The FAA said its Runway Status Lights (RWSL) system is now operational at the 20 large airports approved for the system.

The fully automatic RWSL system combines an airport’s lighting equipment with its surface surveillance system to determine the location of aircraft and vehicles.

Comprised of runway entrance lights (REL) and takeoff hold lights (THL), the advisory system alerts pilots and vehicle operators to stop when runways and taxiways are not safe to enter, cross or begin takeoff.

RELs positioned at taxiway and runway crossings illuminate if it is unsafe to enter or cross a runway. THLs by the departure hold zone illuminate when there is an aircraft in position for departure and the runway is occupied by another aircraft or vehicle.

A report on the effectiveness of the RWSL system at 15 airports where it was operational in 2017 found an overall 52% reduction in the average runway incursion rate, “with 15,484 potential saves,” the FAA said.

Bill Carey,