runway centerline lighting system

The runway centerline lighting system consists of a single light installed at uniform intervals along the runway centerline to provide a continuous lighting reference from threshold to threshold. The lights start from 75 ft (25 m) from the landing threshold and extend to within 75 ft of the end of the runway—the lights themselves are spaced at 50-ft (15 m) intervals. When viewed from the landing threshold, the runway centerline lights are white until the last 3000 ft (900 m) of the runway. The white lights begin to alternate with red for the next 2000 ft (600 m), and for the last 1000 ft (300 m) of the runway, all centerline lights are red. If the runway centerline lights are spaced at 25-ft (7.5 m) intervals, alternate pairs of red and white lights should be used on the section from 3000 to 1000 ft (900–300 m) from the runway end. Where the runway are less than a 6000-ft (1800 m) length, the alternate red and white extends from the midpoint of the runway usable for landing to 1000 ft (300 m) the runway end.