main line
a track that is used for through trains or is the principal artery of the system from which branch lines, yards, sidings and spurs are connected
en-US/ˈmeɪn ˈlaɪn/
en-GB/ˈmeɪn ˈlaɪn/
a track that is used for through trains or is the principal artery of the system from which branch lines, yards, sidings and spurs are connected