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

摘要

This two-part paper presents a comprehensive methodology for lighting calculation of a road pre-tunnel. The adequate lighting of road tunnels, especially in their entrance zone during the day-time hours, is a very important factor to maintain road safety and to ensure a good level of service. These targets are commonly achieved by means of artificial lighting systems. In some cases, nevertheless, it could be preferable to build a pre-tunnel, which reduces and controls the natural lighting contribution in the threshold zone of the tunnel. The structure, in fact, filters the natural light and permits to achieve the required luminance levels on the road pavement, so ensuring the correct visibility to the drivers. Analytical models were developed in the first part of the paper to describe the sky illumination of a clear but not terse sky, which is typical in large cities and industrial areas, and to evaluate the consequences related to the construction of a pre-tunnel lighting (PTL).