Taxiway Lighting
Lead-On / Lead-Off Light for Airfield Ground Lighting
Colour-coded guidance at runway / taxiway transitions
Lead-On and Lead-Off lights are specialized taxiway centreline configurations giving green/yellow, direction-specific guidance for aircraft leaving or entering the runway, selected for runway access, exit routes and low-visibility operations.
Supplied by Precision AGL Solutions
Product Overview
Lead-On / Lead-Off Light
What It Is
Lead-On and Lead-Off lights are specialized taxiway centreline lighting configurations that provide visual guidance when aircraft transition between a runway and the taxiway system.
The colour-coded arrangement distinguishes the runway environment and can identify proximity to the runway holding position or ILS/MLS critical area, depending on the applicable airport design.
Where They Apply
- Leaving the runway and entering a taxiway
- Leaving the taxiway and entering the runway environment
The final configuration should always follow the approved airport lighting layout, applicable aerodrome standard and operational control philosophy.
Lead-On and Lead-Off Functions
Two Functions, Different Directional Guidance
Lead-Off Lights
Guide pilots and vehicle drivers exiting the runway. The colour-coded sequence begins at the runway and progresses toward the taxiway holding / critical-area limit.
FAA guidance specifies alternate green and yellow centreline lights from the runway centreline to one centreline-light position beyond the runway hold or ILS critical-area hold position, ending with a yellow light. Where an odd number of colour-coded fixtures occurs, the first two centreline lights on the runway should be green.
Lead-On Lights
Guide pilots entering the runway. The same green/yellow concept gives visual information about the runway environment and the applicable critical-area boundary.
The FAA arrangement uses green at the runway centreline and progresses through the applicable green/yellow sequence to one light beyond the runway hold or ILS critical-area hold position.
The colour pattern is the same as for lead-off. The fixtures are bidirectional, so one side serves the lead-off function and the other side the lead-on function.
Typical Visual Concept
Runway / Taxiway Transition
RunwayRunway centreline
Green / Yellow sequenceAlternate colour coding
Hold / critical-area limitBidirectional fixture
Taxiway centrelineGreen
The actual sequence, number of fixtures and location must be taken from the approved lighting layout.
Colour-Coded Centreline Lighting
Green / Yellow Colour Coding
Typical Characteristics
- Green light
- Yellow light
- Alternate colour sequence
- Direction-specific visibility
- Inset installation
- Coordination with taxiway centreline lighting
Bidirectional Centreline Fixture
The last coloured fixture of the sequence, one centreline position beyond the runway holding position or ILS/MLS critical-area holding position (the first coloured fixture met from the taxiway side), is a bi-colour, bidirectional fixture:
- Approached from taxiway → Green
- Approached from runway → Yellow
This is a key product-selection parameter and should be identified explicitly on the technical submittal.
Configuration Coordination
What Each Configuration Is Coordinated With
Lead-Off
- Runway centreline
- Taxiway centreline
- Runway holding position
- ILS/MLS critical / sensitive area
- Taxiway route and exit geometry
Lead-On
- Runway holding-position marking
- Stop bar
- Taxiway and runway centreline
- ILS critical / sensitive area
- Surface movement control
Inset Configuration
In-Pavement Centreline Fixtures
Typical Installation
Lead-On / Lead-Off lights are generally implemented using in-pavement centreline fixtures. Fixture and housing should be treated as one coordinated pavement installation.
- Inset centreline fixture and load-bearing housing
- Green/yellow optical assembly and LED module
- Directional optics, gaskets and sealing system
- Drainage, mounting hardware
- Secondary cable, isolating transformer, primary connector
Optical Configuration
Because the system communicates through both colour and direction, the optics are critical.
- Unidirectional / bidirectional output
- Green and yellow beams
- Beam width and horizontal / vertical distribution
- Optical axis, viewing sector, intensity
Runway Interfaces
Coordination With the Runway-Interface Visual System
Potentially associated systems include runway centreline lights, taxiway centreline lights, stop bar lights, runway guard lights, taxiway edge lights, runway holding-position markings and the AGL control and monitoring system. The correct combination depends on runway category, RVR, ILS/MLS installation, airport procedures and applicable standard.
Relationship With Stop Bars
Lead-On / Lead-Off provides directional route and runway-environment information through the centreline. A stop bar provides the controlled red stop indication at the holding position. The systems can be integrated through the airport control system so indications remain consistent.
