Runway Status Lights
Runway Status Lights are an essential FAA system embedded in the pavement of runways and taxiway, designed to automatically signal pilots and vehicle operators when it is unsafe to enter, cross, or begin takeoff. These lights, which are operational at 20 airports across the US, turn red in response to traffic, providing direct, immediate alerts without the need for input from controllers. The system uses complex software algorithms and adjustable parameters to process the Airport Surface Surveillance data and control the airfield lights in accordance with Air Traffic operations, including anticipated separation. The Runway Status Lights system integrates airport lighting equipment with approach and surface surveillance systems to offer visual signals to indicate safety hazards on runways. It includes Runway Entrance Lights (RELs), which signal to aircraft crossing or entering the runway from intersecting taxiways, and Takeoff Hold Lights (THLs), which signal to aircraft in position for takeoff, both of which are critical to maintaining safety and efficiency on the airfield.
- Runway Entrance Lights (RELs): provide signal to aircraft crossing entering runway from intersecting taxiway.
- Takeoff Hold Lights (THLs): provide signal to aircraft in position for takeoff.
Runway Status Lights is a fully automatic, advisory system designed to reduce the number and severity of runway incursions and prevent runway accidents while not interfering with airport operations. It is designed to be compatible with existing procedures and is comprised of Runway Entrance Lights (RELs) and Takeoff Hold Lights (THLs).
The FAA developed Runway Status Lights as part of an ongoing effort to explore new technologies. The system aims to improve air crew and vehicle operator situational awareness through accurate and timely indication of runway usage.
Runway Status Light systems are commissioned at twenty US airports as shown below:
This tab contains video archives on YouTube posted by the Runway Status Lights (RWSL) program team.
Runway Status Lights is a fully automated system that provides runway status information to pilots and surface vehicle operators to indicate when it is unsafe to enter, cross, or takeoff from a runway. The Runway Status Lights system processes information from surveillance systems and activates Runway Entrance Lights and Takeoff Hold Lights in accordance with the motion and velocity of the detected traffic. Runway Entrance Lights and Takeoff Hold Lights are in-pavement light fixtures that are directly visible to pilots and surface vehicle operators. Runway Status Lights is an independent safety enhancement that does not substitute for an Air Traffic Control clearance. Clearance to enter, cross, or takeoff from a runway must still be issued by Air Traffic Control. Although Air Traffic Control has limited control over the system, personnel do not directly use, and may not be able to view, light fixture output in their operations.
Runway Entrance Lights
The Runway Entrance Lights system is composed of flush mounted, in-pavement, unidirectional fixtures that are parallel to and focused along the taxiway centerline and directed toward the pilot at the hold line. A specific array of Runway Entrance Lights include the first light at the hold line followed by a series of evenly spaced lights to the runway edge; and one additional light at the runway centerline in line with the last two lights before the runway edge (See FIG 2-1-9). When activated, these red lights indicate that there is high speed traffic on the runway or there is an aircraft on final approach within the activation area.
- Operating Characteristics – Departing Aircraft: When a departing aircraft reaches 30 knots, all taxiway intersections with Runway Entrance Lights arrays along the runway ahead of the aircraft will illuminate (see FIG 2-1-9). As the aircraft approaches a Runway Entrance Lights equipped taxiway intersection, the lights at that intersection extinguish approximately 2 to 3 seconds before the aircraft reaches it. This allows controllers to apply "anticipated separation" to permit Air Traffic Control to move traffic more expeditiously without compromising safety. After the aircraft is declared "airborne" by the system, all lights will extinguish.
- Operating Characteristics – Arriving Aircraft: When an aircraft on final approach is approximately 1 mile from the runway threshold all sets of Runway Entrance Light arrays along the runway will illuminate. The distance is adjustable and can be configured for specific operations at particular airports. Lights extinguish at each equipped taxiway intersection approximately 2 to 3 seconds before the aircraft reaches it to apply anticipated separation until the aircraft has slowed to approximately 80 knots (site adjustable parameter). Below 80 knots, all arrays that are not within 30 seconds of the aircraft's forward path are extinguished. Once the arriving aircraft slows to approximately 34 knots (site adjustable parameter), it is declared to be in a taxi state, and all lights extinguish.
- What a pilot would observe: A pilot at or approaching the hold line to a runway will observe Runway Entrance Lights illuminating and extinguishing in reaction to an aircraft or vehicle operating on the runway, or an arriving aircraft operating less than 1 mile from the runway threshold.
Whenever a pilot observes the red lights of the Runway Entrance Lights, that pilot will stop at the hold line, or along the taxiway path and remain stopped. The pilot will then contact Air Traffic Control for resolution if the clearance is in conflict with the lights. Should pilots note illuminated lights under circumstances when remaining clear of the runway is impractical for safety reasons (i.e., aircraft is already on the runway), the crew should proceed according to their best judgment while understanding the illuminated lights indicate the runway is unsafe to enter or cross. Contact Air Traffic Control at the earliest possible opportunity.
