Philadelphia is forcing property owners to fix up abandoned buildings to fight crime, and it's actually working.

Abandoned home in North Philadelphia. (Photo: pwbaker/Flickr)

Over the past half-century or so, urbanites have been abandoning America's cities. Post-industrial municipalities like Philadelphia, where manufacturing job losses spurred residential flight, have been hit particularly hard. Philadelphia is home to thousands of abandoned buildings, standing vacant and slowly crumbling from substandard upkeep. To remediate dilapidated neighborhoods, four years ago Philadelphia passed an ordinance requiring vacant property owners to make simple, cheap renovations to building fronts. A recent study by a team of researchers from the University of Pennsylvania, the USDA Forest Service, and the Yale School of Public Health, published this month in the journal PLoS One, sought to quantify the ordinance's effect. They've got some good news: It's working.*

Vacant buildings decrease nearby property values by up to 20 percent in some Philadelphia neighborhoods, costing the city up to $20 million in management costs—along with $2 million in lost property taxes—every year. And research shows these abandoned buildings may also be bad for city-dwellers' health and safety: Neighborhoods with vacant properties tend to have higher rates of crime, drug-related deaths, and sexually transmitted diseases.

The city saw small reductions in total crime around abandoned buildings that made moves to comply with the new ordinance.

To combat such problems, Philadelphia implemented a Doors and Windows Ordinance in 2011, which required property owners to install working, lockable doors and windows on all structures located on streets that were at least 80 percent occupied. The city hoped the ordinance would reduce the appearance of disorder, and thus reduce crime. The research team cross-referenced crime data collected between 2010 and 2013 with geographical data for buildings that complied with the ordinance and buildings that didn't, to find out if the remediation strategy worked.

The researchers found that the restoration plan had a significant effect on crime: Over the study period, the city saw small reductions in total crime, specifically in assaults, gun assaults, robberies, and nuisance crimes around abandoned buildings that made moves to comply with the new ordinance. Even greater reductions were seen around buildings that applied for renovation permits above and beyond the windows and doors.

According to the authors, the findings support the idea that rundown buildings project a tolerance for disorder and crime, a tenet of broken windows theory. "New doors and windows and a newly cleaned building facade likely signaled to potential offenders that a property was occupied," the authors write, "and therefore crimes in general, and violent and nuisance crimes were not tolerated."

Adding functional windows and doors is a relatively cheap alternative to demolishing abandoned buildings—good news for a city that's strapped for cash. The findings suggest that, for other struggling cities, similar ordinances could be a low-cost alternative to combating crime.

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*UPDATE — July 21, 2015: This article has been updated to more accurately reflect the researchers' affiliations.