay valve known as a spool-

type low opening valve. The agency does not anticipate any adverse

safety consequences resulting from amending the pressure differential

requirements.

DATES: Comments. Comments must be received on or before September 12,

1994.

Proposed effective date. The proposed amendments in this notice

would become effective 30 days after publication of a final rule in the

Federal Register.

ADDRESSES: Comments should refer to the docket and notice numbers above

and be submitted to: Docket Section, National Highway Traffic Safety

Administration, 400 Seventh Street, S.W., Washington, D.C. 20590.

Docket hours are 9:30 a.m. to 4 p.m., Monday through Friday.

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

Safety Standards, National Highway Traffic Safety Administration, 400

Seventh Street, S.W., Washington, D.C. 20590. (202-366-6761).

SUPPLEMENTARY INFORMATION: Standard No. 121, Air Brake Systems,

establishes performance and equipment requirements for braking systems

on vehicles equipped with air brakes, including requirements for

pneumatic timing. For purposes of compliance testing, the pneumatic

timing tests for trailers, including trailer converter dollies, are

conducted with the trailer connected to a test rig rather than an

actual tractor. The test rig delivers air to, and releases air from,

the trailer during the timing test. The timing tests for vehicles

designed to tow trailers are conducted with a 50 cubic inch reservoir

connected to rear control line coupling. This reservoir represents the

control line volume of the control trailer used in the compliance

testing.

On August 21, 1992, NHTSA published a final rule amending the

pneumatic timing requirements of Standard No. 121 with respect to the

control signal pressure balance for tractor trailer combinations. (57

FR 37902). The agency added S5.3.5 which specifies a new test procedure

for determining the control line pressure differential in converter

dollies and trailers designed to tow another trailer equipped with air

brakes. Specifically, the rule requires that the pressure differential

between the control line input coupling and a 50 cubic inch test

reservoir shall not exceed 1 psi at all input pressures between 5 psi

and 20 psi and 2 psi at all input pressures greater than 20 psi. Agency

research indicates that input pressures below 20 psi represent routine

braking applications, input pressures between 20 psi and 40 psi

represent moderate to heavy braking applications, and input pressures

above 40 psi represent severe braking applications. As explained below,

NHTSA is proposing to modify the limit above 40 psi to allow a 5

percent differential (which at higher pressures exceeds the current

limit of 2 psi) based on the Society of Automotive Engineer's (SAE's)

Recommended Practice SAE J1505, Brake Force Distribution Test Code

Commercial Vehicles.

The agency explained that the amendment is designed to ensure that

the control signal ``passes'' through a towing trailer or dolly without

being altered along the way. Since the control signal passes through

unaltered, each vehicle in a combination unit receives the same brake

control signal. This serves to increase the braking compatibility of

combination vehicles since each vehicle in a combination has comparable

braking performance.

Sealco Petition

On June 18, 1993, Sealco Air Controls, Inc. (Sealco), a valve

manufacturer, submitted to NHTSA a rulemaking petition to amend

Standard No. 121 with respect to the control line pressure differential

requirements in S5.3.5. Specifically, it requested that NHTSA amend

these requirements to permit the manufacture of its low opening valves

that serve to adjust air flow in control lines. These valves are used

as control line relay valves and service line relay valves in trailers

and converter dollies. The petitioner stated that unlike other relay

valves that use a common poppet,1 the low opening valves have a

balanced spool technology2 that incorporates a low pressure at

which the valve initially opens (i.e., crack pressure) of 1.5 psi.

According to Sealco, the spool technology enables the valve to track

closer between the input control air pressure and the output delivered

air pressure. As a result, it claimed that hysteresis3 is not so

prevalent with low operating valves as with the high crack pressure

poppet design valves.

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\1\ A rising and falling valve consisting of a disc at the end

of a vertically set stem.

\2\ A valve whose primary means of diverting pressure or flow is

through movement of a cylindrical valve mechanism along its axis.

\3\ The time lag in a system in reacting to changes in the

forces affecting it. With respect to braking, the relay valve's

output (apply pressure) lags more than a few psi behind ascending

control line (treadle) pressure, and stays more than one or two psi

above descending control line pressure. Complications may arise when

a second brake application is made before the first one is fully

released.

