The pilot and vehicle operator compliance with established protocol for viewing illuminated red status lights is imperative for the system to be effective. Users of the system are trained to respond to Runway Status Lights in two ways.
Runway Entrance Lights (RELs):
- When RELs are red, the runway is unsafe to enter or cross and pilots /vehicle drivers should stop immediately.
- When the lights are off, pilots/vehicle operators shall not enter or cross the runway without ATC clearance.
Note: When LVP are in force at CDG airport, the REL (available from CAT 1 holding points up to the RWY) behaviour is not changed, and the above protocol for operators is the same (If RELs illuminate red, stop immediately and contact ATC). When LVP are in force the CAT 3 holding points are used and stop bars located at these holding points are active. These stop bars should not be mistaken for RELs; stop bars are operated by the tower controller and their switching off should always be associated with an ATC clearance, whereas RELs are fully automated, and are an additional safety measure.
Takeoff Hold Lights (THLs):
- If lined-up and waiting on the runway and THLs are red, the runway is not safe for takeoff and pilots should remain in position for takeoff.
- If the takeoff roll has begun and the THLs turn red, pilots should safely stop the aircraft and notify ATC that they have stopped because of red lights.
In all cases, if following the established protocol is not safe, pilots should proceed according to their best judgment of safety (understanding that illuminated RWSL indicates a potential conflict exists) and contact ATC at the earliest opportunity. When RWSL lights contradict air traffic clearances, pilots and vehicle operators are trained to respond first to the status lights since they are intended to serve as a backup safety net when the humans in the loop make errors. Conversely, pilots and vehicle operators are trained that RWSL is an advisory safety system only and that RWSL off NEVER should be perceived as an air traffic control clearance. RWSL only has two states:
- On – lights are red;
- Off – lights are switched off.
Note: The RWSL never illuminates green lights to convey safety or clearance.