Interpretation ID: aiam2511
Harley Murray
Inc.
1754 E. Mariposa Road (So. Highway 99)
Stockton
CA 95206;
Dear Mr. Murray: This responds to your January 25, 1977, question whether a row of eigh wheels arranged in a line that is perpendicular to the longitudinal axis of a vehicle constitute an 'axle' as that word is used in S3(b) of Standard No. 121, *Air Brake Systems*. You note that the wheels are not mounted on a single solid axle but rather are mounted on two walking beam assemblies that also constitute the suspension for a separate set of eight wheels across the vehicle.; The answer to your question is yes. When asked for a definition o 'axle system' in connection with Standard No. 121, the National Highway Traffic Safety Administration stated:; >>>In answer to Wagner's request for a definition of 'axle system,' th term is used in the same sense as it is used in the definition of GAWR found at 49 CFR 571.3. 'Axle system' is used instead of 'axle' to avoid confusion in situations where a suspension system does not employ an axle. The term has not created difficulty in the GAWR definition (39 FR 17553, May 17, 1974).<<<; The agency's use of 'axle' in S3 is intended to be identical to its us of the phrase 'axle system.' Thus, 'axle' means the arrangement of wheels that lie across the vehicle in a line that is perpendicular to the longitudinal centerline of the vehicle. This understanding of 'axle' and 'axle system' is used regularly in the assignment of gross axle weight ratings (GAWR) on vehicles that employ independent suspensions in place of solid axles.; From your description, it appears that each row of eight wheels on you trailer constitutes an 'axle' or 'axle system' that could be rated at a GAWR in excess of 29,000 pounds, qualifying the vehicle for exclusion from Standard No. 121.; Sincerely, Frank A. Berndt, Acting Chief Counsel