Project
Design Basis & Geometry
Rule note
φ is the angle from the +X direction of Taxiway A to the first B arm, counter-clockwise. 90° is a square junction; 60° leans the arm toward +X. Fillet radius is the pavement fillet; lights follow it at radius (fillet − offset).
Systems, Lead-On / Lead-Off & Holding Positions
Centreline turning movements
Rule note
One radius for all lead-on / lead-off curves. Tangent length T = R·tan(δ/2) from the centre; the curve leaves the branch and meets Taxiway A tangentially.
Holding-position stop bars (on each branch arm)
Rule note
Distance is measured along the arm from the intersection centre, taken from the approved layout; it is not derived from the standard here. The bar spans the full width of Taxiway B at that position, edge to edge, with the count N + 1 for N equal intervals.
Spacing & Duplicate Control
Design spacing (used to generate)
Each run is divided into N = ⌈length / S⌉ equal intervals, so the actual pitch never exceeds the design spacing.
Maximum spacing (used to check)
Two fixtures of the same colour closer than this are one physical fixture, so a lead-off curve meeting Taxiway A is never double-counted.
Output
Generated Intersection
Top: the whole intersection to scale. Bottom: a zoomed window centred on the intersection. Hover a fixture for its ID and coordinates. Hollow rings mark the lead-off tangent points.
Detail Window
Quantity Schedule
Junction geometry
Calculated / Nominal Quantity — installed fixtures, no serviceability allowance, no spares. A fixture at a joint between two runs, or where two paths meet, is counted once.
Duplicate-Fixture Control
Fixture Schedule
How the Intersection Is Built
Taxiway A lies on the X axis with the intersection centre at the origin. The branch arm leaves the centre at angle φ; a crossing adds a second arm at φ + 180°. Edge lights sit on a light line offset outward from the pavement edge by D.
Centreline lead-on / lead-off curves
For each arm, the inbound heading is the arm direction + 180°. The turn to +X or −X is δ = target heading − inbound heading, wrapped to ±180°. The arc starts on the branch centreline at distance T from the centre and ends on Taxiway A at x = ±T, tangent to both. Taxiway A and the branch centreline are split at the tangent points so a fixture always lands on each one.
Edge lights and fillets
Each corner where the branch edge meets Taxiway A's edge is rounded by a fillet. β is the angle of the grass wedge at that corner, l is the distance from the corner to the tangent points, and the light fillet shares the pavement fillet's centre. Edge lights run along Taxiway A to the tangent point, round the fillet, then continue out along the arm. Nothing is lit across the mouth.
Stop bars
The bar crosses Taxiway B square to its axis at the holding-position distance, edge to edge. The tool warns if the bar sits inside the fillet flare, where the pavement is wider than WB, or inside a lead-off tangent length. Red stop bars are used at runway-holding positions and may also be provided at intermediate holding positions; where they are not, yellow intermediate holding position lights are used instead, which this tool does not generate — confirm the arrangement for each holding position.
Duplicate-fixture control
Runs are generated in a fixed order. A candidate fixture within the tolerance of an already-placed fixture of the same colour is dropped and logged. This removes the doubled light where a lead-off curve joins Taxiway A or the branch centreline, and where two curves leave the branch at the same point. Different colours are never merged.
Colours and pre-filled spacing
| Light | Colour | Straight limit |
|---|---|---|
| Edge | Blue | ICAO 60 m · FAA 200 ft |
| Centreline | Green | ICAO 30 m (15 m below 350 m RVR) · FAA 100 ft (50 ft below 1,200 ft RVR) |
| Stop bar | Red | ICAO ≤ 3 m · FAA 10 ft |
These are editable defaults matching the other taxiway calculators. The centreline curve maximum is taken automatically from the standard’s radius table for the lead-on / lead-off radius when “Centreline — Curve Max” is left blank (ICAO 7.5 m up to 400 m radius; FAA 25 ft under 400 ft radius, 12.5 ft below 1,200 ft RVR). Fillet edge-light spacing depends on radius and is project-entered, and stop-bar spacing comes from the applicable table, so confirm every value against the standard and the approved project layout.
