Taxiway Location Sign
A black sign with yellow text that indicates the aircraft's current position on the taxiway. Provides essential orientation information for pilots, helping them confirm their location and navigate the airfield surface movement network.
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What Is It?
A Taxiway Location Sign is a black sign with yellow text that displays the designation of the taxiway on which the aircraft is currently positioned. These signs are typically installed at taxiway intersections or at points where pilots need to confirm their location. They help pilots maintain situational awareness, especially in complex taxiway networks or during low‑visibility conditions. The sign displays the taxiway identifier (e.g., "A", "B", "C") and may be supplemented by a direction arrow if used in conjunction with other signs. They are a key component of the airfield surface movement guidance system.
Purpose & Function
Where a direction sign tells the pilot where to go, the taxiway location sign answers a different question: where am I right now. That distinction matters most in a sprawling or visually repetitive taxiway network, or when low visibility strips away the external landmarks a pilot would normally use to stay oriented. By confirming the current taxiway identifier at intersections and other decision points, the sign lets the pilot verify their position against the taxi clearance they were given and catch a wrong turn early, before it develops into a taxiway or runway incursion further along the route.
Where Is It Used?
Installed at taxiway intersections, holding points, and other strategic locations where pilots need to confirm their position. They are placed on the side of the taxiway, typically at a height of 1.5 to 2 metres above the pavement, on a frangible support. Taxiway location signs are used at all airfields with multiple taxiways and are especially critical at large international airports with complex layouts.
Installation & Location
Posts are founded at each intersection or strategic confirmation point along the taxiway, set back clear of wingtip clearance for the design aircraft while remaining close enough to the pavement edge to be read from the cockpit at taxiing speed. Because location signs answer a position-confirmation question rather than direct a manoeuvre, they are typically sited immediately after (rather than before) the junction the pilot has just passed, with orientation set out to read squarely to outbound taxi traffic. Illuminated panels are cabled from the nearest taxiway lighting distribution point; retroreflective panels need only the post foundation and mechanical fixing.
How Does It Work?
The sign displays the taxiway designation (e.g., "A", "B", "C") in yellow text on a black background, following ICAO Annex 14 and FAA standards. The sign may be non‑illuminated (using high‑performance retroreflective sheeting) or internally illuminated (LED) for enhanced visibility at night. The sign is positioned so that it is easily readable from the cockpit. It is mounted on a frangible support to break away on impact, minimising aircraft damage. Location signs are often co‑located with direction or destination signs to provide comprehensive navigation information.
System Architecture & Control Logic
Physical Construction
The panel is an extruded aluminium frame around a Class 1/2 retroreflective face with the taxiway designation cut in yellow on black, or a translucent acrylic panel with the same legend as a perforated film backlit by an internal LED module. Unlike the runway exit sign it's often confused with, a location sign is a standalone confirmation marker rather than a signal tied to a specific turn-off point, so its face carries only the designation with no accompanying arrow or exit-timing cue. The frame is gasket-sealed and bolted to a frangible coupling on a below-grade base plate so it shears away cleanly if struck.
Technical Parameters
| Parameter | Typical Value |
|---|---|
| Colour | Black background, yellow text and border (ICAO / FAA) |
| Dimensions | 1.2 m × 0.6 m (typical) or as per site requirements |
| Text Height | 150–200 mm (depending on viewing distance) |
| 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 |
|---|---|
| Legend Luminance (Yellow) | ≥ 30 cd/m² average (illuminated variant), uniformity ratio ≤ 10:1 (max:min) |
| Background Contrast (Black) | Opaque black background against the illuminated yellow legend; contrast ratio ≥ 5:1 |
| Retroreflective Coefficient (Non-Illuminated Variant) | RA ≥ 20 cd/lux/m² (yellow legend/border) per ASTM D4956 Class 1/2 |
| Chromaticity (Yellow Legend/Border) | Within ICAO Annex 14 aeronautical yellow boundary (CIE coordinates) |
| Viewing Angle | ± 5° horizontal, legible from typical cockpit eye height |
| 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
Taxiway location 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 identifier (and any direction arrow) on the panel matches the taxiway layout diagram for that intersection.
