What does four short whistle blasts signal for a train operator?

The signal of four short whistle blasts is a critical communication tool for train operators, particularly in scenarios concerning safety and operational procedures. In this context, four short blasts typically indicate that there is a problem, specifically that the tower operator has mistakenly set the wrong route for the train. This signal serves as an alert to the crew that immediate attention is required to address the situation, ensuring that corrective measures can be taken to prevent accidents or mishaps.

Understanding this signaling is essential for train operators as it enhances safety protocols and allows for quick responses to potentially hazardous situations on the tracks. The other options provided pertain to different scenarios that are communicated through other specific signals or established protocols within railway operations, underscoring the importance of accurate communication to maintain operational safety and efficiency.