FAA: Runway status lights operational

The lights, which are embedded in runways and taxiways, illuminate when conflicting traffic could make takeoffs, landings, and taxiing dangerous. Should sensor systems detect an issue, the lights turn red and provide a clear warning to pilots. While not a substitute for air traffic control clearances, the intent is to prevent runway and taxiway incursions, as well as alert pilots that a takeoff is unsafe.

Although the lights are automated, pilots still need an ATC clearance to enter, cross, or take off from a runway. Because the lights are directional and aimed at pilots, ATC personnel may not be able to see them

The RWSL system consists of two types of lights—runway entrance lights (REL) and takeoff hold lights (THL). The REL system automatically illuminates at all intersecting taxiways when an aircraft taking off reaches 30 knots on its takeoff run. The lights extinguish three to four seconds before the aircraft reaches an intersecting taxiway so that controllers, if the situation dictates, can apply what the FAA calls “anticipated separation” in order to move traffic more expeditiously if safety permits.

The RELs also illuminate when a landing aircraft is on a one-mile final. The timing of their illumination and extinguishing is adjustable by controllers. Lights extinguish when the landing aircraft is three to four seconds from arriving at an intersecting taxiway, until the aircraft slows to 80 knots. Once below 80 knots, any light arrays beyond 30 seconds of the aircraft’s travel extinguish. When below 34 knots, the REL lights go out at all intersecting runways.

THLs illuminate when an aircraft is in position to take off and encroaching aircraft or vehicles are detected. Once an aircraft or vehicle clears the runway, the lights go out. However, this does not constitute a clearance to take off. That must still be issued by ATC.

For additional information, including photos, videos, airport diagrams, and system descriptions, visit the FAA website.