Next to you is a signal switch that will divert the train down a sidetrack or “spur.”
also side-track, "railway siding," 1835, from side (adj.) + track (n.). The verb meaning "to move (a train car) onto a sidetrack" is from 1874; figurative sense of "to divert from the main purpose" is attested from 1881. Related: Sidetracked.