Cable Enclosure Theory
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Traffic & Loading
When selecting an enclosure type, designers and end users must determine if the enclosure will be placed in a trafficable application; whether the traffic is deliberate (e.g. along a driveway) or accidental (e.g. along a footpath); and whether the traffic is of a vehicular or pedestrian nature. In addition to this, consideration must be given to ground topography, soil conditions, and building location.

Pits positioned along a long cable route can typically cross various types of load scenarios. Each pit location should be individually considered.

Non Vehicular Pavements

Enclosures located in footpaths are generally exposed to a high volume of pedestrian traffic but can also be subjected to non deliberate vehicular loads. Good practice requires that enclosures are selected so that only a minimal surface area of a footpath space is occupied, particularly along cycleways, pedestrian alignments, wheelchair access paths or ramps. It is also recommended that cable pits are located outside the‘drip lines’ of footpath vegetation.

Landscaped Areas
Enclosures installed in landscaped areas are generally exposed only to pedestrian traffic. Plastic pits are ideal for this application as long as the sand or soil is stable and vehicles in close proximity to them do not surcharge the soil and introduce side loads to each pit.

Designers must also aim to locate cable enclosures at high points along a terrain so that they do not become significant drainage collection points.

Vehicular Pavements
Cable enclosures located in rigid pavements (e.g. vehicle paths, driveways, cycleways, ramps) are generally subjected to deliberate vehicular traffic. Pit bodies need to be strong enough to support the traffic rated covers bearing the loads and be encased in cement concrete (base and surround). ACO does not recommend the use of plastic pits in these applications.

For these applications, AS/NZS 3084 specifies minimum distances for access holes with respect to each other, roadway corners and other highly trafficked zones.

Unless enclosures are designed for heavy duty applications, they must not be placed in locations where heavy loading is anticipated. Guards or barriers that prevent entry of this type of traffic are recommended. If a heavy duty cable pit is required or where constant deliberate vehicular traffic is anticipated, ACO recommends Rhinocast®, ductile iron access covers to be installed in the slab/ pavement above the enclosure or ACO’s CS System, if surface cable ducting is required.

Designers should avoid locating cable pits in fast moving road applications unless certified by a qualified engineer and approved by the relevant roads authority. Austroads document: AP-G72 provides further guidelines for cable pits and access holes to be located on or near urban or rural roads.

Load Standards
There is no Australian standard that tests for cable pit strengths. AS/ACIF S008 provides basic performance criteria for communications pits and specific telecommunications carriers have their own criteria.

To give designers, installers and users assistance in selecting the correct enclosure, the table below is based on loadings outlined in AS 3996 (Access Covers & Grates). This is cross referenced with international standards, EN 124 and EN 1433, the latter, best suited for surface cable ducting.

ACO has gained NATA accreditation (No. 15193) for its testing laboratory and can provide NATA certified test reports for load tests set out in AS 3996, EN 124 and EN 1433.


NATA accreditation

Load Standards table load classes table

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