Taxiway Centreline VS Runway Centreline
Taxi Route vs Runway Alignment — the green taxiway centreline light guides an aircraft along its intended taxi path, while the white runway centreline light provides the alignment and directional reference during takeoff and landing. Both sit along a centreline, both are commonly inset, but they operate in different phases of flight and answer different pilot questions.
At a Glance
| Feature | Taxiway Centreline | Runway Centreline |
|---|---|---|
| Main purpose | Taxi route guidance | Runway alignment |
| Location | Along taxiway | Along runway |
| Primary function | Directs taxiing aircraft | Aligns aircraft with runway |
| Typical light colour | Green | White; colour changes may occur toward the runway end |
| Typical fixture | Inset | Inset |
| Used during | Taxiing | Takeoff and landing |
| Main pilot message | "Follow this taxi route" | "This is the runway centre" |
| Primary concern | Taxiway navigation | Runway alignment and position |
| Relationship to edge lights | Complements blue edge lights | Complements runway edge lights |
What Is a Taxiway Centreline & Runway Centreline Light?
Taxiway Centreline Light
Provides a continuous visual reference along the intended taxi path. The pilot uses it to answer: "Where should I taxi?"
Provides a reference for
- The designated taxi route
- Steering guidance while taxiing
- Tracking through curves and intersections
- Route guidance at night and in reduced visibility
Runway Centreline Light
Provides a visual reference along the longitudinal centre of the runway. The pilot uses it to answer: "Am I aligned with the runway?"
Provides a reference for
- Runway alignment and positional guidance
- Precise tracking during takeoff roll
- Precise tracking during landing rollout
- Runway reference in low-visibility operations
Green + Taxi vs White + Runway
The fastest way to tell them apart, day or night, is colour combined with the phase of flight they belong to: green centreline → taxi, white centreline → takeoff/landing.
Runway centreline lighting may incorporate other colours in specific portions of the runway, depending on the applicable standard and runway configuration — the green taxiway centreline does not carry that same colour transition.
How They Sit Between the Edges
On a taxiway, the centreline lies between blue edge lights and glows green. On a runway, the centreline lies between the runway edge lights and glows white — in both cases the centreline is the single line the pilot tracks, while the edge lights bound it on either side.
What the Pilot Sees, Phase by Phase
While Taxiing
The green centreline tells the pilot where the aircraft should track along the taxi route — the working instruction is simply "follow the green centreline."
During Takeoff / Landing
The white centreline provides a runway alignment reference — the working instruction is "stay on the runway centre" through the takeoff roll or landing rollout.
The simplest way to remember it: the taxiway centreline answers "where do I go next?" while the runway centreline answers "am I straight?" One is a route to follow; the other is a precise alignment reference.
Both Are Commonly Inset
Both systems commonly use inset fixtures because aircraft can pass directly over the centreline. The physical installation is similar in principle, but the function and operating environment differ — one guides ground movement, the other guides a high-speed, precision-critical phase of flight.
| Installation | Taxiway Centreline | Runway Centreline |
|---|---|---|
| Typical fixture | Inset | Inset |
| Why inset | Aircraft may pass directly over the centreline while taxiing | Aircraft may pass directly over the centreline during takeoff/landing roll |
| Colour | Green throughout | White, with colour changes possible toward the runway end |
Where Each System Provides Guidance
On Curves & at Intersections
Taxiway centreline lighting is particularly important on curves and can guide an aircraft through complex taxiway intersections, helping the pilot identify the intended taxi route.
Straight-Line Reference
Runway centrelines are generally straight along the runway's longitudinal axis. Runway centreline lighting is not primarily intended to function as an intersection-navigation system.
Which Matters More When Visibility Drops?
Both systems become especially valuable when visual references are reduced, but for different reasons. The taxiway centreline provides visual guidance while taxiing, especially on curves and at intersections. The runway centreline provides an important runway reference during takeoff and landing, when precise alignment matters most.
Easy memory: green centreline = taxi route in low visibility; white centreline = runway alignment in low visibility. Neither substitutes for the other — a pilot moves from one system to the other as the aircraft transitions between taxiway and runway.
