Taxiway Light – Airport Taxiway Lighting Systems

Taxiway lights are a cornerstone of modern airport safety and efficiency, forming a key component of the visual guidance system that enables aircraft and ground vehicles to navigate aerodrome surfaces safely in darkness, fog, rain, or other low-visibility conditions. This glossary entry provides an in-depth look at taxiway lighting: its purpose, types, operational standards, and its critical role in preventing runway incursions and ground incidents.

Definition and Purpose

Taxiway lights are specialized, color-coded lighting fixtures installed along airport taxiways. Their primary role is to delineate taxiway edges, centerlines, intersections, holding points, and transitions, providing visual cues that supplement painted markings and signs. These lights are crucial when visibility is compromised—at night, in fog, rain, snow, or during other adverse conditions.

International Civil Aviation Organization (ICAO) and Federal Aviation Administration (FAA) standards strictly regulate taxiway lighting systems, specifying the color, intensity, placement, and operation of each fixture. Properly installed and maintained lights minimize the risk of navigation errors, ground collisions, and unauthorized runway crossings (incursions), especially at busy or complex airports.

Types of Taxiway Lights

Modern taxiway lighting systems comprise several specialized light types, each serving a distinct function:

Taxiway Edge Lights

Taxiway edge lights are omnidirectional blue lights marking the boundaries of taxiways and aprons. Typically elevated, they may be recessed in high-traffic or jet-blast areas. Standard spacing is 60 meters (200 feet), but this can be reduced to 30 meters (100 feet) in curves or intersections. At smaller airports, blue reflectors may substitute for powered edge lights.

Taxiway Centerline Lights

Taxiway centerline lights are in-pavement green lights installed along painted centerlines, providing precise routing—especially important in low-visibility operations or at airports with Category II/III ILS approaches. Standard spacing is 15 meters (50 feet) on straight segments and 7.5 meters (25 feet) in curves or intersections.

Clearance Bar Lights

Clearance bar lights consist of three steady-burning yellow (amber) in-pavement lights, installed at designated holding points or intermediate locations. They are especially useful at complex intersections and are vital in low-visibility conditions to ensure pilots and vehicles stop where required.

Runway Guard Lights (RGLs)

Runway guard lights (RGLs) are high-visibility yellow lights located at taxiway-runway intersections. They can be elevated “wig-wag” pairs (alternating flashes) or in-pavement arrays. Their purpose is to alert pilots and vehicle operators that they are approaching an active runway and must hold unless cleared.

Stop Bar Lights

Stop bar lights are unidirectional red in-pavement lights installed across taxiways just before runway holding points. When illuminated, they indicate an absolute stop—entry to the runway is prohibited. Stop bars are interlocked with ATC and surface movement systems, and only extinguished when it is safe to proceed.

Taxiway Centerline Lead-On and Lead-Off Lights

Centerline lead-on and lead-off lights are in-pavement lights marking the transition between taxiways and runways. They display alternating green and yellow, spaced at 7.5 meters (25 feet), and guide aircraft safely onto or off runways, reducing the risk of navigation errors.

Runway Status Light System (RWSL)

Runway Status Light System (RWSL) is an advanced, automated lighting system using in-pavement red lights—Runway Entrance Lights (RELs) and Takeoff Hold Lights (THLs)—to provide real-time runway occupancy status. RWSL operates independently of ATC using radar and sensors, and pilots are trained not to cross illuminated red RWSL signals, regardless of ATC clearance.

Taxiway Light Colors and Their Meanings

Summary:

• Green: Safe taxi route
• Blue: Taxiway boundary
• Yellow: Caution/hold
• Red: Stop/danger
• Green/Yellow: Transition (taxiway-runway interface)

This standardized color coding ensures universal comprehension by pilots and ground personnel worldwide, minimizing misinterpretation regardless of location or language.

Placement and Spacing Standards

Taxiway light placement and spacing are defined by ICAO Annex 14 and FAA Advisory Circulars:

• Edge Lights: 60m (200ft) apart on straights, 30m (100ft) on curves/intersections
• Centerline Lights: 15m (50ft) apart on straights, 7.5m (25ft) on curves/intersections
• Clearance Bars: Three yellow lights perpendicular to the centerline at holding/intermediate points
• Runway Guard Lights: Elevated pairs or in-pavement arrays at runway holding positions
• Stop Bars: Across the full taxiway width before runway holding markings
• Lead-On/Lead-Off: Alternating green/yellow, 7.5m (25ft) spacing in transition zones

Fixtures in jet-blast or high-traffic areas are usually in-pavement; frangible mounts are used for safety.

Operational Use and Procedures

• Navigation and Routing: Pilots follow green centerline and blue edge lights for safe taxiing, especially in poor visibility.
• Runway Incursion Prevention: Red stop bars, yellow guard lights, and automated RWSL provide immediate stop or caution signals, supplementing ATC clearances.
• ATC and Automation: Air Traffic Control manages taxiway lighting via control panels and automated systems, adjusting intensity, activation, and sequencing based on conditions and traffic.
• Signal Interpretation: Colors and patterns convey clear instructions: green (go), blue (boundary), yellow (hold/caution), red (stop).
• Training: All pilots and ground vehicle operators are trained to interpret and comply with taxiway lighting, always yielding to illuminated stop or caution signals regardless of verbal ATC clearance.

Regulatory Standards

Taxiway lighting must comply with:

• ICAO Annex 14, Volume 1: International standards for airport design and operations
• FAA AC 150/5340-30J: U.S. standards for airport lighting
• Local Civil Aviation Authority Requirements: May add further specifications

Maintenance and Reliability

Regular inspection and maintenance are required to:

• Ensure correct color/intensity
• Replace damaged fixtures
• Clean lenses for maximum visibility
• Test automated and manual control systems

Modern airports employ LED technology for energy efficiency and reliability.

Innovations and Future Trends

• LED Taxiway Lights: Longer life, lower maintenance, variable intensity
• Integrated Surface Movement Guidance and Control Systems (A-SMGCS): Automated, sensor-driven lighting and traffic control
• Data-driven Maintenance: Predictive analytics to prevent failures and optimize replacement cycles
• Remote/Smart Control: Advanced interfaces for ATC and airport operators

Summary

Taxiway lights are a vital safety system for airport ground operations, enabling precise and safe movement of aircraft and vehicles under all visibility conditions. Their color, placement, and operation are strictly regulated to prevent navigation errors, runway incursions, and ground accidents. As airports grow in complexity and traffic volume, the role of advanced taxiway lighting systems continues to expand, integrating automation and smart technology for enhanced safety and efficiency.