“…Among the solutions proposed and implemented for this purpose, we can find semi-transparent structures (Abdul Salam and Mezher, 2014;Peña-García et al, 2010Gil-Martín et al, 2011, Peña-García, 2019; pergolas with empty space between beams (Peña-García and Gil-Martín, 2013) or using diffusive materials to avoid flicker effect on the road (Gil-Martín et al, 2015;Peña-García et al, 2016a); and structures with different patterns of holes (García Garay et al, 2012;Drakou et al, 2015Drakou et al, , 2016Drakou et al, ,2017Cantisani et al, 2018b;Cantisani et al, 2018c). A. Peña-García and J. Cabeza-Lainez 2) Transfer of sunlight inside the tunnel: this solution does not require threshold displacement, but just the installation to collect and distribute the solar luminous flux inside the tunnel.…”