An index RD (Residual Deformation) has been introduced as a measure of estimating to what extent the car body affects occupant protection in a vehicle collision. This RD can be easily determined from the crash stroke-time curve of vehicle body. Calculations using a simple simulation model were made on this RD index. Further, the experimental results of modified bodies during the Experimental Safety Vehicle (ESV) development were rearranged by RD. As a result, the RD index was confirmed to be effective in the evaluation of body characteristics.