What signifies that a driver must stop on the airside?

A red stop sign or an equivalent marking is the universally recognized signal that indicates a driver must stop, especially in high-traffic areas like the airside of an airport. This signal is vital for ensuring the safety of both vehicles and personnel in a busy environment where aircraft are operating. The use of clear and defined signage, such as a red stop sign, helps to minimize confusion and establish consistent traffic control measures. This adherence to visual signals is critical in maintaining safety protocols and preventing accidents on the airside, where the movement of aircraft and vehicles must be carefully coordinated.

In contrast, while a flashing yellow light typically serves as a cautionary signal that indicates drivers should slow down and be aware of potential hazards, it does not specifically require a stop. Similarly, a pause in traffic may indicate an informal stop, but it is not a formal directive, and relying on it can lead to unsafe situations. Lastly, a warning horn from an aircraft serves as an alert for nearby personnel about potential aircraft movements, but it is not an explicit stop signal for vehicle operators. Hence, the red stop sign is the most effective and recognized method for indicating that a driver must come to a complete stop.