up line; inbound line
Refers to a railway line heading toward a major terminal or city center, typically Tokyo in the Japanese context. Opposite of 下り線 (くだりせん).
Trains on the up line head toward Tokyo.
Due to an accident, the up line was temporarily suspended.
Compound of 上り (のぼり, 'going up') + 線 (せん, 'line'). The 'up' direction traditionally refers to movement toward the capital or a major hub.