Definition of "lineside"

Having completed their task, Fireman Page telephoned from a lineside box to the next signal cabin, briefly reported the incident and said that, as no high explosive had dropped and the track was safe, they proposed proceeding "at caution".

1944 July and August, “Top Link Drivers: XXI—Driver H. Blunt, L.N.E.R.”, in Railway Magazine, page 226

My next stop is Oxford, which has also grown with the addition of new platforms to accommodate the Chiltern Railways service to London via Bicester - although, short sightedly, the planned electrification from Paddington was canned. Evidence of the volte-face can be seen along the line at places such as Radley, where mast piles are already sunk or lie discarded at the lineside.

2020 December 2, Paul Bigland, “My weirdest and wackiest Rover yet”, in Rail, pages 67–68