What is the purpose of a locomotive whistle signaling three short pops?

The signaling of three short pops from a locomotive whistle serves the specific purpose of indicating a propelling movement. This is a standardized signal that communicates to other railway personnel and operators that a train is moving backward or propelling another car. It is crucial for maintaining safety on the rail network, as it ensures that all concerned parties are aware of the locomotive's movements and can act accordingly to avoid accidents or conflicts.

Normal train operations rely on a clear and consistent communication system, and the whistle signals are integral to that. Such auditory signals help convey important operational information, particularly in areas where visual communication may be limited or obstructed.