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 identifier (and any direction arrow) on the panel matches the taxiway layout diagram for that intersection.
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 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 Unreadable at Night, Panel Intact 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
Legend Mismatch After Taxiway Renaming
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.
Legend Accuracy Verification
OperationalAfter any taxiway renaming, cross-check the sign's location legend against the current taxiway designation before signing off the work as complete.
Engineering & Expert Notes
Check Adjoining Signs in the Same Pass After a Taxiway Renaming
ComplianceA single mislabelled location sign after a renaming breaks a pilot's ability to confirm position along the whole route — verify the adjoining signs at the same time, not just the one that was flagged.
A Failed Character Can Misidentify the Taxiway Entirely
TroubleshootingA partially failed character on a yellow-on-black location sign can misidentify the taxiway at night (a partial “A” reading as a different letter, for instance). Verify full-character illumination during night checks, not just overall brightness.
Tie the Legend Audit to the Airfield Diagram Revision Cycle
MaintenanceSchedule a location-sign legend cross-check whenever the published airfield diagram is revised, rather than waiting for a pilot report of a mismatch to trigger it.
Check Coupling Condition and Position Together
InspectionA frangible coupling fatigued from cyclic loading often correlates with a sign that has also drifted slightly out of position — verify both in the same visit rather than treating them as separate checks.
Track Face Condition as Its Own Line Item, Separate From Illumination
MaintenanceA location sign can be electrically fine but visually degraded by fade or grime. Include a face-condition check as a distinct item in inspections rather than folding it into a simple “is it lit” pass/fail.
Don't Give Non-Illuminated Units a Longer Inspection Interval by Default
InspectionSheeting degradation on a non-illuminated location sign is a silent failure mode with no bulb to flag it — keep it on the same inspection interval as illuminated units rather than assuming “no bulb, no urgency.”
Frequently Asked Questions
Short answers about the taxiway location sign: purpose, siting, power, standards, maintenance and common faults.
Q1What is a taxiway location sign?
A taxiway location sign is a black sign with yellow text that displays the designation of the taxiway on which the aircraft is currently positioned (for example A, B or C). It helps pilots maintain situational awareness, especially in complex taxiway networks and low-visibility conditions.
Q2What colour is a taxiway location sign?
A black background with yellow text and a yellow border, following ICAO Annex 14 and FAA standards. This is the reverse of a direction sign, which is black on yellow.
Q3Where are taxiway location signs installed?
At taxiway intersections, holding points and other strategic locations where pilots need to confirm their position, at the side of the taxiway, typically 1.5 to 2 metres above the pavement on a frangible support. They are often co-located with direction or destination signs and are especially critical at large international airports with complex layouts.
Q4How does a taxiway location sign differ from a direction sign?
A location sign tells the pilot which taxiway they are on (yellow on black), whereas a direction sign shows which taxiway or taxiways lead away from an intersection (black on yellow with arrows). They are frequently installed together so the pilot gets both pieces of information at once.
Q5What size is a taxiway location sign?
The typical panel is 1.2 m × 0.6 m or as per site requirements, with legend height of 150 to 200 mm depending on viewing distance.
Q6How is an illuminated taxiway location sign powered?
An illuminated taxiway location 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 taxiway location 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 taxiway location sign?
Because the legend is the lit element, the yellow legend on the illuminated variant should average at least 30 cd/m² (uniformity no worse than 10:1) against an opaque black background with a contrast ratio of at least 5:1. The non-illuminated variant needs a retroreflective coefficient of at least 20 cd/lux/m² for the yellow legend and border per ASTM D4956 Class 1 or 2.
Q9How often should taxiway location 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 taxiway location 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. After a taxiway is renamed, a legend mismatch is also a listed failure mode.
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