Takeoff Hold Lights
The Takeoff Hold Lights system is composed of in-pavement, unidirectional fixtures in a double longitudinal row aligned 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 they extend for 1,500 feet in front of the holding aircraft (see FIG 2-1-9). 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. Two aircraft, or a surface vehicle and an aircraft, are required for the lights to illuminate. The departing aircraft must be in position for takeoff or beginning takeoff roll. Another aircraft or a surface vehicle must be on or about to cross the runway.
- Operating Characteristics – Departing Aircraft: Takeoff Hold Lights will 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 (see FIG 2-1-9.) Once that aircraft or vehicle exits the runway, the Takeoff Hold Lights extinguish. A pilot may notice lights extinguish prior to the downfield aircraft or vehicle being completely clear of the runway but still moving. Like Runway Entrance Lights, Takeoff Hold Lights have an "anticipated separation" feature.
When the Takeoff Hold Lights extinguish, this is not clearance to begin a takeoff roll. All takeoff clearances will be issued by Air Traffic Control.
- What a pilot would observe: A pilot in position to depart from a runway, or has begun takeoff roll, will observe Takeoff Hold Lights illuminating in reaction to an aircraft or vehicle on the runway or about to enter or cross it. Lights will extinguish when the runway is clear. A pilot may observe several cycles of lights illuminating and extinguishing depending on the amount of crossing traffic.
- Whenever a pilot observes the red lights of the Takeoff Hold Lights, the pilot will stop or remain stopped. The pilot will contact Air Traffic Control for resolution if any clearance is in conflict with the lights. Should pilots note illuminated lights while in takeoff roll and under circumstances when stopping is impractical for safety reasons, the crew should proceed according to their best judgment while understanding the illuminated lights indicate that continuing the takeoff is unsafe. Contact Air Traffic Control at the earliest possible opportunity.
- When operating at airports with Runway Status Lights, pilots should turn the transponder "ON" with Altitude Enabled when operating on all taxiways and runways. This ensures interaction with the FAA surveillance systems which provide information to the Runway Status Lights system.
- Never cross over illuminated red lights. Under normal circumstances, Runway Status Lights will confirm the pilot's taxi or takeoff clearance. If Runway Status Lights indicates that it is unsafe to takeoff from or taxi across a runway, immediately notify Air Traffic Control of the conflict and confirm your clearance.
- Do not proceed when lights have extinguished without an Air Traffic Control clearance. Runway Status Lights verifies an Air Traffic Control clearance, it does not substitute for an Air Traffic Control clearance.
Air Traffic Control of Runway Status Lights
- Controllers can set in-pavement lights to one of five brightness levels to assure maximum conspicuity under all visibility and lighting conditions. Runway Entrance Lights and Takeoff Hold Lights subsystems may be independently set.
- The system can be shutdown should Runway Status Lights operations impact the efficient movement of air traffic or contribute, in the opinion of the Air Traffic Control Supervisor, to unsafe operations. Whenever the system is shutdown, a NOTAM must be issued, and the Automatic Terminal Information System must be updated.
Runway Entrance Lights: The Runway Entrance Lights system is composed of flush mounted, in-pavement, unidirectional fixtures that are parallel to and focused along the taxiway centerline and directed toward the pilot at the hold line. A specific array of Runway Entrance Lights include the first light at the hold line followed by a series of evenly spaced lights to the runway edge; and one additional light at the runway centerline in line with the last two lights before the runway edge (See FIG 2-1-9). When activated, these red lights indicate that there is high speed traffic on the runway or there is an aircraft on final approach within the activation area.
- Whenever a vehicle operator observes the red Runway Entrance Lights illuminated, that operator will stop at the runway hold short line and remain stopped.
- Vehicle operators may observe several cycles of the Runway Entrance Lights turning on and off while waiting for an Air Traffic Control clearance.
- DO NOT proceed when the Runway Entrance Lights have extinguished without an Air Traffic Control clearance. Runway Status Lights verifies an Air Traffic Control clearance, it DOES NOT substitute for an Air Traffic Control clearance.
- If an Air Traffic Control clearance is in conflict with the Runway Entrance Lights, do not cross over the red lights. Contact Air Traffic Control and advise that you are stopped due to red lights. (ex.: "Orlando Ground, Ops 2 is holding short of runway 36 Left at Echo due to red lights").
- If the vehicle is entering the runway (past the runway hold short marking) and the Runway Entrance Lights illuminate, the vehicle should clear the runway immediately and notify the Air Traffic Control tower.
- What are Runway Status Lights (RWSL)?
