Reference: Lasley, J. (1996). "Designing out" gang homicides and street assaults. Washington, DC: National Institute of Justice, U.S. Department of Justice.

Strategy: Street closures

Matrix Dimensions:
X-axis: Communities/neighborhoods
Y-axis: Focused
Z-axis: Highly Proactive

Results: Statistically significant success
Violent crime drops, but not property crime using two year time-series; no evidence of displacement

Methodological Rigor: Moderate- time series

Abstract: (from NCJRS) The use of traffic barriers to block automobile access to streets was examined to determine whether this tactic could reduce gang crime and violence in Los Angeles. The Los Angeles Police Department (LAPD) operated Operation Cul de Sac (OCDS) in 1990 and 1991 and placed traffic barriers in neighborhoods where gangs and accompanying gang violence had spiraled out of control. These neighborhoods had experienced the highest number of drive-by shootings, gang homicides, and street assaults in the city in the year before the project was launched. OCDS was based on the theory of situational crime prevention. The LAPD noted that in the OCDS target area, gang crime clustered on the periphery of neighborhoods linked to major roadways. The traffic barriers were intended to block the opportunities that the roadways created. Evaluation results revealed that OCDS appeared to reduce violent crime but did not affect property crime. The number of homicides and street assaults declined significantly in both years and increased after the program ended. Crime was not displaced to other areas. Findings indicated that traffic barriers can be used as part of an approach to maximize neighborhood residents' defensible space by increasing their span of control. Zones configured with the barriers heighten the visibility of suspect activities. They can be particularly effective when combined with natural guardians in the form of people who serve as informal sources of surveillance and social control. Further research should evaluate the tactic's effectiveness at other sites.