Estimating the Speed Change and Relative Approach Speed of Aligned Offset Impacts using CRASH3 Techniques

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.