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The accuracy of an accident reconstruction is dependent upon the availability and quality of relevant data. Often by the time an engineer is asked to reconstruct a traffic accident the only source of scene data is a police report. Important scene data, such as the point of impact and the points of rest of the vehicles, usually are set forth in the police report. Occasionally, however, the points of rest are not indicated in the police report and they can not be determined by other means. In a typical scenario a left turning “target” vehicle is struck on its right side by the front end of a “bullet” vehicle. The vehicles are available for inspection and the configuration of the roadway at the scene has not been altered since the time of the accident. The point of impact is set forth in the police report, however, the points of rest of the vehicles are not specified. No other sources of information regarding the points of rest of the vehicles are available.

An automobile equipped with a conventional brake system often will produce four skid marks on a roadway surface during maximum braking. This condition often occurs immediately prior to a collision in a traffic accident. Knowing the length of the skid marks, SS, and using the dynamic coefficient of friction for the roadway surface, μ, a reconstructing engineer can determine the amount of kinetic energy converted to work during the skidding process on a level roadway. The equation used in this process states that, the portion of the kinetic energy of the vehicle that was used to perform the work of slowing the vehicle is equal to the braking force applied to the vehicle through the skidding distance. Solving the equation for the speed of a vehicle that skids to a stop yields, the traditional speed from skids equation. Problems exist with the traditional speed equation that limit its practical use in traffic accident reconstruction.