Past research has shown that vehicles, especially large trucks, offtrack on curves and turns; at low speeds the rear axles track inside the front axle (negative offtracking), and at sufficiently high speeds the reverse is true. New research shows that typical amounts of superelevation tend to increase low-speed, negative offtracking of trucks by 10 to 20%. Superelevation also tends to reduce the amount of high-speed outward offtracking. The magnitude of the superelevation effect is independent of speed. The superelevation effect is greater with more heavily loaded trucks, trucks with newer tires, and trucks with larger roll steer coefficients. This research also shows that body roll affects both high-speed offtracking and the superelevation contribution to total offtracking. Trucks with softer suspensions are more affected. The net effect is to increase outward offtracking at normal and high speeds and to slightly increase negative offtracking at very low speeds.
Abstract