## 3 Case Study (Quseir Road)
### Geological Setting of Quseir Road  
The geological setting of Quseir Road has been extensively studied by various researchers, as documented in prior studies [18; 29; 32]. These studies have revealed a diverse composition of rock formations, including basement rocks, sedimentary rocks, and tertiary basalts. The basement rocks, dating back to the late Proterozoic era, form part of the pan-African belt. The geological studies primarily aimed to identify and characterize the different rock units exposed in the study area and along the proposed road alignments. Fieldwork, employing base mapping, GIS, and navigation techniques, was conducted in two phases: initially to construct base geologic maps and subsequently to produce geological themes for map verification.  
Figure 8: Existing Alignment of 90-km Segment of Quseir Road (Case Study). (**a**) Horizontal Alignment. (**b**) Vertical Alignment. (**c**) Typical Cross-Section.  
The current study focuses specifically on the detailed examination of lithology and lineaments along Quseir Road, with the aim of assessing their environmental potentialities for optimal route selection in the arid desert context (Figure 10). Analysis of the lithological map reveals a wide range of rock units and ages (igneous, metamorphic, and sedimentary), spanning from the Precambrian to Quaternary periods (Figures 10 and 11).  
The predominantly eastern side of the road area is characterized by Precambrian hard rocks, while the western side features soft sedimentary outcrops (Figure 12). Seven distinct rock units have been differentiated and assigned lithological indices to inform road weight scores.  
The rock properties help in determining the preferred road weight and optimal path selection. The rock units are categorized into two groups: hard and soft rocks (Table 3). Five rocks belonging to the hard rock category are ordered from very hard to less hard, including Pink Granite, Hammam Group Sediments, Volcanics and Meta Volcanics, Melange, and Gray Granite, as shown in Figure 11a,b. Meanwhile, the soft group comprises the  
Figure 11: Geological Setting Along the Road. (**a**) Hard Rigid Rocks. (**b**) Sedimentary Rocks of the Gebel Dawi. (**c**) Alluvium Quaternary Deposits Along Wadis. (**d**) Shale Interbeds within LS.  
Figure 12: Cross section of the Proposed Road Zone from East to West.  
Gebel Dawi Limestone with shale interbeds and Quaternary wadi deposits of gravel and loose coarse sand (Figure 11c,d).  
Furthermore, a lineament density map was generated to investigate the fragility and discontinuity of alternative paths (Figure 13). Lineament density was normalized into nine categories (Table 4), with higher density indicating more favorable paths and lower density indicating less favorable ones. Each alternative path is assigned a density score, which is integrated with other parameters to determine the weight and hazard levels associated with each path. The primary cause of road damage from geohazards is extensive excavations that create steep walls. In this study, when considering geological aspects, rock hardness and fracture density were specifically considered. Alignment alternatives were chosen to minimize significant road cuts and fills, considering geological factors along with others. This approach prioritizes line density over rock softness, as denser lines indicate better excavation capabilities, thereby reducing the risk of rockfall by minimizing wall formation through excavation, which is reflected in minimizing the cost of excavation.