Considering the limitations when the handling stability research methods of cars are applied to tractor trailer,a new research method and an improved measure for handling the stability of tractor-semitrailer were proposed.A system dynamic model of tractor-semitrailer including saddle damping parameter was established,and computer simulation was done under 'S' lane-change working conditions.The relative change response characteristics of the tractor's motion parameters,such as the rolling angle and lateral a...