| In recent years, the number of car in our city has increased rapidly, and the road traffic flow has increased sharply, causing with frequent traffic jam phenomenon. The contradiction between supply and demand of urban traffic has been very prominent, and has become increasingly serious. Traffic congestion has become a problem to be reckoned with in the city, affects the sustainable development of the city. Currently, the more effective solution to solve traffic congestion is the traffic control and guidance. But the real time traffic information collection and accurate evaluation of traffic state is the premise of effective implementation of traffic control and traffic guidance.As Cooperative Vehicle Infrastructure System (CVIS) is put forward, developed and applied, research on road traffic information collection and state evaluation based on the CVIS has gotten more attention of many scholars and research institutions. However, road traffic information collection in the environment of CVIS is by the way of sending data to the RSU at a fixed period, rarely considers the actual state of traffic. This way of road traffic information collection has some defects. On the one hand, because all of the vehicles send state information to RSU at a fixed period, when the vehicle density is larger or the requirement of the road condition assessment is low, the frequent delivery status message packet will increase the holding time of wireless communication channel, lead to the waste of communication resources, increase wireless network load, and further affect the other application of CVIS. On the other hand, if we only extend the vehicle delivery status message packet interval to reduce the holding time of wireless communication channel, when the road is congestion, the long sending cycle of message will reduce the number of real time data packets that RSU receives, that will affect the accuracy of road traffic state evaluation.In order to solve the above problems, this paper puts forward a method of road traffic information collection and evaluation based on CVIS. The vehicles can dynamically adjust the cycle of sending status message to the roadside unit with the change of traffic status, to implement the strategy of data adaptive transmission.This paper includes the following works:(1) The road traffic information collection and state evaluation system based on CVIS is built, the structure design is given. The function and related technology of each composition unit of the system are studied.(2) A method of traffic information adaptive collection strategy and state evaluation based on CVIS is put forward. Firstly, we establish the relationship model between traffic status information collection interval and the single parameter traffic state evaluation index El. Then we get the method of calculation of the single parameter traffic state evaluation index EI based on fuzzy. Finally, we give the equation of total benefit of traffic state evaluation accuracy and wireless channel holding time.(3) The simulation of road traffic information collection and state evaluation system based on CVIS is designed. We use VanetMobiSim-1.1/NS2/SQL Server2005 /Visual C++6.0 to simulate the system, and use the system to test and verify the method of road traffic state information adaptive collection strategy and state evaluation based on CVIS. |
