Runway Safety Lighting
Stop Bar Light for Airfield Ground Lighting
Red stop indication at runway holding positions
Stop bar lights provide a highly conspicuous red visual indication at runway holding positions and controlled movement locations, supporting runway-incursion prevention with inset installation, selective switching and project-specific AGL control arrangements.
Supplied by Precision AGL Solutions
Product Overview
Stop Bar Light
What It Is
Stop bar lights provide a highly conspicuous red visual indication at runway holding positions and other controlled aircraft movement locations.
They form part of the airport’s runway-incursion prevention and surface-movement control system by showing where aircraft or vehicles must stop before proceeding toward a protected area. A stop bar is normally installed across a taxiway at the holding position as a row of in-pavement lights oriented to approaching traffic.
Selected According To
- Runway holding-position configuration
- Taxiway geometry
- Low-visibility operating requirements
- Stop-bar length and fixture spacing
- Light direction, red output and beam characteristics
- Selective switching and centreline interlocking
- Series-circuit configuration and AGL control system
- Inset housing arrangement and pavement conditions
- Project technical specification
The final stop-bar system should always be selected against the approved airport lighting/control design and applicable aerodrome standards.
Applications
Where Stop Bar Lights Are Used
Runway holding positionsPrimary application.
Controlled runway entryProtected entry points.
Taxiway / runway intersectionsIncursion protection.
Intermediate holding positionsWhere specifically required.
Low-visibility operationsEnhanced conspicuity.
Runway-incursion preventionSafety-critical function.
Controlled taxiway movementSurface movement control.
Surface movement systemsSMGCS integration.
Rehabilitation / modernizationAGL upgrade projects.
ICAO material describes stop bars as a series of unidirectional red lights embedded in the pavement, installed at right angles to the taxiway centreline at the runway holding position.
Annex 14 requires a stop bar at every runway-holding position serving a runway intended for use in runway visual range below 350 m, subject to the exceptions in the standard, such as suitable aids and procedures that prevent inadvertent runway incursions. At an intermediate holding position, a stop bar is provided where markings are to be supplemented by lights for visual traffic control. Annex 14 also recommends a stop bar where RVR is between 350 m and 550 m, subject to similar exceptions. Confirm against the applicable edition.
Function
A Clear Visual Command: STOP
How It Works
- Illuminated: movement beyond the holding position is not authorized
- Extinguished on clearance, per the airport’s approved operational and control logic
- Pilot or vehicle operator receives an unambiguous stop indication
A stop bar is both a lighting product and a controlled safety function.
The Safety Function Depends On
- Red light output
- Fixture spacing and beam direction
- Stop-bar location and marking alignment
- Selective switching
- Taxiway centreline interaction
- Control-system logic
- Electrical circuit integrity
- Continuous maintenance
Red Light Configuration
Unidirectional Red Toward the Approach
Red Directional Light
Stop bar lights emit red directional light toward the intended approach direction. For runway-holding applications the light is unidirectional in the approach direction.
Under the FAA fixture specification, L-852S is the in-pavement stop-bar fixture classification. FAA AC 150/5345-46F specifies red output for L-852S with minimum intensity and beam-coverage values set in the fixture specification.
Typical Installation Comprises
- In-pavement stop-bar fixture
- Load-bearing light base/housing
- Red optical assembly, LED or approved light source, lens
- Mounting hardware and gasket/sealing system
- Secondary cable and isolating transformer
- Primary circuit connector
- Control/interface equipment
Verify the actual product against the current applicable FAA specification and project requirements.
Stop Bar Layout
Coordinated With the Holding-Position Marking
TAXIWAY
STOP BAR · RUNWAY HOLDING POSITION
RUNWAY
Schematic only. The exact number, spacing and location of fixtures depend on taxiway width, holding-position marking and the governing airport design.
