Study On Control And Guidance Method For Expressway Communication

Since the expressway is a charge roadway constructed and managed by different investment bodies, it is short of the effective coordination mechanism between the administrative systems. At present, most city traffic management system have not taken it into account that the traffic flow running state of the expressway network is the goal of urban traffic control. So the traffic management of the urban road network and the expressway haven't been effectively integrated, which results into traffic jams at rush hour. To improve the traffic throughout and reduce the total vehicle travel time, the control and guidance method for expressway communication management are put forward in this research.Firstly, analyze the influence of traffic flow which exchange between expressway and urban traffic system based on the their relation, take advantage of the equilibrium theory of traffic demand of urban road and traffic capacity of expressway, a hierarchical method is used to coordinate the traffic management system of the expressway and that of urban road. By this method, through monitoring and evaluating the effect of the guidance system, the control and guidance strategy measure can be adjusted and harmonized.Secondly, since the expressway is of separate bi-direction, with the Digraph Theory the expressway network can be established, which expresses the structure and vehicle route of expressway. On the basis of expressway network, applying the feasible flow theory, a traffic flow analysis model of the expressway and the city road that connected to it is set up. According to equilibrium condition and capacity restriction, the method of maximum flow is used to analyze the maximum permitted traffic flow on the basis of the network parameters seted.Thirdly, based on the realtime traffic information, the traffic capacity of each road sections are calculated, the traffic flow control and guidance model is built, which include forecasting model, speeding model, route model, and ramp control model. The traffic administration system should be controlled and guided on the ground of the analysis results of the network traffic flow. This control and guidance system can avoid the problem that the traffic capacity of some sections is affected when other sections are optimized. Combined with control and guidance, this strategy can balance the urban traffic demands and traffic capacity, avoid instability of running state, which impacts the section and even whole urban traffic system.Fourthly, through analyzing the traffic capacity and influence factor of expressway toll station and the crossing of urban road, the model that coordinates the fraffic flow and the capacity is built. The urban traffic administrative system should take the traffic flow and capacity of expressway as the foundation of the traffic control and guidance system. The management system adjusts the running state and the vehicle traveling path based on the urban traffic demand, so the traffic loads are regulated and the demands of the city road according to the traffic capacity of the expressway, preventing the traffic jam of expressway.Finally, on the Microsoft Visual Basic platform, the administrive system simulation model is built, which adopeted MapObjects of ESRI, and the artificial prototype systems software is developd, so as to analyze the traffic load and the traffic capacity and support the expressway traffic management. It can be concluded from the simulation that this model can effectively maintain the running stable state and improve the traffic flow of the expressway system.