In various western European Countries, sodium lamps are considered to be important light sources for traffic lighting applications, primarily for the following reasons: (1) With sodium light one can see better and more quickly and is less troubled by glare than with other light sources. A summary is given of results of investigations in which these advantages of sodium light appear. (2) The application of sodium lamps in place of other light sources make possible considerable savings in initial and running costs. These economic advantages have gained emphasis from recent developmental work which has led to a considerable increase in the efficiency of sodium lamps (up to 112 lumens per watt) and to the production of higher wattage units. Attention is drawn to a method widely used in The Netherlands for guiding inner-town traffic into and through build-up areas by means of the distinctive colour of sodium lighting.
Abstract