Fixture Spacing
Spacing for a Continuous Visual Indication
ICAO
ICAO Annex 14, Volume I (Chapter 5, stop bars) specifies stop-bar lights spaced uniformly at no more than 3 m across the taxiway. ICAO also provides for a pair of elevated stop-bar lights added at each end of the bar where in-pavement lights could be obscured. Confirm the clauses against the edition applicable to the project.
FAA
Stop-bar light spacing and layout are covered by AC 150/5340-30J. Use the spacing shown in the current edition and the approved airport drawing.
Project standards differ — the approved airport drawing and governing standard control the final spacing.
Beam Direction
Beam Direction & Orientation
FAA In-Pavement Installations
The beam axis is oriented away from the runway, perpendicular to the holding-position marking, within the installation tolerance given in the cited FAA guidance and the approved project drawing.
Incorrect Orientation Can Cause
- Reduced conspicuity
- Incorrect photometric output
- Unbalanced light appearance
- Reduced viewing coverage
- Operational confusion
Holding Position
Stop Bar & Holding Position
Installation Must Consider
- Runway protection area
- Holding-position marking
- Taxiway centreline and stop-bar location
- Runway boundary
- Taxiway edge lights
- Runway guard lights
- Clearance requirements
Reference
FAA AC 150/5340-30J provides specific stop-bar installation details and diagrams for runway/taxiway intersections.
Selective Switching
Selectively Switchable Operation
Controlled ON / OFF
- Red stop indication ON → aircraft must hold
- Stop bar OFF → aircraft authorized to proceed, subject to clearance and operating procedures
Reference
ICAO provisions have addressed selectively switchable stop bars in conjunction with taxiway centreline lighting extending beyond the stop bar.
Interlocking
Stop Bar & Taxiway Centreline Interlocking
The Conflict to Prevent
Stop bar = RED / STOP while centreline beyond = GREEN / PROCEED at the same time is a potentially confusing condition and must be avoided.
Guidance
FAA guidance states the stop bar should be interlocked with the taxiway lights. ICAO material describes arrangements in which centreline lights beyond an illuminated stop bar are extinguished for at least 90 m.
Exact logic is established through the airport’s approved AGL/ALCMS control philosophy.
Control System Interface
A Controlled Lighting Function
May Interface With
- AGL control panel and CCR
- ALCMS
- Individual Light Controller
- Stop-bar control module
- Air traffic control interface
- Surface movement guidance and control system
- Runway safety automation
- Interlocking logic
Control May Need To Provide
- ON/OFF and selective switching
- Status and failure indication
- Interlocking
- Remote monitoring
- Local/manual override where specified
- Fault reporting
The actual control architecture should be taken from the approved airport system design.
Electrical Characteristics
Typical AGL Circuit Arrangement
CCR / AGL Power System → Primary Series Circuit → Isolating Transformer → Secondary Cable → In-Pavement Stop Bar Light → Control / Monitoring Interface
Typical Parameters To Verify
- Series-circuit current
- Isolating-transformer rating
- Fixture electrical characteristics
- Power consumption
- Secondary and primary connectors
- Cable type
- Intensity-step compatibility
- Monitoring and switching requirements
Verify Before Replacing or Adding a Fixture
- CCR output current and circuit topology
- Number of stop-bar fixtures
- Transformer rating
- Primary and secondary cable
- Connector type
- Intensity setting and switching method
- Monitoring system and ALCMS interface
Incorrect Compatibility May Result In
- Incorrect intensity
- Circuit instability
- Transformer stress
- Switching problems
- False failure indications
- Premature fixture failure
Photometric Performance
Controlled Optical Performance
Red stop indication must be readily visible from the intended approach direction.
| Parameter | Engineering Requirement |
|---|---|
| Light source | LED / approved technology |
| Colour | Red |
| Direction | Unidirectional for runway holding position |
| Intensity | Standard / project specific |
| Main beam | Fixture-specific |
| Horizontal / vertical coverage | Standard / fixture-specific |
| Optical axis | Critical |
| Chromaticity | Applicable standard |
| Intensity steps | Where applicable |
| Switching | Controlled |
| Photometric verification | Project dependent |
FAA AC 150/5345-46F specifies L-852S minimum beam coverage and red intensity characteristics for the current FAA fixture specification.
