Interpretation ID: aiam3134
Chief Engineer
Brake Products
Wagner Electric Corporation
11444 Lackland Road
St. Louis
MO 63141;
Dear Mr. Kourik:This responds to your September 17, 1979, letter askin whether Standard No. 121, *Air Brake Systems*, permits manufacturers to install antilock devices on only one axle of a multi-axle vehicle. The answer to your question is yes.; As you know, the decision in *PACCAR v. NHTSA*, 573 F.2d 632 (9th Cir 1978), *cert. den'd; , 439 U.S. 862 (Oct. 2, 1978) invalidated the antilock requirements a they apply to trucks and trailers. Accordingly, the antilock provisions of the standard no longer apply to those vehicles. A manufacturer that desires to install antilock devices can do so at its own discretion and to any extent that it considers appropriate. This includes the installation of antilock devices on only one axle. Of course, any installation of devices affecting braking must not impair the brake system's compliance with the standard.; Sincerely, Frank Berndt, Chief Counsel