Traffic Modeling And Simulation Research Of Expressway Based On Cellular Automata

As the increase of China's capital investment of transportation facilities, rapid acceleration of urbanizations and motorization, urban expressway develops rapidly and becomes an important trunk road; In the expressway system, for the short distance between two adjacent ramp, it will form a traffic conflict areas, namely weaving areas; Traffic congestion often happen in the place of entrance ramp and exit ramp, which serious impacts on the important functions of the expressway and becomes a bottleneck of urban transport.For a long time, due to technical reasons of limited means,study of the characteristics of traffic flow is little; As computer technology of traffic simulation, continues to develop,it can be used this to study this.Cellular automata as a discrete microscopic model,which concerns the movement state of individual vehicles and can modifies update rule easily, can be used for flow simulation of expressway traffic.Firstly, this paper analyzed the state of the current research of the traffic simulat -ion, discussed the cellular automata traffic simulation technology and its application. Then we made a study on the pattern of traffic flow and set up producing vehicle model and simulation model. Last on this basis, a simulation prototype system of weaving area was developed. The main work of this paper, are as follows:(1) Basing on the measured data, we studied the arriving law and speed law of the vehicles of weaving area with Statistics and Probability Method and established the model of producing vehicle for weaving area .Then gave out the computer algorithm of this model, used the measured data to determine the relevant parameters and made a fit test. The parameters of model can easily be modified ,which has good versatility.(2) The micro simulation about expressway weaving area which was composed of an off ramp, an on ramp, a main line lane and an assistant road was made through modeling, which was based on Cellular Automata NS model, and was carried on by setting car-following rules and lane-changing rules. The simulation shows the optimal reference value of the length of weaving area and the effect on traffic flow parameters, such as flow, density and velocity, and the simulation model was verified by the calculation result of HCM empirical formula.(3) An simulation prototype system was developed basing on the vehicle producing model and simulation model ;The prototype system can make simulation on weaving area in kinds of traffic flow conditions, which parameters can be modified easily and has good scalability, flexibility and interactivity.