Predetermination of the Luminance in Tunnel Entrances at Day

摘要

The adaptation of the visual system of drivers/observers follows without an appreciable adaptation lag the change in a real luminance. This luminance may be assessed by adding the intrinsic luminance of actual objects and the veiling luminance caused by scatter of light in between. In tunnel lighting practice, only the scatter in the eye, in the windscreen of the car, and in the atmosphere need to be taken into account. For all practical day-time conditions, the required luminance in any portion of the tunnel can be assessed as being a constant fraction of this sum-luminance; the fraction being determined by the traffic situation. The system is applied in several new and renovated tunnels in The Netherlands. The high values of the luminance in the threshold zone are arrived at by applying louvres that are not sun-tight, and by artificial light. New design principles of the louvres are introduced, based on psychological studies, aimed at an optimal guidance and a minimal disturbance of the drivers. Special points are the development of a computer program for the calculation of the veiling luminance, the measurements of windscreen cut-off and the classification and characterization of short tunnels.