Runway Exit Sign
A yellow sign with black text that indicates the designation of a runway exit (taxiway) and provides directional information to pilots during the landing roll‑out. Helps pilots identify and navigate to the correct turn‑off point from the runway.
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What Is It?
A Runway Exit Sign is a yellow sign with black text that identifies a taxiway exit from the runway. It is typically located adjacent to the runway, near the exit point, and displays the designation of the taxiway (e.g., "A", "B", "C") and may include an arrow indicating the direction of the exit. These signs are essential for pilots during the landing roll‑out, helping them identify the correct turn‑off point to clear the runway efficiently and safely. They are part of the airfield surface movement guidance system and are critical for runway safety and capacity.
Purpose & Function
The runway exit sign's job is timing as much as identification: it needs to tell the pilot, at highway roll-out speeds and with attention divided between braking and directional control, exactly which upcoming turn-off leads where, in time to commit to that exit rather than overshoot it. Because runway occupancy time is a direct driver of arrival capacity at busy airports, especially where a rapid exit taxiway is designed for a specific higher-speed turn-off, a pilot who misses the intended exit and has to use the next one down the runway adds delay that compounds across the arrival sequence. The sign exists to make that decision reliable rather than a matter of memorising the airfield layout in advance.
Where Is It Used?
Installed at each runway exit point, typically on the side of the runway, before the actual exit turn‑off. The sign is placed at a height of 1.5 to 2 metres above the pavement, on a frangible support. Runway exit signs are used on all runways that have taxiway exits, including both rapid‑exit and standard‑angle exits. They are especially important at busy airports to ensure pilots can quickly identify and take the correct exit, reducing runway occupancy time.
Installation & Location
Posts are founded on the runway shoulder before the physical exit turn-off, set back clear of the runway strip's load-bearing width and outside the runway end safety area where the exit falls within it, with the exact distance before the turn-off set out from the exit's own geometric design survey so the sign gives the pilot enough advance notice to plan the turn without crowding the following distance-remaining sign. Because timing the sign relative to the exit centreline is the main setting-out consideration (rather than a fixed offset), position is re-checked against the exit's as-built curve if the exit geometry is ever revised. Being a simple retroreflective panel in most installations, the main installation consideration is the frangible coupling given the runway-adjacent location; illuminated variants are cabled from the nearest runway or taxiway lighting distribution point.
How Does It Work?
The sign displays the taxiway designation (e.g., "A", "B") on a yellow background with black text, following ICAO Annex 14 and FAA standards. It may also include a directional arrow to indicate the turn direction. The sign is typically non‑illuminated (using high‑performance retroreflective sheeting) but can be internally illuminated for enhanced visibility at night. The sign is positioned so that it is visible to pilots as they approach the exit point during the landing roll. It is mounted on a frangible support to break away on impact, minimising aircraft damage.
System Architecture & Control Logic
Runway exit signs typically default to the passive control model: most installations rely on high-performance retroreflective sheeting, which has no electrical control path at all — the taxiway designator becomes visible only because the sheeting reflects the landing aircraft's own lights back toward the flight deck, so there is no ALCMS command, no CCR current, and nothing for a control system to monitor. Where a sign is instead internally illuminated for enhanced night visibility, it is wired onto the constant current series circuit for that runway exit or taxiway section: an ALCMS selects the required brightness step, the CCR regulates the entire loop to a fixed current, and the sign panel — fed through its own isolating transformer — burns at the same intensity as every other fixture sharing the loop, with a voltage rise at constant current flagging a loop-level fault rather than one isolated to the sign. Because exit sign visibility during roll-out is timing-critical (see the System Logic section below), a retroreflective sign's conspicuity depends entirely on the aircraft's own landing lights still being on and aimed correctly at that point in the rollout, whereas an illuminated sign is visible regardless of the aircraft's own lighting.
Illuminated variant: ALCMS → CCR → Loop → Sign Panel. Retroreflective variant: no electrical path at all.
