Study for optimizing the daylight 'filter' in a pre-tunnel structure

The elevated lighting demand in tunnel's portal zone to guarantee drivers eye adaptation to the internal luminance has been the subject of previous studies exploring the opportunity to gradually introduce daylight in the threshold zone and thus reduce consumption. A 1:10 scale model of this adaptation zone, called daylight 'filter' structure, has been constructed to investigate uniformity and luminance reduction under panels with different percentages of holed ceiling surface. The trend of the luminance curve compared to CIE curve of luminance led to the optimization of panels' position along the tunnel. Results confirmed the possibility of implementing drivers' vision introducing daylight through the 'filter' structure.