Taxiway Centreline Light

A Taxiway Centreline Light is a critical guidance system installed along the centreline of taxiways to provide pilots with precise directional guidance during ground movement. These lights emit a steady green light, distinguishing them from taxiway edge lights (blue) and providing a clear path for aircraft to follow between runways, aprons, and terminals. Taxiway centreline lights are typically flush-mounted (inset) in the pavement and are essential for low visibility operations, complex taxiway layouts, and busy airports where precise ground navigation is crucial.

A taxiway centreline light's purpose is to give a pilot a single, precise track to follow down the middle of the taxiway, rather than requiring them to judge their position relative to two edge lines on either side — a much higher-precision task, especially where the taxiway is narrow, curved, or shared with other aircraft. Because the light sits exactly on the path the nose and body of the aircraft should follow, it also supports the tighter wingtip clearances of a busy ramp or narrow taxiway, where straying even slightly off track carries real collision risk.

The steady green colour is chosen specifically to be unmistakable against the taxiway edge lights' blue, so a pilot can distinguish 'the path to follow' from 'the limit not to cross' at a glance — a distinction that becomes essential in low visibility conditions where the two light types might otherwise blur together into a single band of light.

Taxiway centreline lights are installed on precision taxiways and busy airports where enhanced ground guidance is required. They are used on:

• Precision taxiways at major international airports
• Complex taxiway intersections where accurate navigation is critical
• Low visibility operations (CAT II/III) requiring enhanced guidance
• Rapid exit taxiways where precise alignment is essential
• Apron taxi lanes connecting gates to taxiways
• Military airfields requiring precise ground movement guidance

Fixtures are recessed into a saw-cut or cored pocket along the taxiway centreline marking, using the standard load-rated inset base can set flush with the pavement surface so the fixture carries full aircraft wheel loads without protruding. Standard spacing is 30 m on straight sections, tightening to as little as 7.5–15 m through curves so the row reads as a continuous guide line to the pilot. Cabling is run in duct beneath the pavement from each base can back to its isolating transformer and on to the taxiway centreline series circuit, with fixture position checked against pavement slab joints during setting-out so no base can straddles a joint or crack.

Taxiway centreline lights operate using standard AGL principles:

• Power: Powered from the constant current series circuit via an isolating transformer (typically 45W – 65W).
• Light Source: Utilizes green LED arrays or green-filtered halogen lamps. The distinctive green colour is universally recognized as a taxiway centreline indicator.
• Beam Pattern: Projects a uni-directional or bi-directional beam pattern along the taxiway centreline, visible to pilots from both directions.
• Intensity Control: CCR-controlled intensity with 3 to 5 steps, allowing adjustment for varying visibility conditions.

Taxiway centreline lights are not individually addressable — control is exercised at the loop level through the constant current series circuit. An Airfield Lighting Control and Monitoring System (ALCMS), operated by the tower or ground movement control, selects the required brightness step based on prevailing visibility, ATC instruction, or traffic density on the taxiway network. This command is passed to the CCR, which regulates the entire loop to the corresponding fixed current (one of 3 to 5 steps). Every fixture on that loop, via its own isolating transformer, draws from the same current and therefore burns at the same intensity simultaneously — there is no way to dim or brighten a single fixture independently of the rest of the circuit, and the green colour itself is fixed by the lens/LED, not by control logic. Fault detection is likewise loop-based: the CCR continuously monitors loop voltage against the commanded current, and a voltage rise at constant current signals increased circuit impedance, typically an open-circuit lamp or a failed isolating transformer, which is reported to the ALCMS as a loop fault rather than pinpointed to an exact fixture without further sectionalised testing.

The fixture body is a low-profile die-cast aluminium housing designed to sit flush with the pavement surface, machined and anodised or powder-coated to resist runway de-icing fluids, fuel spillage, and UV degradation. A toughened, prismatic green lens caps the housing, gasket-sealed with an O-ring or silicone seal to achieve an IP67/IP68 rating against water and dust ingress. The unit seats into an L-852 base can recessed into the pavement, with the top surface load-rated for repeated aircraft wheel loading and designed to shed water away from the lens and cable entry points. Internal wiring 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 the lens-to-housing seal is periodically inspected to guard against moisture ingress under sustained wheel-load flexing.