How does the engineer signal to other train crews?

The engineer signals to other train crews primarily through radio communication or hand signals as appropriate because these methods ensure clear and effective communication in various scenarios. Radio communication is essential in modern rail operations, allowing for instant and direct exchanges of information between crews, especially over long distances or in noisy environments. Hand signals play a crucial role in situations where radios cannot be used, or when visual cues are necessary for safety, such as during train movements in close proximity.

Using train whistles alone is limited in both range and the complexity of messages that can be conveyed, while waving a flag restricts communication to very short distances and specific circumstances. Activating warning lights serves primarily to enhance visibility and alert others to the train's presence rather than communicating specific instructions or messages, which is what is needed when coordinating with other train crews. Thus, the combination of radio and hand signals provides the most reliable means of communication in a variety of situations on the rails.