Analysis of Vehicle Speeds on Two-way Two-lane Expressways with ETC2.0 Data

Abstract

This paper focuses on an analysis of spatial variation of speed on two-way two-lane (TWTL) expressways in Japan with ETC2.0 data recorded at an interval of 200 meters instead of using traffic detector. Speed-profiles are drawn based on relation between speed and flow-rate in the TWTL sections of three representative routes (i.e., Okayama, Tokai-hokuriku and Joban Expressway). The speed-profiles show sections where the level of service is inferior to other sections and factors of slow-down may be found by qualitative analyses. As a result, non-trivial tendencies are found as follows; 1) generally, speed gradually decreases in the TWTL sections with fluctuation, on the other hand, 2) when flow-rate is relatively high (e.g., 800 pcu/h), speed decreases shortly after auxiliary passing lane, 3) sag or ascent section may be an another factor of slow-down. These findings may contribute to selection of sections where auxiliary passing lane is to be added in order to increase speed effectively, and to examination of the existing design guidelines.