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.