Relationship With Taxiway Centreline
Ordinary taxiway centreline is green; the Lead-On / Lead-Off transition is green + yellow. FAA AC 150/5340-30J places both under its taxiway centreline lighting requirements.
Low-Visibility Operations
Enhanced Guidance at Runway / Taxiway Interfaces
Design Should Consider
- RVR and low-visibility procedures
- Taxiway centreline lighting and stop bars
- Runway holding positions
- ILS/MLS critical areas
- AGL control
- Surface movement procedures
Why It Matters
Lead-On / Lead-Off lighting becomes particularly important where visibility requires enhanced visual guidance at runway/taxiway interfaces. FAA AC 150/5340-30J provides specific colour-coding provisions and identifies their function in relation to the runway and ILS critical area.
Photometric Performance
Precision Optical Equipment
| Parameter | Engineering Requirement |
|---|---|
| Light source | LED / approved technology |
| Colours | Green / Yellow |
| Direction | Uni / Bidirectional |
| Operation | Fixed |
| Intensity | Standard / project specific |
| Beam width | Project specific |
| Horizontal / vertical coverage | Applicable requirement |
| Optical axis | Critical |
| Colour coordinates | Applicable standard |
| Colour sequence | Approved runway/taxiway layout |
| Photometric verification | Project dependent |
The selected fixture should demonstrate compliance for each required colour and viewing direction.
LED Technology
Modern Lead-On / Lead-Off Fixtures
Potential Advantages
- Long operating life, reduced lamp replacement
- Lower routine maintenance
- Stable green/yellow output and consistent colour
- Controlled beam distribution
- Fast switching where required
- Compatibility with modern AGL monitoring
Still Required
The final product must satisfy the applicable photometric, electrical, mechanical and environmental requirements.
Electrical Characteristics
Series-Circuit Integration
CCR → Primary AGL Cable → Isolating Transformer → Secondary Cable → Lead-On / Lead-Off Centreline Fixture
Verify Before Adding or Replacing a Fixture
- CCR current and fixture electrical input
- Transformer rating and number of fixtures
- Primary / secondary cable and connector type
- Intensity settings
- Monitoring and control-system requirements
Electrical Mismatch Can Cause
- Incorrect intensity
- Unequal colour output
- Circuit instability
- Transformer stress
- Premature fixture failure
- Monitoring faults
Mechanical & Installation
Pavement, Housing and Alignment
Construction
- High-strength in-pavement housing
- Load-bearing base and optical lens
- Green/yellow LED modules
- Sealing gasket, fasteners
- Cable interface and drainage
Pavement & Housing
- Housing and fixture dimensions
- Installation depth, pavement cut-out
- Seating, drainage, sealing
- Fastener torque, cable routing
- Maintenance access
The approved manufacturer installation drawing controls all dimensions.
Optical Alignment
- Position vs taxiway and runway centreline
- Colour sequence and direction
- Bidirectional orientation
- Holding-position / critical-area reference
- Fixture spacing
Incorrect orientation can display the wrong information to an approaching aircraft.
Commissioning & Testing
Test in Both Directions of Movement
Visual Inspection
- Fixture and lens condition
- Colour, position, spacing, alignment
- Housing and pavement interface
- Cable, connector, moisture evidence
Electrical Testing
- Circuit continuity
- Insulation resistance
- Transformer verification
- Series-circuit current
- CCR and intensity-step operation
Directional Testing
- Taxiway direction: specified green indication
- Runway direction: bidirectional fixture shows yellow
Especially important for the fixture before the holding / critical-area position. Where required, also verify photometric output, beam distribution and colour sequence.
Inspection & Maintenance
Routine Maintenance Coverage
Optical
- Lens cleanliness and damage
- Green and yellow output
- Intensity and beam direction
Mechanical & Electrical
- Fixture seating, housing, fasteners, gaskets
- Pavement interface, physical damage
- Transformer, connector, secondary cable
- Series-circuit current, insulation, moisture
Directional Function
- Green from taxiway side
- Yellow from runway side
- Correct bidirectional operation
- No incorrect colour indication
Common Failure Modes
Typical Faults and Causes
| Symptom | Possible Causes |
|---|---|
| Fixture OFF | Open circuit, light-source / transformer / connector failure, cable fault, internal fault |
| Wrong colour | Incorrect fixture or replacement, optical-module failure, control/configuration error, contamination |
| Correct colour in one direction only | Bidirectional optical failure, one LED channel failed, wiring fault, incorrect orientation |
| Incorrect colour sequence | Installation error, wrong fixture position, incorrect layout, wrong replacement |
| Low intensity | Optical contamination, LED degradation, incorrect CCR setting, electrical mismatch, damaged optics |
A wrong-colour or wrong-direction indication is safety-critical. Report it to airport operations / ATC and follow the airport AGL serviceability procedure.
