Modeling mixed traffic stability with connected automated vehicle platoon

To investigate the impact of platoon characteristic parameters on the mixed traffic stability, this paper proposes a mixed traffic stability analysis framework that considers both maximum platoon size and platoon intensity. First, considering the spatial distribution of vehicles in mixed traffic flow, a Markov chain-based platoon model is developed from the perspective of platoon intensity. Considering the platoon, the vehicle types and proportions in the mixed traffic flow have been determined. Then, stability discriminant criteria for mixed traffic flow considering both maximum platoon size and platoon intensity are derived, and the effects of maximum platoon size, platoon intensity, and CAV penetration rate on traffic stability are analyzed. Finally, simulation experiments are designed to validate the theoretical model. The results indicate that (1) platoon intensity positively affects mixed traffic stability. As platoon intensity increases, the stable speed intervals of mixed traffic flow expand. (2) The smaller platoons are beneficial to the traffic stability. As the platoon size increases, the unstable speed intervals expand while the expansion rate slows down, but its effect depends on platoon intensity. (3) Platoon management modes can enhance mixed traffic stability compared to conventional management modes. The stability is optimal when all CAVs travel in platoons of a certain size. Therefore, the findings of this paper guide platoon management in mixed traffic flow.