Traffic Hierarchical Control Strategy in Mixed Traffic Flow Environment via Perimeter Control and Traffic Guidance

Research on traffic control under mixed flow has become a hot topic. However, most current strategies only focus on traffic efficiency and lack consideration of regional safety. In this study, we developed a traffic hierarchical control strategy based on MFD (Macroscopic Fundamental Diagram) and MSD (Macroscopic Safety Diagram) that integrates traffic guidance and perimeter control in a mixed traffic flow environment, aiming to alleviate regional congestion, improve the trip-completion efficiency of regional traffic flow, and ensure the safety throughout the region. The strategy is divided into two layers. The upper-level controller calculates the critical accumulation in real time that achieves the best balance between traffic efficiency and safety based on MFD and MSD and feedback to lower-level controllers. The lower-level controllers maintain the number of vehicles in an interval near the critical accumulation through perimeter control and path guidance. A simulated network from Suzhou, China, is used to verify the proposed model, and the results show that the model improves both traffic efficiency and safety.