Abstract
The entrance to a long road tunnel can present itself to an approaching driver as a 'black hole' during the daytime, with no possibility for observing any details. In contrast to traditional symmetrical lighting, counter beam lighting aims the light in the opposite direction to incoming traffic. This type of lighting is particularly popular in Switzerland. In the Netherlands, a trial is being conducted in the tunnel at Velsen. The objective of this trial is to study the possibility for creating a lighting system for tunnel entrances using counter beam lighting which, at an equivalent quality, is cheaper than traditional lighting, both with respect to installation and operation. An essential element of the trial is to ./.F3