Urban Fragmentation and Residential Segregation in Medium-Sized Cities: A Multidimensional Urban Territorial Index (UTI) Analysis from Spain

Medium-sized cities are increasingly affected by processes of urban fragmentation and residential segregation, despite having traditionally been perceived as more socially cohesive and territorially balanced than large metropolitan areas. These cities often act as functional connectors between metropolitan hubs and rural regions, yet they are particularly vulnerable to unplanned suburban growth, housing market polarization and uneven access to urban opportunities. This study develops and applies a multidimensional Urban Territorial Index (UTI) to assess socio-spatial inequality in Ciudad Real, a medium-sized city in central Spain, and its functional urban area. The UTI integrates six indicators across three analytical dimensions—socioeconomic, sociodemographic and housing—using a weighted composite approach informed by principal component analysis and implemented through GIS-based spatial analysis. The index is calculated at census-section and neighborhood scales and externally validated against a local Human Development Index, showing a strong correlation (r = 0.87; p < 0.001). The results reveal a pronounced core–periphery polarization. Central and southern neighborhoods associated with strategic infrastructures—such as the university, high-speed rail station and hospital—concentrate higher income levels, educational attainment and land values, while peripheral municipalities and disadvantaged neighborhoods exhibit higher unemployment, lower rents and greater concentrations of migrant populations. The analysis also identifies suburban municipalities with intense housing construction but demographic stagnation, leading to population–housing mismatches, underutilized developments and service provision deficits. Methodologically, the UTI proves to be a robust and replicable tool for capturing multidimensional urban vulnerability in medium-sized cities, where metropolitan-scale indices often fail to detect fine-grained socio-spatial disparities. Substantively, the findings demonstrate that infrastructure-led development and suburban expansion can reinforce fragmentation and segregation in non-metropolitan contexts when not accompanied by integrative planning strategies. The study contributes to ongoing debates on spatial justice, urban governance and sustainable development, offering policy-relevant insights for medium-sized cities across Southern Europe and comparable urban regions.