Green Threshold Light VS Red Runway End Light
Two Colours, One Runway Line — a green threshold light identifies the point at which the portion of the runway available for landing begins, while a red runway end light identifies the physical termination of the runway. The difference comes down to location, viewing direction and operational meaning, and the colour code is the fastest way a pilot reads that meaning, day or night.
At a Glance
| Feature | Green Threshold Light | Red Runway End Light |
|---|---|---|
| Main purpose | Identifies the runway threshold | Identifies the runway end |
| Typical colour | Green | Red |
| Pilot message | Landing starts here | Runway ends here |
| Viewing direction | From the approach direction | From within the runway toward the end |
| Location | At the runway threshold | At the runway end |
| Operational significance | Start of landing distance | End of available runway |
| Typical arrangement | Across the runway width | Across the runway width |
| Relationship | Beginning | Termination |
Where Landing Begins
Green Threshold Light
Identifies the point at which the portion of the runway available for landing begins. Presented to the approaching pilot as green, arranged across the runway width.
Visual message
- GREEN = runway threshold
- "Landing begins here"
- Confirms alignment on final approach
Red Runway End Light
Identifies the termination of the runway. Presented to the pilot moving along the runway toward its end as red, also arranged across the runway width.
Visual message
- RED = end of runway
- "No runway remains beyond this point"
- A clear stop / termination warning
Threshold = Green · End = Red
This is the fastest way to tell the two indications apart, and it is the first colour rule every AGL engineer memorises.
Easy rule: green = going into the runway, red = runway end / stop. The colour difference gives an immediate operational distinction, without the pilot needing to consult anything further.
What Each Pilot Actually Sees
THRESHOLD
RUNWAY END
RUNWAY END
THRESHOLD
The same physical runway extremity can therefore carry different indications depending on the viewing direction — for a runway usable in both directions, the opposite end performs the corresponding function for the opposite runway direction.
Threshold vs Physical Pavement Start
A runway threshold does not always coincide with the physical beginning of the pavement — this occurs with a displaced threshold, where paved runway exists before the threshold but is not available for landing.
Key takeaway: the green threshold light identifies the beginning of the landing portion, which may be displaced from the physical beginning of the runway pavement — not the runway end, and not necessarily the start of the paved surface either.
Green Threshold Light vs Red Runway End Light
| Parameter | Green Threshold Light | Red Runway End Light |
|---|---|---|
| Colour | Green | Red |
| Location | Runway threshold | Runway end |
| Main message | Landing portion begins | Runway terminates |
| Pilot viewing direction | Approach direction | Toward runway end |
| Operational meaning | Beginning | End |
| Displaced threshold relevance | Yes | No direct threshold function |
| Visual purpose | Threshold identification | Runway termination identification |
Threshold/End Combination Light
In many runway lighting arrangements, a single fixture presents both indications at once, depending on the side it is viewed from — this is a threshold/end combination light.
- Green is presented toward the approach side to indicate the threshold
- Red is presented toward the runway side to indicate the runway end
- One physical fixture line, two directional colour outputs
Progressive Visual Indication Along the Runway
A simplified full-runway lighting sequence, in the landing direction, gives the pilot a progressive read of position:
Threshold/End Lights vs Runway Edge Lights
Runway edge lights run along the sides of the runway and define runway width, using their own colour scheme (typically white, with a yellow caution zone near the end on instrument runways). Threshold and runway end lights instead run transverse to the runway, across its width, and identify the beginning and termination points rather than the lateral limits.
Common Terminology Confusion
They are very often the same fixture line at a runway extremity, showing green toward the approach side and red toward the runway side.
Not with a displaced threshold — there, the green threshold marks where the landing portion begins, which can sit some distance beyond the physical start of the pavement.
Red end indications matter for take-off, landing roll-out and any ground movement approaching that extremity — anywhere the physical termination of the runway needs to be unmistakable.
Green Threshold Light vs Red Runway End Light
The green threshold light and the red runway end light are directional readings of position, not two unrelated systems. The fundamental difference is which point on the runway is being identified, and from which side it is viewed.
Green threshold lighting identifies the beginning of the runway portion available for landing; red runway end lighting identifies the physical termination of the runway.
Easy memory: Green → threshold → start. Red → runway end → stop. Start = green, end = red.
Engineering & Expert Notes
Verify Colour for Each Type
ColourCheck chromaticity and not just appearance.
Confirm Direction and Orientation
OrientationLights face specific ways. Check after replacement.
Check Positions Against Survey
PositionDisplaced thresholds make position records important.
Walk the Pattern at Night
InspectionCheck for gaps or dim units.
Frequently Asked Questions
Colour, location and meaning — the green threshold light marks where the landing portion of the runway begins, while the red runway end light marks the physical termination of the runway.
Yes. A threshold/end combination fixture presents green toward the approach side to indicate the threshold, and red toward the runway side to indicate the runway end.
Because of a displaced threshold, where paved runway exists before the threshold but is not available for landing. The green threshold light marks the start of the landing portion, not necessarily the physical start of the pavement.
No. Runway edge lights run along the sides of the runway to define its width. Threshold and runway end lights run across the runway width and identify the beginning and end points instead.
Green means going into the runway (threshold, start of landing), and red means the runway end or stop.
Governing Documents
For an actual project design, always verify the current edition of the applicable documents.
ICAO Annex 14, Volume I
Aerodrome Design and Operations — threshold and runway end lighting colour, siting, intensity and operational requirements, including displaced threshold provisions.
FAA AC 150/5340-30
Design and Installation Details for Airport Visual Aids — threshold and runway end lighting configuration, installation, photometric requirements and electrical systems.
DGCA / AAI Requirements
For Indian airport projects, also verify applicable DGCA requirements, AAI requirements, airport-specific technical specifications, project drawings and contract specifications.
Final Engineering Note
Do not design a threshold or runway-end lighting arrangement from a generic web diagram. The final installation drawing should always be developed from the current governing standard, approved airport design and project-specific requirements.
Green threshold light = start of the landing portion. Red runway end light = physical termination. The same fixture line can carry both, depending on the direction of view.
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