Seoul Subway Line 1
Seoul Metropolitan Subway Line 1 of the Seoul Metropolitan Subway is a rapid transit and commuter rail line which links central Seoul, South Korea to Soyosan Station in the northeast, Incheon in the southwest, and Sinchang via Suwon and Cheonan in the south. The central underground portion of this rail line is the oldest subway section in the Seoul Metropolitan Subway system. Its branches and services cover a large part of the Seoul Capital Area; totaling in route length. The underground section between Seoul Station and Cheongnyangni station, which is referred to as Seoul Metro Line  1 (), is currently operated by Seoul Metro. The line first opened in 1974 as the <nowiki>Korean National Railroad of Seoul</nowiki> with through services to national mainline railways from Seongbuk station (now: Kwangwoon University station) to Incheon and Suwon Stations. At the time, the 7.8 km underground portion was run by Seoul Metro was called Line 1 and labeled red on maps. On the other hand, the remaining sections of the rail line run by Korail were labeled either blue or gray on maps, and the express lines were red. In 2000, the adjacent through-running Korail  services from the Gyeongbu, Gyeongin and Gyeongwon Lines were officially bundled together as part of a greater Line 1, and the labeling on maps was changed to the current dark blue color. Frequent service is provided between Soyosan, Dongducheon, Uijeongbu, Cheongnyangni, Seoul, Yongsan, and Guro, where trains split between Incheon in the west and Byeongjeom and Cheonan in the south. Express trains operate from Yongsan and Seoul stations to Dongincheon and Sinchang stations. Trains run every 3-6 min in the central route between Seoul Station and Cheongnyangni, every 6-9 min between Seoul and Guro, every 8-10 min  between Guro and Incheon and between Guro and Byeongjeom, every 10-15 min from Byeongjeom to Cheonan, and every 35 min between Cheonan and Sinchang and service up to the Dongducheon area and Soyosan station Trains travel along Gyeongbu (Seoul-Cheonan), Gyeongin (Guro-Incheon), Janghang (Cheonan-Sinchang), and Gyeongwon (Hoegi-Soyosan) railway lines. The line runs on the left-hand side of the track, as opposed to the right-hand side of the track like all other Seoul Metropolitan Subway lines (another exception to this is Seoul Subway Line 4 although it runs on the right-hand side until Namtaeryeong  station, and operates on the left-hand side for the parts afterwards) since railways in Korea generally run on the left side. Rapid (Express) trains. Korail operates a variety of express "rapid" (급행, 急行) trains for long distance commuter services on Line 1. These services include: Former express services include: Electric current. Seoul Subway Line 1 is powered by 1500 V direct current between Cheongnyangni station and Seoul Station, and by 25000 V alternating current elsewhere. Because of this different manner of offering electric current, there are neutral sections between Cheongnyangni station and Hoegi station, as well as between Seoul  Station and Namyeong station. Stations. Main Lines. Local lines: Express lines: ※ Only Korail trains are used for express trains. Key: Historical Timeline. 1974 1978 1979 1980 1982 1984 1985 1986 1987 1988 1994 1995 1996 1997 1998 2000 2001 2003 2004 2005 2006 2007 2008 2010 2015 2017 2019 2021 Future Plans. Line 1 will be extended northward from Soyosan Station to Yeoncheon Station on the Gyeongwon Line, replacing the current ""'Tonggeun"" service operating there. Construction on this extension began in September 2014 and is expected to be completed in November 2021. Depots and facilities. "(from north to south)" Seoul