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, and using the dynamic coefficient of friction for the roadway surface, 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. A new speed from skids equation is set forth in this paper that will allow the reconstructing engineer to determine the speed of a vehicle at the onset of maximum braking. (A)
Abstract