LED Light Source
LED Technology in Stop-Bar Fixtures
Potential Advantages
- Long operating life
- Reduced lamp replacement and maintenance
- Consistent red output
- Controlled optical performance
- Fast switching
- Compatibility with monitoring and control systems
Assess the Complete Product
Evaluate photometric, electrical, mechanical and environmental performance — not light-source technology alone.
Construction & Environment
Mechanical, Pavement and Environmental Performance
Fixture May Include
- High-strength in-pavement body and load-bearing base
- Optical lens, LED module, red filter/optical element
- Reflector/optical assembly
- Sealing gasket and fasteners
- Secondary cable connection
- Drainage provisions and pavement housing
Verify With Civil Works
- Base-can type and housing dimensions
- Fixture dimensions and installation depth
- Pavement cut-out and drainage
- Fixture seating and fastener torque
- Cable routing, sealing, maintenance access
Environmental Evaluation
- Water ingress, dust, humidity
- Temperature extremes and UV
- Corrosion and vibration
- Mechanical and aircraft tyre loading
- Pavement contamination, cleaning chemicals
- Jet blast exposure
Inset Installations
Pay particular attention to water ingress + drainage + gasket condition + pavement interface + mechanical loading. FAA guidance identifies L-868 load-bearing bases for in-pavement stop-bar installations.
Installation
Verify Before and During Installation
Holding Position & Alignment
- Correct holding-position reference
- Stop-bar location and marking alignment
- Taxiway centreline relationship
- Optical direction and perpendicularity to marking
- Fixture rotation, housing orientation, beam axis
Spacing & Pavement
- Uniform fixture spacing
- Complete taxiway coverage
- Relationship to taxiway edge
- Housing, installation depth, seating
- Drainage, sealing, cable routing, fastener torque
Commissioning & Testing
Test Both Lighting and Control
Visual & Electrical
- Fixture, lens, red output, alignment, spacing
- Housing, fasteners, pavement interface, moisture evidence
- Circuit continuity and insulation resistance
- Transformer, secondary connection, series-circuit current
- CCR operation, intensity steps, switching
Control & Photometric
- Local and remote ON/OFF, selective switching
- Status and fault indication
- Interlock logic and centreline interaction
- Monitoring and fail-safe behaviour where specified
- Red colour, intensity, beam distribution, consistency across the bar
Maintenance & Inspection
Cover the Fixture, Circuit and Control Interface
Optical & Mechanical
- Lens cleanliness and damage
- Red colour, intensity, beam direction
- Fixture seating, housing, fasteners
- Pavement interface and physical damage
Electrical & Control
- Transformer, secondary cable, connector
- Series circuit, insulation, moisture
- Switching and interlocking
- Monitoring, status indication, fault reporting
Common Failure Modes
Symptoms and Possible Causes
| Symptom | Possible Causes |
|---|---|
| Stop bar light OFF | Open series circuit; failed LED module; transformer failure; connector failure; cable fault; internal fixture failure; control-system command |
| Entire stop bar OFF | Circuit failure; CCR problem; control-system issue; switching relay fault; interlock logic problem; power supply failure |
| Stop bar does not switch | Control-system fault; switching equipment fault; communication failure; interlock condition; individual light-controller problem |
| Centreline interlock incorrect | Incorrect control logic; configuration error; communication fault; relay/contact failure; incorrect software/system configuration |
| Low red intensity | Optical contamination; LED degradation; incorrect CCR setting; electrical mismatch; damaged optical component; alignment issue |
| Uneven stop-bar appearance | Unequal light output; failed/degraded fixture; contaminated optics; incorrect spacing; mixed fixture configurations; control/intensity mismatch |
Engineering Troubleshooting Sequence
Use a Systematic Diagnostic Sequence
Control systemStop-bar command
Interlock logicCheck logic
CCR / powerVerify output
Primary circuitCheck circuit
Isolating transformerCheck
Secondary cableCheck
ConnectorCheck
Stop bar fixtureCheck
Light sourceInspect
Optical alignmentInspect
PhotometryVerify
For a complete failure, test the control path first — the lights may be electrically healthy but intentionally extinguished by the control/interlocking system.
