Red runway status lights used at large U.S. airports such as Chicago O’Hare International and JFK indicate runway status, thereby increasing situation awareness for pilots and vehicle operators. The lights are set in-pavement and illuminate when it is unsafe to enter, cross or begin takeoff.
Status lights operate automatically with input from surface and terminal radar surveillance systems. Sensor inputs command the in-pavement lights to illuminate red when there is traffic on or approaching the runway.
Runway entrance lights (REL), one status-light component, are located on entrance taxiways and indicate to aircraft crossing or entering a runway when it is unsafe to move forward. Takeoff hold lights (THL), another component, are located on the runway and indicate to an aircraft in the takeoff position when it is unsafe to proceed.
Runway Entrance Lights (REL)
Runway entrance lights are flush-mounted, in-pavement, unidirectional light fixtures directed at the pilot. They sit parallel to and focused along the taxiway centerline at the hold line. When activated, the red lights indicate that there is high-speed traffic on the runway or there is an aircraft on final approach within the activation area.
Departing aircraft: When a departing aircraft reaches a speed of approximately 30 knots, all taxiway intersections with REL arrays along the runway ahead of the aircraft will illuminate. As the aircraft approaches an REL-equipped taxiway intersection, the lights at that intersection extinguish approximately three to four seconds before the aircraft reaches it. This allows controllers to apply "anticipated separation" to permit ATC to move traffic more expeditiously. After the aircraft is declared airborne by the system, all REL extinguish.
Arriving aircraft: When an aircraft on final approach is approximately 1 mile from the runway threshold, all taxiway REL intersecting the runway turn red. Lights extinguish at each taxiway intersection approximately three to four seconds before the aircraft reaches it to apply anticipated separation. Once an arriving aircraft slows to approximately 34 knots, it is considered taxiing, and all lights extinguish.
A pilot at or approaching the hold line to a runway will observe REL illuminate and extinguish in reaction to an aircraft or vehicle operating on the runway, or an arriving aircraft operating less than 1 mile from the runway threshold.
Takeoff Hold Lights (THL)
Takeoff hold lights are arranged in a double longitudinal 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. THL extend for 1,500 feet in front of the holding aircraft starting at a point 375 feet from the departure threshold.
Departing aircraft: THL illuminate for an aircraft in position for departure or departing when there is another aircraft or vehicle on the runway or about to enter the runway. Once that aircraft or vehicle exits the runway, the THL extinguish. A pilot may notice lights extinguish prior to the downfield aircraft or vehicle being completely clear of the runway but still moving.
Runway Intersection Lights (RIL)
Runway intersection lights are used to provide an indication to pilots and vehicle drivers that there is high-speed traffic on the intersecting runway and that it is unsafe to enter or cross.
RIL consist of red unidirectional lights installed in a double longitudinal row aligned with and offset to either side of the runway centerline lighting in the same manner as THL.
Final Approach Runway Occupancy Signal (FAROS)
The FAROS uses sensors to detect aircraft or vehicles on the runway.
The system causes the PAPI to flash while the runway is occupied.
At 300 feet agl, contact ATC for resolution if the FAROS indication is in conflict with the clearance. If the PAPI continues to flash, the pilot must execute a go-around.
