What is it about?

Our research explores the relationship between how cities are designed and their impact on the environment. We analyzed the form of 462 cities around the world, looking at factors such as density, compactness, and street connectivity. We found that while high density is often seen as a way to reduce driving and air pollution, it can also lead to less access of the residents to green spaces and increased exposure to air pollutants. We discovered that street connectivity is more effective in reducing air pollution from transportation. Additionally, the impact of urban form on the environment depends on the region and socioeconomic factors, and it is not a one-size-fits-all solution.

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Why is it important?

Once the form of a city has been defined, it is challenging and expensive to alter it significantly. Moreover, the physical shape and structure of cities may lead to adverse environmental impacts such as greenhouse gas emissions. Our findings challenge the commonly held assumption that high density is the key to reduce air pollution, highlighting the need for a more nuanced approach to sustainable urban planning and design. By demonstrating the importance of street connectivity in reducing transportation-related air pollution, our research offers a valuable contribution to the field of urban planning and policymaking. Furthermore, our study indicated that urban form is correlated with income level, and transportation emissions per capita is higher in cities of high-income and upper-middle-income countries compared to the rest of the world. Our research also highlights the context-specific nature of the relationship between urban form and environmental outcomes. This is a crucial consideration for city planners and policymakers, who need to take into account the unique characteristics of their region when designing sustainable cities.


Our research provides valuable insights for policymakers and city planners in designing sustainable and livable cities. We hope that our findings will contribute to the field of urban planning and policymaking and promote the creation of more sustainable cities that prioritize the environment and the well-being of their citizens.

Nazanin Rezaei
University of California Santa Cruz

Read the Original

This page is a summary of: Urban form and its impacts on air pollution and access to green space: A global analysis of 462 cities, PLoS ONE, January 2023, PLOS,
DOI: 10.1371/journal.pone.0278265.
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