The impact of urban configuration types on urban heat islands, air pollution, CO2 emissions and mortality in Europe

Kurzfassung

As cities continue to grow, it is important for urban planners and policymakers to understand how different urban configurations affect the environment and human health. We aimed at identifying European urban configuration types, based on Local Climate Zones and street design variables from Open Street Map, and evaluating their association with motorized traffic flows, Surface Urban Heat Island (SUHI) intensities, tropospheric nitrogen dioxide (NO2), CO2 per capita emissions and age-standardized mortality. We analyzed 919 European cities. To identify distinct urban configuration types, we applied the Uniform Manifold Approximation and Projection for Dimension Reduction (UMAP), followed by the k-means clustering algorithm. Statistical differences between the resulting urban configuration types were evaluated using one-way ANOVA and the post-hoc Tukey-Kramer test for the SUHI exposure and mortality rates, and the Kruskal-Wallis test followed by the Mann-Whitney U test for the traffic flows, NO2 exposure and CO2 emissions. We identified four urban configuration types: Compact-High Density, Open Lowrise-Medium Density, Open Lowrise-Low Density and Green-Low Density. Motorized traffic flows and NO2 levels were significantly higher in Compact-High Density and Open Lowrise-Medium Density cities compared to Green-Low Density and Open Lowrise-Low Density cities. Additionally, Green-Low Density cities exhibited a significantly lower SUHI in comparison to Open Lowrise-Medium Density and Open Lowrise-Low Density cities. Per capita CO2 emissions were significantly lower in Compact-High Density cities compared to Green-Low Density cities. Lastly, Green-Low Density cities demonstrated significantly lower mortality rates compared to all other urban configuration types. While the compact city model has arisen as the way forward to healthier and more sustainable cities, European compact cities still face challenges related to poor environmental quality. Our results have significant implications for urban and transport planning policies in Europe and contribute to the ongoing discussion on which city models bring the greatest benefits for the environment, climate and health.