Study On The Complex Dynamic Properties Of Traffic Flow By Cellular Automata Method

Currently, the rapid development of the society economy and the relative lag of the transportation have been a prominent problem all over the world. The economic expenses and the environment pollutions caused by the traffic congestion become more and more serious. Only the economic expenses caused by the traffic congestion are amazing. The investigation results made by the Texas transportation institute to the thirty-nine main cities show that the traffic congestion causes economic expenses of hundreds of billions of dollars in America every year. Also, the traffic congestion and accidents cause economic expenses of hundreds of billions euros in Europe every year. With the development of the economy, the requirement of traffic is increasing. Although large investment of the road instruction has been made and large amount of traffic establishments have been built in and around cities, the condition of traffic congestion is still serious. Therefore, how to utilize the limited traffic resources adequately and effectively and how to guide the traffic planning, designing, controlling and management with scientific theory become urgent problem. Under such situation, the study of traffic flow theory emerges as the times require.As a recent crossing marginal subject, traffic flow theory research has attracted lots of attentions of researchers from many study fields recently. The purpose of traffic flow theory research is to build traffic flow models which can describe the general characteristics of real traffic and show the basic rules which control traffic flow. Thus, we are able to achieve in the direction of the management of traffic project department, designing and improvement of the traffic network and traffic control system service.As a new kind of traffic resource, the freeway has the advantages of high driving speed, large capacity and low accident rate. The construction and development is the vane of the national economic development level. With the quick development of national economy and large enhancement of flow of goods and persons, the requirement of elevating transportation efficiency and reducing transportation cost is getting more and more urgent. Accelerating the construction of freeway is the need of development of Chinese economy and society. Therefore, how to alleviate the traffic congestion of freeway, how to increase flow rate and capacity and how to reduce the accident rate and enhance the safety of traffic become the urgent problems and the focus of researchers.This paper adopts Cellular Automata model to study the freeway condition in traffic flow research, to build models of the real traffic phenomena and to make computer simulation. Some qualitative advices and suggestions are made to traffic project control and traffic management rules. This paper is arranged as follows:In the first chapter, the practical and academic significance of traffic flow theory, the main objects and the basic methods of traffic flow research are introduced. Then, in the following chapter, the research work listed below is presented.1. Depending on the real situation, we built the Cellular Automata model of mixed vehicles on the two-lane traffic flow system of freeway on the basis of NS model. Utilizing this model, we investigate the road condition of four different lane-changing rules under the periodic boundary condition and the simulation results show that:When the occupancy is not large, lane-changing ban of buses could increases the flow rate clearly. This is because the lane-changing ban of buses effectively avoids the appearance of the"plug"phenomenon.In the aspect of carry capability, the rate of the buses in all the vehicles is higher, the carry capability of road is larger. However, the lane-changing ban of buses cumbers the normal lane-changing of the buses in a certain extent, so the flow rate of the road decreases.When the occupancy is relatively large, lane-changing ban reduce the changing frequency of vehicles; however, when the occupancy is not very large, the exertion increases the lane-changing frequency.The lane-changing ban of the buses avoids the formation of the density inversion under the asymmetric lane-changing rules.2. We built the Cellular Automata model of on-ramp system with an two-lane main road traffic flow system on the basis of NaSch model. With the attention on the problems of single-lane and two-lane on-ramp systems, we advance a new set of lane-changing rules and investigate the traffic state, flow rate and traffic capacity. The simulation results show that:The new asymmetric lane-changing rules don't make qualitative differences on the regions of traffic state diagram. However, under the majority of the condition, it increases the regions of free flow and decreases the regions of congestion.The new asymmetric lane-changing rules enhance the current of road under certain conditions and when the randomization rate is small, it increases the traffic capacity.When the randomization rate is large, the new asymmetric lane-changing rules cumber the normal changing of vehicles and do not improve the traffic condition.The densities of two roads make good explanations about the phenomena. The new asymmetric lane-changing rules effectively weaken the interaction between on-ramp and right lane and improve the traffic condition.Therefore, the structure of this paper is as follows: part 1, the simulation of two-lane freeway is presented in Chapter 2; part 2, the simulation of on-ramp system is presented in Chapter 3. The summarization and the prospect of following research work are presented in Chapter 4.