What is the meaning of an alternating red and green light to pilots or ground vehicles?

• A. Proceed with normal operations
• B. Stop
• C. Proceed with taxi
• D. General warning signal/Exercise extreme caution

Answer: (D)

The key idea here is how to interpret light signals used to communicate with aircraft and ground vehicles. An alternating red and green light is a general warning signal that tells you to exercise extreme caution. It isn’t a permission to proceed or a directive to stop; it’s a cue that conditions are hazardous or something isn’t functioning normally and you should slow down, stay vigilant, and be ready to stop or await further instructions.

Think of it as a caution flag from the signaling system: normal clearances (like go ahead) aren’t in effect, and you should proceed only with heightened awareness and prepared to comply with additional guidance. This is distinct from steady green (proceed with clearance) or steady red (stop), and it isn’t simply a taxi clearance.