Who Sprawls the Most in 2020 and What Has Changed Since 2010? Measuring Metropolitan Sprawl and Tracking a Decade of Changes in the United States

Problem, research strategy, and findings Urban sprawl and its impacts on quality of life remain a long-standing debate in planning, heightened today by challenges of health, housing, and climate crises. In this study we developed a multidimensional compactness index for 233 large and medium-sized U.S. metropolitan areas in 2020, drawing on 21 built environment variables across four urban form dimensions: density, land use mix, centering, and street connectivity. We successfully validated this index against transportation outcomes using both inferential and machine learning approaches. Finally, we developed a comparable index for 2010 and tracked changes in sprawl in the past decade. Results showed wide variations across regions, with Riverside (CA) ranking as the most sprawling (index = 54.32) and San Francisco (CA) as the most compact (index = 242.91) in 2020. According to our longitudinal analysis, metropolitan areas have become slightly more sprawling, but the rankings remained relatively stable. However, a closer look at score changes for individual metropolitan statistical areas (MSAs) revealed a different narrative. Atlanta (GA) is on the top of the list of most sprawling MSAs in both years though it has experienced an impressive increase in its compactness score (mostly centering score) during this period. We further discuss several MSAs with noticeable score changes. Our transportation analyses suggest 120 as a threshold value in which compactness meaningfully increases the predicted share of walking and transit commuting, whereas for the household vehicle ownership and average drive time, the threshold is roughly 100.Takeaway for practice The updated compactness indices and their changes since 2010 provide planners and policymakers with a practical tool to benchmark and monitor metropolitan development patterns. By identifying thresholds where compactness begins to yield significant transportation and sustainability benefits, the index can guide target setting, prioritize interventions, and support planning processes aimed at reducing car dependence and advancing sustainable metropolitan development.