The national government and Tokyo metropolitan government are firming up plans for the extension of the Yurakucho and Namboku subway lines. The extensions could be completed by the 2030s.

Under these plans, the Yurakucho Line could be connected between Toyosu Station and Sumiyoshi Station, over a 5.2-kilometer line. The Namboku Line could be connected between Shirokane-Takanawa Station and Shinagawa Station, over a 2.5-kilometer line.

A two-year environmental impact assessment will be carried out between 2022 and 2024, with Tokyo Metro, the operator of the subway lines, to formulate a business plan. The project costs are estimated to be 156 billion Yen (US$1.36 billion) for the Yurakucho line and 80 billion Yen (US$696 million) for the Namboku line. These costs could likely grow due to the rising cost of labor and materials. The national and Tokyo government will subside 75% of the cost, with Tokyo Metro to obtain public financing for the remainder.

Once approved, construction is expected to take around 10 years. These will be the newest lines in Tokyo since the completion of the Fukutoshin Subway Line in 2008. The Yurakucho line extension is expected to help alleviate congestion between Kiba and Monzennakacho Stations by 19 percentage points, and between Kasai-Rinkai-Koen and Shin-Kiba Stations by 11 percentage points, reducing passenger capacity to 170% during the morning commute.

The Shinagawa Station connection will provide Tokyo Metro passengers with access to the Chuo Shinkansen maglev train which was tentatively scheduled to be operating by 2027, but negotiations over part of the planned route in Shizuoka Prefecture have stalled, with the operations likely to be delayed.

Sources: 
The Tokyo Shimbun, December 25, 2021.
The Asahi Shimbun, December 21, 2021.

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