When must a crew member verify that a drawbridge is in the proper position?

A crew member must verify that a drawbridge is in the proper position when the signal displays a Stop indication because this signals a potential hazard or unsafe condition. The Stop signal alerts crew members that the drawbridge may not be properly aligned or secured for train passage. Verification is essential to ensure the safety of the train and its crew, since proceeding over a drawbridge that is not in the correct position could lead to a catastrophic accident.

While other factors like a Go signal or crew member boarding the train are important in the context of operations, they do not take precedence over the need to guarantee safety in situations involving potential hazards, such as a drawbridge. The requirement for verification primarily arises from the danger associated with operating heavy equipment over unsafe structures.