The Oedo Line (大江戸線) is a subway line run by the Tokyo Metropolitan Bureau of Transportation (東京都交通局). Its radial section runs from Hikarigaoka Station in Nerima, Tokyo, to Tochomae Station in Shinjuku, and its loop runs around central Tokyo and back to Tochomae.
History
The Urban Transport Council (都市交通審議会) planned a subway Line 9, later Line 12. Its report No. 6 on 8 June 1962 named Line 9. Report No. 10 on 10 April 1968 renamed it Line 12. Report No. 15 on 1 March 1972 approved it. On 24 October 1972 the Bureau applied for a licence for the whole line, from Nishi-Shinjuku (now Tochomae Station) to Takamatsu-cho (now Hikarigaoka Station). The licence was granted on 30 August 1974. The plan then called for 20 m cars in 10-car trains and an opening target of 1985. The estimated cost was 6628億8100万円. The 1973 oil shock and the Bureau's money problems led to a freeze in mid-1976. A work approval application filed in December 1975 expired without review.
In May 1978 a Tokyo transport advisory body asked for new traffic forecasts before Line 12 was built. In December 1982 Tokyo's long-term plan set the line for construction. The former Grant Heights site at Hikarigaoka was being redeveloped with a large housing estate. The planners decided on smaller 16.5 m, 8-car trains, with smaller tunnels and fewer station facilities. The route changed in several places around Shinjuku, Roppongi, Shiodome and Iidabashi. The Tochomae station was moved to a route through Nishi-Shinjuku 5-chome. A loop route was studied, but it needed new track between Shinjuku and Shinjuku-Nishiguchi and a second platform at one of the two stations. The ground there was narrow and built up, so the cost and time were feared. The team chose a route shaped like the number six (6の字型). On 9 August 1984 the Hikarigaoka to Nerima section received its city planning decision. On 11 July 1985 the Transport Policy Council placed the line in its plan. On 7 August 1985 the Ministry of Transport approved work on Nerima to Hikarigaoka. On 20 February 1986 the Ministry of Construction approved laying the line under roads. On 18 April 1986 the 12-000 series prototype was unveiled. On 30 June 1986 the line colour was set as magenta. Construction of Hikarigaoka to Nerima began on 1 June 1986.
The Bureau first estimated 2,640億円 for the radial section, 5,850億円 for the loop, and 8,490億円 in total. Planned openings were March 1991 for Hikarigaoka to Nerima, March 1995 for Nerima to Shinjuku, and March 1997 for the loop. Land purchase problems delayed building, and the cost rose to about 1.5 times the plan or more. The final cost was 3,991億円 for the radial section, 9,583億円 for the loop, and 1兆3,574億円 in total. Japanese Wikipedia says this was comparable to national projects such as the Tokyo Bay Aqua-Line and Kansai International Airport. Because the loop had to open all at once, it was built by a third-sector company, Tokyo Metropolitan Subway Construction (東京都地下鉄建設). The company was set up on 28 July 1988. It built the loop as a Class 3 railway operator, and the Bureau took over the facilities and trains over a long period. The Kokuritsu-kyogijo to Shinjuku section was bought early by the Bureau and opened first, because it allowed turn-back trains. On 30 March 1989 the company applied for a licence for Shinjuku to Shinjuku-Nishiguchi, and it was granted on 31 May 1989.
The 12-000 prototype was built in April 1986 and tested at Magome depot. It was the first Toei subway car to use VVVF inverter control. From 6 May 1988 the prototype was converted to linear motor drive and tested until November 1988. On 21 December 1988 the Bureau chose linear motor drive for Line 12. This let the line use sharper curves and steeper slopes, and run under roads and parks instead of private land. The loop stations needed many lifts and escalators. Work was bundled to cut costs, and some foreign firms were brought in. The loop facilities were completed on 29 November 2000, and passed to the Bureau the next day.
Construction of Shinjuku to Nerima began on 1 August 1990. The 12-000 series trains began arriving at Hikarigaoka depot on 17 September 1990. On 10 December 1991 the Hikarigaoka to Nerima section opened as Toei Line 12. The line ran all-night service on New Year's Eve from the start, and it has done so every year since. The other three Toei subway lines stopped it for a time. On 1 February 1992 Tokyo Metropolitan Subway Construction began building the loop. On 25 May 1997 the 12-000 series third batch began service, and all trains changed from six cars to eight cars. On 19 December 1997 the Nerima to Shinjuku section opened.
In 1999 the line needed a name, and the public was asked for ideas. The committee's first choice was Tokyo Loop Line (東京環状線), with the nickname Yume Mogura. Governor Shintaro Ishihara did not like that name, and said he preferred Oedo Line (大江戸線). On 15 December 1999 the committee chose Oedo Line. Some members argued that Shinjuku lay outside the old Edo boundary. The Bureau said the name shows the line circling the area, and the word big shows its reach. On 20 April 2000 the first section, Shinjuku to Kokuritsu-kyogijo, opened under the name Oedo Line. On 12 December 2000 the whole route opened, from Kokuritsu-kyogijo through Roppongi, Daimon, Ryogoku and Iidabashi to Tochomae. Shiodome did not open, because its roads were not finished. The site was used as a passing signal box. The date was chosen to match the planning name Line 12. When the whole line opened, the slogan Tokyo's Anywhere Door was used, and Doraemon appeared as a promotional character. On 2 November 2002 Shiodome station opened. On 1 April 2006 the Shiodome connection line began service and E5000 series trains started running. On 23 October 2007 a power cut between Nakai and Nerima stopped the whole line, and service was restored that morning. Japanese Wikipedia says the cause was an inspection at Nerima substation on 19 October 2007, which left a disconnecting switch unrestored. More trains in the morning rush then overloaded the other circuit, and its current cut out. From 1 April 2008 the loop passed from Tokyo Metropolitan Subway Construction to the Bureau. The company's licence ended, and the whole line ran under the Bureau's own licence.
On 11 March 2011 the Tohoku earthquake stopped the whole line for a time. Service restarted that evening. On 23 April 2011 platform doors were first used on this line at Kiyosumi-shirakawa. On 17 March 2012 the daytime interval was changed to every six minutes. Platform doors were completed at all stations on 27 April 2013, when Nishi-Shinjuku 5-chome started using them. On 31 July 2019 a car decorated in the Thomas the Tank Engine design, with a childcare space, began service. On 18 January 2023 a women-only car was introduced in the weekday morning rush. On 15 October 2025 the Tokyo Metropolitan Government published the status of its study of an extension from Hikarigaoka to a planned Oizumi-gakuen-machi station, with a draft plan.
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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.