Street Lighting Performance

Abstract

The object of traffic route lighting in Britain is to enable vehicles to traverse built-up areas in safety, without the need for head lights. The technique adopted is to project light on to the road to show its direction and features, and to reveal clearly obstacles and other road users in silhouette. To achieve this an average road brightness of 0·2 foot-lamberts without excessive diversity is adequate. Glare from the lighting must be controlled to avoid disturbing a driver's visual adaptation but mainly to minimize his discomfort.

A means of appraisal of the effectiveness of street lighting installations is described and applied to some installations. This should be of value to indicate which of the older installations are adequate and which need raising to a standard that affords an ample margin of safety without the use of head lights.

Since it is left to the discretion of drivers to use head lights when they need them, it is suggested that the limitation in mounting height on other roads be relaxed sufficiently to enable lanterns to project safely over the road in order to effect considerable improvement in lighting, particularly on tree-lined streets.