Figure 1

Figure 2

Federal law states two or more consecutive axles may not exceed the weight computed by the Bridge Formula (Figure 1) even if single axles, tandem axles, and gross vehicle weights are within legal limits. The axle group that includes the entire truck — sometimes called the “outer bridge” group — must comply with the Bridge Formula. Interior combinations of axles such as the “tractor bridge” [1, 2, 3] and “trailer bridge” [2, 3, 4, 5] must also comply with weights computed by the Bridge Formula (see Figure 2).

The maximum gross vehicle weight allowed by 23 USC 127 is 80,000 lbs, except where a lower gross vehicle weight is dictated by the Bridge Formula. For further details see 23 CFR Part 658.

All information provided by the Office of Operations, Federal Highway Administration, U.S. Department of Transportation