What is the role of the "train horn"?

The role of the train horn is primarily to act as a signaling device that alerts people and vehicles near train crossings of an approaching train. This is crucial for safety, as it helps to prevent accidents by warning individuals in the vicinity to be aware of the train's presence and to ensure they keep a safe distance. When a train approaches, the horn is sounded in order to provide a clear and audible signal that can be heard over the noise of the train and nearby environments, allowing pedestrians and motorists to take appropriate action.

While other options touch on various aspects of train operation, they do not accurately capture the essential function of the train horn, which is to enhance safety by warning those who may be potentially in harm's way as a train approaches.