When should a worker initiate a stop signal?

Initiating a stop signal is crucial for ensuring the safety of workers in environments where trains operate. A stop signal should be initiated when a train is approaching and poses a threat to safety because this action directly addresses the imminent danger presented by the approaching train. By signaling for a stop in this scenario, workers can warn others of the impending hazard, allowing for necessary precautions to be taken to avoid accidents or injuries.

In contrast, initiating a stop signal when a train is departing, when maintenance work is complete, or when a signal is unclear does not directly correlate with responding to an immediate threat. Those situations might require communication or other actions, but they do not represent the same urgency as a train that is actively approaching and could endanger workers. Therefore, the correct focus is on the necessity of initiating a stop signal when there is a clear and present danger to safety from an oncoming train.