Estimating the Speed Change and Relative Approach Speed of Aligned Offset Impacts using CRASH3 Techniques 2014-01-0472

CRASH3 techniques are often used to reconstruct aligned offset vehicle impacts. The goal of this study was to evaluate the accuracy of the CRASH3 technique using a series of aligned staged collision with varying degrees of overlap. Five front-to-rear vehicle impacts using the same vehicle model were staged using 25, 33, 50, 75 and 100% overlap. Impact kinematics were measured using overhead high speed video. The CRASH3 coefficients and methods developed previously (SAE 2010-01-0069) were used to reconstruct the impact speed and speed changes of both vehicles based on the residual crush. Overall, the CRASH3 analysis yielded good results for the 33 to 100% overlap collisions: predicted speed changes were within 29% of the measured speed change and predicted impact speeds were within 16% of the measured impact speed. The CRASH3 analysis yielded poor results for the 25% overlap collision: the predicted speed changes were up to 59% different from the actual speed changes and the predicted impacts speeds were up to 54% different from the actual impact speeds. These findings indicated that CRASH3 techniques can be used to reconstruct aligned offset impacts where the overlap is 33% or larger for collisions similar to those staged here.