Interpretation ID: aiam1698
Vice President
H & H Equipment Co.
6050 14th Street
Detroit
MI 48208;
Dear Mr. McGee: This is in response to your letter of November 20, 1974, asking whethe a 'moving van' trailer which utilizes an air over hydraulic brake system is required to comply with Standard No. 121, *Air brake systems*.; 'Air brake system' is defined in S4. of the standard as 'a system tha uses air as a medium for transmitting pressure or force from the driver control to the service brake, but does not include a system that uses compressed air or vacuum only to assist the driver in applying muscular force to hydraulic or mechanical components.'; Since your trailer utilizes air as a medium for transmitting force fro the trailer 'glad hands' to the air/hydraulic actuator, it qualifies as an air brake system and must comply with Standard No. 121.; Yours truly, Richard B. Dyson, Acting Chief Counsel