Why Timing the Sign Matters During Roll-Out
Physical Construction
The panel is an extruded aluminium frame around a Class 1/2 retroreflective face with the taxiway designation cut in black on yellow, or a translucent acrylic panel with the same legend as a perforated film backlit by an internal LED module. Because the sign has to register during a fast roll-out rather than a stationary read, the designation letter is kept large and uncluttered on its own, with no destination text or arrow competing for attention in the moment a pilot is timing the turn-off. The frame is gasket-sealed and bolted to a frangible coupling on a below-grade base plate so it shears cleanly if struck by an aircraft or vehicle straying off the runway edge.
Technical Parameters
| Parameter | Typical Value |
|---|---|
| Colour | Yellow background, black text (ICAO / FAA) |
| Dimensions | Face width ~1.46 m (code 1–2) to ~1.94 m (code 3–4); face height 0.3–0.6 m, per ICAO Annex 14 legend/code table |
| Text Height | 200 / 300 / 400 mm per ICAO Annex 14, set by aerodrome reference code (1–2 / 3 / 4) — not a viewing-distance choice |
| Text Content | Taxiway designation (e.g., "A", "B", "C") |
| Illumination | Non‑illuminated (retroreflective) or internally illuminated (LED) |
| Retroreflective Class | Class 1 or Class 2 (ASTM D4956) |
| Mounting Height | 1.5–2 m above pavement |
| Frangible Support | Breakaway coupling or frangible post |
| Protection Class | IP65 (weatherproof) |
| Operating Temperature | -40°C to +60°C |
Electrical Requirements
| Requirement | Typical Value |
|---|---|
| Circuit Type | Series circuit, constant current (CCR fed) — illuminated variant only |
| Rated Series Current | 6.6A (3 to 5-step: 2.8A / 3.4A / 4.1A / 5.2A / 6.6A) |
| Isolation | Via dedicated isolating transformer, not directly connected to series loop |
| Transformer Secondary | Matched to sign wattage; sized to series circuit rating |
| Cable Type | L-824 single-conductor, direct-burial rated, 5kV or 600V per circuit design |
| Connector | L-823 primary connector, submersible-rated splice |
| Insulation Resistance | ≥ 50 MΩ (megger test, cable-to-ground) |
| Earthing/Grounding | Sign body and base can bonded to airfield earth grid |
| Fault Protection | CCR-level ground fault and open-circuit detection |
| Non-Illuminated Variant | No electrical supply required — passive retroreflective panel only |
Photometric Requirements
| Parameter | Typical Value |
|---|---|
| Background Luminance (Yellow) | ≥ 30 cd/m² average (illuminated variant), uniformity ratio ≤ 10:1 (max:min) |
| Legend Contrast (Black) | Opaque taxiway-designation legend against the illuminated yellow background; contrast ratio ≥ 5:1 |
| Retroreflective Coefficient (Non-Illuminated Variant) | RA ≥ 20 cd/lux/m² (yellow) per ASTM D4956 Class 1/2 |
| Chromaticity (Yellow Background) | Within ICAO Annex 14 aeronautical yellow boundary (CIE coordinates) |
| Viewing Angle | ± 5° horizontal, legible from typical cockpit eye height on the exit taxiway |
| Luminance Tolerance | ± 25% of rated value across the panel face |
| Maintenance Factor | ≥ 50% of new-panel luminance before lamp/LED or sheeting replacement is due |
| Test Method | Luminance meter/photometer at normal and oblique angles, or retroreflectometer for the non-illuminated variant |
Applicable Standards
ICAO Annex 14
Runway exit sign colours, dimensions, and placement
FAA AC 150/5340-18
Standards for Airport Sign Systems — siting, design, and colour convention for this sign type
FAA AC 150/5345-44
Equipment/fixture specification for the sign unit itself (siting, design and colour are governed by AC 150/5340-18 above)
ASTM D4956
Retroreflective sheeting performance standards
IEC 60598
Luminaire requirements for illuminated signs
Installation Requirements
Setting-Out & Siting Survey
CivilSurvey and mark the sign position from the design/siting drawing before excavation, confirming clearance from the taxiway/runway edge safety area and any frangibility height limit.
