In this paper the problem of vehiclular platoons control with time delay and switching topology is considered. Due to data transmitions and sensors mesuarements, time delay should be investigated in system’s modeling and controller design. Changes in communication topology may cause the internal and string instability of the vehicular platoons. Based on constant spacing policy, a robust controller is designed to provide internal and string stability of the vehicular platoons. By using Lyapunov-Krassovski and Lyapunov-Razumikhn theorems, two new approaches are presented to perform the internal stability of the proposed switched linear time-delay system. In continuance, a new theorem is presented to attain conditions satisfying string stability. Several simulation studies are provided to show the effectiveness of the proposed approaches.