Taxiway Edge VS Taxiway Centreline
Two Systems, One Taxiway — taxiway edge lights define the lateral limits of the taxiway, while taxiway centreline lights guide the aircraft along the intended taxi route itself. The fastest way to tell them apart, day or night, is colour: blue marks the boundary, green marks the path.
At a Glance
| Feature | Taxiway Edge Light | Taxiway Centreline Light |
|---|---|---|
| Main purpose | Defines taxiway edges | Provides centreline guidance |
| Location | Along the sides/edges of taxiway | Along the centreline |
| Primary pilot message | "This is the taxiway boundary" | "Follow this line" |
| Typical colour | Blue | Green |
| Installation | Usually elevated or inset | Usually inset |
| Guidance type | Lateral boundary guidance | Longitudinal directional guidance |
| Main use | Taxiway identification and limits | Taxiing alignment and route following |
| Low-visibility importance | High | Very high |
| Relationship to aircraft | Keeps aircraft within taxiway limits | Keeps aircraft on designated taxi path |
What Is a Taxiway Edge & Taxiway Centreline Light?
Taxiway Edge Light
Positioned along the edges of the taxiway to show the pilot where the limits of the taxiway are.
Provides visual reference for
- Taxiway identification
- Lateral boundary awareness
- Staying within taxiway limits
- Low-visibility taxi operations
Taxiway Centreline Light
Positioned along the centreline of the taxi route to show the pilot where to steer.
Provides visual reference for
- Taxiing alignment
- Route following through curves
- Guidance at intersections
- Low-visibility path tracking
Taxiway Edge = Blue · Taxiway Centreline = Green
This is the fastest way to distinguish the taxiway boundary from the taxi route centreline, and the easiest thing to memorise: blue = edge = boundary, green = centreline = guidance.
The colour separation makes it easy to distinguish the taxiway boundary from the taxi route centreline at a glance, day or night.
Path vs Boundary
The simplest way to remember it: centreline lights answer "where should I steer?" while edge lights answer "where are the limits of the taxiway?" Centreline provides the path; edge provides the boundary — together they give the pilot both pieces of information at once.
What Each System Is Guiding
Taxiway Edge Light
Edge lighting tells the pilot where the taxiway ends laterally — it keeps the aircraft "inside" the taxiway boundary rather than steering it along a specific path.
Taxiway Centreline Light
Centreline lighting tells the pilot where to taxi longitudinally — it provides continuous directional guidance along the intended route, especially through curves and at intersections.
Elevated & Inset Fixtures
Taxiway edge lights can be provided using elevated fixtures, and inset arrangements may also be used where required. Taxiway centreline lights typically use inset fixtures, because aircraft wheels may pass directly over the centreline — this is especially important at intersections and other areas where aircraft need to cross the centreline.
| Installation | Taxiway Edge | Taxiway Centreline |
|---|---|---|
| Typical fixture | Elevated or inset | Primarily inset |
| Why | Sits clear of aircraft wheel paths | Aircraft wheels may pass directly over it |
| Critical locations | Full taxiway length | Especially at intersections and crossings |
How Each System Behaves Along the Route
At a Curve
The blue edge lights continue to define the lateral limits of the taxiway around the curve, while the green centreline provides continuous directional guidance through the turn.
At an Intersection
Centreline lighting can help identify the intended taxi route through an intersection. Additional systems such as stop bars and runway guard lights may provide runway-incursion protection.
Which Matters More When Visibility Drops?
Both systems become especially valuable when visual references are reduced, but they serve different roles. Edge lights help identify the taxiway boundaries; centreline lights provide the primary visual path to follow. For basic directional taxi guidance, the centreline lighting is generally the more direct aid — the edge lights provide the complementary boundary reference.
Easy memory: centreline = path, edge = boundary. In low visibility, the pilot leans on the green centreline to know where to go, and the blue edge to know how far they can drift.
Taxiway Edge vs Taxiway Centreline
| Parameter | Taxiway Edge Light | Taxiway Centreline Light |
|---|---|---|
| Position | Taxiway sides | Taxiway centre |
| Typical colour | Blue | Green |
| Primary function | Boundary definition | Directional guidance |
| Pilot reference | Lateral limits | Longitudinal path |
| Typical fixture | Elevated/inset | Primarily inset |
| Curves | Defines edge around curve | Provides path around curve |
| Intersections | Boundary reference | Route guidance |
| Low visibility | Important | Critical guidance aid |
| Easy meaning | "Stay within" | "Follow this" |
Common Taxiway Lighting Confusion
They serve different purposes. Edge lights define the lateral limits of the taxiway; centreline lights guide the aircraft along the intended taxi path — one is a boundary reference, the other is a route reference.
Taxiway edge lights are normally blue; taxiway centreline lights are normally green. This colour separation is one of the most important concepts in taxiway ground lighting.
Centreline lights are typically inset fixtures because aircraft wheels may pass directly over the centreline, whereas edge lights can be elevated or inset since they sit outside the wheel path.
Taxiway Edge Light vs Taxiway Centreline Light
Taxiway edge and taxiway centreline lights are complementary, not interchangeable, systems. One defines where the taxiway ends; the other defines where to steer within it.
Together, edge lighting keeps the aircraft within the taxiway limits while centreline lighting keeps it on the designated taxi path — a pilot relies on both for safe ground movement, especially in low visibility.
Easy memory: Blue → edge → boundary. Green → centreline → guidance.
Engineering & Expert Notes
Check Colour
ColourVerify blue and green.
Test Brightness Steps
ControlCheck controls.
Inspect at Night
InspectionLook for gaps.
Update Records
RecordsKeep drawings current.
Frequently Asked Questions
Colour and function — taxiway edge lights are blue and define the taxiway boundary, while taxiway centreline lights are green and guide the aircraft along the taxi route.
Because aircraft wheels may pass directly over the centreline. Inset fixtures avoid interfering with wheel contact, which is especially important at intersections and other crossing points.
Centreline lighting is generally the more direct aid for basic directional taxi guidance, while edge lighting provides the complementary boundary reference.
Yes. Edge lights continue to define the lateral limits around curves and at intersections, while centreline lights provide the continuous path to follow through them.
Yes, taxiway edge lights can use elevated fixtures, and inset arrangements may also be used where required, unlike centreline lights which are primarily inset.
Neither — stop bars and runway guard lights are separate systems that provide runway-incursion protection, and may work alongside centreline lighting at intersections.
Governing Documents
For an actual project design, always verify the current edition of the applicable documents.
FAA AC 150/5340-30
Design and Installation Details for Airport Visual Aids — taxiway edge and centreline lighting configuration, installation, photometric requirements and electrical systems.
ICAO Annex 14, Volume I
Aerodrome Design and Operations — taxiway edge and centreline lighting colour, siting, intensity and operational requirements.
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 taxiway lighting system 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 edge = blue, defines the taxiway boundary. Taxiway centreline = green, guides the taxi route — two complementary systems, not one.
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