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Exterior Lighting

2005-02-28
Lighting should always be designed to fulfil a specific purpose; efficient, effective lighting installations provide sufficient light for the task in hand without impinging on surrounding areas. Over the years, lighting products have been developed to secure property, to allow people and vehicles to move safely at junctions and in residential areas and to extend the period during which people can work or enjoy leisure activities out-of-doors during the winter months. Lighting equipment has also been developed for advertising commercial premises such as pubs and petrol filling stations and, in a more subtle vein, for enhancing the amenity value of important buildings and historic settlements.

The following articles describe the standards, lighting apparatus and specific procedures for designing the principal types of lighting found in rural and residential areas.

Security Lighting

Security lighting may be designed to illuminate a site area or building for all to see, creating a direct visual deterrent to criminals, or it may consist of a passive infra red or other ‘presence detection system’ which only switches on when someone invades a selected space. Both systems have their place and neither should cause light pollution provided they are carefully designed, correctly installed and well maintained.

Lighting of Roads and Pathways

The principal objective in designing lighting systems for roads and pathways is to promote safe and efficient movement of vehicular and pedestrian traffic. The motorist must be able to discern the presence and movements of objects on or adjacent to the road which may be a potential hazard. Road lighting is therefore 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. However the pedestrian is more concerned with identifying local landmarks and negotiating the correct route. Lighting is necessary to assist in locating the entrance to shops and public buildings, the layout of junctions and the position of the kerb. This normally requires carefully positioned lamps with a relatively low level of light.

The primary responsibility for lighting rural roads and village streets lies at county council level. In general, highway authorities do not have documented policy or procedures for road lighting, but most adopt the following broad standards of provision for rural roads:

no lighting on new rural roads;
lighting on existing roads if accident rate is poor; and
lighting on all roundabouts and some 'T' junctions.

Some authorities are replacing or altering lighting in line with changes in traffic flows on roads which have been detrunked or bypassed as a result of changes in the wider road network.

All new residential estates will usually have road lighting, regardless of their rural location, unless there is strong resistance from local people. However, practice varies considerably and local consultation, with parish councils, and special interest groups is a growing influence. Road lighting schemes are generally designed using British Standard BS 5489. The standard is split into ten codes of practice which cover the principal different categories of lighting and offer a considerable degree of flexibility and interpretation for the designer. It contains flow charts to guide the design of road lighting schemes, but in practice lighting suppliers often provide a design service to engineers, using computer software to calculate the optimum location, height and spacing for alternative lighting solutions.

Lighting of public areas in the countryside and village street lighting may fall into several of the categories within BS 5489, leading to differences in interpretation of the appropriate light level to be used. It is therefore important to maintain a clear, logical approach and to avoid the cumulative intrusive impact of lights designed for different purposes. For example, lighting on subsidiary rural roads should be designed so that pedestrians can orientate themselves and detect vehicular and other hazards. It should provide guidance to motorists, but may be insufficient to reveal objects on the road without the use of headlights.