Operation of Runway Status Indicator Lights (RWSL)


This is the first aviation-related article I will be writing in a while.

Can you explain “runway status indicator lights” out of the blue?

More and more airports are introducing them these days, so let’s study them a little here.

What are runway status indicator lights?

Runway Status Lights(RWSL):These Lights that warn aircraft or vehicles occupying (using) the runway against other aircraft or vehicles attempting to take off or cross the runway.

The way it works is that runway status indicator lights are installed at the end of the runway or at taxiway intersections that cross the runway. The lights automatically turn on or off upon detection of the position of an aircraft or vehicle occupying the runway.

Purpose of runway status indicator lights

The purpose of the runway status indicator lights is to prevent aircraft and vehicles from incorrectly entering or departing on the runway.

Runways are the most important facilities for aircraft takeoffs and landings, but if an aircraft or vehicle crossing the runway accidentally enters the runway, there is a risk of collision with an aircraft taking off or landing.
There is also a risk that an aircraft about to take off may accidentally collide with an aircraft or vehicle crossing the runway.

Applicable airports for runway status indicator lights

There are a total of 5 applicable airports in Japan. (From AIP)

1.New chitose(RJCC)

If you can find commonalities between these 5 airports, you are already a great pilot lol.


There are three types of runway status indicator lights

  • Runway Entrance Light(REL):A red light that warns aircraft attempting to enter the runway.
  • Takeoff Hold Light(THL):A red light that warns an aircraft about to take off.
  • Variable Message Signsz(VMS):VMS is used instead of REL at Tokyo International Airport.

ATC Phrase regarding runway status indicator lights

The RWSL is not operated by air traffic controllers, but only detected by sensors, so there may be discrepancies with the instructions of air traffic controllers.

For example, ATC may say “Cleared for Takeoff” but the THL is lit.

What should the Pilot say at this point?

”Verify THL Illuminated”

It is.

Summary of runway status indicator lights

How was it?

We were not able to provide THL or other images this time, so if you are interested, please check this site.

I think it is also very important to think about how to prevent mis-entry and accidents at airports without these lights, so please consider taking full advantage of the equipment on the plane you are flying.

I have written other aviation-related articles, so if you are interested in any of them, please read them.

3 Reasons Why Flying a Plane is Hard

Airports in Japan (Runway Slope)

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