Seto Ōhashi Bridge

Opened 10 April 1988, this road-rail combined bridge links Kojima in Kurashiki, Okayama with Sakaide, Kagawa across the Bisan Seto strait. Six bridges totalling 9,368 m in bridge length carry the Seto-Chuo Expressway above and the JR Bisan-Seto Line below — the world's longest road-rail combined crossing.

Use

Bridge

Area

Kurashiki, Okayama / Sakaide, Kagawa

Completed

1988

Developer

Honshu–Shikoku Bridge Authority (now Honshu–Shikoku Bridge Expressway Co., Ltd.)

Six Bridges, Five Islands, One Crossing

On 10 April 1988, a bridge network opened across the Bisan Seto — the stretch of the Seto Inland Sea between Okayama and Kagawa Prefectures. Commonly called Seto Ōhashi (the Great Seto Bridge), the crossing is formally part of the Kojima–Sakaide Route of the Honshu–Shikoku Bridge project. It is not a single bridge but a chain of six bridges spanning five islands, with a total bridge length of 9,368 metres. The Honshu–Shikoku Bridge Authority broke ground in October 1978, and after nine and a half years of construction the crossing was complete.

What sets Seto Ōhashi apart from other long-span bridges is its cross-section: road traffic on the upper deck via the Seto-Chuo Expressway, and rail traffic on the lower deck via the JR Bisan-Seto Line. Running both a motorway and a railway through the same structure for 9,368 metres makes Seto Ōhashi the world’s longest road-rail combined bridge — a record it holds to this day.

The Geometry of Six Bridges

The six bridges are: Shimotsui Seto Bridge (suspension, 1,447 m span, central span 940 m, towers 149 m), Hitsuishi-jima Bridge (cable-stayed, 792 m, central span 420 m, towers 152 m), Iwakuro-jima Bridge (cable-stayed), Yoshima Bridge (truss), North Bisan Seto Bridge (suspension), and South Bisan Seto Bridge (suspension, 1,723 m, central span 1,100 m, towers 194 m). The South Bisan Seto Bridge is the largest of the six; its tower tops reach 194 metres. Proceeding from the Okayama shore toward Kagawa, the bridges step across the islands in a sequence of suspension, cable-stayed, truss, and suspension forms — a compact survey of major bridge engineering types in a single journey.

The Yoshima Parking Area on the Seto-Chuo Expressway provides a rare stopping point where drivers can step out and look back across the towers and cables arrayed over the Seto Inland Sea. On misty mornings the far towers disappear before the eye can follow them.

Summary

Opened on 10 April 1988, Seto Ōhashi Bridge spans 9,368 metres with road and rail on separate decks, making it the world’s longest road-rail combined bridge. Its six spans — three suspension, two cable-stayed, one truss — hop across five islands in the Bisan Seto and have reshaped travel between Honshu and Shikoku since the day they opened.

For comparison with other Honshu–Shikoku engineering landmarks, the suspension-bridge record of Akashi Kaikyō Bridge and the truss silhouette of Tokyo Gate Bridge offer different chapters of the same story. For accommodation in Kurashiki, Sakaide, or Marugame, Rakuten Travel covers the area well.