Research On The Traffic Flow Characteristics Of Urban Road Intersection Based On Cellular Automaton Model

Urban road intersection, as a typical traffic bottleneck in the urban traffic network, brings a large number of different directional motor vehicles, non-motor vehicles and pedestrians together. It is easy to cause traffic jams or even accidents in the urban road intersection. These traffic conditions reduce the efficiency of the whole transportation network, produce the negative effects, such as air pollution and noise pollution, and cause great economic loss. These influences severely restrict the sustainable development of the city. Therefore it needs further study on the traffic flow characteristics of urban road intersection, establish the model according to the actual traffic flow characteristics and explore intersection control theory and management methods. These researches not only can enrich the contents of traffic flow theory, but also play a significant role in alleviating urban traffic congestion and promoting sustainable development of the city.Based on the idea of cellular automaton, the thesis proposes some intersection simulation models and researches the traffic flow characteristics of intersection by the numerical simulation. These researches provide theoretical basis for urban intersection control measures and canalization design. The main research contents of this thesis are as follows:(1) Traffic flow characteristics of T-shaped intersection under no signal control.A simulation model is proposed to describe the traffic flow of non-signalized T-shaped intersection. NaSch model is used to simulate the movement of vehicles. Some rules are applied to dispose the conflicts between different directional vehicles and the gridlock. Through the numerical simulation, the influence of different directional vehicles on traffic flow characteristics of T-shaped intersection is analyzed. Simulation results indicate that right-turning vehicles can enhance the flux on the minor road and the inner lane of the major road but restrain the flux on outer lane of the major road in normal conditions. But when the inflow rates of the inner lane in major road is low enough and the inflow rates of the outer lane in major road is high enough, right-turning vehicles in minor road can enhance the flux on outer lane of major road.(2) Traffic flow characteristics of T-shaped intersection under fixed-time signal control.Based on the non-signalized T-shaped intersection model, a new model is proposed by using the fixed-time signal control strategy. Some new rules are used to dispose the conflicts and gridlock. Through the numerical simulation, the influence of green time of main road, vehicle inflow rate and signal phases on the flow and delay of T-shaped intersection are studied respectively. The results show that longer green time can increase the flux and decrease the delay of street which it controls. But for the whole intersection, reasonable green time can obtain the optimal capacity of intersection. When the green time is fixed, the intersection capacity exits the maximum value. Adding a protected left-turning phase can’t increase the flux or decrease the delay of T-shaped intersection. But the purpose of applying protected left-turning phase may be that eliminate the potential conflicts and make vehicles pass the intersection safely.(3) Influence of U-turn movement on the traffic flow characteristics of T-shaped intersection under no signal control.Based on the non-signalized T-shaped intersection model, the U-turn movement vehicles are added in the new proposed model. The new gridlock and conflict avoiding rules are used. Through the numerical simulation, the influence of U-turn movements on traffic flow characteristics of T-shaped intersection is analyzed. The results show that the average control delay is more practical than flux in measuring the performance of intersection. U-turn movements make the traffic conditions of intersection worse, by increasing the range and degree of high congestion. U-turn movements on the different direction of main road have asymmetrical influences on the traffic conditions of intersection. U-turn movements of outer lane in main road have larger influence.(4) Influence of different driving behaviors on traffic flow characteristics of X-shaped intersection.A new simulation model is proposed to describe the traffic flow of X-shaped intersection. NaSch model is adopted to simulate the vehicle movement. The transition of driving behaviors before the intersection obeys Weibull distribution. The game theory is introduced to solve conflict problems among the different driving behaviors in the intersection. Through the numerical simulation, the influence of different driving behaviors on traffic flow characteristics of X-shaped intersection is analyzed. The results show that the existence of the defector can make the traffic conditions of the main road worse. But it improves the traffic conditions of the minor road. The existence of the defector leads to more conflicts. These conflicts sometimes may lead to traffic accidents which makes the intersection does not work for a while or even longer. In the framework of games theory, the phase diagram has a transition regime which is different from former research. In this region, the road flux increases nonlinearly with the increase of inflow rate.(5) Traffic characteristics of mixed bicycle flow and characteristics of interference between vehicles and bicycles in the intersection.A new mixed bicycle model is proposed based on considering three realistic cycling behaviors, which are lane-changing behavior, self-protection behavior and overtaking behavior. Through the numerical simulation, the traffic characteristics of mixed bicycle flow are analyzed and the density-velocity diagram of bicycle flow is obtained. Research results show that the model can simulate the mixed bicycle flow very well, and reflect some phenomena which are observed in realistic traffic. Based on the mixed bicycle model, an interference model between vehicles and bicycles is proposed. The characteristics of interference between vehicles and bicycles are analyzed by numerical simulation.