**6. Conclusions**

Renewal of technologies and energy rationalization processes could contribute to meeting the sustainability targets set by the European Union on climate and energy. Within this framework, ANAS, the Italian government-owned road company launched the Greenlight project to replace HPS tunnel lighting systems with state-of-the-art LED luminaries. The new systems will reduce electricity consumption by up to 50% of the current values; additionally, the lighting quality inside the tunnel will be enhanced thanks to better uniformity and color temperature of the new luminaries.

The initiative is composed of two phases: the first one will account for 45 million euros and the second one for about 110 million euros. Until now, the on-going first phase involves 147 tubes: their new lighting systems cost 30 million euros (allotment volume) and ensure 28 GWh saved energy every year (on average 55% of the current consumption). The economic saving provides a total return over less than seven years and has direct environmental e ffects. According to the European standard EN 15804, the avoided yearly emissions of greenhouse gases are 17,000 t of CO2 eq., while saved abiotic and fossil resources are 19.3 kg of Sb and 230 TJ, respectively.

The presented on-the-field experience permitted us to correlate the tunnel length to the rehabilitation cost per unit length; the high value of the coe fficient of determination corroborated the result, which could be useful to road managers pursuing environmental, economic and safety goals with tunnel LED lighting.

**Author Contributions:** Conceptualization, L.M. and G.C.; Data curation, L.C., F.B., V.C. and S.N.; Formal analysis, L.M. and G.C.; Investigation, L.M. and G.C.; Methodology, L.M. and G.C.; Project administration, L.C.; Software, F.B., V.C. and S.N.; Supervision, L.C.; Validation, F.B.; Visualization, V.C. and S.N.; Writing—original draft, L.M. and G.C.; Writing—review & editing, L.M. and G.C.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
