Geographical analysis of road network efficiency in the wilaya of Sétif: Utilizing a principal component analysis (PCA) to reveal the relation-ship between demographic indicators and accessibility of urban centers

The study uses a quantitative spatial approach to analyze the relationship between the topological structure of the road network and demographic dynamics in sixty urban centers in the wilaya of Sétif, Algeria, in 2021. This approach involves representing the road network as an undirected graph and calculating five demographic and six topological indicators reflecting accessibility and connectivity. These indicators are then standardized and integrated into a principal component analysis (PCA). The analysis revealed that the variables primarily fall within two composite axes: the functional centrality/accessibility axis, which is closely associated with population size, density, and connectivity; and the population hierarchy and concentration axis. Together, these two axes explained 72.98% of the total variance. At the factorial level (F1-F2), four types of urban centers were identified: dominant centers, medium centers, centers with network centrality exceeding their demographic weight, and weakly integrated peripheries. Population growth was more closely linked to the most network-integrated centers (F1) than to their size or rank in the urban hierarchy (F2). This highlights the lack of a direct correlation between topological accessibility and population hierarchy, despite some overlap between the two. The results show that improving road infrastructure affects both the volume of growth and its internal redistribution among centers according to network integration patterns. The results also confirm that the methodological framework, which integrates topological and demographic indicators within PCA, can be applied in other regions to guide investment and reduce spatial imbalances.