Different taxiway fixtures
Edge, centreline, stop bar and runway guard: four taxiway lights that differ in what they mark, how they are mounted, their colour and how they operate.
A taxiway is lit by several fixtures, each with a job and a colour. Four common ones are the elevated edge light, the inset centreline light, the inset stop bar light and the runway guard light. They differ in what they mark, whether they stand above the pavement or sit flush in it, their colour, and how they operate.
Colour carries the meaning: blue marks the edges, green marks the route, red means stop at a holding position, and yellow warns that a runway lies ahead. Lights beside the taxiway can be raised on a frangible coupling, while lights on the paved surface are set flush and built to carry wheel loads. Stop bars and runway guard lights are also switched or flashed, so their operation matters as much as the fixture.
Edge lights and side-mounted runway guard lights. Raised on a frangible coupling above a base can, so the upper part breaks away and the base stays in the ground.
Centreline and stop bar lights. Flush in the pavement, so no break point, but they carry wheel loads and must be re-set after resurfacing.
| Aspect | Edge light | Centreline light | Stop bar light | Runway guard light |
|---|---|---|---|---|
| Marks | Taxiway edges | Taxiway route to follow | A holding position where aircraft stop | The approach to a runway |
| Mounting | Elevated on a frangible coupling above a base | Inset, flush in the pavement | Inset across the taxiway; elevated lights may be added at the sides | Elevated pairs beside the taxiway, or inset across it |
| Colour | Blue | Green; alternating green and yellow on runway exits within the ILS/MLS critical or sensitive area, per standard | Red | Yellow |
| Light direction | Seen from all around | One or both directions, per the design | One direction, toward the approaching aircraft | One direction, toward the approaching aircraft |
| Operation | Steady, switched with the taxiway circuit | Steady; may be switched in sections to guide aircraft | On to stop, off to let an aircraft proceed, under control | Flashing alternately when in use, typically 30 to 60 flashes a minute per light (ICAO) |
| Watch points | Blue colour, height and aim | Height after resurfacing; green colour; sealed joint | Red colour; switching with the centreline lights; wheel damage | Flash pattern and alternation; aim toward the approach |
What to check on taxiway fixtures
Break point as built
Keep the manufacturer’s coupling and fasteners on elevated lights. Never add bracing or a stronger fixing across the break point.
Window and lens
Keep the window or lens clean and undamaged. Dirt, scratches and cracks reduce and distort the light.
Colour of each light
Check the filter or LED colour is correct: blue, green, red or yellow. A wrong colour gives the pilot a wrong message.
Height and flushness
Check elevated height, and inset height against the pavement. Re-check inset height after resurfacing.
Aim and direction
Check each fixture points the way the design says, especially stop bar and runway guard lights.
Switching and flash
Check that stop bars and runway guard lights switch and flash as designed, and that they are controlled with the centreline lights.
Frequently Asked Questions
Q1What are the main types of taxiway light fixture?
Four common ones are the elevated blue edge light, the inset green centreline light, the inset red stop bar light and the yellow runway guard light. They differ in what they mark, whether they stand above the pavement or sit flush in it, their colour and how they operate. Details vary by product and standard.
Q2Why are taxiway edge lights blue and centreline lights green?
Colour tells the pilot what the light means. Blue marks the edges of the taxiway and green marks the route along its centreline. Red marks stop bars and yellow marks runway guard lights, so a pilot can read the meaning of a light from its colour.
Q3What does a stop bar do?
A stop bar is a row of red lights across a taxiway at a holding position, switched on to tell an aircraft to stop and switched off to let it proceed. It works with the taxiway centreline lights beyond it, which are normally controlled so that they are only lit once the aircraft may continue.
Q4What is a runway guard light for?
Runway guard lights warn a pilot or driver that the taxiway ahead leads onto a runway. They are yellow, and in one common form they are pairs of lights beside the taxiway that flash alternately, typically 30 to 60 flashes a minute per light. In another form a row of inset yellow lights lies across the taxiway.
Q5Why are some taxiway lights elevated and others inset?
Edge lights and the side-mounted runway guard lights stand beside the taxiway, so they can be raised on a frangible coupling. Centreline and stop bar lights lie on the paved surface that aircraft run over, so they are set flush in the pavement and built to carry wheel loads.
Q6What limits and requirements apply?
Colour, spacing, intensity, heights and frangibility limits come from the standard (ICAO or FAA), the regulator, the airport's design and the manufacturer's instructions. Always use the requirements for your site rather than a generic list, and isolate and lock out the circuit before working on any fixture.
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