This paper deals with the two-dimensional Collisions of vehicles. The authors have already analysed the vehicle collisions in consideration of vehicle movements during impact. In those studies tire forces acting in the duration of impact were not considered. However, it does not seem that they can be ignored under any impact condition. In the present paper, therefore, the authors introduce the impact forces acting between two vehicle bodies and tire forces acting from the road into the equations of motion of four-wheel vehicles and analyse the vehicle motion throughout the vehicle collisions (pre-impact. impact and post-impact vehicle motion). Finally, they compared the results obtained from the present method with those obtained from the method ignoring tire forces acting in the duration of impact. It is shown from the comparisons that tire forces acting in the duration of impact affect the vehicle velocities after impact and the vehicle trajectories are not predicted correctly if they are neglected.