Abstract
This study aims to identify the causes of traffic congestion around Takarazuka-Higashi Tunnel, Chugoku Expressway by analyzing the phenomena of traffic flow. This section includes several structural features such as sag alignment, contiguous tunnels, and merging and diverging lanes of an interchange that may contribute to multiple causes of capacity reduction and involve complicated traffic phenomena. This study made a detailed analysis of traffic phenomena such as traffic flow rate, travel speed, vehicle headway and platoon that had been observed by vehicle detectors and video cameras installed on several points inside and outside of the tunnel. The mechanism of congestion occurrence was discussed and modeled.
