Which signal indicates 'Stop'?

• A. Steady Red
• B. Flashing Green
• C. Flashing White
• D. Alternating Red and Green

Answer: (A)

In aviation surface signaling, color and whether the light is steady or flashing tell you what to do. A steady red signal is a direct command to stop—you must halt and not cross that point until you receive a green signal or explicit clearance. This makes it the clear, unambiguous stop instruction on the airside. The other patterns convey movement or caution rather than an immediate stop: a flashing green means clearance to taxi or move, a flashing white tells you to return to your starting point, and alternating red and green signals you to proceed with extreme caution. So steady red is the best answer for indicating “Stop.”