noun
down line; outbound line
Refers to a railway line heading away from a central terminal, typically Tokyo. The opposite is 上り線 (のぼりせん).
下り線の電車はまもなく到着します。
The train on the outbound line will arrive shortly.
事故のため、下り線が一時運転を見合わせています。
Due to an accident, the down line is temporarily suspended.