Understanding the role of rail transit in shaping urban population density models: A dual-level analysis of Chinese cities at city and station levels

Urban rail transit is an integral component of urban morphology, which plays a role in guiding the spatial distribution of urban populations. Understanding this dynamic is essential for rational urban planning to mitigate uncontrolled urban sprawl and promote sustainable transit-oriented development. While urban population density models are widely used to quantitatively capture these spatial distribution patterns, the existing literature lacks comprehensive studies integrating city-level and station-level analyses to elucidate how rail transit networks associate with these density dynamics. Using grid-level population data from China’s seventh national census, this study estimates a generalised urban population density model for cities with operational rail transit. We employ XGBoost models to investigate the statistical associations between rail transit features and population density patterns at both the overarching city level and the localised station level. Within the generalised model, we define two key parameters: the Peak Location Index (D), which determines the peak position of the population density curve; and the Decay Radius (r 0 ), which reflects the flatness of overall population density decay. The results show that the population coverage and scale expansion contribute to D and r 0 separately. Station-level studies further corroborate that metro stations are more conducive to population uplift in places far from the city centre. Apart from the effects of built environment factors, station location within the network and years of operation also exhibit notable predictive importance regarding population density. This sheds light on the need for policymakers to rationalise rail transit planning as a tool for urban population redistribution.