An evidence-based approach to LPR deployment means that officers and units should use LPR in ways that reflect what we know about “what works” in preventing crime and maintaining community legitimacy. These are not “best guesses” based on hunches or even anecdotal experience. Rather, evidence-based tactics and strategies are based on rigorous field research that tests for effectiveness.

Given what we know about effective patrol strategies and tactics, optimizing the crime prevention effects of LPR would require:

  1. Using LPRs to support existing tactics and strategies known to be effective in reducing, preventing and detecting crime. Effective strategies include those that are place-based, proactive, and tailored/problem-oriented. Mores information on effective policing strategies can be found in the Evidence-Based Policing Matrix.
  2. In patrol, LPRs should be placed where they can potentially have the most impact for crime prevention and detection, in those specific places, or “hot spots” of crime, auto-theft and traffic-related concerns.
  3. Patrol officers using LPR units should also consider staying in hot spots for 30 minutes or less, following the Koper curve principle, which suggests that officers are more effective in deterring criminal activity when they patrol in focused areas for relatively brief time periods. Though, based on a recent experiment, LPR-enhanced patrol at crime hot spots did not appear to have an elevated effect on crime prevention.
  4. Tailoring your approach to the specific type of area and type of data that you have to work with. See Chapter 3 of the Final Report for more detail, as well as the patrol tips offered on the left side of this page.
  5. For investigations: Tentative evidence suggests that systematic use of LPRs and strategic placement of the devices might contribute to modest improvements in case clearances for auto theft and robbery. Agencies with large numbers of LPRs might consider deploying them at fixed positions in high crime locations to assist with investigation. Further assessment is needed to determine the best uses of LPRs, the optimal scales and methods of LPR deployment, and the full range of costs and benefits associated with LPR use.

Relevant Publications

  • Koper, C.S., & Lum, C. (2018). Effectiveness of License Plate Readers for Patrol and Investigations. The Police Chief, September 2018, 14-15.
  • Koper, C.S., & Lum, C. (2019). The impacts of large-scale license plate reader deployment on criminal investigations. Police Quarterly, 22(3), 305-329.
  • Koper, C.S., Lum, C., Willis, J.J., Happeny, S., Johnson, W.D., Nichols, J., Stoltz, M., Vovak, H., Wu, X., & Nagin, D.S. (2018). Evaluating the Crime Control and Cost-Benefit Effectiveness of License Plate Recognition (LPR) Technology. Final Report to the National Institute of Justice. Fairfax, VA: Center for Evidence-Based Crime Policy, George Mason University.
  • Koper, C.S., Lum, C., Wu, X., Johnson, W., & Stoltz, M. (2022). Do license plate readers enhance the initial and residual deterrent effects of police patrol? A quasi-randomized test. Journal of Experimental Criminology, 18, 725-746.
  • Lum, C., Hibdon, J., Cave, B., Koper, C.S., & Merola, L. (2011). License plate reader (LPR) police patrols in crime hot spots: An experimental evaluation in two adjacent jurisdictions. Journal of Experimental Criminology, 7(4), 321-345.
  • Lum, C., Koper, C.S., Willis, J.J., Happeny, S., Vovak, H., & Nichols, J. (2019). The rapid diffusion of license plate readers in US law enforcement agencies. Policing: An International Journal of Police Strategies and Management, 42(3), 376-393.
  • Lum, C., Merola, L., Willis (Hibdon), J., & Cave, B. (2010). License Plate Recognition Technologies for Law Enforcement: Impact Evaluation and Community Assessment. Fairfax, VA: Center for Evidence-Based Crime Policy, George Mason University.
  • Merola, L., & Lum, C. (2012). Privacy and the impact of emerging surveillance technologies: The case of license plate recognition technology. Judicature, 96(3), 119-126.
  • Merola, L., & Lum, C. (2014). Predicting public support for the use of license plate recognition technology by police. Police Practice and Research, 15(5): 373-388.
  • Merola, L., & Lum, C. (2015). Understanding Citizen Support for License Plate Readers. Translational Criminology, 8 (Spring 2015), 23-25.
  • Merola, L., Lum, C., Cave, B., & Hibdon, J. (2014). Community support for license plate recognition. Policing: An International Journal of Police Strategies and Management, 37(1), 30-51.
  • Merola, L., Lum, C., & Murphy, R. (2018). The impact of license plate recognition technology (LPR) on trust in law enforcement: A survey-experiment. Journal of Experimental Criminology, 15(1), 55-66.
  • Willis, J.J., Koper, C.S., & Lum, C. (2018). The adaptation of license-plate readers for investigative purposes: Police technology and innovation re-invention. Justice Quarterly, 35(4), 614-638.