Abstract: Cooperative adaptive cruise control (CACC) is acknowledged as an efficient solution to relieve traffic congestion while ensuring traffic safety. This paper aims to improve traffic efficiency via both the effective following spacing policy and the CACC with platoon kinematics. Firstly, the correlation mechanism of safety spacing policy and time headway policy is analyzed, a versatile generic spacing model is established, and an efficient spacing policy is proposed by leveraging the concept of safety redundancy. Secondly, based on the “virtual centroid” of the platoon, the CACC upper control strategy with platoon kinematics is proposed to improve traffic efficiency. The strategy is complemented by the design of a sliding mode controller, which precisely allocates longitudinal acceleration. Additionally, a lower controller is developed to track the desired acceleration accurately and rapidly under various driving and braking conditions. Thirdly, eight typical scenarios for urban traffic are reconstructed via three-layer decompositions, and the index named synchronization is proposed to evaluate the performance of CACC with platoon kinematics. Finally, a simulation test is conducted, demonstrating that the proposed CACC strategy synchronously responds to the kinematics of the preceding platoon, reducing the accumulation of response delay, ensuring both vehicle following safety and efficiency.