What this tool does not do
It does not decide which route carries the through centreline, apply the standard's rules on clearance bars, lead-on lights at runway entries, or enhanced centreline, or place intermediate holding position lights, elevated stop-bar lights, signs or markings. Those are project-specific. It lays out the geometry and spacing you specify and checks it.
Taxiway Intersection Lighting: Frequently Asked Questions
Quick answers on how the calculator lays out junction lighting.
What does the Taxiway Intersection Lighting Calculator do?
From one set of junction geometry it generates blue edge lights around the fillets, green centreline lights with lead-on and lead-off curves, and red stop bars at the holding positions, all as X,Y fixtures. The same list drives the plan drawing, the quantity schedule and the SVG, PNG and CSV exports, so they always agree.
Which junction types can I model?
Taxiway A runs straight along the X axis. Taxiway B joins as a T or Y branch at a branch angle φ between 20° and 160°, or crosses it as an X, which adds a second arm at φ + 180°. A branch angle of 90° is a square T-junction.
How are the centreline lead-on and lead-off curves built?
For a turn of δ at radius R, the tangent length is T = R × tan(δ/2) and the arc length is R × δ. The curve leaves the branch centreline at distance T from the centre and meets Taxiway A tangentially. Taxiway A and the branch centreline are split at the tangent points so a fixture always lands on each one.
How are edge lights placed around the fillets?
Each corner is rounded by a fillet, with tangent length l = r ÷ tan(β/2) and light-line radius equal to the pavement fillet radius minus the edge-light offset. Edge lights run along Taxiway A to the tangent point, round the fillet, then continue out along the arm. Nothing is lit across the mouth of the junction.
How are stop bars generated?
The bar crosses Taxiway B square to its axis at the holding-position distance, edge to edge, with N = ⌈W_B ÷ S⌉ intervals and N + 1 lights. The holding-position distance is taken from the approved layout, not derived from the standard. The tool warns if the bar sits inside the fillet flare or inside a lead-off tangent length.
How does duplicate-fixture control work?
Runs are generated in a fixed order. A new fixture within the duplicate tolerance (1 m by default) of an already placed fixture of the same colour is dropped and logged. This removes the doubled light where a lead-off curve joins Taxiway A or the branch centreline. Fixtures of different colours are never merged.
Which spacing limits are pre-filled?
Edge lights: ICAO 60 m, FAA 200 ft. Centreline: ICAO 30 m (15 m below 350 m RVR), FAA 100 ft (50 ft below 1,200 ft RVR). Stop bars: ICAO up to 3 m, FAA 10 ft. These are editable defaults. The centreline curve maximum is filled in from each standard’s radius table when you leave it blank: ICAO 7.5 m up to 400 m radius, FAA 25 ft under 400 ft radius (12.5 ft below 1,200 ft RVR). Fillet edge spacing depends on radius, so confirm it against the standard and the approved project layout.
What does the calculator not do?
It does not decide which route carries the through centreline, apply the rules on clearance bars, lead-on lights at runway entries or enhanced centreline, or place intermediate holding position lights, elevated stop-bar lights, signs or markings. The result is a calculated, nominal layout for design planning, not an issued drawing or a final bill of quantities.
Related Knowledge Hub Resources
Taxiway Centreline
Centreline spacing and quantity.
Taxiway Edge Spacing
Edge-light spacing and quantity.
Taxiway Layout Generator
Plan-view taxiway lighting layout.
Stop Bar Lights
Holding position stop bars.
Lighting Load
kW and kVA by circuit.
BOQ Generator
Turn quantities into a BOQ.
AGL Toolkit
Back to all calculators.
Standards Companion
ICAO/FAA/IEC requirements explained.