What is taxiway centreline configuration?
A taxiway centreline is not one rule but four working together: where the lights sit, what colour they show, how far apart they are, and how all of that changes on a curve, at a junction and on the way off a runway. Read together they give the pilot one unbroken line to follow.
Taxiway centreline configuration is the combined layout of position, colour and spacing that turns individual green lights into a guidance line. The other entries in this group cover each part in depth; this one shows how they fit together along a single taxiway, from the runway exit to the apron.
1Position: on the line, set in the pavement
Centreline lights are normally inset fixtures located on the centreline marking. Where that is not practicable, Annex 14 allows an offset of not more than 30 cm, which should stay uniform along the section so the lit line does not drift against the paint.
2Colour: green, with a yellow warning stretch
The normal colour is green. On a runway exit the lights alternate green and yellow, starting with green at the runway centreline, through the runway strip and to the end of the pattern. In FAA practice that is one light position beyond the runway holding position (or the ILS critical area holding position); under ICAO Annex 14 it is the perimeter of the ILS/MLS critical/sensitive area or the lower edge of the inner transitional surface, whichever is farther from the runway, with the last light yellow. From there they run solid green to the apron.
3Spacing: wide on straights, tighter on turns
On a straight, spacing is kept to not more than 30 m, with up to 60 m accepted where the weather conditions mean it still gives adequate guidance and not more than 15 m for RVR below 350 m. On a curve the lights follow the turn at a constant distance from the outside edge and step down with the radius, because the pilot has to see the shape of the turn before reaching it.
4Continuity: through junctions, never a gap
At a junction the through route runs straight on and each branch curves off tangent to it. Holding is added on top, not by breaking the line: yellow holding lights where ATC needs traffic to wait, and a stop bar where the taxiway meets a runway. For resilience, the lights can also be fed from two circuits in an alternate-circuit arrangement.
| Part of the taxiway | Colour | Spacing | Key point |
|---|---|---|---|
| Lead-off stretch | Alternate green / yellow, green at the runway centreline | Through the runway strip, to the end of the pattern (FAA: one light position beyond the holding position; ICAO: critical/sensitive-area perimeter or inner transitional surface) | Warns that the aircraft is still in the runway environment or ILS critical area |
| Straight section | Green | Not more than 30 m; up to 60 m where weather allows; not more than 15 m for RVR below 350 m | On the marking; offset not more than 30 cm only where not practicable |
| Curve | Green | By radius: 30 / 15 / 7.5 m (RVR 350 m or more); 15 / 7.5 m (RVR below 350 m), with 7.5 m extended 60 m before and after the tightest curves | Constant distance from the outside edge of the curve |
| Junction | Green | Through route continuous; branches spaced by radius | Branches curve off tangent; holding lights and stop bars added on top |
Frequently Asked Questions
Q1What is taxiway centreline configuration?
It is the set of rules that fix where taxiway centreline lights sit, what colour they show and how far apart they are as the taxiway changes from a straight to a curve, a junction or a runway exit. Together they give the pilot one continuous line to follow.
Q2Why are centreline lights green, and why yellow near the runway?
Green is the normal colour of a taxiway centreline. On a runway exit the lights alternate green and yellow, starting with green at the runway centreline, to warn that the aircraft is still in the runway environment or the ILS critical area. They return to solid green at the end of the pattern: one light position beyond the holding position in FAA practice, or beyond the ILS/MLS critical/sensitive area perimeter or inner transitional surface under ICAO Annex 14.
Q3How far apart are taxiway centreline lights?
On a straight section the spacing limit is not more than 30 m, up to 60 m where the weather conditions mean the wider spacing still gives adequate guidance, and not more than 15 m on a taxiway intended for use in RVR below 350 m. Curves use closer spacing that depends on the radius. Confirm the figures against your standard.
Q4Why does the spacing get closer on curves?
On a straight, a few lights show the whole path. On a curve the pilot needs to see the shape of the turn ahead, so the lights follow the turn at a constant distance from the outside edge and are placed closer together. The tighter the radius, the closer the spacing.
Q5Do the lights have to sit exactly on the painted centreline?
They are located on the centreline marking. Where that is not practicable, ICAO Annex 14 allows an offset of not more than 30 cm. Keeping any offset the same along a section stops the lit line drifting against the paint.
Q6What happens to the centreline lights at a junction?
They do not stop. The through route runs straight on and each branch curves off tangent to it, so there is always one continuous line for the route the pilot has been cleared to take. Where ATC needs traffic to hold, yellow holding lights are added on top, and at a runway a stop bar is interlocked with the centreline lights beyond it.
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