Decrease of energy demands of lighting installations in road tunnels based in the forestation of portal surroundings with climbing plants

Abstract The lighting installations demand the biggest part of the energy consumed in road tunnels. This demand is much higher during daytime, when the visual adaptation of the drivers coming from bright environments, requests very intense illumination levels, especially in the first part of the tunnel, the so called threshold zone. The lighting necessities in road tunnels depend on three main critical parameters: maximum speed allowed in the tunnel, tunnel orientation and the characteristics of the portal gate surroundings. In this work, actions on this last parameter have been evaluated: four different species of climbing plants have been tested as candidates to forest the surroundings of portal gates in an environment of Mediterranean climate. The lighting demands in the threshold zone arising from the choice of each species have been quantified by luminance measurement. As a result, the common ivy ( Hedera helix ) is proposed as the best candidate to fully forest the surroundings of portal gates optimizing the binomial energy consumption-landscape integration in a Mediterranean climate.