Engineering Troubleshooting
Troubleshooting Sequence
Control systemCheck
CCRVerify output
Primary circuitCheck circuit
Isolating transformerCheck
Secondary cableCheck
ConnectorCheck
Centreline fixtureCheck
Green/yellow channelsDirectional check
PhotometricsVerify
Sequence problems: Runway centreline → taxiway centreline → holding position → critical-area boundary → colour sequence
Product Selection Matrix
Key Selection Parameters
| Selection Parameter | Requirement |
|---|---|
| Application | Runway/taxiway transition |
| Function | Lead-On / Lead-Off |
| Installation | Inset, in-pavement housing |
| Main colours | Green / Yellow |
| Direction | Uni / Bidirectional |
| Operation | Fixed |
| Optical type | Directional / project specific |
| Holding position / ILS-MLS critical area | Project specific / where applicable |
| RVR | Project specific |
| Intensity and beam | Standard / project specific |
| CCR, transformer, connector | Matching system, matching rating, approved AGL type |
| Control and monitoring | Project specific |
| Documentation | TDS / photometry / certificates |
Product Selection Checklist
Before Ordering, Confirm
- Airport / project
- Runway identification
- Taxiway identification
- Entry / exit function
- Runway holding position
- ILS/MLS critical-area boundary
- Low-visibility requirement
- Taxiway centreline layout
- Runway centreline arrangement
- Colour sequence
- Green output
- Yellow output
- Uni / bidirectional requirement
- Fixture spacing
- Optical beam
- Intensity
- LED / approved light source
- Series-circuit current
- Isolating transformer
- Connector type
- Housing
- Installation depth
- Pavement cut-out
- Drainage
- Control requirements
- Monitoring requirements
- Environmental rating
- Applicable standard
- Manufacturer TDS
- Photometric documentation
- Compliance / type-test documents
- Project approval requirements
Technical Documents
Documents to Request
- Product datasheet
- Technical specification
- Photometric report
- Beam distribution diagrams
- Green chromaticity information
- Yellow chromaticity information
- Bidirectional optical diagram
- Colour-sequence drawing
- Electrical specification
- Rated operating current
- Power consumption
- Transformer requirement
- Connector details
- Housing drawing
- Fixture dimensions
- Installation depth
- Pavement cut-out details
- Mounting details
- Drainage requirements
- Control/interface information
- Monitoring information
- Wiring diagram
- Weight
- Material specification
- Environmental rating
- Installation manual
- Maintenance manual
- Compliance certificates
- Type-test reports
- Warranty information
Safety
Electrical Safety — Isolation and Lock-Out
WARNING — never open a live series circuit. An open series circuit driven by a constant-current regulator can produce dangerously high voltage. Opening, cutting or disconnecting any part of an energised circuit can cause serious injury or death and damage equipment.
- De-energise the circuit at the regulator and apply the site lock-out / tag-out (LOTO) procedure before any work
- Where the circuit must be isolated or shorted, use the series circuit cut-out switch or approved isolation device — not an improvised bypass
- Verify the circuit is de-energised and the output is isolated before touching conductors, connectors, splices or transformers
- Work only under the airport's permit-to-work system, using qualified personnel and the manufacturer's instructions
- Follow the applicable national electrical safety regulations and site procedures
Standards & References
Verify the Applicable Edition
FAA
AC 150/5340-30J (Design and Installation Details for Airport Visual Aids) is listed as active by the FAA. It covers lead-off and lead-on lights, alternate green/yellow coding, bidirectional operation before the hold / critical-area position, and special coding where centreline lights cross a runway. Fixtures are specified in AC 150/5345-46F (L-852 taxiway centreline family). Bidirectional green–yellow combinations are provided by the straight-section, narrow-beam types (L-852A and L-852C); confirm the type against the current edition (AC 150/5345-46F) and the project centreline layout.
