What are Taxiway Lead-off Lights?
Taxiway lead-off lights are alternating green and yellow centre line lights that guide an aircraft off a runway.
Definition
Lead-off light is the FAA name. The FAA calls taxiway centerline lights “lead-off lights” where they give visual guidance to anyone who exits a runway. The ICAO and EASA texts opened for this page do not use the name. They describe the same lights as the taxiway centre line lights on an exit taxiway (ICAO 5.3.17.7, CS ADR-DSN.M.710(c)(2)).
Green and yellow warn the crew that the aircraft is within the runway environment or the ILS critical area. The taxiway centre line light page covers centre line lights in general. This page covers the exit.
How to read the colours
The pattern has three parts. The lights alternate green and yellow. The first light on the runway shows green. The last coded light shows yellow.
| Number of coded lights | Colour order |
|---|---|
| 4 | Green, yellow, green, yellow |
| 5 | Green, green, yellow, green, yellow |
The second row follows from FAA 4.3.2.1.3. If the layout gives an odd number of coded lights, the first two lights on the runway should show green. The pattern then still ends with yellow.
Where the coded section ends differs by system:
- ICAO and EASA. Green and yellow alternate to the perimeter of the ILS or MLS critical or sensitive area. The lower edge of the inner transitional surface may replace it, if that is farther from the runway. After that, all lights show green (ICAO 5.3.17.7, CS ADR-DSN.M.710(c)(2)).
- FAA. Green and yellow alternate to one light position beyond the runway holding position, or beyond the ILS critical area holding position. The last light shows yellow (4.3.2.1.1). AIM 2-1-5 says the stricter of the runway environment and the ILS critical area applies.
The FAA fixture before the holding position is bidirectional. It shows green to a pilot on the taxiway and yellow to a pilot on the runway side (4.3.2.1.2).
Where the lights start
| Exit | ICAO and EASA | FAA |
|---|---|---|
| Fast exit (ICAO and EASA: rapid exit taxiway. FAA: acute-angled exit) | Start at least 60 m before the curve of the centre line. Continue past the curve to where an aeroplane reaches normal taxiing speed | Start 200 ft (61 m) before the point of curvature of the designated taxiway path (4.3.4) |
| Other exit | Start where the marking starts to curve from the runway centre line. Follow the curve at least to where the marking leaves the runway | Start at the point of curvature on the runway, if the runway has minimums below 600 ft (183 m) runway visual range (4.3.5) |
| Spacing, fast exit | At most 15 m, or 30 m where the runway has no centre line lights | 50 ft (15 m) (Table 4-1) |
| Spacing, other exit | At most 7.5 m | See Table 4-1 for the radius and the visibility |
ICAO and EASA add one rule for position. The first light on an exit stands at least 60 cm from any row of runway centre line lights. The sources are ICAO 5.3.17.16 and 5.3.17.18, and CS ADR-DSN.M.715(c)(1) and (d)(1). A rapid exit taxiway is a taxiway that joins a runway at an acute angle. Landing aeroplanes use it to turn off at higher speed. The high-speed taxiway page covers its design.
The FAA gives extra rules:
- Below 1,200 ft (365 m) runway visual range, it recommends lead-off and lead-on lights on other exits (4.3.5.1).
- Where the airport has no operations below 1,200 ft (365 m), lead-off and lead-on lights may not stand within the runway (4.3.5.3).
- A taxiway can meet the runway at a right angle and end there. The light nearest the runway then stands 150 ft (45 m) from the runway centre line (4.3.5.4).
- If an acute-angled exit serves only as an exit, the fixtures are unidirectional. Only the pilots of an exiting aircraft then see them (4.3.4.2).
Position and beam
ICAO and EASA put the lights on the centre line marking. They allow an offset of up to 30 cm where that is not practical (ICAO 5.3.17.12, CS ADR-DSN.M.710(d)(1)). The FAA allows up to 2 ft (0.6 m) to the nearest edge of the fixture, to avoid pavement joints. It asks for the same offset along the row, so the lights do not zigzag (4.3.3.3, 4.3.3.4).
On an acute-angled exit, the FAA toes a unidirectional beam in. The beam crosses the centreline at a point about four times the light spacing along the curve. Bidirectional beams run parallel to the tangent of the curve (4.3.9.4).
