Travel time variation and reliability indices on the basis of license plate identification

Travel time reliability is an emerging evaluation measure for highway network service levels. Many indices for travel time reliability have been proposed hitherto. The behaviors of these indices have been analyzed, and they depend on the highway traffic characteristics. Some studies, however, analyzed them on the motorways in the urban area. They seem to be short in distance and relatively congested. Many types of traffic should be analyzed. Thus, this paper analyses a long distance expressway, and calculates travel time reliability indices and compares them. This paper focuses on three topics as follows: Firstly, this paper presents the travel time variation on the expressway. For this purpose, vehicle identification is introduced. Every vehicle´s travel time is estimated by identifying vehicle license plate information. The distance of expressway in the case study is 134.2km and it is divided into three sections. Secondly, this paper shows the dependency of the vehicle´s driving status between adjacent sections. When this hypothesis of dependency is supported, the calculation of travel time variation for long distance expressway can be easily estimated on the basis of travel time variation for unit length. Thirdly, this paper calculates 11 types of travel time reliability indices, then compares them among the three sections.