Centreline + Edge, Together
Taxiway
Blue lights mark the taxiway edge; green lights mark the centreline — edge defines the limit, centreline defines the path within it.
Runway
Runway edge lights mark the runway limit; the runway centreline marks runway alignment — edge defines the boundary, centreline defines the tracking reference.
What Each Centreline Answers
| Question | Light |
|---|---|
| Where am I? | On the taxi route (Taxiway Centreline) |
| Where should I steer while taxiing? | Taxiway Centreline |
| Am I aligned with the runway? | Runway Centreline |
| What guides me through a curved taxi route? | Taxiway Centreline |
| What guides me during takeoff roll? | Runway Centreline |
| What guides me during landing rollout? | Runway Centreline |
Taxiway Centreline vs Runway Centreline
| Parameter | Taxiway Centreline | Runway Centreline |
|---|---|---|
| Where am I? | On the taxi route | On the runway |
| Where should I steer? | Along taxi route | Along runway axis |
| Primary operation | Taxi | Takeoff / Landing |
| Typical colour | Green | White |
| Curved-path guidance | Yes | Normally not the primary purpose |
| Intersection guidance | Yes | Not primary |
| Alignment function | Taxiway alignment | Runway alignment |
| Typical fixture | Inset | Inset |
| Low visibility role | Taxi route guidance | Runway alignment reference |
Common Colour Confusion
They serve different purposes tied to different phases of flight — the taxiway centreline is a route reference for ground movement, while the runway centreline is a precision alignment reference for takeoff and landing.
Runway centreline lighting may incorporate other colours in specific portions of the runway depending on the applicable standard and runway configuration — the colour scheme itself can carry positional meaning.
Green is characteristic of taxiway centreline lighting, not runway centreline lighting. Runway centreline is normally white, so a green centreline line indicates a taxiway reference, not a runway one.
Taxiway Centreline vs Runway Centreline
Taxiway and runway centreline lights are complementary systems tied to different phases of flight, not interchangeable variants of the same fixture. One tells the pilot where to taxi; the other tells the pilot whether the aircraft is aligned with the runway.
Together with their respective edge lighting, each centreline system gives the pilot a continuous longitudinal reference — green for the taxi route, white for the runway — so the aircraft is never without a clear line to follow, on the ground or during takeoff and landing.
Easy memory: Green + centreline → taxi. White + centreline → runway.
Engineering & Expert Notes
Verify Colour and Pattern
ColourCheck chromaticity and sequence.
Check Alignment
AlignmentVerify level and aim.
Inspect Seals and Drainage
WaterInset units are vulnerable.
Inspect at Night
InspectionCheck for gaps.
Frequently Asked Questions
Colour, function and phase of flight — the taxiway centreline is green and guides taxi route navigation, while the runway centreline is white and provides runway alignment during takeoff and landing.
The colour distinction lets a pilot instantly identify which system — and which phase of operation — the centreline belongs to, even at night or in reduced visibility.
Runway centreline lighting may incorporate other colours in specific portions of the runway, depending on the applicable standard and runway configuration.
Because aircraft can pass directly over the centreline in both cases — an inset fixture avoids interfering with wheel contact along the tracked path.
Yes. Taxiway centreline lighting is particularly important on curves and can guide an aircraft through complex taxiway intersections, showing the aircraft's intended path.
No. Runway centrelines are generally straight along the runway's longitudinal axis, and runway centreline lighting is not primarily intended to function as an intersection-navigation system.
Runway centerline lights are white along most of the runway and change colour near the runway end, and they guide the aircraft during take-off and landing. Taxiway centerline lights are normally green and guide the aircraft along the taxi route at lower speed. They differ in colour, intensity, spacing and function.
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 — taxiway centreline and runway centreline lighting colour, siting, intensity and operational requirements.
FAA AC 150/5340-30
Design and Installation Details for Airport Visual Aids — taxiway and runway centreline 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 centreline 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.
Taxiway centreline tells you where to taxi. Runway centreline helps you stay aligned with the runway.
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