Neighborhoods with a mix of residences, offices and retail outlets are now conventionally thought to have a host of benefits, a departure in thinking from the years of urban planning when cities sought to segregate uses of land, with the houses in one corner of town and the shopping district in another. Mixed-use neighborhoods enable people to walk more, with downstream health benefits. They help cut down on traffic congestion, and therefore pollution. For many people, they create livelier communities and a higher quality of life.

Cities_136x60_transparentThe list of evidence in support of these places is constantly expanding, and proponents can now add one more empirical argument: Mixed-use zoning also appears to cut down on crime.

“People say this makes intuitive sense,” says John MacDonald, the chair of the department of criminology at the University of Pennsylvania. A neighborhood with lunch counters, offices, condos and bars is likely to have more “eyes on the street” at more times of day. And this collective surveillance ostensibly deters criminals.

buente_1_351But in a new study published in the University of Pennsylvania Law Review, MacDonald and colleagues put actual data for the first time behind this notion. They examined eight high-crime neighborhoods in Los Angeles, in residential-only and commercial-only areas, as well as in neighborhoods with a mix of the uses or a change in land use over time.

The commercial-only areas had the highest crime rates – 45 percent higher – when compared to similar blocks that included residences. The researchers also found that neighborhoods experiencing a change in zoning, typically to add residences to a commercial area, saw a 7 percent drop in crime thanks mostly to a decline in automobile theft and break-ins.

The authors can’t definitely account for why these trends occur, although it makes sense that people would feel a greater sense of ownership and care for neighborhoods where they live, relative to those neighborhoods where they simply shop or go to work. Put residences in an otherwise commercial area, and that sense of ownership increases alongside the eyes on the street.

The findings suggests that we should start thinking about zoning laws as one largely overlooked tool in crime prevention. “It’s surely less costly than arresting people and putting them in jail,” MacDonald says.

nyrenulx_3_250More often when police do think about “environmental design” for crime prevention, they focus on interventions like sidewalk cameras, street lighting or new cul-de-sacs. This study, though, suggests they should also think at the level of land use, alongside urban planners.

“We thought if we can see some relationship between zoning – and also the change in zoning – and crime, then we might be a little bit closer to understanding the link between the actual physical environment and crime,” MacDonald says.

Of course, the reverse is true, too: Planners should be conscious of the fact that decisions as fundamental as how to zone a neighborhood could have implications for crime, too.

“There’s a general expectation of ‘how this is going to effect traffic or parking, the sewage system, or trash pickup?’” MacDonald says of planning decisions. “But there’s almost never even a systematic model of ‘what’s this going to do to the crime rate?’”

Reprinted with permission from The Atlantic Cities. Copyright 2013 by The Atlantic Monthly Group.