Taxi Guidance Light

A Taxi Guidance Light is a comprehensive taxiway lighting system that provides pilots with clear, intuitive directional guidance through complex airport ground movement routes. Taxi guidance lights integrate multiple light types and colours to create a seamless visual path from the runway to the gate and back. The system typically includes edge lights (blue), centreline lights (green), lead-on/lead-off lights, stop bars (red), clearance bars (yellow/amber), and curve lights. Together, these lights provide a complete visual language that guides pilots safely and efficiently through the airfield.

The purpose of a taxi guidance light system, taken as a whole, is to remove ambiguity from the entire journey between runway and gate by giving every decision point — go straight, stop, hold, turn, exit — its own distinct and internationally recognised visual signal. A pilot taxiing at night or in fog cannot rely on markings painted on the pavement alone, so the system substitutes a continuous chain of colour-coded light cues that can be trusted to mean the same thing at every airport that follows ICAO conventions.

This matters most at the points where a mistake has the highest consequence: crossing an active runway, entering a holding area, or choosing the wrong branch at a complex intersection. By combining edge, centreline, stop bar, clearance bar, and curve lighting into one coherent visual language, the system lets a pilot's attention move fluidly along the route without needing to stop and re-orient at each new light type.

Taxi guidance lights are used on all taxiways and apron areas that support night and low visibility operations. They are used on:

• All taxiways requiring visual guidance for ground movement
• Precision taxiways at major international airports
• Complex taxiway intersections requiring multiple guidance cues
• Apron areas where aircraft manoeuvre between gates
• Low visibility operations where enhanced guidance is essential
• Military airfields requiring comprehensive ground movement guidance

As a general term covering the taxiway centreline, edge, and stop bar fixtures described in their own entries, taxi guidance lighting as a whole is installed using whichever mounting convention suits the specific fixture and location: inset base cans recessed into paved taxiway and apron surfaces for centreline and stop bar lights, and elevated frangible-mount fixtures along unpaved shoulders for edge lighting. All fixture types are set out from the taxiway centreline and marking survey, fed by armoured cable back to their isolating transformers, and tied into the taxiway lighting series circuit (with independently switched fixtures such as stop bars wired on their own control cable in addition).

Taxi guidance lights operate as an integrated system using multiple light types and colours:

• Edge Lights (Blue): Define the lateral limits of the taxiway, providing pilots with a clear indication of the taxiway boundaries.
• Centreline Lights (Green): Provide precise directional guidance along the centre of the taxiway.
• Lead-on/Lead-off Lights: Guide pilots onto and off the runway, providing smooth transitions.
• Stop Bars (Red): Indicate when it is unsafe to proceed onto the runway.
• Clearance Bars (Yellow/Amber): Three steady-burning in-pavement yellow lights marking a holding position or intersecting taxiway, increasing its conspicuity in low visibility rather than signalling clearance to proceed.
• Curve Lights: Provide enhanced guidance at taxiway curves and intersections.

Taxi guidance is not a single circuit but a coordinated set of them, all commanded by the ALCMS — increasingly working with an Advanced Surface Movement Guidance and Control System (A-SMGCS) for "Follow the Greens" routing. Continuously-lit elements — taxiway edge and centreline lights — run on constant current series loops in the same manner as runway edge lights: a CCR sets one brightness step for an entire loop, and every fixture on it switches and dims together. Selectively-switched elements — stop bars, clearance bars, and lead-on/lead-off lights — are wired so individual sections can be commanded independently, since their whole function is to change with each aircraft's specific route and hold instructions rather than stay uniform. In an A-SMGCS installation, the route-planning system computes the active taxi path and switches on only the centreline segments for that route, extinguishing them section-by-section behind the aircraft as it progresses, while interlocking each stop bar with its paired lead-on lights so the two are never both cleared to proceed at once. Fault reporting mirrors this split: loop faults on the continuous circuits are flagged at the CCR by voltage-rise detection, while individually-switched segments report failure to illuminate or failure to extinguish as discrete faults tied to that specific segment.

Across the edge, centreline, stop bar, clearance bar, and lead-on/lead-off fixtures that make up the guidance system, the fixture body is typically a die-cast aluminium alloy housing, machined and anodised or powder-coated for corrosion resistance against runway de-icing fluids, fuel spillage, and UV exposure. A toughened prismatic lens, coloured to match each fixture's role in the system (blue, green, red, or yellow/amber), caps the optical assembly and is gasket-sealed to the housing with an O-ring or silicone seal to achieve an IP67/IP68 rating against water and dust ingress. Elevated units bolt to a frangible coupling engineered to shear cleanly under aircraft impact loads, seating on a base can set flush with the surrounding grade; inset (flush) units instead seat directly into a base can recessed into the pavement, with the top surface load-rated for aircraft wheel loading. Internal wiring for each fixture terminates at L-823 primary connectors, sealed splice connectors rated for direct burial and continuous immersion, which mate to the secondary leads of the isolating transformer housed in its own base can nearby. Stainless-steel fasteners are used throughout to resist corrosion, and each base can assembly includes a drainage provision to prevent water pooling around the transformer and cable entry points.