Study on Location of the Variable Message Signs Based on Grey Situation Decision

Variable message signs (VMS) is an important tool and method in DRGS (Dynamic Route Guidance System). It can help the driver choose an appropriate way to avoid the traffic congestion, reduce driver´s anxiety, and reduce traffic accidents, improve road traffic conditions, improve road capacity effectively. VMS has been used for more than ten years in China, but up to the present there is not a complete and systemic design criterion, especially to the site selection of VMS, it lacks comprehensive and systemic analytical method. This paper, reference to domestic and foreign research results, firstly, discusses how to identify the best location of VMS based on the grey situation decision method; then, gives a case study of loop expressway in Xi`an, which turns out that the method proposed by the paper has certain popularization and application value, because of its simple operation, definite principle and reliable result.