Proposed New Truck Weight Limit Formula

A formula for limiting truck and combination vehicle weights is proposed. The proposed formula gives the maximum allowable gross vehicle weight as a function of extreme axle spacing, and is intended to replace the existing formula which depends on the number of axles in the string as well as the extreme axle spacing. The advantages of the proposed formula over the existing formula are several. The existing formula does not prevent certain critical vehicles from operating on H15 bridges except by means of a footnote addendum. The proposed formula does protect H15 bridges against such vehicles. The existing formula does not provide adequately for economic operation of proposed long combinations of multiple trailers. An existing 80,000 lb gross vehicle weight limit presently prevents extension of the existing formula to the proposed longer vehicles. Should the existing 80,000 lb limit be increased or removed, the existing formula would not adequately protect HS20 bridges. The proposed formula will protect the bridges in the absence of such a limit.