Product Selection Matrix
Key Selection Parameters
| Selection Parameter | Requirement |
|---|---|
| Application | Runway holding / controlled movement |
| Installation | Inset |
| Light colour | Red |
| Direction | Unidirectional / project specific |
| Fixture type | L-852S (inset) / L-862S (elevated) or applicable authority classification |
| Beam / Intensity | Standard / fixture or project specific |
| Spacing | Approved layout |
| Taxiway width / holding position | Project specific |
| CCR | Matching series-circuit equipment |
| Transformer | Matching rating |
| Connector | Approved AGL type |
| Switching | Selective where required |
| Interlock | Required per control design |
| Monitoring / Control | Project specific; local / remote / ALCMS |
| Housing | Load-bearing inset |
| Environment | Airport specific |
| Documentation | TDS / photometry / certificates |
Product Selection Checklist
Before Ordering, Confirm
- Airport / project
- Runway holding position
- Taxiway identification and width
- Holding-position marking
- Stop-bar length
- Number of fixtures and spacing
- Light colour
- Optical direction
- Beam distribution
- Intensity
- LED / approved light source
- Series-circuit current
- Isolating transformer
- Connector type
- Housing type
- Installation depth
- Pavement cut-out
- Drainage
- Selective switching
- Centreline interlock
- ALCMS / interface
- Monitoring requirements
- Environmental rating
- Applicable standard
- Manufacturer TDS
- Photometric documentation
- Compliance / type-test documentation
- Project approval requirements
Technical Documents
Technical Documents to Request
For technical approval and procurement, request the applicable manufacturer documentation.
- Product datasheet
- Technical specification
- Photometric report
- Beam distribution diagram
- Colour/chromaticity information
- Optical orientation information
- 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
- Switching/interface information
- Control wiring diagram
- Monitoring interface
- Weight
- Material specification
- Environmental rating
- Installation manual
- Maintenance manual
- Compliance certificates
- Type-test reports
- Warranty information
Standards & References
Governing Standards
ICAO
Annex 14 contains requirements for stop bars at runway-holding positions and other applicable locations, describing them as red, unidirectional in-pavement lights, with selective switching and integration with taxiway centreline lighting. Amendment 18 to Annex 14 Vol. I (applicable from 27 November 2025) included visual-aid provisions, so confirm the stop-bar clauses against the amended edition.
FAA
AC 150/5340-30J — Design and Installation Details for Airport Visual Aids, including stop-bar orientation and elevated arrangements.
AC 150/5345-46F — Specification for Runway, Taxiway, Heliport, and Vertiport Light Fixtures (issued September 30, 2024); identifies L-852S.
India — Also Verify
- DGCA requirements
- Airport-specific AGL specifications
- Approved runway-holding-position layout
- AGL/ALCMS control philosophy
- Low-visibility procedures
- Project BOQ and Employer’s requirements
- Applicable Indian Standards
- Airport operator requirements
Always verify the applicable document edition and project-specific requirements before procurement, approval or installation.
Comparison
Stop Bar Light vs Runway Guard Light
| Feature | Stop Bar Light | Runway Guard Light |
|---|---|---|
| Primary function | Stop indication / movement control | Enhanced warning at runway intersection |
| Typical colour | Red | Yellow |
| Typical installation | Inset | Elevated or inset |
| Switching | Selectively switchable where required | May operate continuously/flashing per design |
| Primary location | Holding position | Runway/taxiway intersection warning area |
| Control relationship | Strong integration with centreline and surface movement control | Warning function |
| FAA example | L-852S | L-804 (elevated) / L-852G (inset) or applicable RGL classification |
The project design determines whether one or both systems are required.
