Kansas City Preventive Patrol Experiment

Summary

For decades, the dominant assumption in policing was that more patrol cars on streets reduced crime and made residents feel safer. This landmark RCT tested that assumption directly by randomly assigning patrol beats to receive no proactive patrol, standard patrol, or dramatically increased patrol. No meaningful differences emerged on crime rates, citizen fear, or satisfaction. The null result fundamentally changed the theory of patrol in policing and is among the most cited criminal justice experiments in history.

Research question

"Does increasing routine police patrol levels reduce crime rates?"

Methodology

Result

Null

No significant difference across conditions on any primary outcome

Evidence strength

Strong

Randomized controlled trial with large sample.

Replication status

Partially replicated