When vehicle to vehicle collisions are analyzed using a discrete kinetic time forward simulation, several simulation runs have to be performed, to find a solution, where post impact trajectories and rest positions correspond with the real accident. This paper describes in detail a method to vary the pre-impact parameters automatically and to evaluate the simulation results.In a first step the different pre-impact parameters are discussed. Their influence on the impact and the post impact movement is shown. Furthermore the necessary specifications to define the post crash movement are presented. The necessity to define tire marks and rest positions of the vehicles involved is outlined. An effective evaluation criteria is derived, which is used to calculate a simulation error. This error is then used as a target function to control the optimization process.Two different optimization strategies are presented. Their performance is discussed in relation to the numerical stability, progress rate and accuracy.The optimization method can, in principle, be used together with any discrete kinetic time forward simulation model also in connection with various collision models. For the current paper the simulation models of PC-Crash , ,  were used.In the last part of the paper several sample cases from crash tests and real life accidents are presented together with the result of the automatic optimization process.