Place it at the moment the train appears in the edit, after the danger alarm warns viewers, then cut to the locomotive passing for the payoff, and keep the railway footage centred so the arrival stays the focus.
About this sound
This is a 4-second blast from an EMD ATSF F7A diesel locomotive horn, with the deep, layered chord those classic American engines are known for. It feels bold, commanding and unmistakably railway, the kind of sound that cuts through a quiet scene and makes everyone look up. It comes from Trainz, where it belongs to that locomotive.