When are vehicles typically allowed to use runways?

Vehicles are typically allowed to use runways only when authorized and under coordination with air traffic control. This is crucial for maintaining safety and ensuring that air traffic operations are not disrupted. The air traffic control (ATC) has the responsibility to monitor and manage all movements on the airfield, including the use of runways by vehicles.

When vehicles operate on runways, it must be under the specific guidance and clearance from ATC to prevent any potential conflicts with aircraft that may be landing or taking off. This coordination is especially vital because the runway is an active area of the airport, and any unauthorized presence can lead to serious safety risks.

Using runways under the conditions described in the other choices can lead to unsafe situations. For instance, the ability to drive on runways when the ground is wet, during emergencies, or based solely on a pilot's clearance does not encompass the comprehensive safety measures that ATC coordination provides. Therefore, following established protocols by ensuring ATC authorization is essential for safe runway operations.