If controllers need to indicate a vehicle’s clearance, which signal would they use?

In air traffic control, a steady green signal is used to indicate that a vehicle has received clearance to proceed. This signal is universally understood in aviation and is an essential part of ensuring that all ground operations proceed safely and efficiently. A steady green light communicates a clear and unequivocal message to pilots and vehicle operators that they can move forward without hesitation.

The other options have different meanings: a flashing yellow typically alerts drivers or pilots to exercise caution and prepare to stop, non-verbal cues may lack the clarity or immediacy needed for vehicle clearance, and a flashing green signal is usually employed in different contexts, such as indicating that an aircraft can taxi or take off. Therefore, the steady green light is the most appropriate choice to signal vehicle clearance clearly.