Foundation / Base Plate Installation
CivilExcavate and set the base plate or footing to design depth, keeping the finished mount level and within the frangible height limit for the sign's location.
Frangible Mount Fitting
MechanicalFit the frangible post or breakaway coupling and torque to the specified value, confirming it shears as designed under lateral load and does not bind.
Cable Route & Connector Termination
ElectricalWhere the sign is internally illuminated, lay the duct/cable route to the panel and terminate the L-823 connector per manufacturer procedure, keeping the splice fully submersible-rated before backfill.
Isolating Transformer Matching
ElectricalWhere the sign is internally illuminated, confirm the isolating transformer wattage and ratio match the panel and the series circuit's rated current step before connection.
Panel Legend & Content Setting
QualityBefore the panel is fixed and the position closed out, confirm the taxiway designation and exit arrow match the runway exit layout, and that the sign is sited to be legible within the pilot's roll-out sightline.
Retroreflective Sheeting Application
MechanicalApply and inspect the retroreflective sheeting for correct grade, alignment, and freedom from bubbles or edge lifting before the panel is mounted.
Pre-Backfill Sign-off
DocumentationRecord base/footing position, frangible coupling torque, cable route, and panel content as-built before backfill, since these are not inspectable once the site is closed.
Testing & Commissioning
Insulation Resistance (Megger) Test
Pre-EnergisationWhere the sign is internally illuminated, megger-test the isolating transformer and internal wiring before the circuit is energised, confirming insulation resistance clears the acceptable minimum ahead of backfill.
Loop Continuity & Resistance Test
Pre-EnergisationFor an illuminated installation, verify series loop continuity through the sign and record loop resistance, ruling out open circuits or high-resistance splices before first energisation.
Primary/Secondary Voltage Verification
EnergisationWith the CCR energised, confirm secondary voltage at the illuminated sign's L-823 connector matches the transformer's rated ratio at the commissioned current step.
CCR Brightness Step Response
EnergisationCycle the CCR through every intensity step and confirm an illuminated panel responds correctly at each, ruling out a marginal transformer or a loose connection.
Retroreflectivity / Luminance Verification
Final AcceptanceMeasure sheeting retroreflectivity with a retroreflectometer against ICAO/FAA commissioning minimums; where the panel is internally illuminated, also verify luminance and colour uniformity with a luminance meter.
Legend & Content Verification
Final AcceptanceConfirm the taxiway designation and exit arrow match the runway exit layout, and that the sign is sited to be legible within the pilot's roll-out sightline.
Frangible Coupling & Mounting Verification
Pre-EnergisationConfirm the frangible coupling, base depth, and panel height meet as-built tolerances before the site is finally backfilled.
Documentation & As-Built Sign-off
Final AcceptanceRecord retroreflectivity/luminance readings, and (where illuminated) insulation, continuity, and voltage readings, alongside as-built position in the commissioning dossier for handover.
Inspection & Maintenance
Retroreflectivity Check
AnnualMeasure sheeting retroreflectivity with a retroreflectometer against ICAO / FAA minimums, and budget for sheeting replacement roughly every 5–7 years.
Illumination System Test
AnnualTest internal LED or fluorescent illumination for uniform, even lighting so the sign remains legible at night, especially ahead of low-visibility seasons.
Frangible Coupling Inspection
AnnualCheck the coupling or post for brittleness or corrosion and replace per manufacturer schedule to preserve breakaway performance on impact.
Seal & Cable Gland Check
AnnualInspect housing seals and cable glands for degradation, since moisture ingress through damaged seals is a leading cause of corrosion and electrical faults.
Sign Face Cleaning
QuarterlyClean dirt, de-icing fluid residue, and rubber deposits off the sign face to keep both reflectivity and legibility within spec.
Insulation Resistance Test
AnnualMegger-test internal wiring and any isolating transformer to confirm insulation resistance stays above minimum, catching moisture ingress early.
