Interpretation ID: aiam2487
Kelsey-Hayes Company
Romulus
MI 48174;
Dear Mr. McCuen: This responds to Kelsey-Hayes Company's November 29, 1976, questio 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 no 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 valve 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 valve that is common to both sides of a 'split' service brake system.; Sincerely, Frank Berndt, Acting Chief Counsel