Study On Transfer Mechanism Of Branch Traffic Flow Under Central Isolation

In the process of urban road traffic management, especially the small and medium cities,in order to improve traffic efficiency, the department of transportation management is always implementing central isolation fence to manage and control traffic at the intersection of the main and branch roads, which has solved the negative effect of "left-in and left out" vehicles in the openings within peak hours, but all of the transfer vehicles in the road openings can only concentrate into the nearby intersections to circumambulate, it is bound to bring new traffic pressure by the transfer traffic flows to the node or section of nearby road with limited width resource, which will decrease traffic running efficiency of the surrounding roads and areas.In order to avoid these problems, it is necessary to study the transfer process and effects on the downstream intersection of branch road transfer traffic flow after setting central isolation fence, which is the scientific basis for whether sets the central isolation fence or not at the intersection of main road and branch road.Firstly, to analyze the transfer progress of branch road vehicles paper based on the traffic conflict, Pluggable car gap and other related theories after the main road setting the central isolation fence, then the left turn traffic at the branch road are took as the study goal, learning the basic idea of artificial potential field, combined the attractive and repulsive forces model and the traffic flow theory with each other, making attractive models correspond to efficiency, and repulsive model correspond to safety.To study the car-following behavior and lane changing behavior of branch transfer traffic flow in the main road and using numerical analysis experiment to test the scientific rationality of car-following model and lane changing model based on artificial potential field.Secondly, to analyze the efficiency of the transfer traffic flow. Set the goal of setting central isolation fence is to improve the traffic operation efficiency. Therefore, the traffic operation efficiency is the key issues of setting central isolation fences that is required to focus on. First the travel time and delay model of direct turn left and right turn followed by U-turn were established, then to verify the established models by compared them with related research models of domestic and foreign. On this basis, to get the variation of travel time and delay by compared the traffic operation efficiency between direct turn left and right turn followed by U-turn.Thirdly, from the perspective of safety and efficiency, paper also analyses the influence on the downstream intersection of the transfer traffic flow. For the unsignalized intersections, the transfer traffic flow will have an influence on the headway of main road after setting the central isolation fence, analyzing the capacity of the intersection when the headway distributions of main road are under different circumstances. For signalized intersections,, according to the pilot survey of traffic data, getting the model of U-Turn proportions and mixed average headway by regression analysis to study its impact on the capacity of signalized intersections. Meanwhile, on the basic of regular pattern about travel time and delay on traffic flow change, obtain the threshold of main road traffic flow and the U-Turn proportions, which is proving the data support for setting central isolation fence on urban main road.In a word, the results of above study not only provide theoretical support for central isolation fence setting, but also provide a theoretical basis for urban area transportation organizations optimization and congestion treating.