The Study On Optimal Method Of Urban Traffic Signal Control

Traffic signal is an essential element to manage the transportation network. Nevertheless, it is widely accepted that the benefits of traffic control signal systems are not being fully realized. Along with the movement of Intelligent Transportation System (ITS), traffic signal control remains one of the most heavily funded research and developmeiii. iL~ins. i ne research on traffic signal control is by no means complete. A number of models of the traffic signal control have been developed in the past. Despite substantial differences among them, they can be roughly classified by two approaches. One is developed mainly for unsaturated traffic flow. The other is developed mainly for congested or over-saturated traffic conditions where queues exist in the whole period and can not be cleared. The dynamics of queue formation and dissipation becomes very important. In this dissertation, the principle of the traffic signal control based on intelligent optimization, the basic optimal theories and the methods based on Genetic Algorithm as well as Chaos theory are proposed. Through the study and the analysis of traffic streams in an intersection, the real-time control model of four-phase signal plan according to the objective function of vehicle queue length in an intersection is established. The simulation tests of phase green duration in the model are conducted using Genetic Algorithm method. The simulation results show that the optimal method of Genetic Algorithm is superior to tradition methods, and it is suitable for determining the green split in a single intersection. Based on Genetic Algorithm, a hybrid optimal method is provided. It combines the advantage of global optimization in Genetic Algorithm with the advantage of the fastest dropping in Gradient method. It can also ensure to avoid much time in Genetic Algorithm and to escape from local optimization of Gradient method. The simulation results indicate that this new method increases the search efficiency. With regard to performance index of the average vehicle delay in an intersection, the traffic stream model and a new optimal method based on Chaos theory according to cycle length and green split are developed. Under a given green split, the performance index of average delay in an intersection varies with the cycle in a convex curve. During optimizing, the search step is changed according to the cycle length, an optimal method based on Chaos theory is used according to green split, and a sequential optimal method is used according to cycle length and green split. The simulation results show that the method is superior to those in OSCADY and reference 12. In addition, the optimization of performance index for a series of period is also conducted. A traffic stream dynamics based on Cell Transmission Model (CTM) is established. An optimal method based on Chaos theory according to cycle length and green split for CTM of a network is developed. The simulation tests are conducted in three cases of light, moderate and heavy traffic streams with arterial road of several 4 intersections. The simulation results show that this method is superior to the method of reference 5. The better performance index can be obtained in the new method. After the function characteristics of domestic and foreign traffic signal control machines being known, a new intelligent machine of traffic signal control is studied and manufactured. The constitution of the machine of traffic signal control and its method of programming are...