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In the field of accident reconstruction, there has been a significant amount of effort devoted to the calculation and derivation of vehicle crush energy and vehicle stiffness. Crush energy is usually calculated with a crush profile and crush stiffness. But, oftentimes, crush profiles and/or crush stiffnesses are not available and accident constructionists face the situation of insufficient information. In some such cases, the force balance method can be used to reduce the uncertainty. The method follows from Newton's Third Law, i.e., the impact force exerted on one vehicle is balanced by the force exerted on the other vehicle. With the help of this method, crush profile or crush stiffness can be derived. As a result, the crush energy can then be calculated with improved accuracy. This ultimately increases the accuracy of the overall accident reconstruction. In this paper, examples will be given to illustrate the use of such a methodology.

Delta-V and Barrier Equivalent Velocity (BEV) are terms that have been used for many years to describe aspects of what happened to a vehicle when an impact occurred. That is, they are used to describe some physical change in the vehicle state before the impact as compared to after the impact. Specifically, the Delta-V describes the change in the vehicle velocity vector from just before the impact until just after the impact. The BEV attempts to quantify the energy required to cause the damage associated with an impact. In order to understand what happens to a vehicle and its occupants during an impact, it is necessary to examine the acceleration pulse undergone by the vehicle during the impact. The acceleration pulse describes, in detail, how the Delta-V occurs as a function of time, and is related with the deformation of the vehicle as well as the object contacted by the vehicle during an impact.