Plain English Meaning

A set of red lights built into the runway and taxiway surface that turn on automatically when it is not safe to enter or use the runway. If you see them lit, stop and confirm with the controller before moving.

Full Definition

An automated, advisory airport lighting system that uses red in-pavement lights to alert pilots and surface vehicle operators when it is unsafe to enter, cross, take off from, or land on a runway. RWSL operates independently of air traffic control instructions and is driven by surveillance of aircraft and vehicle positions. The system includes Runway Entrance Lights (RELs) at taxiway/runway intersections, Takeoff Hold Lights (THLs) on the runway centerline near the departure end, Runway Lights (RILs) where two cross, and (FAROS) where installed. Illuminated red lights mean stop or do not proceed; pilots must never cross or pass illuminated red lights, and must not begin when THLs are lit.