ICAO
Under ICAO Annex 14, Volume I (taxiway centre line lights) exit-taxiway lights alternate green and yellow from the runway centre line to the perimeter of the ILS/MLS critical/sensitive area or the lower edge of the inner transitional surface, whichever is farthest from the runway, and are green beyond. This extent differs from the FAA arrangement, so confirm which standard governs. See also ICAO Doc 9157 Part 4.
India
- DGCA India CAR Section 4 requirements
- Airport-specific AGL specification
- Approved lighting layout, LVP, ILS/MLS critical areas
- ALCMS / control philosophy
- BOQ, Employer's requirements, Indian Standards
- Airport operator requirements
Always verify the applicable document edition before technical approval, procurement or installation.
Comparison
Lead-On / Lead-Off vs Related Lighting
| Feature | Lead-On / Lead-Off | Taxiway Centreline | Stop Bar | Runway Guard Light |
|---|---|---|---|---|
| Primary function | Transition guidance | Taxiway route guidance | Stop indication | Runway-entry warning |
| Typical colour | Green / Yellow | Green | Red | Yellow |
| Operation | Fixed | Fixed | Controlled | Alternating / flashing where applicable |
| Installation | Inset | Typically inset | Inset / elevated | Elevated / inset |
| Main location | Runway/taxiway transition | Taxiway route | Holding position | Holding / intersection |
| Direction | Direction-specific | Uni / bidirectional | Directional | Direction-specific |
Lead-On / Lead-Off and Runway Guard Lights may be installed together.
FAQ
Lead-On / Lead-Off Light — Frequently Asked Questions
What are lead-on and lead-off lights?
Lead-on and lead-off lights are specialized taxiway centreline lighting configurations that give colour-coded green and yellow, direction-specific guidance when aircraft transition between a runway and the taxiway system. The arrangement distinguishes the runway environment and can identify proximity to the runway holding position or the ILS/MLS critical area, depending on the airport design.
How is the lead-off and lead-on sequence arranged under FAA guidance?
For lead-off, FAA guidance specifies alternate green and yellow centreline lights from the runway centreline to one centreline-light position beyond the runway hold or ILS critical-area hold position, ending with a yellow light. Where an odd number of colour-coded fixtures occurs, the first two centreline lights on the runway should be green. The lead-on arrangement starts with green at the runway centreline and follows the same green and yellow sequence to one light beyond the hold or critical-area hold position.
Why is the last coloured fixture bidirectional?
The last coloured fixture of the sequence, one centreline position beyond the runway holding position or ILS/MLS critical-area holding position, is a bi-colour, bidirectional fixture. Approached from the taxiway it shows green, and approached from the runway it shows yellow. This is a key product-selection parameter and should be identified explicitly on the technical submittal.
How do ICAO and FAA differ on the extent of the green and yellow sequence?
Under ICAO Annex 14 Volume I, exit-taxiway lights alternate green and yellow from the runway centre line to the perimeter of the ILS/MLS critical/sensitive area or the lower edge of the inner transitional surface, whichever is farthest from the runway, and are green beyond. This extent differs from the FAA arrangement, so confirm which standard governs the project.
Which FAA documents cover lead-on and lead-off lights?
FAA AC 150/5340-30J covers lead-off and lead-on lights, alternate green and yellow coding, bidirectional operation before the hold or critical-area position, and special coding where centreline lights cross a runway. Fixtures are specified in AC 150/5345-46F, the L-852 taxiway centreline family. Bidirectional green and yellow combinations are provided by the straight-section, narrow-beam types L-852A and L-852C, and the type should be confirmed against the current edition and the project centreline layout.
How do lead-on and lead-off lights differ from taxiway centreline lights and stop bars?
Ordinary taxiway centreline lighting is green, while the lead-on and lead-off transition is green and yellow. A stop bar gives the controlled red stop indication at the holding position, whereas lead-on and lead-off lights give directional route and runway-environment information through the centreline. The systems can be integrated through the airport control system so that indications remain consistent.
How are lead-on and lead-off lights installed?
They are generally implemented using in-pavement centreline fixtures, and the fixture and its load-bearing housing should be treated as one coordinated pavement installation. The sequence, number of fixtures and location must be taken from the approved lighting layout, and the manufacturer installation drawing controls the dimensions. Incorrect orientation can display the wrong information to an approaching aircraft.
