Measurement and Modeling of Rollover Airborne Trajectories 2009-01-0109
Much has been written about reconstruction techniques and testing methods concerning vehicle rollovers. To date, most of the literature describes rollovers as one-dimensional events. Rollovers account for a disproportionate fraction of serious injuries and fatalities among all motor vehicle accidents. The three-dimensional nature of rollover sequences in which a rolling vehicle experiences multiple ground contacts contributes to the environment where such injuries occur.
An analytical technique is developed to model the airborne segments of a rollover sequence as a parabolic path of the vehicle center of gravity. A formulation for the center of gravity descent from maximum elevation to full ground contact is developed. This formulation contains variables that may be readily determined from a thorough reconstruction. Ultimately, this formulation will also provide a vertical ground impact velocity at contact.
Measurements of airborne segments from two high-speed rollover events – a dolly rollover test and a real-world rollover crash - are presented as a basis to evaluate the model. The ability to theoretically model two-dimensional trajectory paths is demonstrated and the concept of an effectively airborne rollover segment is presented. Comparisons between vehicle descent predicted by the model and from the rollover tests are presented.
The measured values of descent distance from the rollover tests generally slightly exceed the predicted values. It is shown that accuracy may be improved by careful selection of drag factors based on non-uniform over-the-ground deceleration observed in on-road and soft surface vehicle rollover events. The application of the trajectory model to obtain vertical vehicle motion in real-world rollover crashes involves reconstruction based on the topography of the rollover path and physical evidence related to ground contacts.