Interpretation ID: aiam2031
8400 East Slauson Avenue
Pico Rivera
CA 90660;
Dear Mr. Johnson: This responds to Motac's August 7, 1975, request for a determinatio that two platform trailers which are designed with a primary cargo-carrying surface which is less than 40 inches above the ground would qualify for exclusion from the requirements of Standard No. 121, *Air Brake Systems*, if manufactured before September 1, 1976.; I have enclosed a copy of the amendment to Standard No. 121 whic excludes heavy hauler trailers from the requirements of the standard until September 1, 1976. You should note that the '40-inch cargo-carrying surface' criterion is measured in the unloaded condition, and that the body must not be equipped with sidewalls unless they are easily removable.; There is no requirement that the vehicle be designed for a certain typ of cargo such as heavy machinery. Therefore your semi-trailers may qualify for the exclusion if they meet the criteria listed in the definition of heavy hauler trailer.; Sincerely, James B. Gregory, Administrator