The Truck Trailer Manufacturers Association has expressed concern about a recent proposal to change the way gross combination weight rating is determined.
In a letter to the Federal Motor Carrier Safety Administration, TTMA engineering manager John Freiler said the proposal that appeared in the May 7 Federal Register could lead to overloaded and unsafe vehicles.
The notice of proposed rulemaking would allow the GCWR to be the tractor manufacturer’s rating listed on the FMVSS certification label.
“Given the complexity of power units and trailers that may be combined, we suggest that the rule for GCWR proposed be amended to show that in no case shall the GCWR exceed the sum of the gross axle weight ratings (GAWR) of the power unit and the towed unit(s),” Freiler wrote.
TTMA has published a recommended practice for determining GAWR and GVWR for truck trailer certification. According to that document, the gross axle weight rating and gross vehicle weight rating each independently imposes its own restriction on trailer loading. Therefore, the maximum permissible load should be determined by either the GAWR of each axle or by the GVWR, whichever is the most restrictive.