Natural lighting of road pre-tunnels: A methodology to assess the luminance on the pavement - Part I

The authors expose the theoretical principles and the analysis criteria to control lighting levels in a pre-tunnel lighting (PTL), under various external environmental conditions. The objective of the first part of the paper is to present original analytical models developed by the authors to represent the luminance of clear not terse sky and to assess the illuminance underneath a PTL. The proposed equations permit to compute the sky and PTL contributions considering both direct and reflective radiations, under specific conditions of the examined tunnel (e.g. geometry and materials of PTL, latitude of the site, alignment of the road, etc.). The models and the proposed methodology were also validated by means of an experimental activity, which will be illustrated in the second part of the paper.