What is a Taxiway?

Taxiway

A taxiway is a specially constructed, paved pathway at an airport, designed exclusively for the ground movement of aircraft between runways, aprons, terminals, hangars, and other operational areas. Unlike runways, taxiways are not used for takeoff or landing. Instead, they facilitate the safe and efficient routing of aircraft as they transition between various ground locations.

Taxiways are engineered to support the considerable weight and wheel loads of aircraft, often featuring reinforced pavement and precise geometric layouts to accommodate large commercial jets and smaller general aviation aircraft alike. Their design is governed by international and national standards, notably ICAO Annex 14 and FAA Advisory Circulars, ensuring uniformity in dimensions, markings, lighting, and navigational aids.

Taxiways form the backbone of an airport’s ground movement network, directly influencing capacity, efficiency, and safety. Standard naming conventions involve alphabetical identifiers (e.g., Taxiway A, B, C), often supplemented by numbers (e.g., A1, B2), to facilitate precise ATC instructions and pilot navigation.

Taxiway Markings

Taxiway markings are standardized globally to provide clear visual cues for pilots and ground vehicle operators. Key markings include:

• Centerline Markings: Continuous yellow lines guiding aircraft along the taxiway.
• Enhanced Centerline Markings: Alternating dashed and solid lines before runway holding positions, warning of an approaching runway.
• Edge Markings: Double yellow lines (continuous for edges, dashed for transition zones).
• Runway Holding Position Markings: Two solid and two dashed yellow lines at points where aircraft must hold before entering a runway.
• Intermediate Holding Position Markings: Single dashed lines at intersections or holding bays.
• ILS Critical Area Markings: Ladder or railroad track patterns around sensitive instrument landing system areas.
• Non-Movement Area Boundary Markings: Solid and dashed yellow lines, separating ATC-controlled areas from ramps/aprons.
• Direction, Location, and Destination Markings: Yellow and black color schemes help identify the current taxiway, directions, and destinations.
• Geographic Position Markings: Pink circles with black letters/numbers for low-visibility position reporting.

Taxiway Signs

Taxiway signage is standardized for clarity and visibility, especially in complex or busy airfields:

• Location Signs: Black background, yellow inscription and border. Indicate the current taxiway.
• Direction Signs: Yellow background, black inscription and arrows. Point to intersecting or connecting taxiways.
• Mandatory Instruction Signs: Red background, white inscription. Indicate holding positions and areas requiring ATC clearance.
• Destination Signs: Yellow background, black inscription and arrows. Point to runways, terminals, aprons, or other key locations.
• Information Signs: Black on yellow/yellow on black, for additional instructions.

Signs are illuminated for night/low visibility, positioned per ICAO and FAA standards.

Taxiway Lighting

Taxiway lighting systems provide guidance during night and low-visibility operations:

• Edge Lights: Blue, outlining the taxiway.
• Centerline Lights: Green, embedded in the pavement on major taxiways.
• Clearance Bar Lights: Yellow, at holding positions/intersections.
• Stop Bar Lights: Red, across taxiway at runway holding positions, controlled by ATC.
• Lead-On/Lead-Off Lights: Alternating green and yellow at runway-taxiway intersections.

Lighting forms part of the wider Aeronautical Ground Lighting (AGL) infrastructure, essential for safety in adverse conditions.

Types of Taxiways

Taxiways are categorized by function and location:

• Parallel Taxiways: Run alongside runways, allowing efficient queuing and rapid runway exit.
• Exit (Rapid-Exit/High-Speed) Taxiways: Angled for quick runway exit after landing.
• Connector Taxiways: Link various airport areas.
• Apron Taxiways: Connect taxiway network to parking and service areas.
• Bypass Taxiways: Allow aircraft to circumvent congestion or blocked areas.
• Helicopter Taxiways (Helitaxi Routes): Marked and sized for helicopter movements, distinguished from fixed-wing taxiways.

Aircraft Taxiing Procedures

Taxiing is the controlled ground movement of an aircraft under its own power, excluding takeoff and landing rolls. Procedures are coordinated by ATC for safety and efficiency:

• Arrival: After landing, aircraft vacate the runway via assigned taxiways and follow ATC instructions to the gate.
• Departure: Aircraft push back, start engines, and taxi to the departure runway via a prescribed route.
• Low Visibility Operations (LVOs): Use of enhanced markings, signage, lighting, and SMGCS protocols.
• Runup Areas and Holding Bays: Designated for engine checks and system tests before departure.
• Helicopter Operations: Utilize specialized helitaxi routes, coordinated with ATC.
• Emergency Procedures: Taxiways serve as access for emergency response, with traffic cleared as needed.

Taxiway Design Considerations

Design balances efficiency, safety, and regulatory compliance:

• Aircraft Size/Type: Determines width, strength, turning radii, and clearances. The ICAO Aerodrome Reference Code (ARC) classifies requirements.

• Runway Configuration: Affects taxiway network complexity.
• Traffic Volume: High-traffic airports need multiple taxiways and holding bays.
• Terminal/Apron Proximity: Influences alignment and connectors.
• Pavement Strength: Engineered for heavy, frequent loads.
• Safety Margins: Defined clearances prevent collisions.
• Signage/Markings: Optimized for all conditions.
• Environment: Routing, drainage, and wildlife management minimize impacts.

Safety and Runway Incursion Prevention

Multiple safeguards prevent incidents:

• ATC Control: Pilots must obtain and comply with taxi clearances.
• Runway Incursion Prevention: Enhanced markings, hold short lines, stop bars, and runway status lights.
• Separation/Spacing: Strictly maintained.
• Situational Awareness: Pilots use diagrams, maps, and visual cues.
• Communication: Clear, continuous with ATC.
• Non-Movement Area Vigilance: Extra caution in areas outside ATC control.
• Low Visibility/Emergency Protocols: SMGCS procedures and reporting.

Taxiway Maintenance and Pavement Management

Essential for safety and compliance:

• Pavement Maintenance: Inspections for cracks, rutting, FOD removal.
• Lighting Upkeep: Daily checks, prompt repairs, snow/ice removal.
• Marking Renewal: Regular repainting for visibility.
• Pavement Rehabilitation: Resurfacing/rebuilding as needed.
• Environmental Management: Efficient layouts, drainage, and emission reduction.

Environmental Impact of Taxiways

Taxiways influence airport environmental performance:

• Taxi Time/Fuel Burn: Modern layouts and sequencing systems reduce fuel use and emissions.
• Noise Pollution: Routing and shielding mitigate noise for communities.
• Stormwater Management: Drainage and water quality systems prevent pollution.
• Wildlife Hazard Reduction: Fencing, habitat management, and deterrents lower strike risks.

Summary

Taxiways are essential infrastructure at every airport, enabling safe, efficient ground movement of aircraft. Their design, markings, signage, lighting, and maintenance are governed by stringent regulations to ensure optimal performance in all conditions. Proper taxiway planning and management directly impact airport capacity, safety, environmental performance, and the overall passenger experience.

For airports seeking to enhance ground operations, investing in advanced taxiway systems, regular maintenance, and environmental management yields significant operational and sustainability benefits.