Runway end identifier lights (REIL) (ICAO identifies these as Runway Threshold Identification Lights) are installed at many airports to provide rapid and positive identification of the approach end of a particular runway. The system consists of a pair of synchronized flashing lights located laterally on each side of the runway threshold. REILs may be either omnidirectional or unidirectional facing the approach area. They are effective for:
- Identification of a runway surrounded by a preponderance of other lighting
- Identification of a runway which lacks contrast with surrounding terrain
- Identification of a runway during reduced visibility
- Runway threshold identification lights should be installed:
- at the threshold of a non-precision approach runway when additional threshold conspicuity is necessary or where it is not practicable to provide other approach lighting aids; and
- where a runway threshold is permanently displaced from the runway extremity or temporarily displaced from the normal position and additional threshold conspicuity is necessary.
- Runway threshold identification lights shall be located symmetrically about the runway centre line, in line with the threshold and approximately 10 meters outside each line of runway edge lights.
- Runway threshold identification lights should be flashing white lights with a flash frequency between 60 and 120 per minute.
- The lights shall be visible only in the direction of approach to the runway.
- "Order JO 7340.1Z: Contractions" (PDF). Federal Aviation Administration. March 15, 2007.
- FAA Aeronautical Information Manual, Chapter 2 (Aeronautical Lighting and Other Airport Visual Aids), Section 1 (Airport Lighting Aids) Archived 2009-09-04 at the Wayback Machine
- "Aerodrome Design and Operations" (PDF) (3 ed.). July 1999. Archived from the original (PDF) on 2012-07-23. §5.3.8, "Runway threshold identification lights"