Lead-On Lighting VS Lead-Off Lighting
Onto vs Off — lead-on lighting guides an aircraft from the taxiway toward the runway, while lead-off lighting guides an aircraft from the runway toward the taxiway. Both are directional transition/continuation systems at the runway/taxiway interface, built to make that hand-off between guidance systems conspicuous rather than to replace the normal centreline lighting.
At a Glance
| Feature | Lead-On Lighting | Lead-Off Lighting |
|---|---|---|
| Direction | Taxiway → Runway | Runway → Taxiway |
| Main purpose | Guides aircraft onto the runway | Guides aircraft off the runway |
| Primary operation | Entering runway for departure | Vacating runway after landing |
| Pilot message | "Follow this path onto the runway" | "Follow this path to the taxiway" |
| Main benefit | Smooth taxiway-to-runway transition | Smooth, conspicuous runway exit |
| Typical location | Taxiway/runway entrance area | Runway/taxiway exit area |
| Directional function | Inbound to runway | Outbound from runway |
| Easy meaning | LEADS ONTO | LEADS OFF |
What Is Lead-On & Lead-Off Lighting?
Lead-On Lighting
Provides a visual continuation from the taxiway toward the runway. The pilot's basic message is: "follow this route toward the runway."
Can help an aircraft
- Identify the runway entry path
- Maintain visual continuity between taxiway and runway
- Recognise the intended transition point
- Improve conspicuity at night or in reduced visibility
Lead-Off Lighting
Provides a visual path from the runway toward a taxiway exit. The pilot's basic message is: "follow this route to vacate the runway."
Can help an aircraft
- Identify an available runway exit
- Transition from runway centreline guidance to taxiway guidance
- Vacate the runway efficiently
- Maintain visual guidance after landing
Engineering detail — this is implemented as taxiway centreline lighting, not a separate fixture type. Per the FAA AIM/AC 150/5340-30, lead-on and lead-off guidance is provided by alternating green-and-yellow taxiway centreline lights, beginning with green from the runway centreline out to one light position beyond the runway holding position (or the ILS critical area boundary, whichever is more restrictive). Where the same light position must serve both functions, the fixture is bidirectional — one side of the fixture displays the lead-on colour pattern and the other side displays the lead-off pattern, so a fixture showing yellow for lead-off must also show yellow for lead-on.
Lead-On = Onto the Runway · Lead-Off = Off the Runway
This is the fastest way to tell them apart, and the easiest thing to memorise: lead-on leads you onto the runway, lead-off leads you off the runway.
Before takeoff, a pilot follows lead-on lighting from the taxiway toward the runway. After landing, the pilot follows lead-off lighting from the runway toward the intended taxiway exit — same interface, opposite direction of travel.
How Each System Runs at the Interface
Lead-on lighting carries the aircraft's eye from the taxiway environment into the runway environment. Lead-off lighting carries it back the other way — the two systems mirror each other across the same interface.
Onto vs Off — The Easy Memory
The simplest way to remember it: lead-on leads the aircraft ONTO the runway; lead-off leads the aircraft OFF the runway. Both are transition/continuation lighting that make the runway/taxiway hand-off conspicuous — they are not a replacement for the normal taxiway or runway centreline systems.
A Two-Way Transition at the Same Interface
Think of the runway/taxiway interface as a two-way transition: lead-on carries traffic inbound to the runway, lead-off carries traffic outbound from it.
| Movement | System |
|---|---|
| Taxiway → Runway | Lead-On |
| Runway → Taxiway | Lead-Off |
Continuation, Not Replacement
Lead-On
Sits between the taxiway centreline and the runway, extending visual guidance across the gap so the transition from taxiway lighting to the runway visual environment is conspicuous.
Lead-Off
Sits between the runway and the taxiway centreline, extending guidance the other way so the pilot can transition from runway centreline guidance to taxiway guidance after landing.
Lead-on and lead-off lighting should be understood as transition/continuation lighting at the interface, not as substitutes for the normal taxiway or runway centreline systems they connect.
