Junction (Point Where Taxiways Meet) – Airport Operations Glossary

Definition: What is a Taxiway Junction?

A taxiway junction—also known as a taxiway intersection or node—is a designated point on an airport’s movement area where two or more taxiways converge, or where a taxiway connects with runways, aprons, or ramps. These points are fundamental to the airfield’s ground movement network, enabling aircraft to transition safely and efficiently between gates, hangars, runways, and ramps. At its core, a taxiway junction is a decision point for pilots and ground controllers, channeling the flow of aircraft on the ground.

The physical characteristics of a taxiway junction depend on the types and numbers of surfaces involved, their intersection angles, and the airport’s operational requirements. Junctions can be as simple as a T-intersection or as complex as multi-path intersections with several taxiways and runways. Each is designed in strict accordance with international standards such as ICAO Annex 14 and FAA Advisory Circulars (e.g., AC 150/5300-13B), which dictate requirements for geometry, markings, signage, and lighting to ensure both safety and efficiency.

Taxiway junctions are vital navigational landmarks for pilots and air traffic controllers (ATC), clearly identified on airport diagrams and referenced in ATC communications. Their design, marking, and maintenance are critical to preventing incidents like runway incursions or ground collisions, especially in low visibility or high-traffic situations.

Operational Context and Significance

Taxiway junctions form the backbone of an airport’s surface movement area. Their configuration, marking, and management affect ground movement efficiency, pilot awareness, runway safety, and ATC workload. Well-designed junctions minimize stops and turns, reduce bottlenecks, and enable smooth transitions between airfield areas.

Operationally, a taxiway junction is a decision point. Pilots must interpret signage, surface markings, and ATC instructions to select the correct route. Confusion or poor marking can lead to runway incursions (unauthorized presence on a runway), ground collisions, or near-misses. The complexity of a junction and the clarity of its markings directly impact its risk profile.

From an ATC perspective, junctions increase the complexity of ground control. Each extra node adds possible routes and requires clear, unambiguous instructions—especially during peak periods or poor weather. ICAO Doc 9870 (Manual on the Prevention of Runway Incursions) and FAA guidance both stress regular review and, where needed, redesign of complex junctions. Many busy airports use advanced surface movement guidance systems (A-SMGCS) and designate certain junctions as “hot spots” requiring extra caution.

The operational context is also shaped by airport size, aircraft types, and local conditions. Major hubs may require complex multi-node intersections due to space constraints, demanding enhanced visual cues and procedures. Even at small airports, clear marking and design are essential for pilots of all experience levels.

Types of Taxiway Junctions

Standard Three-Node Junction

The standard three-node junction is the preferred design, where no more than three taxiways (or a combination of taxiways and runways) meet at a single point. This T- or Y-shaped configuration simplifies decision-making and reduces complexity for both pilots and controllers. It’s endorsed by both FAA (AC 150/5300-13B) and ICAO Annex 14 as the baseline for new airport layouts.

Three-node junctions offer safety and operational advantages:

• Reduced confusion: Fewer possible routes minimize pilot errors.
• Standardized signage: Predictable locations for signs and markings.
• Easier control: Controllers can issue simpler, clearer instructions.

Physically, these junctions are designed for the largest aircraft expected, with widened corners (fillets) to accommodate turning radii. ICAO Doc 9157, Part 2, details fillet and pavement transition design.

Complex Intersections

A complex junction involves four or more converging taxiways, or has ambiguous/nonstandard geometry (e.g., skewed angles, multiple branches). These often arise from legacy layouts or expansions and are more challenging for pilots to navigate, increasing the risk of misrouting and operational errors.

Complex junctions can feature X-shaped, star-shaped, or irregular layouts, requiring more signage, markings, and lighting. Even so, complexity increases risk—especially in low visibility or high workload situations. Both FAA and ICAO recommend designating such intersections as “hot spots” and, where possible, redesigning them as three-node junctions.

Aligned (In-line) Taxiways

An aligned taxiway (in-line or straight-through) is where a taxiway centerline runs directly into a runway or another taxiway with no turn. This design is prohibited for taxiway-to-runway junctions by both FAA and ICAO due to the high risk of inadvertent runway entry (“runway incursion”). A forced turn of at least 30 degrees before the runway threshold is required, along with clear hold-short markings and signage.

