Lum, C., Merola, L., Willis, J., & Cave, B. (2010). License plate recognition technology (LPR): Impact evaluation and community assessment. Charleston, SC: Space and Naval Warfare Systems Command (SPAWAR).
Lum, C., Hibdon, J., Cave, B., Koper, C. & 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.
Location in the Matrix; Methodological Rigor; Outcome:
Micro-places, General, Proactive; Very Rigorous; No evidence of an effect
What police practice or strategy was examined?
The study examined the impact of hot spot patrols with license plate recognition (LPR) technology. LPRs scan the license plates of moving or parked vehicles and can do so while either mounted on a moving patrol car or attached to a fixed location, such as a toll plaza. Once a plate is scanned and its alphanumeric pattern is read by the LPR system, the technology compares the license plate against an existing database of plates that are of interest to law enforcement. If a match is found, officers are alerted to proceed with further confirmation, investigation, and action. The LPR allows an officer to scan and check hundreds of vehicles within minutes. The LPR deployment evaluated in this study involved brief hot spot patrols by LPR-equipped patrol cars. An LPR patrol unit would conduct a “sweep” through the hot spot location and then conduct fixed surveillance in the location for up to 30 minutes (visits to hot spots were limited to 30 minutes based on the Koper Curve principle of hot spots patrol).
How was the intervention evaluated?
The study was a multi-jurisdiction randomized experiment that tested the impact of LPR deployment on vehicle theft, theft from auto, other auto-related crimes (i.e., driving while intoxicated and reckless driving), and general crime and disorder (as measured by crimes against persons and property, weapon-related crimes, disorderly behaviors, and drug activity). The authors used GIS to identify thirty hot spots of auto theft in across two jurisdictions and then randomly allocated LPR patrol to half of these hot spots. In each jurisdiction, two officers conducted separate LPR patrols in marked police units for 26 to 30 days spread over multiple months. On these days, each LPR officer was assigned to patrol five hot spots, chosen at random from the experimental hot spots in that officer’s jurisdiction (thus not all LPR locations were patrolled each day). The officers generally patrolled each of their assigned locations once per day, conducting a mix of roaming and fixed surveillance with the LPRs for up to 30 minutes in each spot.
What were the key findings?
Examination of the effects of LPR patrol revealed no discernable differences in the levels of crime during or after the intervention period between experimental and control hot spots. Similarly, the authors found no evidence of program effects on auto theft or other auto-related crimes.
What were the implications for law enforcement?
The results could indicate that LPR deployment does not lead to measurable crime-reduction effects. However, the authors strongly urged agencies and researchers to consider further testing of police technologies before coming to that conclusion. In particular, it is possible that more intensive LPR deployment and/or expanding the database underlying LPR systems (the data used in this project consisted primarily of state and national data on stolen vehicles) could lead to greater effects.
Where can I find more information about this intervention, similar types of intervention, or related studies?