Citation

Schmidt B. Collision 2010; 5(2): 76-85.

Copyright

(Copyright © 2010, Collision Publishing)

DOI

unavailable

PMID

unavailable

Abstract

The relationships between principle direction of force (PDOF), change in velocity (∆V), and time developments of longitudinal and lateral acceleration/∆V values obtained from event data recorders are often misunderstood by accident reconstructionists. This paper discusses these related, yet different, phenomena. The PDOF vector and ∆V vector of a vehicle must point in the same direction, according to Newton's second law of motion. However, the two vectors usually will be offset from each other since the PDOF passes through the approximate centroid of the damage and ∆V describes the motion of the vehicle center of gravity. This offset affects the vehicle's rotation due to the collision, but not ∆V. Although these two vectors have the same direction, the numerical description of their directions can differ substantially. Examining the detailed time development of the acceleration values recorded by an EDR as well as the final values of the ∆V components can be useful. Two examples using actual EDR data are provided to illustrate time development of these ∆V components and calculations of ∆V and PDOF.