What type of signs are used to restrict access to certain runway areas?

Mandatory instruction signs are specifically designed to communicate important instructions or restrictions to pilots and vehicle operators on the airport surface. These signs indicate actions that must be taken, such as holding short of a runway or an area to which access is restricted. They are typically displayed in red with white text, making them easily identifiable and conveying critical information that must be followed to maintain safety and compliance within the airport environment.

Location signs, while informative about the position of a vehicle or aircraft on the airport, do not impose restrictions. Designation signs primarily identify the location or number of a runway or taxiway, and distance remaining signs indicate how much distance is left on a runway and do not restrict access. Thus, while these other types of signs provide valuable information for navigation and distance awareness, they do not serve the specific purpose of restricting access to particular runway areas as mandatory instruction signs do.