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D.A. Schreuder
Energy Saving in Tunnel Entrance Lighting Dr., Duco Schreuder Consultancies, Leidschendam, The Netherlands L.Swart Ing., Building Department, Ministry of Transport Utrecht, The Netherlands Abstract Tunnel entrances may present themselves during the days as a "black hole" in which no details can be perceived. In order to ensure safe and comfortable driving also at high speeds, the entrance zone must be lit to a high luminance level. This level is closely related to the luminance level outside the tunnel, and also to the (equivalent) veiling luminance a car driver experiences when approaching the tunnel. Typical design values are 200 to 500 cd/m_2. It is the aim of the research to minimize the high expenditure in money and energy values. Modern tunnel lighting technology is focused on two aspects: reducing the veiling luminance by constructional methods, and reducing the installed power required to fulfil the tunnel entrance lighting requirements. In this respect, quality of the tunnel entrance can be "scored" on a quantitative scale. The research focuses on three items: the energy (and money) saving capability of "counter beam" lighting under the conditions prevailing in the Netherlands compared to traditional lighting, and assessing the "score" of existing tunnel entrances, using the contrast sensitivity of drivers in real traffic situations as a parameter. The set-up and the methodology of the research will be discussed in the paper. The method is based on the measurement of the contrast sensitivity threshold in different locations in tunnels. Making these measurements in different tunnels allows for the comparison of the "quality" of different lighting systems. Accident data are used to select the objects from which the contrast threshold will be made. Additional measurements are needed to allow the assessment of the quality (e.g. the internal contrast of the object, its recognition, the veiling luminance and the meteorological visibility.)
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