Common Field Issues
Retroreflective Sheeting Degradation
UV exposure, weathering, and abrasion can reduce reflectivity, making signs hard to read at night or in low visibility. Regular inspection and replacement (typically every 5–7 years) is recommended.
Internal Illumination Failure
For illuminated signs, LED or fluorescent lighting can fail, reducing nighttime legibility. Regular testing of the illumination system and replacement of failed components is essential.
Frangible Support Fatigue
Breakaway couplings can become brittle over time due to weather and vibration. Regular inspection and replacement as per manufacturer guidelines are required to ensure breakaway performance.
Moisture Ingress
Water ingress through seals can cause corrosion and electrical faults. Routine seal checks and use of desiccants are recommended.
Troubleshooting Guide
Legend or Arrow Unreadable at Night, Fine by Day
Illuminated Sign Dark or Flickering
Moisture or Condensation Inside Housing
Sign Leaning, Loose, or Misaligned
Failure Modes & Root Causes
LED Panel / Internal Light Source Failure
Retroreflective Sheeting Degradation
Frangible Coupling Fatigue / Impact Damage
Power/Circuit Connector Degradation
Reduced High-Speed Roll-Out Legibility
Safety & Operational Notes
Circuit Isolation Before Access
Electrical SafetyDe-energise and lock out the feeder circuit at the CCR or panel, then verify zero energy at the base can before opening the housing or handling cable connectors.
Airside Work Coordination
OperationalAny work on or near the movement area requires ATC/airside coordination and a NOTAM where the sign will be dark, obscured, or out of tolerance, with vehicle and personnel movement kept clear of the taxiway or runway strip per the aerodrome's safety management procedures.
Frangibility Not to Be Defeated
MechanicalNever substitute the frangible coupling with a rigid fitting or over-torque it during installation or repair; the coupling must still shear cleanly on aircraft impact to limit damage under the frangibility requirement.
FOD Control at the Base
OperationalKeep tools, fasteners, and removed gaskets accounted for at all times when the base can or housing is open, and secure or remove any loose material before reinstating the sign, to prevent foreign object debris on the movement area.
Insulation Test Before Re-Energisation
Electrical SafetyAfter any cable, connector, or panel work, megger test the affected circuit before restoring power, since a residual fault at re-energisation can trip the feeder circuit or damage healthy units on the same loop.
PPE & Grounding
Personnel SafetyUse insulated tools and appropriate PPE when working on circuit connections, and confirm the sign housing and base can are bonded/grounded per the electrical design before reconnecting the circuit.
High-Speed Roll-Out Legibility Verification
OperationalBecause this sign must be read by flight crews decelerating at high speed, verify photometric output and sheeting condition against the tighter legibility margin the high-speed roll-out application requires, and prioritise its repair over lower-speed-taxiway signage.
Engineering & Expert Notes
Jump This Sign Ahead of Slower-Speed Taxiway Signage in the Repair Queue
OperationalWhen triaging faults, a dark or faded runway exit sign should outrank apron or standard taxiway signage almost automatically — crews are reading it at landing roll-out speed with the least time to react.
Fold This Sign Into Any Taxiway Renumbering Project
ComplianceIf the taxiway network is renumbered or an exit redesignated, update this sign in the same project rather than as an afterthought — pilots rely on it in real time to identify the correct high-speed turn-off.
Check Full-Character Illumination, Not Just Overall Brightness
TroubleshootingAn exit designation is often alphanumeric; a single failed segment can turn one character into another (a partial “B” reading as “8”, for instance). Verify every character, not just that the sign is generally lit.
Take a Measured Reflectivity Reading Ahead of Low-Visibility Season
InspectionSchedule a measured reading rather than a walk-by “looks fine” check before the season when landing roll-out signage matters most.
Time Coupling Checks to the Runway's Peak Landing Season
MaintenanceInspect frangible coupling condition ahead of the runway's busiest landing period rather than on a generic annual date — exit signs see their highest consequence-of-failure exposure during peak arrival banks.
