The Tozai Line (東西線) is a railway line run by Tokyo Metro (東京地下鉄). It runs from Nakano Station in Nakano Ward, Tokyo, to Nishi-Funabashi Station in Funabashi, Chiba.
History
A plan for the line dates from 1917, when a transport committee set up by the Home Ministry proposed the Ikebukuro to Suzaki route. In 1920 a licence was given to Tokyo Railway. After the Great Kanto Earthquake of 1923, that licence and others were cancelled because construction had not started. Tokyo City (東京市) obtained the licence for line 5 on 16 May 1925. In 1941 the licences passed to the Teito Rapid Transit Authority (Eidan Subway, 営団地下鉄). In December 1946 the post-war reconstruction office listed the line as one of five planned lines.
In 1949 Eidan changed its licence to match the 1946 plan, and the change was approved on 23 May 1949. In 1956 a plan to add capacity on the JNR Chuo Line failed because land was hard to buy, and it was then concluded that linking the planned Tozai Line with the Chuo and Sobu local trains would make it easier to reach central Tokyo. The route was revised on 17 June 1957. On 2 August 1960 Eidan decided to build the line. In August 1961 Eidan and the JNR agreed to through running with the Chuo Line, and the planned track gauge was changed to narrow gauge so that trains could run through. In 1964 the transport council set the route to Urayasu and Gyotoku, and on 27 March 1964 Eidan decided to extend the line to Nishi-Funabashi.
On 23 December 1964 the first section, Takadanobaba to Kudanshita, opened. On 16 March 1966 Nakano to Takadanobaba opened, along with Kudanshita to Takebashi. Through running to Ogikubo on the JNR Chuo Line began on 28 April 1966, at first only one way. Takebashi to Otemachi opened on 1 October 1966, when JNR 301 series trains were brought in for through running. Otemachi to Toyocho opened on 14 September 1967. The last section, Toyocho to Nishi-Funabashi, opened on 29 March 1969, which completed the whole line, and rapid trains began. On 8 April 1969 through running on the Chuo Line was extended to Mitaka, and JNR Sobu Line trains ran to Tsudanuma.
On 1 November 1977 some trains began running as ten-car sets. On 28 February 1978 a gust of wind on the Arakawa bridge between Kasai and Minami-Sunamachi derailed three cars of a Nakano-bound train, and two of them overturned. Twenty-some people were injured. The gust was later found to have come from a tornado. On 1 October 1979 Nishi-Kasai Station opened, and on 27 March 1981 Minami-Gyotoku Station opened. In 1987 the through partner became East Japan Railway Company (JR East). Air-conditioning began on 1 June 1988. On 20 June 1990 all of Eidan's own trains became ten-car sets, and in December 1991 all trains on the line were ten-car sets.
In 1974 Eidan decided to extend the line from Nishi-Funabashi to Katsutadai, after a local council formed in May 1973 had repeatedly asked for it. Keisei Electric Railway objected, calling the plan a matter of survival for its business, because the two competed on the route. In 1980 a final plan was agreed. A third-sector company would build the extension, with local governments, banks and rail companies investing, and Keisei would run it. The Toyo High-Speed Railway (東葉高速鉄道) was set up on 1 September 1981, and Eidan withdrew its application on 15 February 1982. The Toyo High-Speed Line opened on 27 April 1996 with through running to the Tozai Line. On 1 April 2004 Eidan was privatised as Tokyo Metro, and the line became the Tokyo Metro Tozai Line (東京メトロ東西線).
On 17 March 2007 the 5000 series ended its service on the line. On 9 September 2009 a maintenance vehicle collided head-on with a parked train at Toyocho Station, and service was stopped between Takadanobaba and Kasai. Japanese Wikipedia says about five hours passed before the whole line resumed. On 7 May 2010 the 15000 series began service. After the March 2011 earthquake, rolling blackouts began on 14 March 2011, and through running with the JR Chuo Line, the JR Sobu Line and the Toyo High-Speed Line, and rapid trains, were suspended. Through running and rapid trains returned on weekday rush hours on 18 March 2011, weekend rapid service was fully restored on 11 June 2011, and weekday service returned to normal on 12 September 2011.
On 26 November 2012 mobile phones became usable between Nihombashi and Nishi-Kasai, and the stretch from Nakano to Kudanshita followed on 7 February 2013. On 18 September 2022 rainwater flowed onto the track between Iidabashi and Kagurazaka from a sewer works site. The line was suspended from Takadanobaba to Nihombashi for about eight hours. On 11 and 12 May 2024 track changeover work at Minami-Sunamachi suspended service between Toyocho and Nishi-Kasai, with replacement buses. On 28 March 2026 platform screen doors came into use at Haraki-Nakayama Station, and Japanese Wikipedia says this completed installation at all 180 Tokyo Metro stations, except some platforms at JR-managed Nakano Station and at Minami-Sunamachi, which is under improvement work.
See the live map and facts in the Data view →
Written by an AI from the line's history on Japanese Wikipedia, nothing else, and checked by a program for dates and numbers that are not in those facts. It can still be wrong. Adapted from Japanese Wikipedia, CC BY-SA 4.0; this text is shared under the same licence.