What is the purpose of signaling with a train whistle when two yellow caution lanterns are displayed?

Signaling with a train whistle when two yellow caution lanterns are displayed serves as a warning to nearby operators. This is crucial in maintaining safety in rail operations, as the yellow caution lanterns indicate that there may be a potential hazard or that the train should exercise caution as it approaches an area. The whistle acts as an audible signal to alert those in the vicinity, including other train crews and personnel, that the train is approaching and that they should be prepared to respond accordingly.

While acknowledging the situation, communicating with passengers, or requesting clearance might seem relevant in different contexts, the primary purpose in this specific scenario is to ensure that other operators are made aware of the train's presence, thereby enhancing overall safety.