Aeronautical Information Manual (AIM), page 106
AIM 12/10/15 pilot's taxi or takeoff clearance previously issued by Automatic Terminal Information System (ATIS) ATC. If RWSL indicates that it is unsafe to takeoff must be updated. from, land on, cross, or enter a runway, immediately notify ATC of the conflict and re-confirm the 2-1-7. Stand-Alone Final Approach clearance. Runway Occupancy Signal (FAROS) 4. Do not proceed when lights have extin- a. Introduction: guished without an ATC clearance. RWSL verifies an The stand-alone FAROS system is a fully automated ATC clearance; it does not substitute for an ATC system that provides runway occupancy status to clearance. pilots on final approach to indicate whether it may be 5. Never land if PAPI continues to flash. unsafe to land. When an aircraft or vehicle is detected Execute a go around and notify ATC. on the runway, the Precision Approach Path Indicator (PAPI) light fixtures flash as a signal to indicate that g. ATC Control of RWSL System: the runway is occupied and that it may be unsafe to land. The stand-alone FAROS system is activated by 1. Controllers can set in-pavement lights to one localized or comprehensive sensors detecting aircraft of five (5) brightness levels to assure maximum or ground vehicles occupying activation zones. conspicuity under all visibility and lighting condi- The stand-alone FAROS system monitors specific tions. REL, THL, and RIL subsystems may be areas of the runway, called activation zones, to independently set. determine the presence of aircraft or ground vehicles in the zone (see FIG 2-1-10). These activation zones 2. System lights can be disabled should RWSL are defined as areas on the runway that are frequently operations impact the efficient movement of air occupied by ground traffic during normal airport traffic or contribute, in the opinion of the assigned operations and could present a hazard to landing ATC Manager, to unsafe operations. REL, THL, RIL, aircraft. Activation zones may include the full-length and FAROS light fixtures may be disabled separately. departure position, the midfield departure position, a Disabling of the FAROS subsystem does not frequently crossed intersection, or the entire runway. extinguish PAPI lights or impact its glide path function. Whenever the system or a component is Pilots can refer to the airport specific FAROS pilot disabled, a NOTAM must be issued, and the information sheet for activation zone configuration.FIG 2-1-10 FAROS Activation Zones Clearance to land on a runway must be issued by Air control over the system and may not be able to view Traffic Control (ATC). ATC personnel have limited the FAROS signal. 2-1-10 Airport Lighting Aids
Page 106 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures