In Philadelphia, the local authority has undertaken a project to green vacant lots, with the aim of improving the city.
Research by Charles Branas, a professor of epidemiology at the University of Pennsylvania, has shown that not only did this have the desired aesthetic effect, it also lead to a reduction in violent crime in those areas.
He joins Brian Johnston, IP's editor in chief, to discuss his work.
Read the full research: http://injuryprevention.bmj.com/content/19/3/198