Neighborhood – Lasley (1998)

Study Reference:

Lasley, J. (1998). “Designing out” gang homicides and street assaults. Washington, DC: National Institute of Justice, U.S. Department of Justice.

Location in the Matrix; Methodological Rigor; Outcome:

Neighborhood; Focused; Highly Proactive; Moderately Rigorous; Effective

What police practice or strategy was examined?

Operation Cul de Sac (OCDS), a program developed by the LAPD, placed traffic barriers in neighborhoods where gangs and accompanying gang violence had spiraled out of control. The majority of drive-by shootings and violent gang encounters occurred in clusters on the periphery of neighborhoods linked to major thoroughfares. To stem the violence, the police closed all major roads leading to and from the identified hot spots by placing standard cement K-rails (freeway dividers) at the end of the streets that led directly to these roads. This reconfiguration, which essentially created cul-de-sacs, was completed within the relatively short period of a week. Later, the K-rails were replaced with fixed iron fences which featured a locked gate that could be opened to permit access by emergency vehicles. Most of the traffic barrier configurations generally allowed one unrestricted roadway entrance/exit point. OCDS was tested in a 10-block area (roughly the size of a census tract) that in 1989 experienced the highest average number of drive-by shootings, gang homicides, and street assaults in the city of Los Angeles.

How was the intervention evaluated?

The program was fully functional from January 1990 to December 1991. The researchers studied crime in the target area from 1989 to 1992 to compare crime levels before the program began, while it was implemented, and after the barriers were removed. The study focused on gang-related homicides, gang-related aggravated assaults, and property crimes. The patrol division surrounding the OCDS site served as a comparison. The researchers also examined whether crime had been displaced from the OCDS site to the contiguous comparison area.

What were the key findings?

The number of homicides and assaults in the OCDS area fell significantly during the 2 years the program was operating and rose after it ceased operations. In the comparison area, the level of these crimes remained constant. Property crime decreased substantially during the first year of the program, but also decreased in the comparison area. The statistically significant rise in homicide and assault in the OCDS area after the program ended coincided with the reopening of traffic access to selected gang hot spots.

What were the implications for law enforcement?

Putting up barriers to reduce traffic flow and increase defensible space can reduce violence in high-risk areas. The general approach is to use barriers to make suspect activity more visible in neighborhoods.

Where can I find more information about this intervention, similar types of intervention, or related studies?