Daylighting of road tunnels through external ground-based light-pipes and complex reflective geometry

The transfer of solar light to the interior tunnels complement electrical lighting during daytime, contributes save energy and decrease number installed projectors. solutions traditionally implemented, based on light-pipes hanging from vault, seemed reasonable because leakages can emit luminous flux like projectors, but had disadvantage needing higher clearance gauges with consequent costs in drilling, building materials, works maintenance. Furthermore, these cannot be working if they were not foreseen initial project. In this article, a new concept injection distribution is proposed. It consists coupling three main elements: collectors, light-pipes, one reflecting vault whose design optimized ensure photometric requirements pavement. proposed system collect more than 1.5 Mlm excessively large collectors ground road shoulder, project them that finally distributes towards With flux, average illuminances 3478 lx uniformities 0.73 achieved, which means pavement luminance around 350–400 cd/m2, good agreement daytime. savings 40 %. Besides savings, easily implemented existing tunnels. proposal some estimations are discussed.