What must operators do before crossing a runway?

Receiving clearance from air traffic control is essential for ensuring safety when crossing a runway. This procedure is designed to maintain order and prevent collisions on the airside of an airport. Air traffic control is responsible for managing the flow of aircraft and vehicles, which includes granting permission for ground vehicles to cross active runways.

By obtaining clearance, operators are made aware of any aircraft movements in the vicinity and can ensure that it is safe to proceed. This communication is vital for maintaining situational awareness, not only for the vehicle operator but for all personnel and aircraft operating in the vicinity as well.

While other options may highlight the importance of vigilance or signaling, they do not hold the same level of authority and safety assurance that clearance from air traffic control does. Thus, following the correct protocol of getting clearance prioritizes safety and adherence to operational standards at the airport.