Nihonbashi Expressway Undergrounding

A ¥320 billion project to move 1.8 km of the Shuto Expressway's Inner Circular Route underground between Kandabashi and Edobashi junctions, dismantling the elevated structure that has shadowed Nihonbashi Bridge since 1963 and restoring open sky above the river by 2040.

Returning the Sky to Nihonbashi

For more than sixty years, the historic Nihonbashi Bridge has stood beneath a shadow it did not invite. When the Shuto Expressway’s elevated structure was rushed into service ahead of the 1964 Tokyo Olympics, the girders of the Inner Circular Route were planted directly above the Nihonbashi River — obscuring the sky that the 1911 stone arch bridge had always expected to see above it. The Nihonbashi Expressway Undergrounding project is the answer to a question Tokyo has been asking for decades: what would it take to give that sky back?

The answer is approximately 1.8 kilometres of new underground road between Kandabashi Junction (Chiyoda City) and Edobashi Junction (Chuo City). The project received national government approval in March 2020 and metropolitan planning approval in April of the same year. The section carries approximately 100,000 vehicles a day; alongside the landscape restoration goal, the aging elevated structure also needed a long-term engineering solution.

Scope and Method

The most complex part of the work — the shield-tunnel section beneath the Nihonbashi River — was awarded to Taisei Corporation, with a construction period running from March 2024 to March 2034. Non-open-cut methods are used to protect the riverbed and adjacent existing structures during excavation. Total project cost is approximately ¥320 billion, shared among the Shuto Expressway Company (the largest share), Tokyo Metropolitan Government, Chuo Ward, and private-sector partners.

The schedule calls for the underground tunnel to open to traffic in fiscal year 2035, with demolition of the existing elevated structure completed by fiscal year 2040. When that work is done, the Nihonbashi River will once again run beneath open sky, and the bridge that has named the area for centuries will finally stand free of the overpass above it.

Summary

The Nihonbashi Expressway Undergrounding project targets the 1.8 km stretch of the Shuto Inner Circular Route between Kandabashi and Edobashi junctions, approved in 2020 and scheduled for completion in 2040. The ¥320 billion scheme will bury the elevated road that has shadowed Nihonbashi since 1963 and return the open sky above one of Tokyo’s most storied streets. While the decade-long tunnel construction is well underway, the old elevated ramps are still there — and a walk along the Nihonbashi riverbank, looking up at what is about to disappear, remains one of the best ways to understand how much the city has changed, and how much it is still changing.

Related: Edobashi Junction / Inner Circular Route (C1)

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