Analyzing the impact of mixed vehicle platoon formations on vehicle energy and traffic efficiencies

Connected and automated vehicles (CAVs) offer promising prospects for the future of transportation. However, the longstanding dominance of human-driven vehicles (HDVs) in the transportation system, resulting in coexisting CAVs and HDVs in the form of mixed vehicle platoons. This situation raises questions about how the formation of a mixed vehicle platoon, defined as the spatial distribution of CAVs and HDVs in the platoon, can be utilized to improve the overall traffic performance. To gain insights into this question, this study analyzes the impact of mixed vehicle platoon formations on energy and traffic efficiencies. The research involves several key steps: first, a mixed platoon model with heterogeneous vehicles is formulated, using pertinent car-following models to simulate the diverse driving behaviors of CAVs and HDVs. Next, five representative vehicles are selected for simulation, and three distinct test cases are defined based on the platoon driving mode. These scenarios encompass a range of platoon formations, considering various numbers of vehicles and CAVs. Extensive simulations are then conducted to explore the influencing factors, potentials, and mechanisms of mixed vehicle platoons under different formations. The results reveal that the energy and traffic efficiencies of mixed vehicle platoons are significantly influenced by their formation. Variations in formation can impact energy efficiency by 1.24 % to 26.27 % and traffic efficiency by 0.49 % to 29.47 %. The optimal formation is determined by platoon sizes, CAV penetration rates, and driving modes. This study delves into the mechanisms governing the optimal spatial distribution of CAVs within mixed vehicle platoons, providing insights into strategies for maximizing energy and traffic efficiencies. These findings highlight the importance of considering platoon formation to optimize the performance of mixed vehicle platoons.