## 2 The Sustainability Coefficient of Outdoor Lighting Ambiences  
The sense of sight is generally the preferred and most valuable sense to perceive and interact with the environment [35]. Trends in urban cityscape dynamics rely heavily on the visual perception of citizens to carry out their daily life [36]. In urban environments, the focus of lighting goes beyond linear structures (streets). It also includes public places such as squares [37; 38] and parks [39; 40; 41] that serve as gathering places where people engage in various activities in open spaces [42]. These activities include walking, running, standing, sitting, socializing, playing, in-line skating, rollerblading, and sightseeing [43]. While many of these activities occur primarily during daylight hours, there is a desire to extend them to nighttime hours as well. However, these areas, which are characterized by architectural and advertising lighting, tend to be unevenly lit. [PERSON] [44] reveals a quartet of recurring elements in the design of nocturnal urban landscapes. First, the illumination of significant and iconic urban features improves navigability and enhances the unique character of the city after dark. Second, creating safe thoroughfares that connect communities and lighting community centers fosters community spirit. Third, lighting historic sites or areas with unique ambiance adds to the nighttime charm. Finally, engaging with private stakeholders and citizens is critical to creating a unified aesthetic for the city at night. Nowadays, human-centric lightning is a major aspect of interest to influence mental states [45]. This influence of light on humans can impact positively or negatively through visual perception of radiation [29]. In urban environments, various forms of experiential information, such as images, sounds, and artifacts, contribute significantly to how individuals interact with the space around them [46]. For instance, the images from murals, billboards, and decorations on buildings not only serve aesthetic purposes but also convey specific messages associated with the city's identity and functions. Determining the optimal lighting level, whether it is \"just right\", \"too much\", or \"too little\", is a complex task. Often, emphasis is placed on illuminance criteria without considering the overall target environment. A well-lit object that stands out against a dark background is visually arresting. However, reducing the contrast between the illuminated object and the dark environment can make it difficult to perceive spatial order, while excessive darkness is also undesirable. Sometimes the quality of lighting is in line with all standards and recommendations, but users still feel unsafe and uncomfortable [47]. Therefore, the question arises as to what extent the lighting makes sense. The first preliminary empirical study to solve this challenge was conducted by [PERSON] et al. [48]. The sustainability coefficient (S) as the subjective quotient of the mean value of the illumination likability (L) and the perceived illuminance intensity (I) were presented (Equation (1)). \[\text{S}=\text{L}/\text{I} \tag{1}\]  
The sustainability coefficient (S) is a subjective measure that has no physical basis, as both values--illumination likability and illuminance intensity--are determined based on the average ratings of the subjects' opinions. Illuminance intensity is a subjective factor and is not compatible with the technical factor of illuminance. However, the coefficient very effectively expresses our expectation to achieve the highest possible likability with the lowest possible illuminance. A preliminary study--Phase 1--was already partially presented [48] in 2023. Table 1 is now supplemented with additional locations or objects. The empirical study comprised a group of 200 participants, equally divided into 100 men and 100 women aged between 18 and 35 years. All participants were students of different disciplines at the University of Maribor in Slovenia.