IMPROVEMENT IN THE DAY AND NIGHT VISIBILITY OF SIGNALLING DEVICES. APPLICATIONS OF PHOTOMETRY AND COLORIMETRY

This study comes within the scope of the research described in research project IRRD 500733. Its aim is to widen the knowledge of the efficiency of signalling devices thanks to a better approach to their photometric and colorimetric properties. It deals with traffic signals and reflecting devices. Measurements were made of the light intensity, colour and ghosting effect of the different types of traffic signals used in France. Based on a bibliographic analysis of the visual efficiency of traffic signals and a comparison of measurement results with draft recommendations by the CIE (International Commission for Lighting), elements are proposed for the drafting of future standards. A measuring method was developed for determining the variation in the light intensity of flashing lights as a function of time for flashes which last approximately 100 microseconds. It is then possible to calculate their effective light intensity by the Blondel-Rey method. Their colour is defined using the trichromatic coordinates of the filter. Among reflecting devices, a special study was conducted of carriageway markings, reflecting studs and reflectorized films. The values characterizing the photometric and colorimetric properties of this equipment are defined together with methods of measuring them in the laboratory. (TRRL)