Evidence-Based Policing Matrix
Micro Places – Chaiken et al. (1975)
Chaiken, J. M. (1974). The impact of police activity on crime: Robberies on the New York City subway system. New York, NY: New York City Rand Inst.
Location in the Matrix; Methodological Rigor; Outcome:
Micro places, General, Proactive; Moderately Rigorous; Effective
What police practice or strategy was examined?
The study examined the deployment practices of the Transit Authority Police Department (TAPD, a separate police force with jurisdiction over the New York City subways) and their impact on subway crime. In 1965, a tripling of the Transit Police force (including both patrolman and detectives) was ordered by the Mayor, increasing the force from 1,219 to over 3,100 officers, to patrol every station and train in the system from 8 p.m. to 4 a.m. and to conduct investigations of robbery incidents as a response to a rising subway crime rate. The intervention remained fairly constant between 1965 and 1971, which constitutes the main study period of this evaluation. This article examined the treatment impact, and in particular, it examined subway robbery incidence patterns and how they changed over time with the new deployment practice.
How was the intervention evaluated?
The study reviewed robbery incidence patterns, along with characteristics of robbery and the men who committed them. It examined the deployment, activities, and arrest rates of the TAPD before and after the intervention and compared to changes in subway robbery and other felony and misdemeanor crimes during this time. This study also compared crime during the intervention hours and non-intervention hours, and compared subway robbery crime with bus and taxicab robbery crime during the intervention to evaluate any possible displacement or diffusion effects.
What were the key findings?
The uniformed patrol reduced both minor and felony crimes, with a greater effect on felonies. There was no evidence for displacement of crimes to other times in the short run. Rather, they found a “phantom effect”, in which crime also decreased during the non-intervention hours for approximately eight months. After that, crime increased largely during the day time non-intervention hours.
The author was unable to determine whether displacement to other targets took place, as the number of subway robberies deterred in 1965 was small compared to the above-ground robbery rates. The robbers tend to concentrate in certain stations, located in areas with high surface crime rates. In addition, the stakeout techniques developed by detectives increased the arrest rates (cases cleared with an arrest made) of token booth robbers but did not appear to deter crime.
What were the implications for law enforcement?
Increases in subway patrols reduced robbery and other crimes in the subway system. Police should adopt a flexible deployment schedule to cover the most risky time periods and places in order to more effectively control subway crime. Temporary redeployments of officers might also maximize the “phantom effects” of patrol by creating greater uncertainty about police patterns among offenders. This might also reduce patrol expenses.
Where can I find more information about this intervention, similar types of intervention, or related studies?