When a rule calls for the lights
| System | Rule |
|---|---|
| ICAO | Centre line lights on an exit taxiway for use below 300 m runway visual range, as a Standard. A recommendation for night use at 300 m or more, particularly on exit taxiways (5.3.17.1, 5.3.17.2) |
| EASA | The same, as a recommendation, with 350 m (CS ADR-DSN.M.710(b)(1), (b)(2)) |
| FAA | Recommended on exits other than acute-angled exits below 1,200 ft (365 m) runway visual range (4.3.5.1). At an airport approved for scheduled air carrier operations below that value, AC 120-57 and the approved surface movement plan set the lights (4.2) |
ICAO and EASA allow one exception. The lights need not stand where traffic is light and the edge lights and the centre line marking give adequate guidance.
Lead-off and lead-on lights
Lead-on lights guide an aircraft into the runway. They use the same colour pattern as lead-off lights. The AIM says that lead-on fixtures are bidirectional. One side gives the lead-on light, and the other side gives the lead-off light. A fixture that shows yellow for lead-off must also show yellow for lead-on (AIM 2-1-5).
At a controlled stop bar, the lead-on lights run from the stop bar toward the runway. The stop bar goes off when ATC gives the clearance, and the lead-on lights come on (AIM 2-1-10). The stop bar page covers the red bar.
Maintenance
For a taxiway for use below 550 m runway visual range, EASA sets one objective. No two adjacent centre line lights may be unserviceable (ADR.OPS.C.015(b)(5)). Lead-off lights are centre line lights, so the objective applies to them on such a taxiway.
A light is unserviceable if its main beam average intensity is below 50 percent of the specified value. It is also unserviceable if its filter is missing or damaged, or if the beam has the wrong colour (ADR.OPS.C.015(c)). On a lead-off exit the colour matters more than on other lights, because the colour carries the message.
What an inspection checks
An inspection of an exit taxiway covers these items:
- The first light on the runway shows green.
- The colours alternate in the order that the rule sets, and the last coded light shows yellow.
- The coded section ends at the right position for the system that applies.
- The FAA bidirectional fixture shows green from the taxiway and yellow from the runway.
- The spacing and the offset from the marking are within the limits above.
A drone flight can record whether each light is lit, its colour and its position. TarmacView’s taxiway lights inspection does this for the taxiway network. It does not measure intensity in candela.
Frequently Asked Questions
- What are taxiway centerline lead-off lights?
- Taxiway centerline lead-off lights are alternating green and yellow centre line lights that guide an aircraft off a runway. The FAA uses the name. ICAO and EASA describe the same lights as taxiway centre line lights on an exit taxiway.
- What colour are lead-off lights?
- They alternate between green and yellow. The first light shows green, and the light nearest the end of the coded section shows yellow. The yellow warns the crew that the aircraft is within the runway environment or the ILS critical area.
- What do the yellow lights on a taxiway exit mean?
- The yellow lights warn pilots and vehicle drivers that they are within the runway environment or the ILS critical area. The FAA uses the stricter of the two. After the last yellow light, the lights on an ICAO or EASA exit taxiway show green.
- Where do lead-off lights start and end?
- They start at or near the runway centre line. ICAO and EASA end them at the perimeter of the ILS or MLS critical area, or the lower edge of the inner transitional surface. They use whichever is farther from the runway. The FAA ends them one light position beyond the runway holding position or ILS critical area holding position, with a yellow light.
- What is the difference between lead-off and lead-on lights?
- Lead-off lights guide an aircraft out of the runway. Lead-on lights guide it into the runway. They use the same green and yellow pattern. The FAA fixture next to the holding position is bidirectional, so each pilot sees the colour that suits the direction of travel.
- Are lead-off lights required?
- ICAO requires centre line lights on an exit taxiway for use in runway visual range below 300 m. EASA recommends them below 350 m. The FAA recommends lead-off and lead-on lights below 1,200 ft (365 m) on exits other than acute-angled exits.
- How far apart are lead-off lights?
- On a rapid exit taxiway ICAO and EASA allow at most 15 m, or 30 m where the runway has no centre line lights. On other exit taxiways they allow at most 7.5 m. The FAA spacing on an acute-angled exit is 50 ft (15 m).
References
- icao-annex-14-vol1
- Annex 14 to the Convention on International Civil Aviation, Aerodromes, Volume I, Aerodrome Design and Operations, Ninth Edition (July 2022, consolidated with later amendments) ICAO
- easa-ear-aerodromes
- Easy Access Rules for Aerodromes (Regulation (EU) No 139/2014), including CS-ADR-DSN Issue 7 EASA
- faa-ac-150-5340-30j
- AC 150/5340-30J, Design and Installation Details for Airport Visual Aids FAA
This is a reference entry. TarmacView provides drone inspection services and doesn't sell the equipment or materials described in this glossary.
