Green’s Dictionary of Slang

1. (US) rough whisky [? as drunk by railroad workers and tramps].

1838		J.C. Neal Charcoal Sketches (1865) 63: A glass of what the shopman was pleased to call racky mirackilis, a fluid sometimes termed ‘railroad’ from the rapidity with which it hurries men to the end of their journey.
1843		T. Haliburton Sam Slick in England I 262: The drinks ain’t good here; the hante no variety in them nother; no white-nose, apple-jack, stone-wall, chain-lightning, rail-road.

2. (drugs) the scars that accompany repeated injections of narcotics into one’s veins [tracks n. (1)].

1972

B. Rodgers Queens’ Vernacular 167: railroad (fr narc sl tracks = hypodermic needle marks) the arm of a hardcore drug addict.