Drag Factor Attenuation for Rotating Vehicles

An often misunderstood concept in the field of crash reconstruction is the effect yaw rotation has on vehicle deceleration and the associated drag factor. In order to quantitatively investigate this effect, a series of parametric dynamic vehicle simulations, encompassing a wide range of vehicle rotation rates, translational velocities, and frictional conditions, were carried out. Results of this analysis show that even for scenarios in which all wheels/tires are locked, vehicles that undergo significant yaw rotation relative to their translational movement, exhibit effective drag factors that are well below the values exhibited during straight-line braking. The analysis also demonstrated that for vehicle maneuvers that involve rotation, there exists a well defined nonlinear relationship between the effective vehicle drag factor and the distance the vehicle travels per rotation. Relationships defined in this paper were developed with input variable requirements that comport with routinely available scene data, and can therefore be used by the practicing crash reconstructionist to evaluate real-world crashes involving vehicle yaw rotation.