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Runway Status Lights Questions and Answers

  1. What is Runway Status Lights (RWSL)?
  2. RWSL is comprised 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.

  3. What are Runway Entrance Lights (RELs)?
  4. 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.

  5. What are Takeoff Hold Lights (THLs)?
  6. 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.

  7. 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.

  8. How do the lights work?
  9. 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.

  10. What precautions should be taken if verbal clearance is received from the tower, but the lights are illuminated?
  11. Pilot/vehicle operators should hold short of the runway and advise Air Traffic Control they are holding for red lights.

  12. What airports are receiving RWSL?
    The following airports are scheduled to receive RWSL production 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

  13. What do the lights look like and how are they installed?
  14. 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.

  15. How are the lights different from other runway warning lights?
  16. 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.

  17. Does RWSL communicate with other safety systems?
  18. 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.

  19. How does the system vary from one designated airport to the next?
  20. 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.

  21. What is the program doing to educate people?
  22. 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.



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This page was originally published at: https://www.faa.gov/air_traffic/technology/rwsl/faqs/