## 5 Discussion and Conclusions
In fact, by exploiting the correlations between spatial indicators and lighting parameters, it will be possible to set in advance the lighting requirements that lighting systems will have to satisfy for each road, without the use of specific methods for roads classification based on the traffic volumes (usually expensive if traffic observation campaigns are adopted). As clearly described, the correlations have been analysed for a single case study; verifications of these correlations, on an experimental basis conducted by different research groups, will be useful to obtain confirmation of what has been found and to generalise the results obtained in this research. All the authors contributed in equal parts to the research activity and to the paper writing. This research received no external funding. The authors declare no conflict of interest. The Emilia Romagna Region local regulation [55] is a useful tool for energy classification of luminaires and street lighting systems. According to the energy classification introduced by the local regulation of Emilia Romagna, the energy classes of the luminaires can be evaluated in function of the _IPEA_ (Luminaire Energy Efficiency Indicator) values. The energy class of a luminaire can be selected on the base of Table 11. The minimum class required by the Emilia Romagna regulation is the class C. The _IPEA_ indicator can be calculated with the following equation. \[IPEA=\eta_{l}\cdot\eta_{s}\cdot D_{lqr}\] \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Scenario**} & \multirow{2}{*}{**Carriageway**} & \multicolumn{2}{c}{**Sidewalk**} & \multicolumn{2}{c}{**Sidewalk**} \\  & & **(on Luminaire Side)** & **(on the Opposite Luminaire Side)** \\ \cline{2-5}  & \(L_{\text{ap}}\) [cd/m\({}^{2}\)] & \(E_{h,att}\) [lx] & \(E_{h,att}\) [lx] & \(E_{h,att}\) [lx] & \(E_{h,att}\) [lx] \\ \hline
1 (present status) & \(7.6\times 10^{-4}\) & 0.16 & 0.33 & 0.08 & \(4.7\times 10^{-3}\) \\
2 (design status) & 0.63 (63\%) & 0.48 (32\%) & 0.39 (6\%) & 0.43 (35\%) & 0.41 (41\%) \\
3 (ideal case) & 0.67 (67\%) & 0.53 (37\%) & 0.53 (20\%) & 0.53 (45\%) & 0.53 (53\%) \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Comparison of the coefficient of determination \(R^{2}\) in the three scenarios (between brackets the percentage increments of \(R^{2}\) with respect to the Scenario 1 is shown). where \(\eta_{l}\) is the luminous efficacy of the lamp, \(\eta_{s}\) is the power supply efficacy (ratio between the lamp nominal power and the input power supply) and \(D_{lor}\) is the ratio between the luminous flux emitted downwards by the luminaire and the total luminous flux emitted by the lamps. According to the energy classification introduced by the local regulation of Emilia Romagna, the energy classes of the lighting systems designed on the basis of illuminance can be evaluated in function of the \(IPEI_{E}\) (Lighting system Energy Efficiency Indicator) values while the lighting systems designed on the basis of luminance can be evaluated in function of the \(IPEI_{L}\). The energy class of a lighting system can be selected on the base of Table 11. The minimum class required by the Emilia Romagna regulation is the class B. The IPEI indicators can be calculated with the following equations. \[IPEI_{E}=K_{1}\left(\frac{E_{h,av}}{E_{h,av,R}}+K_{2}\right)\text{; }IPEI_{L}=K_{1}\left(\frac{L_{av}}{L_{av,R}}+K_{2}\right)\]  
where \(K_{1}\) is a constant equal to 0.476, \(K_{2}\) a constant equal to 0.524, \(E_{h,av}\) is the average horizontal illuminance on the road surface, \(E_{h,av,R}\) is the limit value of the illuminance for the corresponding lighting class, \(L_{av}\) is the average luminance on the road surface and \(L_{av,R}\) is the limit value of the luminance for the corresponding lighting class. The values of \(E_{h,av,R}\) and \(L_{av,R}\) are given in the local regulation of Emilia Romagna Region [55].