Strategy Research On VMS Information Coordinated Release For Expressway Networks

As an important part of Advanced Traveler Information System (ATIS), Variable Message Sign (VMS) can provide drivers with traffic information and guidance in order to reduce traffic congestion and enhance the road traffic flow efficiency. As the number of VMS in the expressway networks increases, it is of practical significance to work out a good strategy of information coordinated release which can be used in the information release system.The relationships among the content, scope and time of information released by VMS were studied in this paper and then a strategy of information coordinated release was proposed.First, the content release methods in overseas and domestic were studied and the situation of the present information release system used in Shanxi Province was analysed. Then a classification of content for information coordinated release strategy of VMS was provided and prioritized to be a theoretical basis for the strategy of information coordinated release.Second, a strategy of information coordinated release was developed. The definitions of two kinds of feature points were proposed, which respectively were the influence range point of traffic incident and exit feature point. On this basis, the upstream region of event point was divided into three regions, which are high level advisory information region, low level advisory information region and no response information region. Alternative route information region was then defined. The linear regression model was constructed to predict traffic incident duration and the influence range of traffic incident was calculated by traffic wave theory and queueing theory. Then high level advisory information region, low level advisory information region were determined and the scope and time of information released of responding VMS were calculated. The scope and time of information released in alternative route information region was obtained according to the method of travel time under abnormal traffic condition proposed in this paper. Then the final strategy of information coordinated release was determined by validity of information and the shortest release time limit and message priority.At last, the strategy of information coordinated release was validated by a traffic accident occurred in Taiyuan Expressway. And it was compared with the present method of information coordinated release to analyse the advantages and demonstrate the feasibility and rationality.