Taxiway Centerline Light – Light Marking Taxiway Center – Airport Lighting

Overview

Taxiway centerline lights are green, in-pavement lights embedded along the centerline of airport taxiways. Their primary function is to provide clear, continuous visual guidance to pilots and ground vehicles, especially in low-visibility conditions such as night, fog, or heavy precipitation. Unlike taxiway edge lights (which are blue and mark the taxiway’s boundaries), centerline lights define the exact path aircraft should follow, reducing the risk of ground incidents and enhancing operational efficiency.

Modern airports, especially those that support all-weather operations and high traffic density, rely heavily on centerline lighting as part of an integrated airfield lighting system. These lights are mandated by regulatory bodies such as ICAO (International Civil Aviation Organization) and the FAA (Federal Aviation Administration) for airports conducting low-visibility operations.

Function and Purpose

Taxiway centerline lights serve several vital roles at airports:

• Precise Path Guidance: By marking the center of taxiways, these lights help pilots keep their aircraft correctly aligned, even when painted markings are obscured.
• Safety in Low Visibility: Centerline lighting is most crucial during periods of poor visibility (night, fog, rain, or snow) when pilots cannot see painted lines or other ground references.
• Runway Incursion Prevention: The lights reinforce hold-short locations and runway boundaries, working with stop bars and lead-on/lead-off lights to prevent accidental runway entries.
• Efficient Ground Movement: Continuous centerline lighting allows more predictable and safer taxiing, especially at complex or crowded airports, supporting advanced surface movement guidance systems.

Technical Specifications

Color Coding

• Standard Color: Steady green.
• Transition Zones: At runway or ILS critical area crossings, lights alternate green and yellow (amber) to signal pilots of important boundaries.
• Contrast: The green color stands out against blue taxiway edge lights and white/red runway centerline lights.

Spacing and Placement

• Straight Taxiways: Max 30 m (100 ft) apart; reduced to 15 m (50 ft) in low-visibility operations (RVR < 350 m).
• Curves: Tighter spacing on sharper curves: 7.5 m (25 ft) for radius ≤ 400 m; 15 m (50 ft) for radius 401–899 m; 30 m (100 ft) for radius ≥ 900 m.
• Minimum: At least 4 lights per taxiway segment.
• Regulatory References: ICAO Annex 14, FAA AC 150/5340-30J.

Light Fixtures and Installation

• Type: Always in-pavement (flush-mounted), bidirectional (visible from both directions).
• Materials: Corrosion-resistant (aluminum/stainless steel housings), impact- and weather-resistant lenses.
• Light Source: Predominantly LED for energy efficiency and longevity; some use incandescent lamps for deicing benefits.
• Maintenance: Designed for easy access and replacement; must withstand aircraft wheel loads and jet blast.
• Offset: May be installed up to 30 cm (ICAO) or 2 ft (FAA) off the painted centerline to avoid pavement seams or reduce wear, but must remain visually aligned.

Operational Use Cases

Low Visibility Operations

Taxiway centerline lights are required at all airports supporting Category II or III instrument operations (RVR < 350 m / 1,200 ft). In these conditions, painted lines and even edge lights may be invisible, so green centerline lights provide the sole reliable guidance to pilots.

At major airports like London Heathrow or Amsterdam Schiphol, centerline lights are integrated with stop bars, runway guard lights, and advanced surface movement guidance systems (A-SMGCS). This allows dynamic lighting control by ATC for safe, efficient routing—even in “zero-zero” visibility.

Pilot Visual Cues

Pilots use the green centerline lights to:

• Align the aircraft nosewheel over the correct route.
• Confirm they are on the correct taxiway.
• Recognize transitions (green/yellow) at runway or ILS boundaries.
• Avoid obstacles, edges, or non-movement areas.
• Receive tactile/audible feedback when taxiing over inset lights, reinforcing correct positioning.

Ground Movement Safety

Centerline lighting helps:

• Prevent runway incursions by reinforcing stop bars and hold points.
• Enable ATC to manage ground traffic efficiently and safely.
• Integrate with surveillance/radar systems for real-time movement monitoring.
• Maintain operations during sudden weather changes, reducing the need for ground stops.

Examples

• Fog at a Major Airport: In dense fog, pilots at a busy hub safely taxi using the unbroken path of green centerline lights, even with zero outside visibility.
• Night Taxi at a Regional Airport: Pilots use green centerline lights to avoid unlit hazards and construction zones during a late-night arrival.
• Coordinated Lighting Sequences: ATC uses stop bars and alternating green/yellow lead-on lights to safely route aircraft across active runways in heavy rain.

Related Lighting Elements

• Taxiway Edge Lights: Blue, omnidirectional lights marking taxiway boundaries (spaced 15–60 m apart).
• Lead-On/Lead-Off Lights: Alternating green/yellow in-pavement lights at runway/taxiway intersections for transition guidance.
• Stop Bar Lights: Red, unidirectional lights across taxiways at runway holding points; extinguished only when safe to proceed.
• Clearance Bar Lights: Three yellow lights indicating a stop-and-wait point within taxiway intersections.
• Runway Guard Lights: Flashing yellow lights (elevated or in-pavement) warning of approaching active runways.

Regulatory Standards

• FAA:
  • AC 150/5340-30J: Design/installation of taxiway/runway lighting.
  • AC 150/5340-28: Taxiway centerline lighting requirements.
  • AIM, Chapter 2: Overview of visual aids.
• ICAO:
  • Annex 14, Volume I, Para 5.3.15: Centerline lighting requirements for low-visibility ops.
  • Paras 5.3.15.10–13: Offset and spacing standards.

Troubleshooting & FAQs

• Not at Every Airport: Only required at airports with frequent night/low-visibility ops.
• Reporting Outages: Pilots should report extinguished lights to ATC/airport ops; multiple outages can create hazards.
• Pilot Control: At major airports, lighting is ATC-controlled; at some small airports, pilots can activate lights via radio.
• Offset Installation: Lights may be offset from the painted line to avoid pavement seams or reduce maintenance.

Glossary of Related Terms

Sources and References

• ICAO Annex 14, Volume I – Aerodrome Design and Operations
• FAA AC 150/5340-28 – Low Visibility Taxiway Lighting Systems
• FAA AC 150/5340-30J – Design and Installation Details for Airport Visual Aids
• FAA Aeronautical Information Manual (AIM), Chapter 2
• FAA Airfield Standards
• ICAO Aerodrome Standards

Taxiway centerline lights are a cornerstone of modern airport safety and efficiency, ensuring that pilots always have a reliable, illuminated path—even in the most challenging conditions.