Simultaneous optimization of evacuation route and departure time based on link-congestion mitigation

摘要

Link-level congestion, such as link spillback and long intersection queues, should be avoided during emergency evacuation. The reason is that these local traffic incidents can cause traffic safety risks and hinder evacuation tasks. To determine reliable routes and departure times for the whole evacuation, we establish the link-congestion mitigation-based dynamic evacuation route planning (LCM-DERP) model. The distinct difference with the typical DERP model lies in the objective composition. The system cost objective in our model consists of not only total evacuation time but also external congestion cost. The penalization for link spillback and long intersection queues is used to represent external congestion cost. An improved cell transmission structure, composed of tail cell and head cell and approach cell, is proposed to simulate dynamic traffic flow. Specifically, tail cell and head cell can detect the information of link spillback and long intersection queue separately. This function enables the representation of external congestion cost expressed by multiplying link-level congestion vehicles with penalty parameter. A method of successive average, including a calculation of the local path marginal cost, is used to solve the model. We applied the LCM-DERP model on a road network around Olympic Stadium in Nanjing, China, to test its effectiveness in the aspect of link-congestion control. Compared with the typical DERP model, our method can improve system cost, especially in the high demand range, wherein the reduced external congestion cost is larger than this reduced system cost.