Interpretation ID: 77-1.7

TYPE: INTERPRETATION-NHTSA

DATE: 01/18/77

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Kelsey-Hayes Company

TITLE: FMVSS INTERPRETATION

TEXT: This responds to Kelsey-Hayes Company's November 29, 1976, question whether an antilock valve (incorporating the function of a relay valve) is subject to the requirement of S5.7.1 of Standard No. 121, Air Brake Systems, that a truck or bus be capable of stopping within a specified distance following failure in the service brake system of a part designed to contain compressed air or brake fluid (with the exception of certain parts that are common to both sides of a "split" service brake system).

From your description, the antilock valve in question, whether or not it incorporates the function of a relay valve, is a part of the service brake system designed to contain compressed air, and would be one of the components whose failure would be subject to the requirement of S5.7.1. I assume that the value would be in the subsystem to the front axle or to the rear axles of a truck or bus and, as such, would not be a value that is common to both sides of a "split" service brake system.

Sincerely,

ATTACH.

KELSEY-HAYES COMPANY

November 29, 1976

Frank Berndt -- Chief Counsel, National Highway Traffic Safety Administration

RE: Request For Interpretation FMVSS-121 Air Brake Systems S 5.7.1 Emergency Brake System Performance

Dear Mr. Berndt:

Kelsey-Hayes Company hereby requests an interpretation of the above cited provision. Specifically, we ask whether an antilock air valve, which incorporates the function of a relay valve, constitutes a part designed to contain compressed air, such that a failure of this valve requires conformance to the emergency brake system performance requirements.

Your prompt attention to this request will be appreciated.

Very truly yours, John F. McCuen -- COUNSEL