Tunnel entrances may present themselves during the day as a "black hole" in which no details can be perceived. In order to ensure safe and comfortable driving at high speeds, the entrance zone must be lit to a high luminance level. Modern tunnel lighting technology is focused on two aspects: (1) reducing the veiling luminance by constructional methods; and (2) reducing the installed power required to fulfil the tunnel entrance lighting requirements. The research focuses on three items: a) the accurate assessment of the veiling luminance in the design stage; b) the energy and money saving capability of "counter beam" lighting under the conditions prevailing in the Netherlands compared to traditional lighting; and c) assessing the luminance "score" of existing tunnel entrances. This paper discusses the design and methodology of the research. The method is based on the measurement of the contrast sensitivity threshold in different locations in tunnels.
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