Great Train eXpress

Groundbreaking for GTX Line A was held on December 27, 2018, with service expected to commence in 2023.[4] However, the project has been officially delayed due to land compensation issues and the discovery of archeological ruins dating from the Joseon period.[5] The Suseo-Dongtan section is now scheduled to be completed in 2023 and the rest of the line to open in 2024.[6] Samseong Station being even further delayed and will remain closed after the rest of GTX A opens until 2028.[7] As of October 2021, the project was only about 20% complete, leading to speculation that GTX A is more likely to be completed around 2024 or 2025 or even later.[8][5] Approximately 30 kilometers of the line are expected to share the same rail as the SRT, and a further 9 km towards the western end of the route are expected to be completely underground.[9]

Station number	Station name			Transfer	Line name	Distance	Total distance	Location
	English	Hangul	Hanja
TBA	Unjeong[upper-alpha 1]	운정	雲井		GTX A	—	0.0	Gyeonggi-do	Paju
	KINTEX[upper-alpha 2]	킨텍스	킨텍스			—	—		Goyang
	Daegok	대곡	大谷	Seohae Line		—	—
	Yeonsinnae	연신내	연신내			—	—	Seoul	Eunpyeong
	Seoul Station	서울역	서울역			—	—		Jung
	Samseong[upper-alpha 3]	삼성역	三成			—	—		Gangnam
	Suseo	수서역	水西			—	—
	Seongnam	성남역	城南		Suseo–Pyeongtaek HSR (shared)	—	—	Gyeonggi-do	Seongnam
	Yongin	용인역	龍仁			—	—		Yongin
	Dongtan	동탄역	東灘			—	—		Hwaseong

Construction of GTX Line B is expected to start in 2023.

Station number	Station name			Transfer	Line name	Distance	Total distance	Location
	English	Hangul	Hanja
TBA	Songdo Station[upper-alpha 4]	송도	松島		GTX B	—	0.0	Incheon	Yeonsu
	Incheon City Hall	인천시청	仁川市廳			—	—		Namdong
	Bupyeong	부평	富平			—	—		Bupyeong
	Dangarae	당아래	당아래			—	—	Gyeonggi	Bucheon
	Sindorim	신도림	新道林			—	—	Seoul	Guro
	Yeouido	여의도	汝矣島			—	—		Yeongdeungdo
	Yongsan	용산	龍山			—	—		Yongsan
	Seoul Station	서울역	서울			—	—		Jung
	Cheongnyangni	청량리	淸凉里			—	—		Dongdaemun
	Mangu	망우	忘憂			—	—		Jungnang
	Byeollae	별내	別內		Gyeongchun Line (shared)	—	—	Gyeonggi	Namyangju
	Pyeongnaehopyeong	평내호평	坪內好坪			—	—
	Maseok	마석	磨石			—	—

Construction of GTX Line C is expected to start in 2022. According to the latest plans and following the selection of a preferred bidder for the construction of this line, 2 additional stations, Indeogwon Station and Wangsimni Station are likely to be added to the line.

Station number	Station name			Transfer	Line name	Distance	Total distance	Location
	English	Hangul	Hanja
TBA	Suwon	수원	水原		Gyeongbu Line (shared) Gwacheon Line (shared)	—	0.0	Gyeonggi	Suwon
	Geumjeong	금정	衿井			—	—		Gunpo
	Gwacheon[upper-alpha 5]	과천	果川		GTX C	—	—		Gwacheon
	Yangjae	양재	良才			—	—	Seoul	Gangnam
	Samseong	삼성	三成			—	—
	Cheongnyangni	청량리	淸凉里			—	—		Dongdaemun
	Kwangwoon University	광운대	光云大		Gyeongwon Line (shared)	—	—		Nowon
	Chang-dong	창동	倉洞			—	—		Dobong
	Uijeongbu	의정부	議政府			—	—	Gyeonggi	Uijeongbu
	Deokjeong	덕정	德亭			—	—		Yangju

Plans for a Line D were announced in 2021 by the previous government. However, the proposed route faced a lot of opposition, and has not been approved yet. The new government of Yoon Seok-youl has pledged to build 3 new lines (Line D, E and F), for which the routes have not been decided yet, but which would likely include plans for a longer Line D than the one announced by the previous government.

Station number	Station name			Transfer	Line name	Distance	Total distance	Location
	English	Hangul	Hanja
TBA	Janggi	장기	場基		GTX D	—	0.0	Gyeonggi	Gimpo
	Geomdan	검단	黔丹				—	Incheon	Seo
	Gyeyang	계양	桂陽			—	—		Gyeyang
	Daejang	대장	大壯			—	—	Gyeonggi	Bucheon
	Dangarae	당아래	당아래			—	—

Critics argue that GTX project would increase the social and economic centripetal force towards Seoul leading to increased primacy and the collapse of other provincial cities.[10]