Bridge Formula Law and Legal Definition

For determining the legality of a tractor-trailer's gross weight, an officer can apply the overweight formula, commonly known as the bridge formula. The bridge formula is found in 23 USCS § 127, which sets the allowable vehicle weights on the Interstate highways. The bridge formula was designed to protect bridges from catastrophic overloads by restricting the weight of each of a vehicle's axle groupings and by limiting vehicle gross weight. The Motor Carrier handbook includes a reference table, which permits operators to calculate the maximum gross weight allowable, without having to actually solve the formula codified in the statute.