Analysis on influencing factors of traffic congestion in expressway exit ramp area—Take an exit ramp in Shanghai as an example

Traffic congestion often occurs in the exit ramp area of the expressway. The systematic study of its congestion influencing factors is extremely important to improve the effectiveness of road networks. Both the traffic status of the connected expressway and ordinary road need to be considered at the regional level. And it should be analyzed at the lane level rather than at the cross-sectional level. By analyzing traffic parameters including traffic flow, lane operating capacity, speed, etc., this paper constructs seven variables to build a panel regressing model. The model is selected to analyze each lane of the expressway in the exit ramp area. The main congestion influencing factors in the exit ramp area are identified from the seven variables based on the regression results. The data is from loop detectors of the North-South Expressway exit ramp area in Shanghai. The results show that the influencing factors which have a significant effect are exit ramp traffic flow and the ratio of flow to lane operating capacity in the ordinary road connected by the exit ramp. The outermost lane is more affected by ramp approach traffic than the inner lane near the centerline of the road. It provides a reference for the refined traffic management of expressway.