The Surface Transportation Assistance Act of 1982 caused significant changes in US truck transportation and truck configurations. The act made possible the increased usage of vehicles with setback front axles, which represents an important development. Trucks with setback front axles offer several improved performance characteristics which contribute to higher vehicle productivity and safety.
The STAA, however, did not change the Federal Bridge Formula-B. Constraints prevail on the usage of setback axle vehicles in many truck operations, notably those depending on shorter trucks or trailers, and especially those hauling high density commodities.
Ongoing research activities concerning future revision of the bridge formula offer a positive outlook to eliminating the gross vehicle weight penalties related to the placement of front axles. The paper analyzes how current size, weight and bridge formula constraints affect front axle placement and reviews the ride quality, maneuverability, entry and egress, and other benefits of the setback axle configuration.