the control tower. In FAROS, automated line-of-sight runway sensors detect if a vehicle has committed a runway incursion, and if so, will flash the PAPI lights to alert the pilot of an aircraft on final approach that the runway is currently occupied. The pilot then becomes responsible for resolving the conflict by notifying the air traffic controller and executing a go-around. Once the tower has ascertained that the runway has been cleared, the ground controller resets the PAPI so that landing operations may resume normally. See also Approach lighting system (ALS) Pilot controlled lighting (PCL) Visual approach slope indicator (VASI) Instrument landing system (ILS) Runway end identifier lights (REIL) Runway edge lights (HIRL, MIRL, LIRL) Optical landing system Leading lights References Airport lighting Types of final approach (aviation)