"You remove the abandoned automobiles, all the abandoned trash where you can hide firearms," said lead author Charles Branas, an associate professor of epidemiology at Penn's Perelman School of Medicine. "All of a sudden, it makes it more challenging for illegal guns to move around the neighborhood."
The authors said the decrease in crime might also be partly explained by the "broken-windows" theory, which proposes that boarded-up windows, vandalism, and other signs of decay can serve as a magnet for serious crime, because they suggest that no one is in control.
Told of the study findings, Police Commissioner Charles H. Ramsey said both explanations made sense - the elimination of hiding places for guns, and the broader perception that an environment is safe.
"If you bring something special to a neighborhood, it helps to make people feel a little bit better about where they are and where they live," Ramsey said, adding that he expects the city's Mural Arts Program to have a similar impact.
Other studies have linked crime rates with elements of the surrounding environment, including a Penn study on take-out liquor stores. But the new research appeared to be the first to look at the effects of transforming vacant lots.
The greening program, a major effort begun under Mayor John F. Street that has received national attention as a weapon against urban blight, involves trash removal and the planting of grass and a few trees. A low wooden fence is typically erected around the border.
