When do the runway edge lights change color?

The runway edge lights are designed to provide guidance to pilots during takeoff and landing, particularly in low visibility conditions. The correct answer indicates that the lights change to yellow in the last 2,000 feet or the final half of the runway. This is significant because the yellow lights serve as a warning to pilots that they are approaching the end of the runway, encouraging them to prepare for landing or to assess their distance from the threshold.

This transition to yellow helps increase awareness and enhances safety during the critical phases of landing. The other options do not accurately describe the function of runway edge lights; they do not change to red at the threshold, nor do they remain white throughout, as that would not provide the necessary warning for pilots regarding their proximity to the runway's end. Hence, the change to yellow is an essential operational feature that helps ensure flights can land safely.