What is displaced threshold lighting?
The lighting that tells a pilot where landing begins when the threshold sits further down the runway than the start of the pavement: red edge lights before it, a green bar at it.
A displaced threshold is a landing threshold set back from the physical start of the runway. The pavement before it is still there and still useful, but a pilot must not land on it. The lights say so in colour: red edge lights across the displaced area, then a green bar where landing begins.
1What a displaced threshold is
The threshold is moved down the runway to clear an obstacle in the approach, to reduce noise, because the pavement is not suited to landing, or temporarily for works. The pavement before it can normally be used for taxiing, take-off, and the landing roll-out of aircraft arriving from the opposite direction. The landing distance available is shorter by the displacement, and the declared distances are published.
2Lights in the displaced area
The runway edge lights between the start of the pavement and the displaced threshold show red in the approach direction and white in the opposite direction (yellow where the caution zone of an instrument runway applies). That is why they are bidirectional fixtures with a red face and a clear face. A pilot landing the other way sees ordinary edge lights. A pilot taking off in the approach direction looks at the same red faces, so the roll starts between red edge lights with the green bar ahead, and the lights turn white beyond it. Red here means landing cannot begin before this point, not that the pavement is closed.
3Lights at the displaced threshold
A row of green threshold lights runs across the full runway width at the displaced position, seen from the approach. It does the job the threshold bar does on any runway: it marks the start of the portion available for landing. The pilot reads the sequence directly: red edge lights, then green.
4What follows the displaced threshold
Everything that is set out from the landing threshold follows it: the approach lighting, the visual approach slope indicator and the touchdown zone lights. Where the inner approach lights would fall on paved surface they are inset rather than elevated. The runway end lights do not move: they stay at the physical end of the runway.
| Feature | With a displaced threshold |
|---|---|
| Edge lights in the displaced area | Red in the approach direction (seen by landing and by taking-off traffic that way), white or yellow the other way |
| Centreline and TDZ lights before the threshold | Not used for landing; often not fitted or blanked in the landing direction (practice varies by standard) |
| Threshold bar | Green toward the approach, across the runway, at the displaced position |
| Edge lights beyond the threshold | White, as on any runway |
| Runway end lights | Stay at the physical runway end |
| Approach lights, VASI/PAPI, TDZ lights | Set out from the displaced threshold |
| Markings | White arrows on the centreline and a threshold bar at the displaced position |
| Landing distance available | Reduced by the displacement and declared |
Frequently Asked Questions
Q1What is displaced threshold lighting?
It is the lighting that shows where landing begins when the threshold is set back from the physical start of the runway. Edge lights in the displaced area show red toward the approach, and a green threshold bar marks the displaced threshold itself.
Q2What colour are the lights before a displaced threshold?
The runway edge lights between the start of the pavement and the displaced threshold show red to an aircraft on approach and white (or yellow in a caution zone) in the opposite direction. A pilot on approach sees red edge lights, then the green threshold bar. A pilot taking off in the same direction sees the same red edge lights and the green bar ahead.
Q3Can aircraft use the pavement before a displaced threshold?
Yes, but not for landing in the approach direction. The pavement can normally be used for taxiing, for take-off, and for the landing roll-out of aircraft arriving from the opposite direction.
Q4Where are the runway end lights on a runway with a displaced threshold?
They stay at the physical end of the runway, facing along the runway in red for traffic arriving from the opposite direction. The displaced threshold is marked by the green threshold bar, not by end lights.
Q5Do PAPI, touchdown zone lights and approach lights follow the displaced threshold?
Yes. Visual approach slope indicators, touchdown zone lighting and the approach lighting system are set out from the threshold used for landing, which is the displaced threshold, not the start of the pavement.
Q6What changes when a threshold is displaced temporarily for works?
The lights and markings have to change together: the displaced position is marked and lit, edge lights in the closed-to-landing area are set red toward the approach, and the new landing distance is published. The exact method depends on the standard and the aerodrome's procedures.
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