2-1-3. Runway End Identifier Lights (REIL)
REILs are installed at many airfields 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:
a. Identification of a runway surrounded by a preponderance of other lighting.
b. Identification of a runway which lacks contrast with surrounding terrain.
c. Identification of a runway during reduced visibility.
2-1-4. Runway Edge Light Systems
a. 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.
b. 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.
c. 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.
2-1-5. In-runway Lighting
a. Runway Centerline Lighting System (RCLS). Runway centerline lights are installed on some precision
approach runways to facilitate landing under adverse visibility conditions. They are located along the runway
centerline and are spaced at 50-foot intervals. When viewed from the landing threshold, the runway centerline
lights are white until the last 3,000 feet of the runway. The white lights begin to alternate with red for the next
2,000 feet, and for the last 1,000 feet of the runway, all centerline lights are red.
b. Touchdown Zone Lights (TDZL). Touchdown zone lights are installed on some precision approach
runways to indicate the touchdown zone when landing under adverse visibility conditions. They consist of two
rows of transverse light bars disposed symmetrically about the runway centerline. The system consists of
steady-burning white lights which start 100 feet beyond the landing threshold and extend to 3,000 feet beyond
the landing threshold or to the midpoint of the runway, whichever is less.
c. Taxiway Centerline Lead-Off Lights. Taxiway centerline lead-off lights provide visual guidance to
persons exiting the runway. They are color-coded to warn pilots and vehicle drivers that they are within the
runway environment or instrument landing system (ILS) critical area, whichever is more restrictive. Alternate
green and yellow lights are installed, beginning with green, from the runway centerline to one centerline light
position beyond the runway holding position or ILS critical area holding position.
d. Taxiway Centerline Lead-On Lights. Taxiway centerline lead-on lights provide visual guidance to
persons entering the runway. These "lead-on" lights are also color-coded with the same color pattern as lead-off
lights to warn pilots and vehicle drivers that they are within the runway environment or instrument landing
system (ILS) critical area, whichever is more conservative. The fixtures used for lead-on lights are bidirectional,
i.e., one side emits light for the lead-on function while the other side emits light for the lead-off function. Any
fixture that emits yellow light for the lead-off function must also emit yellow light for the lead-on function.
(See FIG 2-1-12.)
e. Land and Hold Short Lights. Land and hold short lights are used to indicate the hold short point on certain
runways which are approved for Land and Hold Short Operations (LAHSO). Land and hold short lights consist
of a row of pulsing white lights installed across the runway at the hold short point. Where installed, the lights
will be on anytime LAHSO is in effect. These lights will be off when LAHSO is not in effect.

2-1-6

Airport Lighting Aids