## 1 Introduction and Related Works  
High-voltage power lines (HVPLs) are artificial structures with many controversial effects. On the one hand, they are facilities that enhance human activity by responding to the increasing demand for power supply and capillary distribution as well as serving the widespread development of renewable energy sources. On the other hand, they are huge and massive human artefacts with many potential consequences on people's health and safety, but also affecting the natural landscape. Leaving out health considerations, the scope of this research activity is focused on the visual impact of these facilities on the landscape, with consequences for society, tourism, and ecology. HVPLs mainly consist of tall tower-like pylons, which are generally lattice structures supporting conductors, guard ropes, and hood and pin insulators. However, the element having the greatest visual impact for HVPLs is the pylon, with a disrupting effect on the aesthetics and the perception of natural and rural landscapes. In all the published papers in the related literature [1; 2; 3; 4], the burying of cables is found to offer the best mitigation of the visual impact of the HVPLs: this solution produces social benefits and a lack of visual impact on the landscape but presents some limitations. The first one is the high real cost associated with burying lines. [PERSON] et al. [5] quantified that in Norway the costs of underground cables of higher voltage lines are up to 8-10 times greater than the costs of overhead lines; it is difficult for municipalities to bear an additional cost compared to overhead lines. The second limitation on buried power lines is the presence of landscape/environmental constraints and natural barriers, as in the case of natural reserves, rivers, valleys, mountains, and so on, which do not allow the installation of this kind of solution. Therefore, in the majority of cases, overhead power lines are still the most frequently used solutions, with the main drawback being their visual impact. This has originated multiple attempts of solutions from governments and organizations in most countries. The first trend is the development of studies and guidelines provided by national institutions (e.g., [6; 7; 8]) for the mitigation of the visual impact of infrastructures. These sources consider all the development phases (siting, design, production, installation, decommissioning). In accordance to the scope of this work, the most important guidelines regard the structure design. [PERSON] [7] recommends the use of custom-designed structures in key areas when such designs would soften the visual impact and blend more effectively with the surroundings, as well as of different kinds of structures (monopole, guyed, and lattice structures/towers) to be used with regard to the given landscape setting. The Environmental Protection Department [8] highlights how the visual impact varies in consideration of the degree of change to the baseline conditions. With particular respect to electric pylons, [PERSON] and [PERSON] [1] provide two main statements:  
* The design of high voltage pylons is particularly critical since they are visible from a long distance. * The visual impact depends on the landscape, the pylon position, the angle of the observer, and the contrast. Similarly, [PERSON] et al. [3] propose a measure of the visual impact of different pylons in the same situation as the multiplication of three terms: the visibility of the facilities, the fragility of the landscape (which increase or decrease the impact), the nature of the area (industrial, commercial, rural, etc.). Again, [PERSON] [7] suggests that the selection of materials and surface treatments should repeat the form, line, color, and texture of the surrounding landscape. However, since the visual impact is a subjective perception, most of the guidelines provide advice and/or requirements about the assessment of the potential visual impact that the designer is required to consider but they still depend on the designer's subjectivity.