Interpretation ID: aiam2234
Sales Engineer/Coordinator
Bock Products
Inc.
1901 West Hively Avenue
P.O. Box 1208
Elkhart
IN 46514;
Dear Mr. Fisher: This responds to your February 11, 1976, question whether two traile designs you describe would qualify as 'Heavy Hauler Trailer[s]' as defined in Standard No. 121, *Air Brake Systems*. A copy of that definition is enclosed for your information.; Both of your trailer designs include a primary cargo-carrying surfac that inclines from a height of 24 inches in the rear to a height of 47 inches in the front of the trailer. In one case, part of the inclined portion is removable, leaving a 6-foot length of the surface that is flat and 40 inches above the ground in the unloaded condition. In both cases somewhat more than one-half of the primary cargo-carrying surface is 40 inches or less in height.; The exclusion from Standard No. 121 for heavy hauler trailers applie (in relevant part) only to trailers 'whose primary cargo-carrying surface is not more than 40 inches above the ground in an unloaded condition.' The trailer designs you describe would not qualify for the exclusion, because only a portion of the surface qualifies as 'not more than 40 inches above the ground.'; Sincerely, Frank Berndt, Acting Chief Counsel