Plain English Meaning

A line of lights set into the surface of the runway, right down the middle, to help the pilot stay centered when taking off or landing in poor visibility. The colors change near the end of the runway to warn the pilot that the runway is running out.

Full Definition

A row of flush-mounted, high-intensity lights installed along the centerline of a runway, spaced at uniform intervals, used to provide guidance during takeoff and landing in low-visibility conditions. The lights are white for most of the runway length, alternate red and white over the final 3,000 feet, and become solid red over the last 1,000 feet to indicate the runway end is approaching.