From the FAA Safety Team
What Are Runway Status Lights?
Runway Status Lights (RWSL) are a series of red in-pavement lights that warn pilots of high-speed aircraft or vehicles on runways. They operate independently of Air Traffic Control. Runway Status Lights have two states: ON (lights are illuminated red) and OFF (lights are off) and are switched automatically based on information from the airport surface surveillance systems. RWSL will improve airport safety by indicating when it is unsafe to enter, cross, or takeoff from a runway.
The RWSL system has two types of lights. Runway Entrance Lights (RELs) are installed at taxiways and Takeoff Hold Lights (THLs) on runways.
Runway Entrance Lights
Runway Entrance Lights (RELs) are a series of red in-pavement lights spaced evenly along the taxiway centerline from the taxiway hold line to the runway edge. One REL is placed before the hold line and one REL is placed near the runway centerline. RELs are directed toward the runway hold line and are oriented to be visible only to pilots entering or crossing the runway from that location. RELs that are ON (illuminated red) indicate that the runway ahead is not safe to enter or cross. Pilots should remain clear of a runway when RELs along their taxi route are illuminated. Lights that are off convey no meaning.
The system is not, at any time, intended to convey approval or clearance to proceed into a runway. Pilots remain obligated to comply with all ATC clearances, except when compliance would require crossing illuminated red RELs. In such a case, the crews should hold short of the runway for RELs, contact ATC, and await further instructions.
Takeoff Hold Lights
The Takeoff Hold Light (THLs) system is composed of red in-pavement fixtures in a double row on either side of the runway centerline lighting. Fixtures are focused toward the arrival end of the runway at the “Line Up and Wait” point and extend in front of the holding aircraft beginning 375’ beyond the runway threshold and extending for 1,500’. Illuminated red lights provide a signal, to an aircraft in position for takeoff or rolling, that it is unsafe to takeoff because the runway is occupied or about to be occupied by another aircraft or ground vehicle. THLs that are ON (illuminatedred) indicate that the runway ahead is not safe to takeoff. Pilots should refuse takeoff clearance if THLs are illuminated. Red THLs mean do not takeoff.Whenever a pilot observes the red lights of the THLs, the pilot will stop or remain stopped. The pilot will contact ATC for resolution if any clearance is in conflict with the lights. Lights that are off convey no meaning. The system is not, at any time, intended to convey approval or clearance to takeoff. Pilots must still receive an ATC clearance to takeoff.
RWSL are in operation at MCO and IAD. The system will be operational at PHX and IAH in 2013.
Pilots are encouraged to learn more about RWSL at: