For proper analysis of traffic accidents, it is important to properly evaluate the work on vehicle deformation based on the extent of damage of the vehicle. The Institute of Forensic Engineering, University of Zilina, carrried out a series of vehicle crash tests focused on evaluation of the vehicle deformation work. This article focuses on the recording and processing data from crash tests and the evaluation of the vehicle deformation work, of the EES (energy equivalent speed), the comparison of stiffness tests of cars (production year around 2000) and older generation of vehicles (which were subject of tests - Crash tests DSD LINZ 1996).