Abstract
THE increasing use of double carriage-way arterial roads has given new problems to the street lighting engineer. Some of these are discussed in a paper on the revealing power of street lighting installations read by J. M. Waldram to the Illuminating Engineering Society on November 8. On a double carriage-way road where each carriage-way carries traffic proceeding in one direction only, an ordinary street lantern throws much of its light in the direction where it may be doing no good, that is, in the same direction as the traffic flow. This light is not only wasted, but sometimes also does harm by lighting up vertical surfaces and reducing their contrast against the bright background of the road surface. Elimination of light sources not actively producing road brightness, should result in a great increase of comfort to the drivers. The G.E.C. Research Laboratories have evolved a system of uni-directional lighting which they have tested on the carriage-way of the Great Chertsey Road in the Twickenham area. On this road the standards exist on a double staggered formation ; the height of the lantern is 25 ft. and the average spacing of the standards about 189 ft. Each lantern was equipped with a 250-watt horizontal burning lamp and was uni-directional. Both visibility and revealing power were found to be very good. Driving in the opposite direction on the other carriage-way, the road lighted with back cut-off lanterns disappeared completely. Traffic moving on it could be distinguished quite easily by the vehicle lights, but apart from this the impression produced was that of driving down a single carriage-way road with no traffic in the oncoming direction. The back cut-off lanterns on the other carriage-way were completely invisible. The conclusions drawn are that it is practicable to light a 'one-way' road with lanterns giving light only in the direction opposed to the traffic. An installation of this nature saves 50 per cent of lamp wattage.
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Uni-directional Lighting on Roads. Nature 142, 1152 (1938). https://doi.org/10.1038/1421152b0
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DOI: https://doi.org/10.1038/1421152b0