The Chūō–Sōbu Line (Local) (中央・総武緩行線) is the name for the local all-stop service run by East Japan Railway Company (JR East). It runs from Chiba Station in Chiba city to Mitaka Station in Mitaka city, through Ochanomizu Station.
History
Before the 1923 Great Kanto Earthquake (関東大震災), the Sōbu Main Line (総武本線) started at Ryōgoku-bashi Station (now Ryōgoku Station), on the east bank of the Sumida River. Many passengers already used the Tokyo city trams across the river, and the crowding was severe. During the rebuilding after the quake, a line into central Tokyo was planned, with a plan to run trains into the Chūō Main Line (中央本線). The elevated line from Ryōgoku to Ochanomizu was finished on 1 July 1932. The extra tracks from Ochanomizu to Nakano were finished on 15 September 1933. In 1943 Manseibashi Station, on the Chūō Main Line between Kanda and Ochanomizu, was closed.
The Chūō and Sōbu lines began running into each other in 1933. At first express trains (now rapid trains) ran only in the weekday morning and evening rush hours. Local trains ran from the Sōbu line through Ochanomizu to Nakano at those times. Before the war, most Chūō trains to Nakano turned back at Ryōgoku. After the war, passengers from east of the Sumida River and from Chiba grew sharply, so the turnback at Ryōgoku ended. On 9 November 1959 the weekday timetable allowed express service all day except early morning and late night. On 28 April 1966 the holiday timetable did the same, and most Sōbu trains then ran through to Nakano. On 1 October 1968 rapid trains began running from Nakano to Narita and Kisarazu, about one or two an hour.
The Nakano to Ogikubo section was widened to four tracks in 1966, when Tokyo Metro's Tōzai Line (東西線) began running into it. The Ogikubo to Mitaka section followed in 1969 with new local tracks, so Chūō–Sōbu trains reached Mitaka. In 1963, 101 series trains began moving to the line when Yamanote Line (山手線) received new 103 series trains. By 1969 all cars on the line were 101 series. On 15 July 1972 the rapid trains were separated from the local trains by a new Tokyo to Kinshicho section and four tracks from Kinshicho to Tsudanuma. Rapid trains from Nakano were then abolished. Tsudanuma to Chiba still had only two tracks, so local and rapid trains shared it. The Sōbu Rapid Line from Tsudanuma to Chiba was completed in 1981, and the service became almost the same as today.
Air-conditioning came late. The line was the only one on the Tokyo-area suburban network with no air-conditioned cars. On 29 July 1978 air-conditioned 101 series cars were introduced. On 14 August 1982 201 series trains began replacing the 101 series. In summer 1988 new 205 series trains were built and 103 series cars were converted, so all cars became air-conditioned, except the cars that run through to the Tōzai Line. Weak-cooling cars began running in summer 1989. Cars that run through to the Tōzai Line were air-conditioned between 1988 and 1990, and Tōzai Line 5000 series trains ran without air-conditioning until summer 1994. In the late 1990s the 103 series broke down often, and the media criticised the line for running old trains. The 209 series 500 番台 trains were introduced in 1998, and E231 series trains in 2000, and the old 103 series were replaced in a short time. The 201 and 205 series were moved to other lines, including the Keiyo Line (京葉線), Ome Line (青梅線) and Itsukaichi Line (五日市線).
Until the last train on 13 March 2020, trains in the early morning and late night did not run through. They were split at Ochanomizu, the original junction station. From 14 March 2020 a new timetable ran trains through all day between the Chūō Main Line and the Sōbu Main Line. In 2021, on 20 January, the government issued an emergency declaration over COVID-19 and asked for cuts. Some trains were cancelled. Eastbound, trains leaving Tsudanuma after 1:06 were cancelled, and last trains ran up to about 20 minutes earlier. Westbound, trains leaving Nakano after 0:57 were cancelled, and last trains between Nakano and Mitaka ran about 20 minutes earlier. On weekday timetables the last trains between Chiba and Tsudanuma ran about 14 minutes earlier.
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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.