Which System Is Active When
| Operation | Lighting Direction |
|---|---|
| Taxiing toward departure runway | Lead-On |
| Entering runway | Lead-On |
| Takeoff | Lead-on transition completed |
| Landing | Runway lighting |
| Vacating runway | Lead-Off |
| Taxiing away from runway | Lead-off transition completed |
What Each System Answers
| Question | System |
|---|---|
| How do I get from the taxiway onto the runway? | Lead-On |
| How do I vacate the runway after landing? | Lead-Off |
| Which direction am I being guided in? | Depends which side of the interface you're on |
| Does this replace centreline lighting? | No — continuation lighting for both |
Lead-On Lighting vs Lead-Off Lighting
| Parameter | Lead-On | Lead-Off |
|---|---|---|
| Direction | Taxiway → Runway | Runway → Taxiway |
| Main operation | Departure/takeoff preparation | Landing/runway vacation |
| Function | Entry guidance | Exit guidance |
| Pilot objective | Reach runway | Vacate runway |
| Location | Runway entrance transition | Runway exit transition |
| Main benefit | Entry conspicuity | Exit conspicuity |
| Memory | LEADS ONTO | LEADS OFF |
Common Lead-On / Lead-Off Confusion
They are transition/continuation systems that supplement the normal taxiway and runway centreline lighting at the interface — not a replacement for either.
They serve opposite directions of travel. Lead-on guides an aircraft toward the runway for entry; lead-off guides an aircraft away from the runway to vacate it — one is inbound guidance, the other outbound.
Lead-off lighting improves conspicuity and helps a pilot follow an identified exit route after landing; the operational clearance and intended routing still come from the applicable ATC procedures, markings, signs and other aerodrome controls.
Lead-On Lighting vs Lead-Off Lighting
Lead-on and lead-off lighting are directional mirror images of each other at the same runway/taxiway interface. One carries the aircraft's eye onto the runway; the other carries it off.
Both exist to make the hand-off between the taxiway visual environment and the runway visual environment conspicuous — for departure in one direction, for landing and runway vacation in the other — while the normal centreline systems continue to do the underlying guidance work.
Easy memory: Lead-ON → leads you ONTO the runway. Lead-OFF → leads you OFF the runway.
Engineering & Expert Notes
Check Direction of View for Each Light
OrientationLights are seen from specific directions. Verify orientation after replacement.
Confirm Colour and Pattern
ColourVerify colours and sequence for the correct guidance.
Drive the Route at Night to Check the Pattern
InspectionLook for gaps or misleading breaks.
Update Records After Layout Changes
RecordsKeep drawings aligned with the field.
Frequently Asked Questions
Direction — lead-on lighting guides an aircraft from the taxiway toward the runway, while lead-off lighting guides an aircraft from the runway toward the taxiway.
While taxiing toward a departure runway and entering it — lead-on lighting provides visual continuity between the taxiway guidance system and the runway visual environment.
After landing, while identifying and following the intended exit route to vacate the runway and transition back to taxiway guidance.
No. They are transition/continuation lighting at the runway/taxiway interface, working alongside the normal taxiway and runway centreline systems rather than replacing them.
Yes — lead-ON leads you ONTO the runway, and lead-OFF leads you OFF the runway.
No. It improves conspicuity and helps the pilot follow the intended route, but operational clearance still comes from the applicable ATC procedures, markings, signs and other aerodrome controls.
Governing Documents
For an actual project design, always verify the current edition of the applicable documents.
ICAO Annex 14, Volume I
Aerodrome Design and Operations — general requirements for aerodrome visual aids, including transition and guidance lighting at the runway/taxiway interface.
FAA AC 150/5340-30
Design and Installation Details for Airport Visual Aids — configuration, installation and photometric guidance for taxiway and runway lighting systems, including transition elements.
DGCA / AAI Requirements
For Indian airport projects, also verify applicable DGCA requirements, AAI requirements, airport-specific technical specifications, project drawings and contract specifications.
Final Engineering Note
Do not design a lead-on/lead-off lighting arrangement from a generic web diagram. The final installation drawing should always be developed from the current governing standard, approved airport design and project-specific requirements.
Lead-on = onto the runway. Lead-off = off the runway — two directions of the same transition, not two competing systems.
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