Central Circular Route (C2)

Tokyo's second ring expressway, completed on 7 March 2015 as the first of the Greater Tokyo three-ring network to open in full. At its core is the Yamate Tunnel — 18.2 kilometres long, Japan's longest road tunnel and the world's longest expressway tunnel.

A Loop Buried Eighteen Kilometres Underground

Tokyo’s ring expressways build outward from the centre: the Inner Circular Route (C1) encircles the Imperial Palace, while Route C2, the Central Circular Route, traces a larger arc roughly one ring further out. Starting at Oi Junction in Shinagawa, C2 passes through Meguro, Shibuya, Shinjuku, Itabashi, Kita, Katsushika, and Edogawa wards before rejoining the Bayshore Route at Kasai Junction — a full circuit of approximately 47 kilometres.

The centrepiece of C2 is the Yamate Tunnel, which runs beneath Yamate-dori (Ring Road No. 6) from Ohashi Junction in Meguro northward to the Takamatsu on-ramp in Toshima. Its total length is 18.2 kilometres, making it Japan’s longest road tunnel. Among expressway tunnels — excluding those for ordinary roads — it holds the world record. From the street, the only visible trace of the tunnel is a series of modest ventilation towers standing quietly along Yamate-dori.

Half a Century to Close the Ring

Construction of C2 began in earnest in the 1980s, with the eastern arc along the Arakawa floodplain (Kasai to Kohoku Junction) as the first sections to open. The route extended incrementally: the Oji section opened in 2002; the northern portion of the Yamate Tunnel (Kumanomachi to Nishi-Shinjuku, opened December 2007); the southern portion (Nishi-Shinjuku to Ohashi, March 2010). Each stage involved increasingly complex engineering as the alignment moved deeper into dense urban ground.

The final section — approximately 9.4 kilometres between Ohashi and Oi junctions — opened on 7 March 2015, and C2 became the first of Tokyo’s three planned ring routes to be completed. The project, from initial concept to full opening, had taken roughly half a century. By diverting traffic away from the perpetually congested C1 corridor, C2 significantly increased the capacity of the entire Shuto network for freight and commuter traffic alike.

Summary

The Central Circular Route (C2) is a ring expressway of approximately 47 kilometres running through the inner wards of Tokyo, opened in full on 7 March 2015. Its defining feature, the Yamate Tunnel (18.2 km), holds records as Japan’s longest road tunnel and the world’s longest expressway tunnel. Although almost entirely underground, the route leaves its mark on the streetscape: find the ventilation towers along Yamate-dori and you have found the spine of the city beneath your feet.

Related: Shibuya Scramble Square / Shibuya Hikarie

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