RWSL is composed of red in-pavement airport lights which signal a potentially unsafe situation on taxiways and runways. The system is automated based on inputs from surface and terminal surveillance systems. The system is comprised of two areas: Runway Entrance Lights provide a warning signal to aircraft crossing or entering a runway from intersecting taxiways; Takeoff Hold Lights provide a warning signal to aircraft in position for takeoff.
- What are Runway Entrance Lights (RELs)?
RELs are a string of lights located around the center of taxiways/runway crossings and illuminate red when there is high-speed traffic on or approaching the runway to signal that it is unsafe to enter the runway.
- What are Takeoff Hold Lights (THLs)?
THLs are located in the center of the runway at takeoff hold point. They are laid out as 16 double rows of lights, for a total of 32 lights making up each Takeoff Hold Lights group. The lights will illuminate red when there is an aircraft in position for departure and the runway is occupied by another aircraft or vehicle.
- What are the benefits of RWSL?
The RWSL system was implemented to:
- Aid in the reduction and severity of runway incursions
- Increase situational awareness for aircrews and airport vehicle drivers
- Serve as an added layer of safety while accommodating individual airport operations without impacting traffic flow
RWSL automatically provide a clear, prompt indication of runway status directly to pilots and ground vehicle operators. The RWSL system is designed to supplement existing air traffic controller tools and procedures without increasing the controller workload. RWSL acts as an independent safety enhancement and does not replace air traffic control issued clearance. The RWSL system provides a vital layer of redundancy in runway safety and is a reinforcement of controller guidance.
- How do the lights work?
The lights are automated based on inputs from terminal and surveillance systems. The lights will illuminate red to serve as a warning signal for pilots and/or vehicle operators to indicate that it is unsafe to enter, cross, or begin takeoff on a runway. RWSL indicate runway status only; they do not indicate clearance. Pilots and vehicle operators should continue to follow standard rules of clearance required from controllers prior to proceeding.
- What precautions should be taken if verbal clearance is received from the tower, but the lights are illuminated?
Pilot/vehicle operators should hold short of the runway and advise Air Traffic Control they are holding for red lights.
- What airports have RWSL systems?
The following airports have operational RWSL systems:
- Orlando International Airport
- Phoenix Sky Harbor International Airport
- Las Vegas McCarran International Airport
- Chicago O'Hare International Airport
- Charlotte Douglas International Airport
- Minneapolis-St. Paul International Airport
- Washington Dulles International Airport
- George Bush Intercontinental Airport
- Seattle-Tacoma International Airport
- Fort Lauderdale/Hollywood International Airport
- LaGuardia Airport
- Baltimore-Washington International Airport
- Los Angeles International Airport
- Detroit Metropolitan Wayne County Airport
- San Francisco International Airport
- Newark Liberty International Airport
- John F. Kennedy International Airport
- Boston Logan International Airport
- Dallas/Fort Worth International Airport
- San Diego International Airport
- What do the lights look like and how are they installed?
There are two kinds of lights: THLs and RELs. The lights are unidirectional aluminum disc-shaped fixtures that illuminate red. They are almost 12" in diameter by 4" deep and rise .25" above the pavement surface. The lights and their duct banks and conduit are installed by boring into the runway or taxiway pavement. THLs fixtures conform to FAA AC 150/5345-46D Type L-850T. RELs fixtures conform to FAA AC 150/5345-46D Type L-852S.
- How are the lights different from other runway warning lights?
RELs and THLs illuminate solely when it's unsafe to enter, cross, or takeoff from a runway. Most runway warning lights, such as yellow guard lights, flash or light up continuously.
- Does RWSL communicate with other safety systems?
At all but one airport, RWSL communicates with Airport Surface Detection Equipment - Model X (ASDE-X). The system receives airport approach and surveillance data from ASDE-X through an interface with the ASDE-X Data Distribution Unit. At the San Francisco International Airport, it communicates with Airport Surface Surveillance Capability (ASSC). ASSC provides cooperative surface surveillance capability similar to ASDE-X.
- How does the system vary from one designated airport to the next?
The number of THLs and RELs varies by airport. The brightness of the lights can be adjusted to five different levels and the intensity of the THLs and RELs can be set independently. Overall, the amount of adaptation is minimal. It is usually a matter of timing the light deactivation so as to not interfere with how Air Traffic Control runs their traffic at a given airport. The difference is a few seconds at most. From a pilot's perspective, they will not notice any difference from one airport to the next.
- What is the program doing to educate people?
RWSL has an active outreach program and is educating pilots, air traffic controllers, airlines, pilots unions, aviation enthusiasts, and the general public about the system. The program is teaming up with the FAA Runway Safety Office to reach attendees at the largest aviation trade shows in the country. Articles about the program have been featured in numerous trade publications and information can be found on this website. DVDs and brochures are available upon request.