Street lights are a common sight to the majority of the worlds population, yet who plans where they go and how far apart should they be?
The short answer is; it depends. The majority of street lights and their locations are planned by the local authority - this is seen on major improvement works and replacement schemes. When new roads are being constructed the lights are typically designed by an external consultant and the authority will check and approve the design ensuring it meets their requirements.
In terms of how far apart they will be, is influenced by many factors; these factors include:
Road geometry:
Typically the wider the road width the closer together the street lights will be. This is because the required light spread is greater.
Column heights:
Dependent upon the road type (minor residential / main A road etc.) the column heights will be different. We usually see 8m and above column heights for main roads and 6m and below for residential streets. The higher the column the greater the spread of light and the further apart the lights can be placed (in theory).
Lighting class:
Each road will have a lighting class allocated by a lighting engineer (from the authority or a consultant). This class will be selected through criteria set out within the BS5489 and EN13201 standards. Lighting classes will vary based on road speed / user / usage / crime rates / environmental zone.
Specification:
The street lighting heads (lanterns) vary in performance and with the advancement of LEDs and optics, each lantern can have numerous variations available. The optics play an important role and allow the lighting designer to adjust and tweak the light spread to suit the area being lit and select the most economical solution.
So how far apart?
You are likely to see street lights spaced approx. 30m to 50m apart - they are often spaced closer at junctions and on bends.
Regards
Peter