City streets safer than suburban roads, study finds - Plan Philly

New research from the University of Pennsylvania shows that denser cities and towns can save lives.

The four-year long study compared Pennsylvania Department of Transportation records of all car accidents in a five-county region with population data, socioeconomic factors, different road types, and other factors. The resulting analysis, which examined collision data from 2010 and 2014, showed that the densest parts of the region –– like downtown Philly or suburban town centers –– had lower accident rates than more sprawling areas.

“In general, at least in a relatively dense city like Philadelphia, you see traffic safety benefits coming with high density,” said Erick Guerra, co-author of the study and an assistant professor of urban planning at Penn.

Fewer roads and slower traffic speeds in Philly explain some of the difference in crash rates. The region’s densest census tracts house 28% of the Delaware Valley’s population, but just 6% of all roadways and far fewer high-speed boulevards or highways. Across the five-county region, roads with average speeds of 45 miles-per-hour witnessed 10 times more deaths on average than roads with 25 miles-per-hour speed limits, the study found.

But Guerra said those results come with a big caveat that may raise questions about traffic planning in suburban Bucks, Montgomery, Delaware and Chester counties.

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