Visual Performance and Sense of Confidence

Abstract

During the daytime, the eyes of a driver approaching a tunnel entrance are adapted to the high level of daytime luminances surrounding that entrance. In order to keep the level of visual performance and the sense of confidence of drivers high enough, the lighting level inside the tunnel should not decrease too quickly. The basic problem is the lack of full adaptation to the lower lighting levels in the tunnel. During the drive through the tunnel, adaptation gradually becomes more complete again. Consequently, the different zones in the tunnel, require different lighting. The lighting requirements for these zones, called the threshold zone, the transition zone, the interior zone and the exit zone, are based mainly on fundamental research carried out in the sixties and seventies of the last century. Much of this research will be described in this Chapter. The limited amount of more recent research available today, will, of course, be dealt with as well. From all this, it will become clear that lighting requirements have to be specified in terms of lighting level, uniformity, glare and flicker restriction. A distinction is made between long tunnels on the one hand and short tunnels and underpasses on the other. As will be shown, under certain conditions no daytime lighting is needed for short tunnels and underpasses.