Nuisance provisions of the Public Health etc (Scotland) Act 2008: guidance

SECTION 6 - STREETLIGHTING

BEST PRACTICE GUIDANCE ON STREETLIGHTING

Requirements

Streetlights are generally operated throughout the hours of darkness as a service to the residents and road users of the area. The principle role is to promote safe movement of traffic and providing for the security to people and property.

Road lighting is designed to create an even luminance on the road surface as it is seen by the motorist; other details of forms and textures are unimportant. Pedestrians are more concerned with identifying local landmarks and negotiating the correct route.

Design Characteristics

Road lighting schemes are generally designed using British Standard BS 5489. The standard is split into ten codes of practice that cover the principal different categories of lighting schemes. The design process involves careful consideration of the specific locations for lighting columns to give the best distribution of light. For example, on straight roads a staggered arrangement will produce an optimal effect, but on curves the luminaires are placed on the outside of the curve to ensure reflection off the road surface and at T-junctions a column is always positioned opposite the minor road approach.

Lighting is normally required at at-grade roundabouts for reasons of safety. It concludes that a reduction in lighting at isolated junctions is unlikely to affect road safety but would result in less overall environmental intrusion.

In general local highways authorities use high pressure sodium lamps with flat glass horizontal cut-off ( HCO) luminaires for new rural road and junction lighting schemes. Columns are usually 10-12m high, with 8m high columns sometimes being preferred at isolated locations. Individual lamp light outputs normally vary between 12,000 and 50,000 lumens. Non- HCO low pressure sodium luminaires may require fewer columns and be more energy efficient, but high pressure sodium luminaires normally have a lower whole life cost if the columns are over 8m high and may therefore be preferred. Most road lamps are installed in fixed angle luminaires, whose main beams of light radiate out, up and down the road at between 60 and 75 degrees to the downward vertical. There is normally no need for any light to radiate above the horizontal and it is becoming more common to stipulate that luminaires have a full HCO.

Lighting installations for pedestrian pathways are normally scaled down versions of the above, although many use more decorative luminaires. Mounting heights are usually between 4-6m and light outputs vary between 3,000-6,000 lumens.

Controls

1. The simple use of front and/or back shields can improve illumination on the road whilst reducing intrusion elsewhere.

2. As most street lighting is alight throughout the night, the obtrusive light levels to be adhered to should be those given for all night, i.e. after curfew.

3. In addition, the Scottish Government's 'Lighting in the Countryside: Towards good practice' includes street lighting, and is applicable to towns as well as country.

4. Reduce the number of columns to a minimum - a single column may be sufficient on many small roundabouts;

5. Consider colour of lighting columns in relation to surrounding landscape, ie use a dark colour if the columns are set against backdrop of vegetation;

6. Give priority to the use of high pressure sodium lights which give some degree of colour rendition, and to the use of luminaires with full horizontal cut-off, wherever a lit junction is necessary;

7. Carry out a visual appraisal and design lighting scheme to minimise visual intrusion of light at night and of structures by day.