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).
上り線の電車は東京方面へ向かいます。
Trains on the up line head toward Tokyo.
事故のため、上り線が一時運転を見合わせました。
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.