## 1 Introduction
[14] revealed that the error of the estimation model was relatively higher in mountainous areas, with higher spatial complexity than in plains or urban areas. Moreover, although GIS and decision-making approaches are suitable for investigating site selection for PV plants at a national scale, the application of PV site-selection techniques to planning infrastructures (e.g., highway networks) and energy management remains unknown. Previous studies on PV-plant site selection have largely focused on investigating candidate sites at a national scale by analyzing the impacts of various factors (e.g., solar irradiation, slope, aspect, proximity to transmission, proximity to the road) on electrical-power production. For instance, [PERSON] et al. [15] proposed the AHP and GIS-based method for site selection of PV power plants in Algeria. They indicated that geographically suitable area is extracted from analyzing the various factors (e.g., proximity to the electric grid, global solar irradiation, proximity to the major roads network, proximity to cities, distance to land use, soil type, and slope), and estimated the annual potential of electrical energy using an equation proposed by [PERSON] et al., 2017 [16] that multiplies global solar irradiation in horizontal area, the total area of suitable land, the fraction of the active area on the total area (70%), and the efficiency of PV systems converting sunlight into electricity. Although existing approaches have included meaningful results and contributions, not all of the estimated suitable areas for PV plants can be fully utilized because of low economic feasibility, such as additional installations of electrical facilities in areas far from transmission facilities or the high purchase price of land in private areas. As an alternative, recent studies have applied site-selection approaches to directly evaluate how much power can be produced in civil infrastructure areas, such as unused areas near highway networks (e.g., noise barriers or slopes in highways). For example,Faturrochman et al. [17] integrated a noise barrier into PV systems located in the vicinity of roadways. This integrated approach has the advantage of collecting direct and reflected radiation from both directions of the road. In addition, [PERSON] et al. [12] conducted an economic analysis and computation of the solar-power generation resulting from the installation of panels in the unused interchange areas of highways. In particular, the slopes on both sides of the highway have potential benefits; highway slopes are generally unused land, which leads to cost savings, such as purchasing land for power-plant construction [18]. Proximity to roads can enable the trading of electricity produced from PV plants without installing additional electrical facilities, such as power lines or inverters [12]. Furthermore, in recent studies, visualization of data in three-dimensional (3D) space is important to support decisions of predicting solar irradiation in realistic 3D objects (e.g., the roofs on buildings) [19]. For example, [PERSON] et al. [19] and [PERSON] and [PERSON]. [20] presented the assessment of solar potential using 3D models with GIS. They predict the annual [20] or hourly [19] solar irradiation map in buildings and surrounding terrain. In particular, [PERSON] et al. [21] represented to search of PV installation on roofs and predict PV generation with GIS and computer-aided design (CAD) software. They segmented suitable areas of roofs that satisfied geographical features (e.g., slope, aspect, hill shade) through a 3D model from the LiDAR data. Utilizing a site-selection approach for PV plants in highway construction or design leads to efficient energy management and planning for highway projects [12,18]. However, for better-informed site selection, a geo-spatial analysis is necessary to capture geographical and topographical features that can vary the solar-power output [11].