Definition

Final Approach Runway Occupancy Signal

Description

Final Approach Runway Occupancy Signal (FAROS)) is a concept which was developed in the USA in the early 2000s as part of the overall enhancement of safety nets designed to reduce Runway Incursion hazards.

It works by providing a visual signal to aircraft on final approach to land that the runway ahead is occupied by another aircraft or a vehicle. This is done by adapting the VASIS or PAPI system to alter from steady lights to flashing mode whilst the identified hazard remains. Externally, the PAPI or VASI system is unaltered and continues to function normally in its primary role as an angle of approach awareness indicator whether or not a FAROS input has temporarily caused the flashing mode to activate.

The input signal to the FAROS visual signal is provided automatically by the embedded inductive loops which are installed at all runway entry and exit points at certain airports for various operational uses and which are able to detect transiting traffic by the disturbance of the loop magnetic field which it causes. The system was tested at Dallas Fort Worth (DFW) airport. An enhanced FAROS (eFAROS) using ASDE-X data and developed approximately ten years after its initial invention was tested at Logan International airport (BOS), but is not part of the current FAA surface safety portfolio. FAROS is provided to enhance pilot awareness only. It does not substitute for, or interfere with, existing ATC authority or flight crew procedures, and activation does not affect the validity of an existing ATC Landing Clearance. In many cases, it may be activated on short finals as another aircraft departs from the same runway or an aircraft or vehicle cross it in accordance with their ATC clearances. However, it is NOT intended to act as an effective safety net in the case of the collision hazard which may arise during simultaneous operation of intersecting runways.

Further Reading

• Surface Safety Portfolio, FAA website, last updated 19 March 2025