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Runway Guard and Status Lights
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| Article Information | ||
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| Category: | Runway Incursion | 
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| Content source: | SKYbrary | 
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| Content control: | EUROCONTROL | 
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Contents |
Description
Improving the awareness of both flight crew and vehicle drivers of the entrance points to active runways, continues to be a major feature of attempts to reduce runway incursions. In addition to this, various enhancements to prior awareness of conflicting runway occupancy, in the form of controllable visual annunciations, are being developed and deployed. This is especially so at airports where either the traffic density, or the configuration of the movement area, or both are conducive to a high risk of conflicting runway occupancy.
Runway Guard Lights (RGLs)
RGLs are the first line of defence against an unintended incursion of an active runway by an aircraft or vehicle. They serve to raise situational awareness but do not provide or preclude authority to pass. The term was formally introduced by ICAO in 1995 when introducing a new Standard for what had previously been a Recommended Practice for installation of ‘taxi-holding position lights’. In their basic form, they consist of a pair of unidirectional yellow lights which flash continuously. They are positioned at each side of a taxiway at the marked and signed Holding Point where the taxiway is about to join a runway; both aircraft and vehicles are required to wait at this point until given clearance by ATC to proceed. They are sometimes colloquially referred to as ‘wig-wags’. The lights are required to have equal intervals lit and unlit and to flash at between 30 and 60 cycles per minute. They must be in operation whenever RVR is less than 1200 metres and must be switched independently of any stop bar lights (see below). They are often elevated, but this is not a requirement.
The current version of ICAO Annex 14 also requires that where a taxiway, which is used in low visibility conditions, has a ‘wide throat’ as it nears a runway intersection and a stop bar is not installed but additional conspicuity is required, an alternative RGL may be used. This consists of a row of unidirectional yellow lights in line at 3 metre intervals across the taxiway at the Holding Point, inset into the pavement. Adjacent lights must be alternately illuminated and alternate lights should illuminate in unison.
Stop Bars
Lighted and remotely selectable Stop Bars are provided where LVP operations occur and may also be provided at fixed low intensity for night operations. A Stop Bar consists of a row of unidirectional lights embedded in the pavement and spaced equally across the taxiway at the associated holding point, normally at right angles to the centerline. They show red towards an approaching aircraft when lit. Stop Bars are sometimes installed in association with green Lead-on Lights which are a continuation of the taxiway centreline lighting beyond the Stop Bar. The Lead-on Lights are interlinked with the Stop Bar so that when the Stop Bar is red, the green centreline beyond the Stop Bar is unlit and vice versa.
Runway Status Lights
Additional alerting to specific runway occupancy conflict has been developed in recent years ahead of any Regulatory action. Whilst various versions exist, all are designed to be intuitive in their activation even to visiting flight crew who may be unfamiliar with them. Most of them are linked to the introduction of automated remote sensing of aircraft and vehicle ground position which have recently become much moré widespread. This sensing is required to facilitate the higher levels of A-SMGCS, of which the ASDE-X systems being deployed in the USA are an example. The sensed information is then used to automatically activate alerting systems on the movement area (and in some cases beyond it as, for example in the FAROS system found in the USA) using appropriate data feeds.
In the USA, where the term Runway Status Lights (RWSL) is most prevalent, it refers to lights which are automatically activated based upon the remotely detected position of aircraft and vehicles. It includes two different automated lighting systems: Runway Entrance Lights (RELs) and ‘Take-Off Hold lights’ (THLs). More information can be found at RWSL website.
Runway Entrance Lights (RELs)
RELs are also a recent development not subject to any international standard and are most likely to be found in the USA as part of A-SMGCS developments there. They are intended to warn pilots approaching the runway holding point area that another aircraft is in the course of either landing (within 0.75 NM of the landing threshold) or departing on the same runway and currently located prior to the imminent runway intersection and detected at a speed higher than 20 knots. They consist of a line of red in-pavement lights installed longitudinally and immediately adjacent to the marked taxiway centerline. The line begins just prior to the marked Holding Point and continues to the runway edge after which one additional REL is installed near the runway centerline in line with the last two lights on the taxiway. The longitudinal spacing for the lights is such that, typically, 3 to 4 lights are positioned between the hold line and the runway edge.
Take Off Hold Lights (THLs)
These are intended to warn pilots who are about to begin a take-off that another aircraft is on their runway or is predicted to enter it. As currently being installed, they consist of a line of in-pavement red lights parallel and immediately adjacent to the runway centreline. They extend from the first entry point in the direction of take off until after the last one, so that an aircraft lining up from it would be able to see a sufficient indication ahead to attract their attention.
Take off Hold Lights from above:
Pilot view of Take off Hold Lights:
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Further Reading
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