FAQ
Stop Bar Light — Frequently Asked Questions
What is a stop bar light?
Stop bar lights provide a highly conspicuous red visual indication at runway holding positions and other controlled aircraft movement locations. They form part of the airport's runway-incursion prevention and surface-movement control system by showing where aircraft or vehicles must stop. A stop bar is normally installed across a taxiway at the holding position as a row of in-pavement lights oriented to approaching traffic.
When does ICAO require a stop bar?
Annex 14 requires a stop bar at every runway-holding position serving a runway intended for use in runway visual range below 350 m, subject to the exceptions in the standard, such as suitable aids and procedures that prevent inadvertent runway incursions. At an intermediate holding position, a stop bar is provided where markings are to be supplemented by lights for visual traffic control. Annex 14 also recommends a stop bar where RVR is between 350 m and 550 m, subject to similar exceptions. Confirm against the applicable edition.
How does a stop bar work and how is it switched?
When the stop bar is illuminated, movement beyond the holding position is not authorized. It is extinguished on clearance, per the airport's approved operational and control logic, so the aircraft is authorized to proceed subject to clearance and operating procedures. A stop bar is both a lighting product and a controlled safety function, and it is selectively switchable where required.
What are the red light characteristics of a stop bar?
Stop bar lights emit red directional light toward the intended approach direction, and for runway-holding applications the light is unidirectional in the approach direction. Under the FAA fixture specification, L-852S is the in-pavement stop-bar fixture classification, and FAA AC 150/5345-46F specifies red output for L-852S with minimum intensity and beam-coverage values set in the fixture specification. Verify the actual product against the current applicable FAA specification and project requirements.
How are stop bar lights spaced and oriented?
ICAO Annex 14, Volume I (Chapter 5, stop bars) specifies stop-bar lights spaced uniformly at no more than 3 m across the taxiway, and provides for a pair of elevated stop-bar lights added at each end of the bar where in-pavement lights could be obscured. For FAA installations, the spacing and layout are covered by AC 150/5340-30J, and the beam axis is oriented away from the runway, perpendicular to the holding-position marking, within the tolerance in the cited FAA guidance and the approved project drawing. The approved airport drawing and governing standard control the final spacing.
Why must a stop bar be interlocked with taxiway centreline lights?
A stop bar showing red while the centreline beyond shows green is a potentially confusing condition and must be avoided. FAA guidance states the stop bar should be interlocked with the taxiway lights, and ICAO material describes arrangements in which centreline lights beyond an illuminated stop bar are extinguished for at least 90 m. The exact logic is established through the airport's approved AGL/ALCMS control philosophy, and the control system may interface with the AGL control panel and CCR, ALCMS, individual light controllers, a stop-bar control module, air traffic control and surface movement guidance and control systems.
What electrical checks apply before replacing or adding a stop bar fixture?
A typical arrangement runs from the CCR through the primary series circuit and isolating transformer to the secondary cable and the in-pavement stop bar light, with a control and monitoring interface. Verify the CCR output current and circuit topology, the number of stop-bar fixtures, transformer rating, primary and secondary cable, connector type, intensity setting and switching method, and the monitoring system and ALCMS interface. Incorrect compatibility may result in incorrect intensity, circuit instability, transformer stress, switching problems, false failure indications or premature fixture failure.
What should be verified for the pavement and installation?
Verify the holding-position reference, stop-bar location and marking alignment, taxiway centreline relationship, optical direction and perpendicularity to the marking, uniform fixture spacing, complete taxiway coverage and the relationship to the taxiway edge. For the pavement, check the housing type and dimensions, installation depth, pavement cut-out, drainage, fixture seating, fastener torque, cable routing and sealing. FAA guidance identifies L-868 load-bearing bases for in-pavement stop-bar installations.
What is tested at commissioning?
