What does three short pops of a locomotive whistle indicate?

Three short pops of a locomotive whistle is a standard signal indicating that a propelling movement is about to be performed. This specific sound from the locomotive serves as a warning to crew and personnel nearby that the train will be moving in a reverse or "propelling" manner. This is crucial for safety, as it alerts anyone in the vicinity to the potential hazards associated with the train's movement.

In operational procedures, signals like the three short pops are part of the widely used communication system that ensures safety on railways. Recognizing these signals is key to maintaining awareness of train movements, particularly when they may be less visible to workers and the public.

Understanding this signal is important in safe work practices, as it prevents accidents and ensures that everyone is informed about the train's intentions before any movement occurs.