Delta-V: Basic Concepts, Computational Methods, and Misunderstandings

Vehicle crush deformation and energy equivalence relationships are widely accepted as technical accident reconstruction tools for estimating the change in velocity (Delta-V) during an impact. Delta-V has been accepted as a basis for evaluating damage severity and potential injury severity. Emori, Campbell and McHenry's work led to CRASH derivative type programs which are based upon a relationship between crush magnitude and Delta-V. SMAC derivative type programs utilize these principles while generating a time dependent analysis (simulation) by maintaining a continuous equalization of forces between the vehicles during the impact phase. This paper reviews basic principles and the relationships between Delta-V, kinetic energy, conservation of momentum, and barrier equivalent velocity which must be adhered to while performing this type of analysis. Several examples and frequently seen misunderstandings of these relationships are discussed. This paper is intended to assist not only the unseasoned reconstructionist in developing an understanding for Delta-V, but is also intended for the seasoned reconstructionist to assist in demonstrating that their application and interpretation of Delta-V is correct.