The Study Of A Cellular Automaton Traffic Flow Model With Public Transit

Modern societies generally face the serious traffic problem, only according to building the urban road and other traffic facility not enough to solve the traffic jam problem in the city, if can't understand, predict, manages and control the traffic flow in the urban network correctly, greatest improve the efficiency of traffic capacity, the urban traffic will unable be improved forever. The traffic flow theory is the science that multi-disciplinary knowledge such as a applied mathematics, physics and mechanics are comprehensive, it has high-level randomness, dynamics and complexity on the time and space, it is a course through sets up the mathematical model of the traffic flow, then carry on the numerical simulation and solve. Hydromechanical model, speed model and cellular automata were often adopted in current stage traffic research. Because traffic flow is a dispersed system in fact, adopt dispersed cellular automata (Cellular Automata, abbreviated as CA) describes the real traffic behaviour have unique superiority. cellular automata is a net dynamics model which dispersed on time and space state, it has some characteristics, such as strong complicated computing function, computing capability, highly dynamic characteristic and high flexibility, etc. it has very strong ability to simulate dynamically change on the space-time of the complicated traffic transportation system.The city road is generally made up of many lanes, different performance or type vehicles mix and go, But some CA model set up at present, having mostly only considered a factor among them. compared with highway, the city traffic flow most prominent characteristic is that the occupation rate of the road is high, the travel speed of vehicle is relatively low, but most city CA model of traffic flow not consider these characteristics, adopt the same length and travel speed as highway CA model, this is the main factor to cause simulation result inaccurate of city CA model of traffic flow;City road have a large number of public transport vehicle, which have some characteristic such as fixed operation circuit, arrival and departure time, fixed bus stop, loud style and running speed low, the impact on urban traffic flow is very obvious, among existing city CA model of traffic flow have not considered the impact of public transport vehicle and bus stop on city traffic flow, imitate the artificial result greatly different from the real traffic condition.This paper have an overall analysis to existed classical CA model of traffic flow, combine city traffic characteristic of our country, demarcate the parametes such as length of the cellar automata, operation speed, random slow mechanism,vehicle's generating function and the max speed etc, set up the regulation of vehicle changing lane and public transport vehicle nearby bus stop must arrival at slow speed and depart at high speed.And have separately set up four mixed multi-speed CA model of traffic flow in four chapter, 1) CA model of traffic flow under cycle border condition on two-lane which considered normal bus stop and public transport vehicle .2) CA model of traffic flow under open border condition on two-lane which considered normal bus stop and public transport vehicle.3) CA model of traffic flow under cycle border condition on single lane which considered harbour bus stop and public transport vehicle. 4) CA model of traffic flow under cycle border condition on two-lane which considered harbour bus stop and public transport vehicle.Regard C program language as the platform, through the numerical simulation of the computer, have analyzed the relation between three parameters of traffic flow, and the impact on traffic flow of bus occupation rate, bus stop time, vary lane count, have found various non-linear phenomena appearing in the traffic system. The result reveals this model can well reproduce the relation between every traffic parameter, announce the law of public transport vehicle impact on traffic flow. Combine the real traffic condition, has carried on analysis and research to the characteristic of the mixed traffic.In a word, the studies of this paper have a profound function to traffic control and management.