## 3 The Integral Role of Lighting in Urban Environment
### Understanding the Role of the Sustainability Coefficient (Sn) in Measuring Environmental Well-Being
The question of the questionnaire was the following: \"Evaluate the illumination Likeability and the Illuminance Intensity of the listed locations\". The results are given in Table 2 and shown in Figures 1-3. The sustainability coefficient (Sn) varies from place to place, suggesting that people do not perceive lighting uniformly in different urban environments. This could be due to the different architectural features, the purpose of the areas, or the environmental conditions. The research results in Table 3 show that the value of Sn varies from 0.96 to 1.26. This means that there are significant differences among the studied locations, which can also be seen in Figure 2.  
For streets, the Sn values are quite close to 1.00 (between 0.96 and 1.14). This indicates that the illumination likability and intensity on the streets are close. L4 Vojasniska Street stands out with the highest quotient of 1.14, indicating relatively higher likability compared to perceived brightness. In the squares, the Sn values are very close to 1.00 and range from 0.98 to 1.09, indicating that the lighting in the squares seems to be generally balanced in terms of likability and brightness. L5 Stukelj Square has a still s  
Figure 1: Display of illumination likability (L) and illuminance intensity (I) values by locations. The standard deviations in illumination likability and intensity are quite close for most locations. This indicates that participant responses may be consistent. However, some locations such as L2 Postna Street show a notable difference in the standard deviations of likability and intensity. As seen in Figure 2, no location has a significantly low Sn value, indicating that the lighting of a location is perceived as too bright compared to its attractiveness. The majority of locations have an Sn value \(\geq\)1, indicating that the lighting compliance is achieved. This indicates that most of the locations have succeeded in balancing the illumination likability with the perceived brightness. No location is far below the threshold, three of them (L1 Gosposka Street, L3 Kocljeva Street, and L7 Liberty Square) are just below 1.00, indicating that lighting compliance has not been fully achieved in these areas. All three locations show a relatively high average value for illuminance intensity (l) value (3.30; 3.71; 3.40) compared to the other locations, but a relatively low illumination likability (L) value (3.12; 3.49; 3.25). The Pearson product-moment correlation coefficient (r) between the average values of illuminance intensity and illumination likability is r = 0.841. This indicates a high positive correlation between the two variables. In principle, the higher the illuminance intensity, the greater the illumination likability. This situation is best illustrated by the example of L5 Leon Stukelj Square. However, it can happen that we illuminate too much and thus do not achieve greater illumination likability. In this case, unnecessary energy consumption and light pollution will only increase. The limit value Sn = 1.00 indicates the value up to which it makes sense to increase illuminance intensity in order to fulfil the two basic attributes of sustainability--reasonable energy consumption and low light pollution.