A study on the progress of expressway tunnel portal design in Japan

摘要

A tunnel portal has a psychological resistant effect on drivers. As a result, not only it makes driving less comfortable but also it can cause sometimes a bottleneck of expressway traffic flow. The improvement and refinement of the tunnel portal design are necessary to solve such problems. In this research, the designs of about a thousand expressway tunnel portals are analyzed to get basic data needed for improvements of portal design. The tunnel portal database contains 1,119 portal data sets based on the survey of all expressways (37 routes) serviced by The Japan Highway Public Corporation. The shape and decorated design of expressway tunnel portals are classified in detail and their progress and improvement since 1963 to 1995 are analyzed based on the tunnel data-base.