Can increasing preventive patrol in large geographic areas reduce crime? A systematic review and meta-analysis

Research summary: We conducted a systematic review and meta-analysis examining whether increasing preventive patrol in large areas reduces crime. Our review included experimental and quasi-experimental studies that focused on areas such as beats, precincts, or entire jurisdictions and that measured a crime outcome either through official data or surveys. We identified 17 studies to include in our review. We used two methods for assessing study impacts: an approach which identified a primary/general outcome measure and a second approach which used robust variance estimation (RVE) and included all effect sizes across each study. Both approaches showed small crime prevention benefits (RVE: 9% decline; primary/general: 6% decline), but only the RVE model was significant at conventional levels (p < 0.05). There was no significant evidence of displacement. Moderator analyses suggest that as dosage increases so do the crime prevention impacts. In RVE models, preventive patrol was associated with significant reductions in property and violent crime, but nonsignificant increases in drug and disorder offenses. Policy implications: Increasing preventive patrol activities has the potential to reduce crime in large administrative areas. At the same time, existing studies offer little guidance as to how such preventive patrol should be carried out. Deterrence theory, as well as evidence from studies of hot spots policing, suggests that the greatest benefits will be gained from informing patrol efforts about where and when crime occurs. Although more research is needed regarding patrol allocations in large areas, present knowledge suggests that the more such patrols can be targeted at specific places at specific times, the greater will be the crime control benefits. In this context, we argue that police agencies may want to apply a hybrid approach to police patrol, which would include a combination of hot spots policing units and general patrol units informed by data on where crime is concentrated.