Abstract: The lateral dynamic performances of vehicles are calculated with the vehicle/track coupling model and the traditional vehicle model to investigate the differences. The software TTISIM that has been verified by many field experiment results is used for the calculation. The results show that the lateral wheel/rail forces obtained with the traditional model are higher than those with the vehicle/track coupling model when vehicles running on tangent, curved tracks or turnouts, that the critical speed of hunting stability based on the vehicle/track theory is lower than that based on the traditional theory, and that there is not obvious difference in vertical and lateral vibrations determined with the two models.