RECONSTRUCTION OF MOTOR VEHICLE ACCIDENTS: A TECHNICAL COMPENDIUM. FRONTAL CRUSH ENERGY AND IMPULSE ANALYSIS OF NARROW OBJECT IMPACTS

This paper examines methods of estimating the energy dissipated by the frontal crush of automobiles which impact narrow objects such as poles or trees. The method originally developed by Campbell for full frontal crashes is found to underestimate the energy for narrow object impacts by as much as 68 percent in those cases investigated. A correction factor equivalent to that used by NASS to account for induced bowing is found to improve the estimation in all cases investigated, improving the error to 37 percent in the worst case. An exploratory study using a previously reported technique of approximating a single high speed crash with a series of repeated low speed crashes is presented with promising results. The unique nature of narrow object impacts in impuulse analysis is also discussed. It is shown that the principal direction of force is not necessarily the same as the direction of crush of the car outer surface.