Research On The Dynamic Modeling Of Traffic Flow And Dynamical Traffic Light Control Strategy In Urban Road Network

In recent years,a series of traffic problems such as traffic congestion,traffic pollution,have become the main bottleneck in restricting the sustainable development of the city.The theoretical research of traffic flow in urban road network is very important since it can help to alleviate the increasingly prominent urban traffic congestion.In this thesis,based on the two-dimensional cellular automata BML model of traffic flow,several improved dynamic models are proposed to study traffic flow by considering the failure of traffic lights,the running characteristics of vehicle（e.g.,slow-to-start effect）and dynamical traffic light control strategies,respectively.And the dynamic characteristics and various nonlinear phenomena under different topological structures for traffic flow in urban road networks are studied via theoretical analysis and numerical simulation,and the formation mechanisms and traffic jams are also explored.Furthermore,we put forward some suggestions for the reductions of traffic congestion and traffic energy consumption,and management and optimization of traffic flow in urban road networks.Three main contents of the thesis are as follows:（1）An extended two-dimensional cellular automata traffic flow model is proposed to simulate urban traffic flow by considering faulty traffic lights.The effects of symmetrical and asymmetrical failures of traffic lights in different directions and the effect of system size are studied.Furthermore,the formation mechanism of traffic jams induced by faulty traffic light is also discussed in detail.The simulation results show that the new model can better describe some essential characteristics of urban road traffic flow,such as self-organization and phase transition.In the low density（i.e.,free-flow state）,the failure of traffic lights can improve the overall movement efficiency of the traffic system.At this time,the average speed and average flow are not affected by the system size.However,at medium and high densities,the failure of traffic lights can easily induce traffic congestion,and lead to traffic disorder and traffic paralysis.The above research can provide some valuable suggestions for the treatment of urban road traffic emergencies and the reasonable control of traffic lights.（2）Based on the BML-NaSch model,a new Manhattan-like urban network traffic model is constructed to simulate urban road traffic flow by considering the slow-to-start effect.The influences of slow-to-start effect under different road lengths on the dynamic evolution characteristics of the traffic flow and energy consumption are investigated.The simulation results show that the slow-to-start effect can capture the dissipation procedure of traffic waves.The reduction of the number of intersections and the increase of the length of the road section can effectively reduce the occurrence of urban traffic congestion.In addition,in spite of the slow-to-start effect leads to the low-speed movement of vehicles,it is not easy to induce complete congestion in the traffic system,and can effectively reduce traffic energy consumption.The above research can provide a scientific theoretical basis for the alleviation of urban traffic congestion and the reduction of energy consumption.（3）Based on the communication method between the vehicle and the roadside unit（V2R）in the Internet of Vehicles,a novel dynamical traffic light control strategy is proposed to study urban road traffic by introducing traffic density information feedback.The influences of the dynamical traffic light green ratioα,the weight factorβof the vehicle density information in the inflow lane,the static green light time T_static,and the traffic light period T on the Manhattan-like urban traffic flow and energy consumption are investigated.The simulation results show that the new dynamical traffic light control strategy is significantly better than the fixed period traffic light control strategy under certain conditions.It can effectively control the traffic alleviate traffic congestion at intersections,improve road capacity,and reduce energy consumption.The above research can provide a certain theoretical basis for the optimization of traffic light control strategies and the alleviation of urban traffic jams.The final chapter of this thesis is devoted to a summary and a prospect of further study of the traffic flow.