5 0 0 ▁V ▁DC . ▁ ▁Until ▁ 2 0 1 8 , ▁the ▁St . ▁G allen – T ro gen ▁line ▁was ▁also ▁of ▁met re ▁gauge , ▁but ▁ran ▁independently . ▁▁▁ ▁From ▁ 2 0 1 6 ▁to ▁ 2 0 1 8 , ▁the ▁App enz eller bah nen ▁under to ok ▁a ▁large ▁construction ▁project ▁to ▁connect ▁the ▁App enz ell - St . ▁G allen ▁and ▁St . ▁G allen - T ro gen ▁lines . ▁ ▁The ▁three ▁points ▁of ▁in compat ibility ▁were ▁elect r ification ▁( the ▁St . ▁G allen - T ro gen ▁line ▁was ▁ 1 0 0 0 ▁V ▁DC ▁with ▁a ▁brief ▁stretch ▁at ▁ 6 0 0 ▁V ▁DC ▁shared ▁with ▁the ▁St . ▁G allen ▁t rol ley bus ▁system ), ▁different ▁( but ▁phys ically ▁adjacent ) ▁term ini ▁in ▁St . ▁G allen , ▁and ▁maximal ▁gr ades ▁( the ▁ra ck ▁railway ▁approach ▁to ▁St . ▁G allen ▁from ▁App enz ell ▁was ▁too ▁ste ep ▁for ▁ad hes ion - based ▁St . ▁G allen - T ro gen ▁rolling ▁stock ). ▁ ▁So ▁the ▁new ▁project ▁re - elect r ified ▁the ▁St . ▁G allen - T ro gen ▁line ▁at ▁ 1 5 0 0 ▁V ▁DC ▁and ▁constructed ▁a ▁new ▁tunnel ▁through ▁St . ▁G allen . ▁ ▁The ▁old ▁alignment ▁through ▁St . ▁G allen ▁closed ▁in ▁April ▁ 2 0 1 8 , ▁and ▁the