, ▁it ▁was ▁taken ▁over ▁by ▁another ▁private ▁railway , ▁the ▁Ch osen ▁Railway ▁( the ▁largest ▁of ▁colonial ▁Korea ' s ▁priv ately ▁owned ▁railway ▁companies ). ▁The ▁Ch osen ▁Railway ▁owned ▁the ▁line ▁until ▁all ▁rail ways ▁in ▁Korea ▁were ▁national ized ▁after ▁ 1 9 4 5 . ▁However , ▁since ▁December ▁ 2 8 , ▁ 2 0 0 4 , ▁the ▁Su in ▁Line ▁is ▁being ▁re construct ed ▁with ▁standard ▁gauge ▁and ▁double ▁tracking ▁as ▁an ▁integral ▁part ▁of ▁the ▁Se oul ▁Metropolitan ▁Sub way ▁network ▁and ▁is ▁opening ▁in ▁three ▁phases . ▁ ▁All ▁north bound ▁trains ▁terminate ▁at ▁O ido , ▁all ▁south bound ▁services ▁terminate ▁at ▁In che on . ▁Express ▁train ▁service ▁serves ▁only ▁O ido , ▁S ora ep og u , ▁In che on ▁Non h ye on , ▁W on in ja e , ▁Ye ons u , ▁In ha ▁University , ▁and ▁In che on . ▁ ▁Tra ins ▁along ▁the ▁line ▁are ▁ 6 ▁cars ▁long . ▁Platform s ▁at ▁stations ▁are ▁built ▁for ▁ 8 ▁cars ▁in ▁prepar ation ▁for ▁the ▁mer ging ▁of ▁the ▁Bund ang ▁Line ▁with ▁the ▁Su in ▁Line , ▁and ▁are ▁prepared ▁for ▁ 1 0 ▁cars ▁when ▁the ▁extension ▁occurs . ▁ ▁Tra ins ▁run ▁at ▁an ▁interval ▁of ▁ 1 5 ▁minutes ▁throughout ▁the ▁day . ▁ ▁History ▁▁ 2 0 1 2 : ▁June ▁ 3 0 : ▁The ▁re built ▁Su in ▁Line ▁is ▁officially ▁opened ▁from ▁O