Seoul Subway Line 1

Seoul Subway Line 1 (dubbed The Dark Blue Line) of the Seoul Metropolitan Subway is a rapid transit and commuter rail line which links central Seoul, South Korea to Yeoncheon in the northeast, Incheon in the southwest, and Sinchang via Suwon and Cheonan in the south. The central underground portion of Line 1, running underneath Sejongno, Jongno, and Wangsan-ro avenues along Seoul's traditional downtown area, is the oldest subway-operated section in the Seoul Metropolitan Subway system. Its branches and services cover a large part of the Seoul Metropolitan Area; totaling 218.3 km (135.6 mi) in route length.
The underground section between Seoul station and Cheongnyangni station, which is referred to as Seoul Metro Line 1 (7.8 km [4.8 mi]) after its operator, is currently operated by Seoul Metro, and is electrified at the subway standard of 1.5 kV DC. The line first opened in 1974 as the Korean National Railroad of Seoul with through services to newly-electrified (at the mainline KNR standard of 25 kV AC 60 Hz) national mainline railways from Seongbuk station (now: Kwangwoon University station) to Incheon and Suwon stations. This was the first electrified rapid transit line and service in South Korea and the second in the Korean Peninsula after the Pyongyang Metro in North Korea opened the year before.
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.
Service to Yeoncheon is approximately once per hour, limited due to the single track section approaching Soyosan station. This service is meant to be the replacement for the Gyeongwon line commuter trains, which began at Dongducheon station prior to its closure.
Trains travel along Gyeongbu (Seoul-Cheonan), Gyeongin (Guro-Incheon), Janghang (Cheonan-Sinchang), and Gyeongwon (Hoegi-Yeoncheon) 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.
Korail operates a variety of express "rapid" (Korean: 급행 geup-haeng, Hanja: 急行) trains for long distance commuter services on Line 1. These services include:
Former express services include:
Seoul Subway Line 1 is powered by 1500 V direct current on the underground tunnel segment between Cheongnyangni station and Seoul station, and by 25000 V alternating current (60 Hertz frequency) on the rest of the line. Underground DC system was implemented in order to prevent possible telecommunication malfunction by AC current on telephone lines, following the opposition from the Ministry of Postal Service (currently Ministry of Science and ICT). 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. All Line 1 rolling stock are similarly required to be multi-system compatible with both electrification systems.
Until 2000, the 7.8 km (4.8 mi) underground city-center portion run by Seoul Metro Corporation—one of Seoul Metro's predecessors—was the only section properly referred to as Line 1 and labeled red on maps. On the other hand, the remaining sections of the rail line run by Korail were referred to as Korean National Railroad of Seoul and the local all-stop services labeled either blue or gray on maps, while the express services were labelled thin red. Since 2000, all adjacent through-running Korail services from the Gyeongbu, Gyeongin and Gyeongwon Lines, as well as later Korail-operated extensions and branches, are officially bundled together with the aforementioned underground portion as part of a greater Line 1, and the labeling on maps was changed and standardized to the current dark blue color (as illustrated in the map below); also to avoid confusion with Line 4's light blue color. (A slightly different shade of red is now used to label the Shinbundang Line which opened in 2011.)
Local lines:
Express lines:
※ Only Korail trains are used for express trains. Key:
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(from north to south)