Street Lighting – Understanding some of the terminology.

As with all industries, there are always lots of technical terms to reference different processes and also the different items that we commonly use in the field of street lighting. This simple post sets out a few of the more commonly used references and explains them in their simplest terms.

MF – Maintenance Factor.
When carrying out street lighting design calculations, we apply a Maintenance Factor as a correction factor. The correction factor takes into account the depreciation of the lamp lumen output over time and the build-up of dirt on the luminaire.

DNO – Distribution Network Operator
A Distribution Network Operator is a company licensed to distribute electricity in the UK. These companies own and operate the system of cables and towers that bring electricity from the national transmission network to homes and to items of street furniture. In a high percentage of cases street lighting columns owned by the local authorities across the country have DNO electricity cables, these are fed off a mains DNO low voltage cable normally running in the highway.

PCN – Private Cable Network
Private Cable street lighting Networks can be designed for situations where DNO’s cannot supply mains cables across a given area. If a feeder pillar can be supplied at the edge of a development site for example, then a PCN can be designed to supply electricity to lamp columns on the site. Private cables can also be fed from DNO fed lamp columns to illuminated signs and bollards, some local authorities insist on this approach on their networks. We have an experienced team of designers who can carry out private cable lighting designs within street lighting projects.

S/P Ratio – Scotopic/Photopic Ratio.
This is another correction factor applied to street lighting designs and is a calculation of the Scotopic lumens the lamp produces divided by the Photopic lumens.

Conflict Area
As detailed in the Institute of Lighting Professionals PLG02 document and BS5489:2003, the definition of a conflict area is as follows “Conflict areas are typically junctions, intersections, roundabouts and pedestrian crossings, where significant streams of motorised intersect each other, or, with other road users such as cyclists”.

CMS – Central Management System
A specifically developed piece of asset management software, which allows users to remotely monitor and control, lighting systems and apply dimming or switching controls and regimes.

Lux – Luminous Flux
This is the quantity of light (luminous flux) falling on an area of a surface. In some instances you will see this figure represented by the symbol E.

The lumen output from a light source demonstrates the power emitted by the specific source.

PECU – Photo-electric Control Unit
Device that comprises a photoelectric sensor that responds to variations in illuminance combined with a means of switching an electric load.

NEMA Socket
A receptacle, into which a one-part PECU can be inserted.

UMS – Unmetered Supply
Any electronic equipment that has an incoming electricity supply from the local DNO, where energy consumed is not measured by a meter.

Charge Code
A Charge code is a 13 digit number assigned to apparatus that UMS Customers wish to add to their inventories. Charge codes are used within the UMSO systems to calculate volumes of electricity consumed.

The above are just a snap shot of some of the more frequently used abbreviations and descriptions used in lighting industry. We hope to put add more to this list and build it up over time into a ‘one stop shop’ for lighting terminology – watch this space!

Additional websites and reference documents that may be of assistance when dealing with ecological sensitive sites are detailed below:-

If you would like to discuss your street lighting design project or development site with us, then please feel free to give us a call on 0118 321 5636. We will be more than happy to talk through the best lighting design approach and hopefully work with you to assist in gaining full planning permission and discharging your planning condition. Alternatively please send your enquiry to and we will get back to you as quickly as we possibly can.