Research On Traffic Flow Model At Signalized Intersections Based On Circuit Theory

Intersections are significant joints of road network and throat of traffic. Solving intersection problems is crucial to solve traffic problems. Road intersections are facilities linking roads, which can make roads play a network function. They are the main concentrated spots with people and vehicles. The traffic congestion mainly happens at intersections. In the whole road network, traffic bottleneck arise from the lack of intersection's capacity. It can bring about traffic jam. Due to vehicles'interweaved running, intersections become the traffic black spots and are focused on in traffic safety aspect.To solve the intersection's problem, its traffic flow characteristics should be researched first of all. The dissertation is supported by the subject"The Organization and Optimization of Traffic systems"which is part of the National Basic Research Program(973 Program)"The basic science problems of traffic bottleneck in metropolis''and the Key Project of National Natural Science Foundation"Study on the critical theory and simulation technique of dynamic traffic management and control in urban network". The traffic flow characteristics of signalized intersections are researched in the paper. Its results will have important meaning in two aspects: One is these fruits can develop and consummate the traffic flow theory academically. There are seldom researches on traffic flow characteristics at signalized intersections dynamically and quantitatively, whereas there are some qualitative researches. This paper can complement this aspect. The other is these fruits can supply reference for traffic control theoretically. Delay is a important factor to evaluate the level of service at signalized intersections and is a significant criterion to estimate the intersection's signal timing design. At the same time, delay is so related to the rules of vehicles'arrival and departure that the researches on traffic flow's departure rules at signalized intersections give a reference to calculate delay theoretically.The rules of traffic flow's departure at signalized intersections are studied emphatically in this paper. Firstly, the statistical distribution of traffic flow characteristic parameters is tested with the probability statistics'method. Moreover, traffic flow model by simulating circuit at signalized intersections is set up in the paper, which can dynamically and quantitatively describe the traffic flow's departure characteristics at signalized intersections. In the of the paper., the model is applied to calculate saturation flow rate and forecast the flow of the point downstream of the signal. The full paper is composed of five chapters and every one is arranged as follows:Chapter One first introduces the development and main models of traffic flow briefly and then points out the thesis's value, method and content. It sets a basis for the continued research.Chapter Two, based on the traffic survey data at a representative intersection in the city of Changchun, researches the traffic flow's departure characteristics at signalized intersections. The thesis researches the statistical distribution's characteristics at signalized intersections with probability theory. The distributions of traffic flow parameters headway and speed are both verified. And the time dependent characteristics are analyzed. This chapter is the theoretical basis of the founding of the traffic flow model by simulating circuit.Chapter Three, based on circuit theory, sets up traffic flow model at signalized intersections. The research of Chapter Two indicates traffic flow at signalized intersections holds the time dependent pulse characteristics which is similar to the capacitance in circuit. It can only get traffic flow's statistical characteristics but can't obtain the time dependent characteristics with the probability statistics'method. In order to describe the traffic flow's the time dependent pulse characteristics quantitatively at signalized intersections, this chapter, based on circuit theory, thoroughly analyses the comparability of the signalized intersection and RLC circuit. And then traffic flow departure model is set up according to a designed circuit for simulating the signalized intersection. Immediately after that the model is verified by the practical traffic survey data at a representative intersection in the city of Changchun and the error brought about by the model is given. Lastly, rationality of quantitatively describing the traffic flow's departure rules at signalized intersections is analyzed.Chapter Four applies the traffic flow model by simulating circuit. Based on the very model, saturation traffic flow calculating model and the flow forecasting model on the point downstream of the signal are both set up. At first, saturation traffic flow calculating model is deduced from the traffic flow model by simulating circuit. The calculating model is verified according to the practical traffic investigation data and is compared with the calculating result of the improved headway calculating model. Then, based on the premise of platoon dispersion the flow forecasting model on the point downstream of the signal is deduced from traffic flow model by simulating circuit. After practical traffic data processed, the forecasting model is verified and the cause of the model-bringing error is then analyzed.Chapter Five is the conclusion of the thesis. The research process and main contents of it are looked back. The deficiency is pointed out and the problems that need to further study is put forward.