Acute and 90-Degree Intersections

90-degree intersections are standard for taxiway and runway junctions, maximizing pilot visibility and simplifying movement and signage. Acute-angled intersections (less than 90 degrees) are discouraged except for specific cases like high-speed runway exits, where aircraft can vacate the runway quickly. Acute angles can reduce visibility and complicate maneuvering or marking, so they are reserved for clearly defined operational benefits.

Markings, Signs, and Lighting at Junctions

Taxiway Centerlines and Hold Short Markings

• Taxiway centerlines: Continuous yellow lines guiding aircraft safely through junctions, curving or branching as needed.
• Hold short markings: Two solid and two dashed yellow lines perpendicular to the centerline at runway/taxiway intersections. The solid lines face the taxiway; the dashed, the runway. Enhanced dashed markings alert pilots as they near a hold-short position.

Regular maintenance ensures markings stay visible under all conditions. In low visibility, retroreflective paint or in-pavement lighting may be used.

Direction, Location, and Mandatory Instruction Signs

• Mandatory instruction signs: Red background, white text (e.g., “RWY 27”), marking prohibited entry points without ATC clearance.
• Location signs: Black background, yellow text (e.g., “A” for Taxiway Alpha), indicating current position.
• Direction signs: Yellow background, black text/arrows, showing routes to taxiways from the junction.
• Runway boundary signs: Yellow background, black text, marking the edge of the runway environment.

Standards for these signs are set by ICAO Annex 14 and FAA AC 150/5340-18G. Proper placement, illumination, and maintenance are required for safety, especially at complex junctions.

Lighting Systems

• Runway guard lights (“wig-wags”): Flashing yellow lights at runway holding positions.
• Clearance bar lights: Steady yellow in-pavement lights at taxiway holding points.
• Stop bar lights: Red in-pavement lights at runway/taxiway intersections, controlled by ATC.
• Taxiway edge lights: Blue lights marking taxiway edges.
• Taxiway centerline lights: Green in-pavement lights guiding along the taxiway centerline.

Lighting requirements (intensity, color, spacing) are set by ICAO and FAA to ensure global standardization and safe operations in all conditions.

Design Considerations and FAA Standards

FAA Three-Node Concept

The three-node concept limits intersections to three converging routes, minimizing complexity and risk. It’s central to FAA AC 150/5300-13B and ICAO guidance and is now a best practice for airport ground layout design. Existing multi-node junctions should be redesigned where feasible; if not, extra signage and procedures are required.

Geometry: Angles and Visibility

90-degree intersections are preferred for visibility and ease of movement. Acute angles are allowed mainly for high-speed exits, with additional design precautions for sight lines and marking. Large paved areas should be avoided or clearly marked to prevent confusion.

Taxiway Fillets and Pavement Width

Taxiway fillets are widened pavement at junction corners, designed to accommodate the largest aircraft turning at the junction. Dimensions must match the airport’s Taxiway Design Group (TDG) or Aerodrome Reference Code, ensuring all aircraft can maneuver safely without leaving the centerline or damaging surfaces.

Safety Management and Hot Spots

Airports must identify, monitor, and mitigate risks at taxiway junctions, especially at complex intersections or those with a history of incidents. Designating “hot spots” on airport diagrams, conducting regular safety reviews, and updating signage or geometry as needed are all part of a proactive surface movement safety program.

Best Practices for Airport Operators

• Standardize to three-node junctions where possible.
• Maintain clear, visible markings and signage.
• Use enhanced lighting at complex or high-risk junctions.
• Regularly review junction layout and incident history.
• Provide training for pilots and controllers on local junction layouts and hot spots.

Summary

Taxiway junctions are among the most critical features of airport ground infrastructure. Whether simple or complex, their safe design and operation are fundamental to preventing runway incursions, ensuring efficient ground movement, and supporting safe airport operations for all users.

For more on airport layout and safety, or to discuss optimizing your airfield’s taxiway network, contact us .

References:

• ICAO Annex 14, Volume I: Aerodrome Design and Operations
• FAA AC 150/5300-13B: Airport Design
• ICAO Doc 9870: Manual on the Prevention of Runway Incursions
• FAA AC 150/5340-1M & 150/5340-18G: Marking and Signing Standards

For further details or a consultation on optimizing your airport’s ground movement safety, get in touch with our experts.