High profile vehicles such as SUVs, vans and trucks are likely to roll over in a loss of control yaw or a post-impact spinout. This side slide tipping mechanism occurs when the available tire/pavement friction factor *f* is greater than the ratio of one-half the track width *w* to the height *h* of the center of gravity where both *w* and *h* are adjusted for tire bending and compression, suspension yielding, and load shifting. That is, *f* > *w*/2*h*.

Low profile passenger cars will generally not roll over when sliding sideways unless tripped by striking a curb or other object, or by furrowing into soft ground. The minimum velocity required to induce a complete rollover can be found by using conservation of energy to determine the kinetic energy and, therefore, the velocity required to raise the center of gravity to *CG’* as shown in the diagram below.Equating the kinetic energy * *to the change in potential energy

yields

where

This velocity *V* is simply the minimum value required to produce a rollover, but is not necessarily the actual speed at the initiation of the rollover caused by this tripping event.

There are currently available computer programs for use in the analysis of the rollovers due to tripping and/or tipping that may, due to some apparent confusion, be incorrectly applied. It is important to distinguish between these two rollover mechanisms and to realize that neither can be used to determine the actual vehicle speed at the initiation of the rollover.

A more detailed discussion of rollovers, including derivation of the preceding formulae, can be found in *Highway Accidents: Investigation, Reconstruction and Causation* available at: Amazon.com. Information about the book and author is available at: www.bmorrow.com.