Some states, such as Arizona, use the FBF to determine the axle weights for overweight vehicles.32 The Federal Bridge Formula B33 is defined as: W = [LN/N-1 + 12N + 36] where: W = the maximum weight in pounds that can be carried by a group of two or more axles to the nearest 500 pounds L = the distance between the outer axles of the group N = the number of axles in the considered group The FBF is