Rapid Exit Taxiway Indicator

A Rapid Exit Taxiway Indicator Light (RETIL) system is a set of fixed, unidirectional yellow lights installed on the runway itself, on the same side of the centreline as an upcoming rapid exit taxiway, that count down the distance remaining to that exit. RETIL consists of six yellow lights arranged in a three-two-one sequence spaced 100 metres apart, with the single light positioned 100 metres before the start of the exit turn. Rapid exit taxiways are typically angled at 25° to 45° to the runway centreline, allowing aircraft to exit the runway at higher speeds than standard 90° exits. RETIL gives a landing pilot an unambiguous, low-visibility-proof cue of how much runway remains before the exit, improving runway occupancy time and overall airport capacity.

RETIL exists to give a landing pilot a precise, count-down cue of the distance remaining to a rapid exit, without asking them to judge the position of an angled, hard-to-see taxiway junction visually during rollout. Because the shallow exit angle is geometrically harder to spot in time than a perpendicular one, especially at night or in low-visibility conditions (RETIL is specifically recommended where RVR is below 350 m or traffic density is high), the three-two-one light sequence lets the pilot judge exactly how much runway is left before deciding whether — and at what deceleration rate — to make the turn. This directly shortens the time an aircraft occupies the runway after landing, which is the practical purpose behind the system: reducing runway occupancy time increases the number of landings an airport can safely handle in a given period, making RETIL as much a capacity tool as a safety one.

Rapid exit taxiway indicators are installed on precision approach runways at busy airports where efficient runway clearance is critical. They are used on:

• Precision approach runways (CAT II and III) with high traffic volumes
• Major international airports where runway capacity is a constraint
• Rapid exit taxiway intersections where high-speed exits are provided
• Runways with multiple rapid exit points for efficient aircraft flow
• Low visibility operations where clear guidance is essential

RETIL fixtures are installed on the runway pavement, not on the taxiway — on the same side of the runway centreline as the associated rapid exit, upstream of the physical divergence point. The six lights are set out in the fixed three-two-one arrangement, spaced 100 metres apart, with the single light 100 metres before the start of the exit turn, so the array reads the same way at every exit regardless of that exit's own curve radius or divergence angle. Cabling runs in pavement ducting back to the runway lighting series circuit that already serves that section of runway (typically the runway centreline or edge circuit), sharing its isolating transformers and CCR rather than needing a dedicated feed. Setting-out is tied to the runway centreline survey and the exit's start-of-turn point, since the whole point of the fixed 100 m spacing is that it stays consistent airport-wide rather than varying with the individual exit's geometry.

RETIL operates as a fixed-pattern, distance-to-go cue rather than a continuously guiding system:

• Identification: Six fixed, unidirectional yellow lights on the runway pavement, aligned to be visible to a landing aircraft, mark the approach to a specific rapid exit.
• Count-down Indication: The lights appear in groups of three, two, and one as the aircraft moves down the runway — 300 m, 200 m, and 100 m before the start of the exit turn respectively — giving the pilot a simple visual count-down.
• Decision Cue: Seeing the reducing groups lets the pilot judge deceleration and confirm they will reach taxiing speed in time to make the turn onto the rapid exit.
• Hand-off: Once the aircraft turns off the runway, guidance continues from the taxiway centreline lights and lead-off lights on the exit taxiway itself, which RETIL does not control.

RETIL is not a stand-alone controlled system — electrically, each of the six lights is simply another branch fixture on whichever runway series circuit already covers that section of runway (normally the runway centreline or edge lighting circuit), stepped in brightness by the same CCR and, where fitted, reported through the same ALCMS loop. There is no separate RETIL controller, no independent intensity schedule, and no sign component: all six lights share the runway circuit's current step, so they brighten and dim together with the rest of that circuit's fixtures under low-visibility procedures. This matters for fault-finding: a RETIL light going dark while the rest of the runway circuit stays lit points to a fixture-level fault (LED array, isolating transformer, or connector) rather than a loop-wide problem, while a full-loop fault takes down RETIL along with every other fixture on that circuit. Downstream of the exit itself, guidance responsibility passes to the taxiway centreline and lead-off lights, which are separate fixtures on the taxiway's own circuit.

Each RETIL light is built as a low-profile, inset (flush) fixture that seats into an L-868 base can recessed into the runway pavement, with the top surface load-rated to withstand repeated aircraft wheel loading during landing rollout. The housing is a die-cast aluminium alloy body, anodised or powder-coated to resist de-icing fluid, fuel spillage, and abrasion from tyre contact. A high-strength polycarbonate or borosilicate glass lens covers the LED array, gasket-sealed to the housing with an O-ring to achieve an IP67/IP68 rating against water and dust ingress. Internal wiring terminates at L-823 primary connectors, which mate to the secondary leads of the isolating transformer housed in an adjacent base can. Stainless-steel fasteners are used throughout, and the base can assembly includes a drainage provision so water does not pool around the transformer and cable entry points beneath the pavement surface.