Green’s Dictionary of Slang

to kill someone by pushing them from a moving train.

1932		D. Hammett ‘Too Many Have Lived’ in Nightmare Town (2001) 313: What’s the circus and carnival slang for kicking a guy off a train while it’s going? Red-lighting. Sure, that’s it.
1949		Monteleone Criminal Sl. (rev. edn) 191: red light [...] to kill.
1953		F. Brown Madball (2019) 122: The time on the freight train when he’d red-lighted the loud-mouthed shade.
1962		Ragen & Finston World’s Toughest Prison 815: red light – To do away with.