Place it at the cut where a locomotive first appears in the edit, then follow with the Inception Horn as the next beat, keeping the train moment first and that horn second.
About this sound
This is a 0.1-second blast from a Nathan K3LA train horn on an ATSF FP45 locomotive, a sharp three-chime note cut off almost as soon as it starts. It feels sudden and jarring, like a warning sounded at full volume in a tiny burst. It comes from the horn used on Santa Fe diesel locomotives, captured here as a single quick toot.