The Studies Of Mixed Traffic Flow With Cellular Automata Models

With the harmonious development of our society and economy, the transportation has now become the focal point of the expand of the city in many countries in the world, and also become a bottleneck to restrict the development of the city. The developments of economy and society, even society stabilization, have been influenced strongly by traffic jam, traffic pollution and traffic accidents. In our country, numerous civil population and diversiform traffic tools aggravate the acuity of traffic problems. How to scientifically administer and control mixed traffic flow is a problem that needs imminently to solve.Recently, the domestic and overseas experts have attached importance to traffic problems and have presented all kinds of traffic models, in which the studies of the cellular automaton models for traffic flow have been widely concerned. Cellular automaton is a mathematical model in which time, space and variables are all discrete. It has so many predominant characteristics—for example, its clear physical pictures, being completely parallel, having no interceptive errors and having no computational errors and so on—that it is an effective tool by which to study nonlinear complicated systems.In this dissertation, based on the existing research on the cellular automata models for traffic flow, several models for traffic flow with mixed vehicles in accordance with real traffic in China are proposed. We present various nonlinear phenomena in traffic system by using computer numerical simulation. The characters of traffic flow in mixed models are presented and analyzed.This dissertation consists of the following three main parts.1. With respect to the mixed traffic in realistic life, based on the NaSch model, a cellular automaton traffic model with different maximum length and speed vehicles mixed on single lane on periodic boundary condition is proposed. By using computer numerical simulation, we find that the flux and average velocity of mixed traffic flow is much related with the variety of mixed proportion coefficient on single lane. The share critical of mixed traffic flow increases with the increase in mixed proportion coefficient; when less than share critical, traffic flow will decrease with the increase in mixed proportion coefficient and average velocity has no relationship with mixed proportion coefficient; when more than share critical, traffic flow has no relationship with mixed proportion coefficient basically and average velocity will increase with the increase in mixed proportion coefficient.2. We studied a cellular automaton traffic model with different length and speed vehicles mixed on single lane on periodic boundary which was based on the NaSch model and ACC model. A vehicle equipped with ACC is believed to influence the properties of traffic flow and safety. In ACC model the constant time headway policy is adopted. Using computer numerical simulation, the results show that with the increase of the ratio of ACC vehicles, the jam is gradually suppressed. The average speed of the system decreases with the increase of T。Nevertheless the enhancement of the traffic stability is increase.3. Considering that roads of real traffic system always contain several lanes, in order to reflect more practically real traffic phenomena, we present the adaptive cruise control vehicles in the cellular automaton NS-and-WWH mixed model on a two-lane roadway based on the NS model, the ACC model and the WWH model for one-dimensional cellular automaton traffic flow. By using computer numerical simulation, the results show that with the increase of T and f_NS, the maximum flow, average velocity, critical density of the mixed traffic flow is decrease. When 0.0≤f_NS≤1.0, the three peak values become two peak values in the lane-changing frequency--density diagram. When the value of R is increase from 0.0 to 1, the two peak values decrease in the lane-changing frequency-density diagram. When R = 1.0, there is no vehicle changing its lane. With the increase of T , the three peak values become one peak value in the lane-changing frequency-density diagram. However, the occupancy of each lane is weak affected by the ratio of the NS vehicles f_NS, the ratio of ACC vehicles R and the specified headwayT .Finally, we conclude and show the implications and future researches.