Kansas City Preventive Patrol Experiment

The Kansas City Preventive Patrol Experiment was a landmark study in policing that demonstrated the ineffectiveness of traditional preventive patrol, opening the door for innovations in policing.

The Kansas City Preventive Patrol Experiment was a significant study in the history of policing that aimed to investigate the effectiveness of preventive patrol, one of the most commonly used policing strategies in the United States at the time. The study was conducted in 1972 by the Kansas City Police Department with the assistance of researchers from the Police Foundation.

The experiment was designed to test the belief that increasing police patrols in certain areas would decrease crime rates. The researchers divided a 15-square-mile area of Kansas City into three groups: a control group where patrols remained unchanged, an experimental group where patrols were increased, and a third group where patrols were decreased. The study lasted for a year and analyzed crime rates, citizen perceptions of police, and response times.

Many law enforcement professionals and researchers were surprised by the experiment’s findings. The study revealed that increasing the level of police patrols did not significantly reduce crime rates, and decreasing patrols did not lead to an increase in crime rates. The study also found that citizens’ perceptions of police were not significantly affected by the level of police patrols.

The results of the Kansas City Preventive Patrol Experiment had significant implications for the field of policing. They challenged the traditional belief that more police patrols equate to greater public safety. The findings of the study led to a shift in policing strategies towards community-oriented policing, problem-oriented policing, and other approaches that prioritize problem-solving and building relationships between police officers and the community they serve.

One of the main takeaways from the experiment was the need to focus on crime prevention strategies that are evidence-based and supported by data. It also demonstrated the importance of evaluating the effectiveness of policing strategies to determine their impact on crime rates and the community.

The Kansas City Preventive Patrol Experiment had a significant impact on the field of policing and continues to inform police practices and strategies today. It is considered one of the most influential studies in the history of policing and serves as a reminder of the importance of evidence-based practices and evaluation in the field of criminal justice.

The Experimental Design

The Kansas City Preventive Patrol Experiment illustrates how a carefully planned field study can be conducted within a police department to test fundamental assumptions about policing. First, project planners clearly stated the hypothesis: Would reducing or increasing routine preventive patrol in certain areas affect crime rates, arrests, fear of crime, or citizen attitudes? The next step involved selecting a suitable area—15 police beats that reflected diverse socioeconomic characteristics. These beats were then randomly assigned to one of three conditions: reactive, control, or proactive.

Random Assignment. Each of the 15 beats was placed into a group of three based on comparable crime data and population factors. Within each group, one beat was designated as reactive (no routine patrol), one remained at the usual patrol level (control), and one received two or three times the normal patrol (proactive). By assigning beats randomly within matched groupings, the study isolated patrol level as the key independent variable while ensuring that other potential influences—such as neighborhood conditions—were distributed across all test groups.

Operational Guidelines. Officers in reactive beats entered only to handle dispatched calls, then left immediately to resume patrol in adjacent proactive beats. Control beats kept their standard staffing, and proactive beats received additional marked units. Officers were otherwise free to handle their shifts as usual. Police command staff verified compliance by monitoring crime reports and officer assignments; the study could be suspended if crime surged in the reactive beats. It never did, which allowed the research to continue a full year.

Multiple Measurements. Evaluators gathered diverse data to capture how different patrol dosages might influence outcomes. Beyond departmental crime statistics, independent victimization surveys were conducted with residents and businesses to detect unreported crimes. Attitudinal surveys measured fear of crime and satisfaction with police. Observers rode along with officers to capture how citizen encounters and officer behaviors might vary by experimental condition. Response times were timed from dispatch to actual contact with the caller. Commercial surveys were used to gauge any protective measures adopted by businesses. This multi-pronged approach allowed evaluators to cross-check official figures against firsthand accounts of crime and policing.

Maintaining Rigor. By imposing clear rules and systematically measuring patrol levels, the study retained strong internal validity. Monitors ensured officers assigned to reactive beats did not drift into routine patrol. Specialized units, such as canine or helicopter divisions, were held to their usual service patterns to avoid “flooding” one area. When unanticipated problems arose—such as personnel shortages or confusion over guidelines—leadership paused the study, corrected the issues, and restarted.

Value for Policing. This experiment showed that departments can implement robust field designs to test standard practices without jeopardizing public safety. Random assignment, close monitoring, consistent measurement tools, and a willingness to rethink conventional methods were crucial. These principles can apply to many policing strategies, from traffic enforcement initiatives to neighborhood foot patrol. The Kansas City Preventive Patrol Experiment thus stands as a model of how true experiments in policing can be organized and carried out.

The Kansas City Preventive Patrol Experiment was designed and conducted as a true experiment. Its key defining feature was the random assignment of 15 matched beats into reactive, control, or proactive conditions. Because random assignment balances out potential differences across beats and isolates the effect of patrol levels as the main variable, it meets the core requirement of experimental research. The study also maintained strict protocols to ensure each patrol condition was delivered as intended, further reinforcing its credibility as a genuine field experiment in policing.

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