Commissioning tests both lighting and control. That includes fixture, lens, red output, alignment and spacing, circuit continuity and insulation resistance, transformer and secondary connection, series-circuit current, CCR operation and intensity steps, local and remote ON/OFF and selective switching, status and fault indication, interlock logic and centreline interaction, and monitoring and fail-safe behaviour where specified. Photometric verification covers red colour, intensity, beam distribution and consistency across the bar.
What are common stop bar failure modes and how are they diagnosed?
Typical symptoms are a single light off, the entire stop bar off, a stop bar that does not switch, an incorrect centreline interlock, low red intensity and an uneven stop-bar appearance. For a complete failure, test the control path first, because the lights may be electrically healthy but intentionally extinguished by the control or interlocking system. The diagnostic sequence runs through the control system, interlock logic, CCR and power, primary circuit, isolating transformer, secondary cable, connector, fixture, light source, optical alignment and photometry.
How is a stop bar different from a runway guard light?
A stop bar gives a stop indication and movement control, is red, is typically inset, and is selectively switchable where required, with a strong link to centreline and surface movement control. A runway guard light is an enhanced warning at a runway/taxiway intersection, is yellow, may be elevated or inset, and may operate continuously or flashing per design. FAA examples are L-852S for the stop bar and L-804 (elevated) or L-852G (inset) for runway guard lights, and the project design determines whether one or both systems are required.
Which standards apply to stop bar lights?
ICAO Annex 14 contains requirements for stop bars at runway-holding positions and other applicable locations, describing them as red, unidirectional in-pavement lights with selective switching and integration with taxiway centreline lighting. Amendment 18 to Annex 14 Vol. I (applicable from 27 November 2025) included visual-aid provisions, so confirm the stop-bar clauses against the amended edition. FAA references are AC 150/5340-30J and AC 150/5345-46F, and in India DGCA requirements, airport-specific AGL specifications, the approved holding-position layout and the AGL/ALCMS control philosophy should also be verified.
What should be confirmed before ordering a stop bar?
Confirm the airport and project, runway holding position, taxiway identification and width, holding-position marking, stop-bar length, number of fixtures and spacing, light colour, optical direction, beam distribution and intensity, series-circuit current, isolating transformer, connector type, housing type, installation depth, pavement cut-out and drainage. Also confirm selective switching, centreline interlock, the ALCMS interface, monitoring requirements, environmental rating, applicable standard, and the manufacturer datasheet, photometric and compliance documentation.
Why Precision AGL Solutions
A Safety-Critical, System-Level Approach
We treat stop-bar lighting as a safety-critical controlled visual-aid system, not simply a red runway light. Our approach considers:
Holding Position → Stop Bar Layout → Fixture → Optics → Pavement Housing → Transformer → Series Circuit → CCR → Switching → Interlocking → ALCMS → Monitoring → Photometry
This helps ensure the selected solution suits both the physical airfield layout and the operational control philosophy.
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 Stop-Bar Technical Selection
Planning a new runway holding position, low-visibility taxiway, runway-incursion protection upgrade or AGL rehabilitation project? Submit your runway/taxiway layout, holding-position marking, taxiway width, existing stop-bar arrangement, low-visibility requirement, BOQ, technical specification, fixture quantity, CCR/series-circuit details, existing transformer information and AGL/ALCMS control requirements. Precision AGL Solutions can review the requirement and support selection of the appropriate stop-bar fixture, optical configuration, electrical interface and switching/control arrangement.
- Emailprecisionaglsolutions@gmail.com
- Websiterahulsharmaagl.in
- LinkedInPrecision AGL Solutions
- Phone+91 98214 96412
Engineering Note
A stop bar is a controlled runway-safety visual aid. The correct solution depends on holding-position geometry, red optical output, fixture spacing, beam direction, pavement installation, series-circuit operation and selective control/interlocking.
The fixture should be selected together with its AGL circuit and control-system requirements, rather than treated as a standalone red light.
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.