Previous research has shown that residential segregation often aligns with urban fragmentation in contexts where explicit segregation policies were historically implemented. However, it remains unclear whether this alignment also emerges in contemporary urban contexts where segregation is driven by market mechanisms and residential preferences. Here we analyze 520 cities across eight Western European countries using high-resolution demographic data and a Monte Carlo approach to test whether residential segregation of non-EU migrants aligns with urban fragmentation by railways, motorways, and waterways. We find that the relationship between residential segregation and urban fragmentation is highly heterogeneous across Europe. Rather than a uniform trend, our results reveal regional divergence: while the Netherlands and Germany exhibit a significant alignment, Spain, the United Kingdom, and Italy show less alignment than expected by chance. These findings suggest that urban barriers do not generally function as social frontiers in European contexts, with country-specific urban development potentially influencing the observed regional differences.

This thesis explores the relationship between urban fragmentation and the spatial segregation of non-EU immigrant communities in Europe. While previous research has linked infrastructural barriers to ethnic group boundaries in American cities, this study argues that such findings cannot be universally applied due to unique historical contexts in different regions. The study aims to not only identify connections between urban fragmentation and segregation but also to contextualize these connections within the local dynamics of various European cities. We employ a mixed-method approach. The quantitative component involves constructing spatial patterns of urban fragmentation using OpenStreetMap data and segregation patterns using data from the European Commission's Data for Integration (D4I) initiative. These patterns are compared using mutual information to assess their similarity. Synthetic urban fragmentation patterns are also generated to ensure observed similarities are not the result of random chance. The qualitative component involves examining the local contexts of selected cities to understand the specific factors influencing segregation. From the 106 cities analyzed, only 33 showed statistically significant relationships between urban fragmentation and segregation patterns, with 26 showing positive and 7 showing negative correlations. These findings indicate that the relationship between urban fragmentation and immigrant segregation is not a generalizable phenomenon in Europe. The city-level analysis of nine cities across seven countries reveals that factors such as urban decay and housing quality, rather than infrastructure, are more closely associated with immigrant concentration. Future research should investigate segregation patterns among other social groups and explore broader impacts of infrastructure on vulnerable populations beyond urban fragmentation.