How are lead-on and lead-off lights tested?
Test in both directions of movement. From the taxiway direction the specified green indication should show, and from the runway direction the bidirectional fixture should show yellow, which is especially important for the fixture before the holding or critical-area position. Electrical tests cover circuit continuity, insulation resistance, transformer verification, series-circuit current and CCR intensity-step operation, with photometric output, beam distribution and colour sequence checked where required.
What are the common faults, and why is a wrong colour serious?
Typical faults are a fixture that is off, a wrong colour, the correct colour in one direction only (a bidirectional optical failure, a failed LED channel, a wiring fault or incorrect orientation), an incorrect colour sequence and low intensity. A wrong-colour or wrong-direction indication is safety-critical and should be reported to airport operations or ATC, following the airport AGL serviceability procedure.
What should be confirmed before ordering lead-on and lead-off lights?
Confirm the airport and project, the runway and taxiway identification, the entry or exit function, the runway holding position and ILS/MLS critical-area boundary, the low-visibility requirement, the colour sequence, whether the fixture is unidirectional or bidirectional, the fixture spacing, the series-circuit current, isolating transformer and connector type, housing, installation depth and pavement cut-out, control and monitoring requirements, the governing standard and the datasheet and photometric documentation.
Is it safe to work on lead-on and lead-off fixtures while the circuit is energised?
No. An open series circuit driven by a constant-current regulator can produce dangerously high voltage, and opening, cutting or disconnecting any part of an energised circuit can cause serious injury or death. De-energise the circuit at the regulator, apply the site lock-out / tag-out procedure, use the series circuit cut-out switch or an approved isolation device and work under the permit-to-work system. See the electrical safety warning on this page.
Why Precision AGL Solutions
A Complete-System Approach
We treat Lead-On / Lead-Off lighting as part of the complete runway/taxiway transition lighting system:
Runway Geometry → Holding Position → Critical Area → Centreline Layout → Colour Sequence → Fixture → Optics → Housing → Transformer → Connector → Series Circuit → CCR → Control → Photometry → Maintenance
This helps ensure the selected fixture provides the correct information in the correct direction.
Procurement Information for Indian Projects
Indian public tenders commonly ask for the documents below. State which ones your tender requires when you send the enquiry, so they are covered in the quotation.
- Manufacturer / OEM authorisation
- Country of origin and local-content declaration (for Make in India purchase preference)
- Type-test and routine-test certificates, and the FAA / ICAO / IEC compliance documents named in the specification
- Datasheets, drawings and installation instructions
- Warranty, delivery period and spares support
- GeM catalogue or tender-portal requirements, where applicable
Request Lead-On / Lead-Off Lighting Configuration
Planning a runway entry/exit upgrade, low-visibility taxiway, ILS-critical-area installation or AGL rehabilitation project? Submit your runway/taxiway layout, centreline arrangements, holding-position marking, ILS/MLS critical-area information, existing arrangement, RVR requirement, BOQ, technical specification, fixture quantity, series-circuit and housing details, control requirements and existing fixture TDS. We can review the transition and support selection of the fixture configuration, colour arrangement, optics and electrical interface.
Request Lead-On / Lead-Off Lighting Configuration
Submit Runway/Taxiway Layout or Tender Specification
- Emailprecisionaglsolutions@gmail.com
- Websiterahulsharmaagl.in
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- Phone+91 98214 96412
Engineering Note
Lead-On / Lead-Off lights are a specialized taxiway centreline lighting configuration, not a general apron or aircraft-stand guidance product.
Key parameters are direction of travel, green/yellow colour coding, bidirectional operation where required, holding-position / critical-area relationship, optical distribution, centreline geometry and AGL control integration.
Product Disclaimer
Product availability, configuration, dimensions, electrical characteristics, photometric performance, certifications and compliance status depend on the selected manufacturer and project specification. The technical values published on this page should not be treated as a substitute for the manufacturer's current approved Technical Data Sheet.
Final selection shall be based on the approved project specification, applicable aviation standards, authority requirements, manufacturer documentation and site conditions. Use of this page is also subject to the Legal Notice, Disclaimer & Terms of Use.
Standards and editions referenced on this site are listed on the Standards Reference page.