High-Speed Taxiway (Rapid Exit Taxiway): Glossary and Technical Overview

Definition and Function

A high-speed taxiway—also known as a rapid exit taxiway (RET)—is a specialized taxiway designed to enable aircraft to vacate the runway at higher speeds than traditional 90-degree exits. By intersecting the runway at acute angles (typically 25–45 degrees), and providing larger turn radii, high-speed taxiways allow aircraft (including widebodies like the Boeing 777, Airbus A350, or A380) to exit at up to 50–60 knots, depending on aircraft type and pavement conditions.

This design reduces the time aircraft occupy the runway after landing (“runway occupancy time”), thereby increasing runway throughput and operational efficiency. RETs are strategically placed according to the deceleration profiles of the airport’s aircraft mix, using tools such as the FAA’s REDIM and following standards from the FAA (AC 150/5300-13B) and ICAO (Annex 14 Volume I). High-speed taxiways are essential at busy airports, those with parallel or intersecting runways, and those handling large or high-speed jets.

Geometric and Structural Design Elements

High-speed taxiways differ from standard exits in several key ways:

Exit Angle

• Acute angles, usually 25–45 degrees (standard is 30 degrees in the US).
• Allows for smoother, higher-speed transitions from runway to taxiway.
• Angle selection depends on aircraft fleet mix, landing speeds, and available runway length.

Turn Radius

• Minimum turn radius of 1,500 ft (457 m); larger for Code E/F aircraft (Boeing 747, A380).
• Ensures directional control and tire grip at higher taxi speeds.

Taxiway Width & Pavement Strength

• Width determined by Taxiway Design Group (TDG); up to 100 ft (30 m) or more for widebodies.
• Pavement strength designed for maximum anticipated wheel loads at high speeds.

Fillet and Intersection Design

• Fillet radii accommodate the swept path of the largest aircraft using the RET.
• Reverse turn designs (curving back toward terminal) require larger inside fillet radii.

Markings and Lighting

• Enhanced centerline markings, arrows, and signage (conforming to ICAO/FAA standards).
• Green centerline lights (mandatory for CAT II/III), blue edge lights, and illuminated signage for visibility in low-light conditions.

Placement and Integration in Airfield Layouts

Strategic Location

• RETs are placed to enable aircraft to exit after touchdown without excessive braking.
• Placement is optimized using simulation tools (e.g., FAA REDIM) based on deceleration profiles, touchdown points, and fleet mix.

Configuration Types

• Standard RETs direct aircraft parallel to landing rollout.
• Reverse turn RETs (curving back toward terminal) are used when space is limited, but require more deceleration and are less efficient.

Separation and Sequencing

• Minimum separation between exits is mandated to prevent confusion and facilitate signage/lighting.
• Not co-located with crossing taxiways to avoid wide, ambiguous pavement areas.

Integration with Navigation Aids

• Dedicated guidance signs, centerline lighting, and surface markings integrated per ICAO/FAA requirements.

Markings, Lighting, and Guidance

Markings

• Taxiway Centerline: Continuous yellow, possibly enhanced or dashed at exits.
• Runway Exit Markings: Arrows or chevrons highlight direction and suitability.
• Hold Position Markings: Yellow lines for mandatory runway holding.

Lighting

• Centerline Lighting: Green, embedded for visibility in low light or poor weather.
• Edge Lighting: Blue, marking taxiway boundaries.
• Runway Guard Lights: Flashing yellow at intersections.
• Supplemental Guidance: Directional arrows or illuminated signs as needed.

Surface Guidance Systems

• Advanced Surface Movement Guidance and Control Systems (A-SMGCS) integrate lighting, signs, and surveillance for real-time routing at complex airports.

Signage

• Runway Exit Signs: Yellow-on-black with taxiway ID.
• Direction Signs: Indicate path to terminals, aprons, or other taxiways.
• Mandatory Instruction Signs: Red-on-white for critical stop points.

Operational Benefits

Reduced Runway Occupancy Time

• Aircraft can exit at up to 50–60 knots, reducing time on runway by 20–40%.
• Example: Mumbai’s airport increased capacity from 32 to 44 movements per hour after adding new RETs.

Enhanced Safety

• Less time spent on active runways reduces risk of incursions/collisions.
• Improved emergency response access.

Increased Airport Capacity

• More aircraft movements per hour, especially important at slot-constrained airports.

Environmental and Economic Benefits

• Less taxi/idle time reduces fuel burn, emissions, and noise.
• Direct cost savings for airlines.

Air Traffic Flow Optimization

• Enables flexible sequencing and scheduling, even during peak or low-visibility operations.

Planning, Safety, and Regulatory Considerations

Planning

• Fleet Mix Analysis: Design must suit the largest/fastest aircraft (AAC/ADG/TDG).
• Separation: ICAO/FAA standards dictate minimum distances between runway/taxiway centerlines.
• Location Optimization: FAA REDIM and similar tools used for placement.
• Avoid Co-location: Prevents confusion and navigation errors.

Safety

• Exit Only: RETs are not for runway entry due to visibility and approach angle limitations.
• Surface Navigation Aids: Maintenance is vital, especially for low-visibility ops.
• Conflict Avoidance: Geometry prevents direct access to other runways/aprons.
• Reverse Turn Cautions: Less efficient, require more deceleration.

Regulatory Standards

• FAA AC 150/5300-13B: US design standards.
• ICAO Annex 14: Global standards for taxiway angles, geometry, lighting, and markings.

Detailed Design Parameters

Engineering Calculations

• Turn radius based on largest aircraft at desired exit speed (gear geometry, friction, deceleration).
• Pavement strength/thickness determined by aircraft weights, Pavement Classification Number (PCN), subgrade.
• Fillet design accommodates full swept path of widebodies.

Design Tools

• FAA REDIM: Optimizes location/geometry for minimal occupancy time.
• Acute Angle Exit Tool: Calculates design for standard/reverse RETs.

Drainage & Environmental

• Drainage prevents hydroplaning/pavement damage.
• Environmental review ensures compliance with noise/emissions/habitat regulations.

Real-World Examples

Mumbai Chhatrapati Shivaji Maharaj International Airport

• Handles intersecting runways and Code F aircraft.
• Added new RETs, increasing movement capacity from 32 to 44/hour.
• Geometry/placement determined by modeling aircraft performance and landing data.

London Heathrow, Frankfurt Main, Atlanta Hartsfield-Jackson

• Multiple RETs per runway to accommodate diverse fleet and maximize hourly throughput.
• Essential for simultaneous arrivals/departures at major hubs.

Parallel & Intersecting Runway Operations

• Airports like LAX and Singapore Changi rely on RETs for rapid clearance, supporting independent parallel ops.
• Intersecting runways benefit from RETs by expediting egress and reducing conflicts.

Impact on Airport Operations

High-speed taxiways have transformed airport operations globally:

• Increased Throughput: Directly supports higher aircraft movement rates, vital at busy and slot-constrained airports.
• Improved Safety: Less runway occupancy time reduces incursion and collision risks.
• Environmental Gains: Reduced taxi/idle times lower emissions and noise.
• Operational Flexibility: Facilitates efficient sequencing, especially in adverse conditions.

By integrating high-speed taxiways—designed and placed per best practices and regulatory standards—airports can achieve significant gains in safety, efficiency, and capacity, supporting the needs of modern aviation.