For more than 10 years, practical experiments have been conducted in the Netherlands on the lighting of tunnel entrances. Common practice is to have the CIE recommended illuminance value of +/- 10.000 lux installed under the most difficult conditions. The very high illuminance value of 10.000 lux is criticised by theoreticians and also government officials who try to prove by a theoretical approach that the recommended value is exaggerated. The authors believe that this is a kind of self deceit, as the only reason for reducing the level of lighting is an economic one. Experiments in the Netherlands demonstrate that instead of 10.000 lux, an illumination level of +/- 30.000 lux is necessary to guarantee good visibility and safe driving in the tunnel entrance. This paper gives a detailed description of these experiments and the consequent results.
Abstract