Interpretation ID: aiam1472
Director of Transportation
Heavy & Specialized Carriers Conference of American Trucking Associations
1155 Sixteenth Street
N.W.
Suite 711
Washington
DC 20036;
Dear Mr. Hughes: This responds to your April 23, 1974, request for an explanation of th meaning and use of the term 'Gross axle weight rating' (GAWR) in Federal motor vehicle safety standards.; The concept of GAWR and 'Gross vehicle weight rating (GVWR) ar interrelated, and the two terms are defined as follows:; >>>'Gross axle weight rating' or 'GAWR' means the value specified b the manufacturer as the load-carrying capacity of a single axle system, as measured at the tire-ground interfaces.; 'Gross vehicle weight rating' or 'GVWR' means the value specified b the manufacturer as the loaded weight of a single vehicle.<<<; In both cases it is the manufacturer who specifies the values, and h is free to specify whatever values he himself decides are correct. Both the NHTSA in its compliance tests, and the Bureau of Motor Carrier Safety on the road, will judge the vehicle on the basis of the values assigned. Therefore it is in the interest of the manufacturer to assign values which accurately reflect the load-bearing ability of the vehicle and its suspension.; The sum of the GAWR's must at least equal the specified GVWR to avoi overloading the axle systems, and the GAWR sum may, of course, exceed the GVWR. Typically the manufacturer balances the commercial advantage of specifying a higher GVWR against the expense of higher GAWR's.; The GAWR is measured at the tire-ground interfaces which means that th tires, wheels, brakes and suspension components are included in the determination. Typically an axle assembly is rated by its manufacturer, who takes into account the braking ability of the axle to stop the load. Although this factor should always have been taken into consideration, the advent of Standard 121 may cause axle and brake manufacturers to reassess the values they have assigned to brake systems in the past.; Yours truly, Richard B. Dyson, Assistant Chief Counsel