know that vehicle #2, a Ford Escort sedan with a single occupant, was slowing to a. Stop for :1 rcd light. Vehicle #1, a Honda. C ivic carrying two occupants, was ...
Mark S. Erickson, P.E. Wilson C. Hayes, Ph.D. .nce rhe early 1960's, rhe conscious drive to in crease auromorive
~
-afery has greatly advanced rhe
field of accident reconstruction .
Over chese years, scientists, engineers and investigam[s have developed and validated numerous techniques to analyze morar vehicle collision (MVC) events. 111cse techniques include methodologies based on rhe conservation of momentum, conservation of energy as well as ernpiricalbased approaches. Among rhe in pm data required for application of these variolls techniques are: area of impact, post impact
res t posi tions, post-impact trajectories, effect ive drag factors, vehicle weights, crush profiles, etc. I n a controlled crash setting, acquisition of these data reprcsems a fairly st raightfo rward process of scene dacumenradan and vehicle measurement. However, the complicating factor for the typical accident reconstructionist involved in (he realm of civil litigation is (hat by the dme the accidem reconstrucrionist
34 Collision
is retained (often years after the event), physical evidence associated with rhe collision sce ne is often scarce. From time-to-time, depending on the severity of the collision, the investigating police agency may have documented the roadway evidence, final rest positions of .he vehicles and relevant debris fields. More often than nor, reliable scene ev id ence is unavailable. Under these circumstances, and given thar the damaged vehicles are sometimes available long after the collision, the analyst will ofren choose to implement a damage-based collision reconstruction. ll1is technique allows rhe derermination of collision severity level (delta-V) based on (he crush damage induced to each vehicle. Input data required for a damage-based reconstruction includes, btl[ is not limited to, vehicle weights, structural stiffness coefficienrs and measurem ents of rhe postimpact crush profiles for each vehicle. A further frustration that occurs all too ofren is that by the time the accident
reconsrructionist is ret:lined, just one of the vehicles involved in rhe collision event rem:lin s in existence. 111is situation further complicates the analysis and immediately raises a red Hag, as we know that one of the physical requiremenrs of a crush analysis is that the deformation induced ro both vehicles must be considered (6). Although mi ss ing a vehicle prese nts a complicating factor, if good crush profile data arc available for one of rhe vehicles and crush stiffness data, vehicle weights, and impact oriemation is known for barh vehicles, a force-balance reconstruction technique can often be implemented. 111is technique allows the damage energy absorbed by the missing vehicle to be c!lleuillted based on the peak collision force along with the vehicle's structure stiffness coefficients. In rhe following, a general derivarion of the force-balance reconstruction methods will be presented. For simplicity, the equ
