What allows crews to leave equipment on the main track without protection?

The correct choice emphasizes the importance of formal communication protocols in ensuring safety on the railway. Formal notification from the train dispatcher establishes an official and documented process that confirms the crew is authorized to leave equipment on the main track. This notification is critical because it ensures the dispatcher is aware of the situation and can manage train movements accordingly, mitigating the risk of collisions or unsafe conditions.

By relying on formal notification, crews are assured that the decision has been made with the full awareness of operational conditions and safety requirements, as the dispatcher has a comprehensive view of train movements and can provide the necessary assurance that it is safe to leave equipment on the main track. This procedure is a vital part of maintaining safety and operational efficiency on the railway network.