What is a cable crossing?
Where an AGL cable has to cross a runway, taxiway or another service — through ducts beneath the pavement, with spare ducts and handholes, so it can be replaced without cutting the surface again.
A cable crossing is a place where an AGL cable has to cross something in its path: a runway, taxiway or road, a drain, or another buried service. Across a pavement the cable goes through ducts beneath the surface, normally encased as a duct bank, with a handhole or manhole on each side for pulling, slack, splicing and testing.
The key feature is the spare ducts: with them, a failed cable can be replaced, or a new circuit added, by pulling cable through an existing duct, so the pavement never has to be cut again. Where an AGL cable crosses another service it does so at right angles, with the separation the design and the standard require. Record every crossing on the as-built drawings, and treat the cable as live until the circuit has been isolated, locked out and proved dead.
- Plan. Locate the crossing and the handholes either side from the design.
- Install ducts. Lay the duct bank beneath the pavement, with spare ducts, before the surface is finished.
- Prove. Check the ducts are clear and continuous.
- Pull the cable. Pull through the chosen duct and leave slack in each handhole.
- Seal & protect. Seal duct ends as the design requires and close the handholes.
- Test & record. Test the circuit and mark the crossing and spare ducts on the as-builts.
Frequently Asked Questions
Q1What is a cable crossing in airfield ground lighting?
A cable crossing is a place where an AGL cable has to cross something in its path, most often a runway, taxiway or road, but also a drain or another buried service. It is built so the cable is protected and can be replaced without disturbing what it crosses.
Q2How are runways and taxiways crossed?
In ducts installed beneath the pavement, normally encased as a duct bank, with spare ducts. The cable is pulled through one duct from a handhole or manhole on one side to the other, so it never has to be cut into the pavement.
Q3Why are spare ducts installed?
Cutting a trench across an active pavement is slow, costly and disruptive. Spare ducts mean a failed cable can be replaced, or a new circuit added, by pulling cable through an existing duct instead of breaking the pavement again.
Q4Why are there handholes on each side of a crossing?
They give access to pull the cable through the duct and to splice, test and trace it, and they hold the slack that lets the cable move or be replaced. They are placed clear of the pavement so work there does not need the pavement closed.
Q5How should AGL cables cross other buried services?
Normally at right angles, with the separation the design and the applicable standard require, and with protection where that separation cannot be achieved. Crossings are marked on the as-built drawings so other work can avoid them.
Q6How is a crossing checked and recorded?
The ducts are proved clear before use, the cable is tested for continuity and insulation resistance once pulled in, and the crossing, duct usage and spare ducts are recorded on the as-built drawings.
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