Environment and roads

Preventing light pollution

Careful consideration at the design planning stage can ensure that the task can be achieved while controlling light pollution. The first question has to be “do I need to light it?” If this is the case then the design must ensure that only the necessary amount of light is provided for the required task and that it is properly controlled to avoid light pollution.

National guidance

The Institution of Lighting Engineers has published a document “Guidance notes for the reduction of light pollution” which establishes four Environmental Zones. Each of these has a different approach to the provision of external lighting. These zones establish ‘Obtrusive Lighting Limitations for External Lighting Installations’ and include the effects of ‘Sky Glow’ and light into windows. The document also includes ‘source intensity’, the potentially obtrusive direction of light outside the area being lit.

The four environmental zones are defined as follows: -

E1 “National parks”, “areas of outstanding beauty” or other “dark landscapes”

E2 Areas of “low district brightness” (e.g. in a rural location but outside a zone E1);

E3 Areas of “medium district brightness” (e.g. in an urban locations);

E4 Areas of “high district brightness” (e.g. in an urban centre with high night-time activity).

Concern over light pollution is comparatively recent but growing. Hertfordshire County Council appreciates that there are many bad examples of lighting installations with poor optical control. However it is recognised that where this relates to highways that this lighting was installed sometime ago. Most modern highway lighting units have improved design and optics although this is not generally the case with most post top lanterns. It will however take some time to address the old installations and therefore reduce the sky glow seen over may towns.