The world’s first two double-deck bridges (the shape of four eyes) – Wasyuzan Tunnel

Wasyuzan Tunnel was bored through Mt. Wasyu at Kurashiki City in Okayama Prefecture in 1988. There are two tunnels for cars in the upper part and two tunnels for trains in the lower part. This structure of two double-deck bridges (the shape of four eyes) was used for the first time in the world.

Wasyuzan Tunnel was completed in 1985 and opened to traffic on April 10, 1988. The Tunnel is connected to Seto-Ohashi on the Kojima-Sakaide route, which links Honshu and Shikoku. There are three routes between Honshu and Shikoku: Kobe-Naruto, Kojima-Sakaide and Onomichi-Imabari. Of the routes, Kojima-Sakaide opened to traffic first in 1988.

The length of the upper tunnels is 205 meters. The lower tunnels measure 230 meters.  The upper routes are the up and down lines of the Seto-Chuo Expressway, while the lower routes are the Hon-Shi-Bisan Line (Seto-Ohasi Line). The Shikoku Shinkansen is going to pass there in the future, too.

Leveling the mountain was the initial plan, but because Mt. Wasyu is in Setonaikai National Park, its preservation must be observed. Thus, the method to tunnel through was adopted.