Estimating Truck's Critical Cornering Speed and Factor of Safety

Abstract

Fully laden trucks are prone to rollover when exceeding a critical cornering speed. After an accident, authorities, both highway engineers and the police, often need to establish a vehicle's speed from tire marks and other physical evidence. This paper outlines the relative precision of equations of varying complexity used to estimate a truck's critical rollover speed based on tire marks. An error analysis is compared with a limited tachometer data base to evaluate the accuracy of the speed-estimating equations. The study shows that for most situations with fully laden, rigid trucks, the simple lumped-parameter model gives an acceptable estimate of the rollover speed for highway design engineers and the police. Also, a review of the lateral acceleration generated by a vehicle negotiating a minimum-radius curve found that the acceleration is very close to the level needed to tip over a truck. Based in part on these findings a method for developing a reasonable estimate of level of safety is discussed.