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Hysteresis in a valve may cause the valve not to track (i.e.,

follow closely) the control line pressure properly, which may cause the

brakes in the trailer to lag behind the control signal. For example,

when the driver applies the brakes, the valve's hysteresis may not

allow the same pressure to be applied to the trailer brakes, which will

cause less braking in the trailer and cause the trailer to ``push'' the

tractor. Similarly, when the driver releases the brake, the hysteresis

in the valve may not allow the brakes in the trailer to be released

quickly enough and will still have the brakes applied while the driver

is trying to accelerate, causing the kingpin to jerk on the inside of

the fifth wheel. On more extreme conditions where the driver goes

through several fast brake applications and releases in rapid

succession, the jerking and pushing of the trailer or trailers could be

difficult to control.

Sealco stated that the use of low operating valves would further

NHTSA's goal of ensuring balanced braking in combination vehicles.

However, the petitioner claimed that while its valve meets the

amendment's application requirements, it does not meet the provision

requiring release at high pressure ranges, given the valve's mechanics.

To comply with the amendment, Sealco has drilled a hole in the valves'

piston, thereby allowing pressure to bleed to the supply side. This

action prevents the valves from cracking open when tested according to

S5.3.5. Sealco believes that this modification to allow compliance with

the amendment has reduced the valves' effectiveness. Sealco also

criticized the test procedure which it believed did not simulate actual

braking conditions. It stated that slow and fast ascending and

descending control line pressures should be used to check the valves'

ability to respond appropriately.

Agency's Decision To Issue Proposal

After reviewing the petition, NHTSA has decided to propose an

amendment to Standard No. 121 to permit the use of low operating

valves. Specifically, the agency is proposing to amend S5.3.5 to

account for input pressures over 40 psi. Under the proposal, the

pressure differential would not be permitted to exceed 2 psi at any

input pressure between 20 psi and 40 psi and it would not be permitted

to exceed 5 percent at any pressure over 40 psi. In other words, the

pressure differential requirements would remain the same, except for

applications resulting in pressures over 40 psi. The agency requests

comments about whether the modification to pressure levels over 40 psi

is appropriate.

NHTSA is proposing the value of 40 psi based on SAE J1505, Brake

Force Distribution Test Code Commercial Vehicles. The agency has

tentatively determined that the safety problem addressed by the

requirement in S5.3.5, i.e., slow heat build up and brake fade caused

by long gradual down hill runs at relatively low air pressure, is not a

problem for severe brake applications over 40 psi. In formulating this

proposal, NHTSA contacted all the major valve manufacturers. Other than

Sealco, no other valve manufacturer stated that they had to drill holes

in the valve or otherwise modify the valve in a way that might

adversely affect their real-world dynamic braking performance in order

to comply with the test in S5.3.5. Aside from Sealco, the valve

manufacturers believed that the existing test was a realistic,

reasonable assessment of low pressure differential performance.

NHTSA has tentatively determined that this amendment would

facilitate the use of spool valve technology, while not being

detrimental to safety. The agency's primary concern in these

rulemakings addressing control line pressure differentials is brake

performance in the low end of the air pressure range since the vast

majority of stopping occurs there. Specifically, in the August 1992

rule, the agency sought to improve low end brake performance with

respect to slow heat build up and brake fading brought about by

relatively low brake applications during long gradual downhill

descents.

After further review, the agency now believes that the current

requirement may unnecessarily extend the 2 psi requirement into the

higher pressure ranges where it is not necessary for safety. As noted

above, the requirement is designed to prevent brake fade during

relatively low brake applications below 20 psi and is not applicable to

hard brake applications, i.e., those exceeding 40 psi. Accordingly, the

agency has tentatively decided to modify the differential requirements

at levels over 40 psi. Notwithstanding the agency's tentative

conclusion, the agency request comments about whether this amendment

poses any risk of adverse safety consequences.

