AIM Text
- Runway edge lights are used to outline the edges of runways during periods of darkness or restricted visibility conditions. These light systems are classified according to the intensity or brightness they are capable of producing: they are the High Intensity Runway Lights (HIRL), Medium Intensity Runway Lights (MIRL), and the Low Intensity Runway Lights (LIRL). The HIRL and MIRL systems have variable intensity controls, whereas the LIRLs normally have one intensity setting.
- The runway edge lights are white, except on instrument runways yellow replaces white on the last 2,000 feet or half the runway length, whichever is less, to form a caution zone for landings.
- The lights marking the ends of the runway emit red light toward the runway to indicate the end of runway to a departing aircraft and emit green outward from the runway end to indicate the threshold to landing aircraft.
Source: FAA Aeronautical Information Manual · current edition · paragraph 2-1-4.
The short answer
This AIM section is FAA advisory guidance on runway edge light systems, which outline runway edges during darkness or restricted visibility. The systems are classified by intensity as High Intensity (HIRL), Medium Intensity (MIRL), and Low Intensity (LIRL) runway lights, and the section explains the white, yellow caution-zone, red, and green threshold colors a pilot sees.
Research Notes
Common Questions
What is the difference between HIRL, MIRL, and LIRL?
Runway edge light systems are classified by the intensity or brightness they produce: High Intensity Runway Lights (HIRL), Medium Intensity Runway Lights (MIRL), and Low Intensity Runway Lights (LIRL). The HIRL and MIRL systems have variable intensity controls, whereas the LIRLs normally have one intensity setting.
Why do some runway edge lights turn yellow near the end?
Runway edge lights are white, except on instrument runways where yellow replaces white on the last 2,000 feet or half the runway length, whichever is less, to form a caution zone for landings.
What do the red and green lights at the runway ends mean?
The lights marking the ends of the runway emit red light toward the runway to indicate the end of runway to a departing aircraft, and emit green outward from the runway end to indicate the threshold to landing aircraft.