Interpretation ID: aiam2365
Staff Engineer
Blue Bird Body Company
P.O. Box 937
Fort Valley
GA 31030;
Dear Mr. Milby: This responds to Blue Bird Body Company's June 21, 1976, questio whether S5.3.1 of Standard No. 121, *Air Brake Systems*, requires the installation of an antilock system, or whether the stopping distance and 'no lockup' requirements may be met using modulation of the service brake control by the vehicle driver.; Section S5.3.1 requires that vehicles subject to it must be capable o stopping under specified conditions, within the stopping distance set forth in Table II without leaving a 12- foot-lane and without 'uncontrolled' lockup of certain wheels of the vehicle. There is no requirement for the installation of an antilock system. Also, there is no test condition that specifies a full brake application and modulation of the service brake may be used to reduce or eliminate lockup.; Yours truly, Frank Berndt, Acting Chief Counsel