Optical coupling of grouped tunnels to decrease the energy and materials consumption of their lighting installations

The increasing improvement of tunnelling technology allows more and more complex tunnels every day. Thus, together with the classical road tunnels through mountains, with lengths generally under two or three of kilo-meters, longer and longer underground roads under rivers and seas, as well as tunnels in geomorphically complex terrains, are being opened continuously. Besides the geotechnical difficulty of these infrastructures, the consumption of their lighting installations in terms of energy and raw materials due to the high number of projectors, total cost and maintenance, are a major concern between public administrations in many countries. In this scenario, there is an especially critical kind of tunnels due to their high energy consumption: the groups of tunnels under very near mountains, that is grouped tunnels separated by opencast roads with lengths about few hundred meters. Due to the special characteristics of the human visual adaptation, whenever one driver leaves one tunnel during daytime (when most displacements take place), his visual system loses adaptation to darker environments, and needs a new threshold zone with high luminance levels when entering a new tunnel even if it begins in just a few meters. This converts grouped tunnels in paradoxical infrastructures: the cost of their lighting installations is much higher than if there were only one tunnel going under the whole mountains chain. In this work, it is proposed an optical coupling of grouped tunnels with translucent red structures to avoid the loss of visual adaptation to weakly illuminated environments and the consequent high demands of lighting levels. The savings with of proposal are presented and compared with the current situation in the groups of tunnels around the world.