What is a stale green light?

• A. A green light that is about to change because it has been green for a long time.
• B. A green light that has just turned green.
• C. A red light that is about to turn yellow.
• D. A yellow light that has stayed on too long.

Answer: (A)

A stale green light means the green phase has been flowing for longer than usual and is near its end, so the signal is likely to change soon. This is a warning to be prepared to stop or slow as the light will transition to yellow or red shortly. The option that describes this exactly is the one about a green light that is about to change because it has been green for a long time. The other choices describe a fresh green, a red about to turn yellow, or a yellow that has stayed on too long, none of which capture the idea of a green signal that has lasted too long and is about to change.