What are closed taxiway and unserviceability lighting?
When part of the movement area cannot be used, the lighting has to say so. A closed taxiway goes dark and is marked, and an area aircraft must avoid is outlined with fixed red lights.
A closed taxiway must not be used by any aircraft. An unserviceable area is only part of the surface that is unfit, and aircraft can still go around it. The two are shown differently, and the lighting is what stops a night-time pilot from being led into either one.
1Closed: mark it and switch it off
A closed taxiway is shown with a closed marking, a cross which is yellow on a taxiway, at least at each end of the closed part. Its edge and centreline lights are not lit, except when needed for maintenance. A lit green line would look like a usable route and could draw an aircraft in.
2Unserviceability lights outline the problem
Unserviceability lights are fixed red lights. They go across the entrance of a closed taxiway that opens off a lit taxiway, and round a part of the movement area that is unfit but can be bypassed. Across the entrance of a closed taxiway they are placed not more than 3 m apart, where a usable runway or taxiway used at night meets it. Elsewhere they are spaced close enough to read as one boundary, and bright enough to be conspicuous against nearby lights.
3Closed and unserviceable need different cues
On a closed taxiway the message is do not enter, so the route goes dark and a marking is shown. On an unserviceable area the message is keep clear of this spot, so the taxiway around it stays lit and the red lights fence off only the bad area. By day, cones, flags or boards do the same job.
4Keeping the lights true
Unserviceability lights are often portable battery or solar units or run from a separate supply, because works move. A failed red light leaves a hazard unmarked, so they are checked often. When the closed section's lights are switched off it is isolated like any other circuit, and when the taxiway reopens the red lights come out and the lights are tested before release.
| Situation | Lights | Marking or marker | Why |
|---|---|---|---|
| Whole taxiway closed | Edge and centreline off | Yellow closed marking | Nothing leads an aircraft in |
| Closed branch off a lit taxiway | Fixed red across the entrance, not more than 3 m apart | Closed marking beyond | Turns away aircraft on the lit route |
| Part unfit, bypass possible | Fixed red round the area | Cones, flags or boards by day | Shows where not to go, route stays open |
| Back in service | Red lights removed, circuit tested | Marking removed | Reopen only when checked and published |
Frequently Asked Questions
Q1What is an unserviceability light?
It is a fixed red light placed to mark part of a taxiway, apron or other movement area that is unfit for aircraft. It is used where aircraft can still bypass the area, and at the entrance to a closed taxiway that leads off a lit taxiway.
Q2Are the lights on a closed taxiway left on?
Normally no. Lights on a closed taxiway or part of one are switched off, except when they are needed for maintenance. A lit green centreline or blue edge would look like a usable route and could draw an aircraft in.
Q3Why are unserviceability lights red and fixed?
Red is the colour of danger and prohibition on the movement area, and it stands apart from the blue edge and green centreline lights. They are steady, not flashing, so they read as a boundary rather than as a signal that changes.
Q4What is the difference between closed and unserviceable?
A closed taxiway must not be used by any aircraft and is shown with a closed marking. An unserviceable area is only a part of the surface that is unfit, and aircraft can still pass around it, so it is outlined with red lights or markers instead.
Q5Can unserviceability lights be portable?
Yes. They are often battery or solar powered units, or are fed from a separate supply, because the work area keeps changing. Whatever the source, they must be checked regularly, since a failed red light leaves the hazard unmarked at night.
Q6Who decides that a taxiway is closed?
The aerodrome operator, with air traffic control. The closure is published, for example by NOTAM, and the airfield electrical team then switches off the closed lights and sets out the markings and unserviceability lights as the procedure requires.
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