The University of Pennsylvania Law Review published a far-reaching study of Los Angeles by four researchers who found that mixed-use areas have lower crime rates than mono-use commercial areas. The authors summarize:
First, we conducted a study of the effect of zoning on crime using 205 blocks selected in eight different relatively high crime neighborhoods in Los Angeles that have similar demographic characteristics but different forms of zoned land use. We find that mixed commercial- and residential-zoned areas are associated with lower crime than are commercial-only zoned areas. Second, we matched neighborhoods undergoing zoning changes between2006 and 2010 with neighborhoods that underwent no zoning changes during this period but had similar preexisting crime trajectories between 1994 and 2005. The primary zoning change in these neighborhoods was to convert parcels to residential uses. We find that neighborhoods in which there was a zoning change experienced a significant decline in crime. Our results suggest that mixing residential-only zoning into commercial blocks may be a promising means of reducing crime.
The authors give credence to Jane Jacobs' "eyes on the street" theory as a crime deterrent (though they disagree with her with respect to the impact of taverns and question the theory's efficacy when inserting commercial in a residential area), published in 1961's The Death and Life of Great American Cities:
Individuals who act as “eyes on the street” and are proactive in calling the police, or asking questions of potential criminals, may be more prevalent in areas where natural surveillance makes the observation of strangers on the street easier. The process by which individuals living in neighborhoods actively intervene in ways that discourage problem behaviors has been termed “collective efficacy.”
The authors state that "increasing walkability through zoning changes could substantially influence the crime rates on city blocks in Los Angeles." That makes sense. Its hard to give meaningful surveillance when in a car speeding at 45 miles per hour.