Interpretation ID: 1982-2.28

DATE: 08/01/82

FROM: AUTHOR UNAVAILABLE; Diane K. Steed; NHTSA

TO: Larry Pressler; U.S. Senate

TITLE: FMVSS INTERPRETATION

TEXT:

Dear Senator Pressler:

This responds to your July 23, 1982, letter enclosing correspondence from your constituent, Mr. Clyde Pritchard. Mr. Pritchard questioned the applicability of the National Highway Traffic Safety Administration's Standard No. 121, AirBrakes, to certain "heavy hauler trailers." He also questioned a portion of that standard that indicated that manufacturers of some vehicles may comply with the standard or, alternatively, with Part 393.43 of the regulations of the Bureau of Motor Carrier Safety (BMCS).

Only some types of heavy hauler trailers must comply with Standard No. 121. The applicability section of the standard states that a vehicle with a width in excess of 102 inches or a heavy hauler trailer with a gross vehicle weight rating (GVWR) in excess of 120,000 pounds need not comply with any of the requirements. Therefore, any vehicle designed by Mr. Pritchard falling within these categories would be excepted from the standard. A heavy hauler trailer with a width less than 102 inches and a GVWR less than 120,000 must comply with the standard.

Mr. Pritchard appears most interested in the specific requirements for parking brakes on heavy hauler trailers. Paragraph S5.6 of Standard No. 121 states that heavy hauler trailers shall comply with the requirements of Standard No. 121 for parking brakes or, alternatively, with BMCS regulation 393.43 for breakaway. Accordingly, the manufacturer of such a vehicle has the option of complying with either provision; parking brakes under Standard No. 121 or the breakaway and emergency braking section of the BMCS regulation. The citation in Standard No. 121 to BMCS regulation 393.43 is correct. The agency did not intend to permit optional compliance with BMCS regulation 393.41 as suggested by Mr. Pritchard. That regulation does not require separate brakes on trailers which the agency has always deemed necessary.

I hope this clarifies the air brake issue for your constituent. Please contact me if you need additional information.

Diane K. Steed Administrator