The impact of transport accessibility on demographic dynamics in Russian agglomerations: breakpoint analysis and zonal levels

This study provides the first quantitative assessment of how transport accessibility affects population dynamics in 73 Russian urban agglomerations across the intercensal periods 1989–2021. Using OpenStreetMap data, we calculated accessibility to agglomeration centers for more than 2,800 settlements. The methodology combines a hierarchical segmentation of agglomerations (main city, urban area, urban agglomeration, and zone of influence) with breakpoint analysis to detect demographic boundaries. We show that actual, demographically grounded agglomeration boundaries differ substantially from the normative 1.5-h isochrone and are positively correlated with the population size of the core city. Spatial polarization has intensified: in the 2010s, demographic growth concentrated in high-accessibility zones (within 35–50 km of the center), while the periphery shifted to persistent depopulation. Based on the results, we develop a typology of 16 agglomeration types that differ in spatial development patterns—from metropolitan “super-expansion” to polycentric systems with a strong periphery and depopulating old-industrial cores. We further show that fixing city administrative boundaries stimulated “explosive” suburban growth. The findings confirm the deepening of the core–periphery model in Russia and support a shift toward flexible, demographically calibrated agglomeration boundaries in spatial planning practice.