Road tunnel entrance/exit - allowing driver to adjust eyesight to darkness

摘要

Separate tunnel structure at entrance and exit of road tunnel comprises openings covered with light-transmitting matl. of which the degree of transmission decreases towards the tunnel interior, pref. coloured plexiglass, polycarbonate, PVC or cellulose ester. Several surface elements of light-transmitting matl. of different light intensity stages may be used, replacing an increasing no. of elements of one stage by so many of the next stage in the transition zone between two stages in each row of surface elements.