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What Are Runway Status Lights?
January 2017 - 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. RWSL 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 take off 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.
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.
The THL 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 feet beyond the runway threshold and extending for 1,500 feet. Illuminated red lights provide a signal to an aircraft in position for takeoff or rolling that it is unsafe to take off because the runway is occupied or about to be occupied by another aircraft or ground vehicle. THLs that are on (illuminated red) indicate that the runway ahead is not safe to take off. Pilots should refuse takeoff clearance if THLs are illuminated. The pilot should contact ATC for resolution if any clearance conflicts 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 take off.