Seohae Line

After the completion of planning, the project was written out as a build–lease–transfer (BLT) project, and Daewoo was selected[3] as preferred bidder in September 2008.[1] Construction was scheduled to last from October 2009 to March 2013.[4] Due to the global financial crisis, it was difficult to gather investors to finance the project, and negotiations stalled.[1] An agreement was finally signed on December 21, 2010, with construction set to start in the first half of 2011.[1] Project costs are 1.5248 trillion South Korean won, the contractor has altogether seven years for design and construction, and will manage and maintain the line for the first 20 years of operation.[1]

The first section began construction in 2011 and opened on June 16, 2018.[5]

The second section runs north from Sosa to Daegok on the Gyeongui-Jungang Line and Seoul Subway Line 3. There are transfers to several other lines. It was proposed to open on June 29, 2021, but was postponed. The first section of the extension (Sosa-Daegok) was successfully opened on July 1, 2023. The rest of the extension (Daegok-Ilsan) was opened at the end of August 2023.

On September 1, 2010, the South Korean government announced a strategic plan to reduce travel times from Seoul to 95% of the country to under 2 hours by 2020. As part of the plan, the first section is to be further upgraded for 230 km/h (140 mph) the Wonsi–Hwayang extension is to be projected for 250 km/h (160 mph), and the line may see KTX service.[6]

Tentative plans foresee the upgrade and incorporation of the Gyooe Line, a single-track non-electrified line without passenger service that connects Neunggok station (with a junction just before Daegok station) and Uijeongbu station in Uijeongbu. The Uijeongbu–Daegok–Sosa–Wonsi Line would then provide orbital metro service as a northern semicircle around Seoul, complementing the southern semicircle formed by the Suin–Bundang Line.

Another part of the tentative 2010 plans was a southern extension from Wonsi, connecting up with the Janghang Line before Hongseong station.[7][8] As of April 2023, the construction of this section was 92% completed and expected to be opened in the second half of 2024.[9]

• Transportation in South Korea
• Korail