However, NHTSA disagrees with Sealco's statements that the test

procedure in S5.3.5 does not simulate actual braking conditions. The

agency notes that this test procedure was based on the agency's own

testing and extensive test data and recommendations by trailer

manufacturers in response to previous agency proposals. Specifically,

the agency disagrees with Sealco's statement that ``Slow and fast

ascending and descending control line pressures should be used to check

CLV performance.'' As discussed in earlier notices, NHTSA sought

pressure rises and decays that were neither too fast nor too slow. As

trailer manufacturers and other commenters to the earlier proposal

stated, if the pressure rise were too slow, test personnel would waste

time waiting for the event to occur, and if the pressure rise were too

rapid, pressure differentials could not be read quickly enough. In

addition, pressure surges from a fast rate would likely result in a

loss of normal valve hysteresis and subsequent errors in crack pressure

readings. Accordingly, the agency believes that the test accurately

evaluates real-world dynamic braking without creating any significant

negative safety effects.

Rulemaking Analyses and Notices

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

DOT Regulatory Policies and Procedures

This proposal was not reviewed under E.O. 12866. NHTSA has analyzed

this proposal 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, if adopted, would have no mandatory effects. Instead, the

proposal would permit spool valve technology. Therefore, this

rulemaking would not have any cost impacts.

2. Regulatory Flexibility Act

In accordance with the Regulatory Flexibility Act, NHTSA has

evaluated the effects of this action on small entities. Based upon this

evaluation, I certify that the proposed amendment would not have a

significant economic impact on a substantial number of small entities.

Vehicle and brake manufacturers typically would not qualify as small

entities. This amendment would affect small businesses, small

organizations, and small governmental units to the extent that these

entities purchase vehicles. However, this amendment would not have any

cost impact on vehicles. For these reasons, vehicle manufacturers,

small businesses, small organizations, and small governmental units

which purchase motor vehicles would not be significantly affected by

the proposed requirements. 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 proposed rule would not have sufficient Federalism

implications to warrant preparation of a Federalism Assessment. No

State laws would be affected.

4. National Environmental Policy Act

Finally, the agency has considered the environmental implications

of this proposed rule in accordance with the National Environmental

Policy Act of 1969 and determined that the proposed rule would not

significantly affect the human environment.

5. Civil Justice Reform

This proposed rule would 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.

Public Comments

Interested persons are invited to submit comments on the proposal.

It is requested but not required that 10 copies be submitted.

All comments must not exceed 15 pages in length. (49 CFR 553.21).

Necessary attachments may be appended to these submissions without

regard to the 15-page limit. This limitation is intended to encourage

commenters to detail their primary arguments in a concise fashion.

If a commenter wishes to submit certain information under a claim

of confidentiality, three copies of the complete submission, including

purportedly confidential business information, should be submitted to

the Chief Counsel, NHTSA, at the street address given above, and seven

copies from which the purportedly confidential information has been

deleted should be submitted to the Docket Section. A request for

confidentiality should be accompanied by a cover letter setting forth

the information specified in the agency's confidential business

information regulation. 49 CFR Part 512.

All comments received before the close of business on the comment

closing date indicated above for the proposal will be considered, and

will be available for examination in the docket at the above address

both before and after that date. To the extent possible, comments filed

after the closing date will also be considered. Comments received too

late for consideration in regard to the final rule will be considered

as suggestions for further rulemaking action. The NHTSA will continue

to file relevant information as it becomes available in the docket

after the closing date, and it is recommended that interested persons

continue to examine the docket for new material.

Those persons desiring to be notified upon receipt of their

comments in the rules docket should enclose a self-addressed, stamped

postcard in the envelope with their comments. Upon receiving the

comments, the docket supervisor will return the postcard by mail.

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 proposes to amend 49

CFR Part 571 as follows:

PART 571--[AMENDED]

1. The authority citation for Part 571 would be revised 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, S5.3.5 introductory text and S5.3.5(a) would be

revised to read as follows:

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

* * * * *

S5.3. 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) and (2) under the conditions specified in S5.3.5(b) (1) through

(4)--

(1) 1 p.s.i. at all input pressures equal to or greater than 20

p.s.i., but not greater than 20 p.s.i.; and

(2) 2 p.s.i. at all input pressures from 20 p.s.i. to 40 p.s.i.;

and

(3) not more than a 5 percent differential at any input pressures

above 40 p.s.i.

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Issued on July 6, 1994.

Patricia P. Breslin,

Acting Associate Administrator for Rulemaking.

[FR Doc. 94-16913 Filed 7-12-94; 8:45 am]

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