How are taxiway centreline marking and lights aligned?
A taxiway has one centreline, drawn twice. The yellow paint is the path by day and the green lights are the same path by night, so the two have to run together along straights, curves and the join to the runway.
Taxiway centreline lights are located on the centreline marking. The pilot should never have to choose between a painted line and a lit line, because both describe the same path.
1One line, drawn twice
The marking is a continuous yellow line and the lights are green. The colours differ, but the geometry is the same, so a pilot who follows the paint by day follows the lights by night without any change in the path.
2On the line, or a small uniform offset
Lights are set on the marking. Where that is not practicable, ICAO Annex 14 allows an offset of not more than 30 cm. Keeping the offset the same along a section stops the lit line from drifting against the paint. The inset fixtures sit in the pavement and the paint is applied around them, not over the lens.
3Through curves and into the runway
On a curve the marking follows the turn and the lights continue at a constant distance from the outside edge, spaced closer together so the shape of the turn is visible ahead. Where the taxiway joins the runway, the marking curves onto the runway centreline and the lights run on to the same point. The marking does not stop at the point of tangency: it is extended parallel to the runway centreline marking for at least 60 m beyond it where the code number is 3 or 4 (at least 30 m for code number 1 or 2). On an exit taxiway, the lights alternate green and yellow from the runway centreline out to the perimeter of the ILS/MLS critical or sensitive area or the lower edge of the inner transitional surface, whichever is farther from the runway.
4Keeping them aligned
The two drift apart when a pavement is overlaid, when markings are repainted from the old line, or when a fixture turns or settles. The fix is to survey the pavement centre and the lights, then repaint or relocate as the aerodrome decides, and to check the result by day and at night.
| Situation | Marking | Light | Alignment check |
|---|---|---|---|
| Straight taxiway | Continuous yellow line | Green, on the line | No offset, or not more than 30 cm and uniform |
| Curve | Yellow line follows the curve | Green, closer spacing | Lights trace the marking round the turn |
| Join to the runway | Curves onto the runway centreline | Alternate green and yellow near the runway | Both end at the same point on the runway |
| After resurfacing | Repainted from a new set-out | Re-levelled or repositioned | Survey, then a day and night check |
Frequently Asked Questions
Q1How close to the marking must the centreline lights be?
They are located on the centreline marking. Where that is not practicable, ICAO Annex 14 allows them to be offset by not more than 30 cm. Keeping the offset the same along a section stops the lit line from wandering against the painted line.
Q2Why is the marking yellow and the lights green?
Yellow is the colour of taxiway markings and green is the colour of taxiway centreline lights. They are different colours doing the same job, so the pilot reads one path by day from the paint and by night from the lights.
Q3Do the lights follow the marking round a curve?
Yes. The marking follows the curve, and the centreline lights continue at a constant distance from the outside edge of the curve, so both trace the same path. The lights are spaced closer together in the turn so its shape is visible ahead.
Q4Why do some centreline lights alternate green and yellow?
On a runway exit taxiway the lights alternate green and yellow from the runway centreline out to the perimeter of the ILS/MLS critical or sensitive area or the lower edge of the inner transitional surface, whichever is farther from the runway, as a warning that the aircraft is still close to the runway. The lead-on and lead-off lighting entries cover this stretch in detail.
Q5What if the markings and the lights disagree?
Treat it as a defect and report it. The team surveys the pavement centre and the lights, then repaints the marking or relocates the lights as the aerodrome decides, so that the two again form one line.
Q6How is the alignment checked?
By measuring the offset of the lights from the marking, and by driving the route in daylight and at night. The check also confirms that no paint or sealant covers a lens and that no fixture has turned or shifted.
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