noun
track no. 1; platform 1
Used at train stations to refer to the first track or platform. Often heard in announcements.
一番線に電車がまいります。
The train is arriving at track no. 1.
一番線はどこですか。
Where is platform 1?
General word for 'platform'; 一番線 specifies the numbered track/platform.
Compound of 一番 (number one) + 線 (line/track). A straightforward station numbering term.