Railway track or line; the rails and route on which trains run.
線路に石を置くのは危険だからやめなさい。
Don't put stones on the tracks — it's dangerous.
電車は線路沿いに走っていった。
The train ran along the railway line.
線路の点検が終わるまで運行は見合わせます。
Service will be suspended until the track inspection is complete.