Match Legibility Standard to the Exit's Actual Design Speed
ComplianceA rapid-exit taxiway's sign may warrant a tighter legibility margin than a standard 90° exit sign — don't apply one blanket standard to every exit sign on the airfield.
Frequently Asked Questions
Short answers about the runway exit sign: purpose, siting, power, standards, maintenance and common faults.
Q1What is a runway exit sign?
A runway exit sign is a yellow sign with black text that identifies a taxiway exit from the runway. It displays the taxiway designation (for example A, B or C) and may include an arrow showing the direction of the exit, helping pilots identify the correct turn-off during the landing roll-out.
Q2Where is a runway exit sign installed?
On the side of the runway, before the actual exit turn-off, at each runway exit point, at a height of 1.5 to 2 metres above the pavement on a frangible support. It is used on all runways with taxiway exits, both rapid-exit and standard-angle. Its distance before the turn-off is set out from the exit's own geometric design survey, and re-checked if the exit geometry is revised.
Q3Why does the runway exit sign matter for runway capacity?
Runway occupancy time is a direct driver of arrival capacity at busy airports, especially where a rapid exit taxiway is designed for a specific higher-speed turn-off. A pilot who misses the intended exit and has to use the next one adds delay that compounds across the arrival sequence, so the sign is there to make the exit decision reliable rather than a matter of memorising the layout.
Q4Is a runway exit sign illuminated?
Most installations use high-performance retroreflective sheeting with no electrical path, so the designator is visible only because the sheeting reflects the landing aircraft's own lights, and its conspicuity depends on those lights still being on and aimed correctly during the roll-out. An internally illuminated (LED) version is visible regardless of the aircraft's own lighting.
Q5What size is a runway exit sign?
Face width is roughly 1.46 m for aerodrome reference code 1 to 2 up to about 1.94 m for code 3 to 4, with a face height of 0.3 to 0.6 m. Legend height is 200, 300 or 400 mm according to the reference code (1-2, 3 or 4), not a viewing-distance choice.
Q6How is an illuminated runway exit sign powered?
An illuminated runway exit sign is wired onto the constant current series circuit for its section of the airfield and fed through its own isolating transformer rather than directly from the loop. The Constant Current Regulator (CCR) holds the loop at a fixed current (up to 6.6 A, with steps of 2.8, 3.4, 4.1, 5.2 and 6.6 A) and the ALCMS selects the brightness step, so the sign burns at the same intensity as the other fixtures on that loop. The non-illuminated variant is a passive retroreflective panel with no electrical supply.
Q7Which standards apply to runway exit signs?
ICAO Annex 14 covers colours, dimensions and placement, and FAA AC 150/5340-18 covers siting, design and colour convention. FAA AC 150/5345-44 is the equipment specification for the sign unit, ASTM D4956 sets retroreflective sheeting performance, and IEC 60598 covers luminaires for illuminated signs.
Q8What are the photometric requirements for a runway exit sign?
On the illuminated variant the yellow background should average at least 30 cd/m² (uniformity no worse than 10:1) with an opaque black legend giving a contrast ratio of at least 5:1. The non-illuminated variant needs a retroreflective coefficient of at least 20 cd/lux/m² for yellow per ASTM D4956 Class 1 or 2, and the yellow must fall within the ICAO Annex 14 aeronautical yellow boundary.
Q9How often should runway exit signs be inspected and maintained?
Typical intervals are quarterly for cleaning dirt, de-icing fluid residue and rubber deposits off the sign face, and annual for retroreflectivity measurement, illumination testing, frangible coupling inspection, seal and cable gland checks, and insulation resistance (megger) testing. Retroreflective sheeting is usually budgeted for replacement every 5 to 7 years.
Q10What are the common field issues with runway exit signs?
Four issues recur: retroreflective sheeting degradation from UV, weathering and abrasion (replacement is typically due every 5 to 7 years); failure of the internal LED illumination, which cuts night visibility; frangible support fatigue, as breakaway couplings turn brittle with weather and vibration; and moisture ingress through damaged seals or cable glands, which causes corrosion and electrical faults. Routine seal checks and desiccants are recommended.
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