To improve the control performance of vehicle in automated highway systems,we studied the longitudinal control for vehicle following using front and back information in the presence of parametric uncertainty.Based on the longitudinal dynamical model of vehicle,with constant spacing safety policy in a platoon,the longitudinal directed adaptive sliding mode control laws for each vehicle in a platoon was designed depending on the information from the immediate predecessor,the immediate follower and the platoon leader available for feedback.By using vector Lyapunov function and the properties of M-matrix,the asymptotic stability domain of the controller parameters of string of vehicle was established.The simulation results show that,when the speed of the lead vehicle changes,the convergence rate of spacing errors of the vehicle with parametric uncertainty is fast.