Research review: Identifying the benefits of ALPR systems
How law enforcement agencies can use research findings to get community support and funding for ALPR systems
A scholarly article evaluating automated license plate reader (ALPR) use appeared in the May 2016 edition of The Police Journal. The author, Murat Ozer, a professor of criminal justice at the University of Cincinnati, studied the deployment of ALPR systems in eight patrol cars operated by the Cincinnati Police Department (CPD). Below are some of the highlights of Dr. Ozer’s study.
Efficiencies of ALPR systems
One of the reasons that ALPR systems are so effective in improving the efficiency of police officers is that at least 70% of crimes involve the use of a motor vehicle. Vehicles operated on public highways must be registered and bear license plates. ALPR systems scan license plates continuously and automatically, use optical character recognition software to translate the scans into text and compare the result against one of more “hotlists” loaded into the system.
Using the traditional method of either calling in each plate to a dispatcher over the radio or keying plate numbers into a mobile data terminal, an officer can check a maximum of 150 plates per hour. This assumes the officer is not interrupted and can devote his full attention to the task. By comparison, an ALPR system can scan 3,600 vehicles in the same period, and does not require the officer’s attention, other than to verify hits generated by the system.
Early deployments of alpr systems
The efficacy of ALPR systems has been apparent from the beginning.
One of the earliest trials of the technology was in the United Kingdom in 2002, using systems that were primitive as compared to those available today. In 13 months, the British police stopped 180,543 vehicles based on hits generated by ALPR systems. These stops resulted in 13,499 arrests, recovery of 1,152 stolen vehicles, seizure of £380,000 in illegal drugs, and recapture of £640,000 of stolen property. The number of arrests was about 10 times more than the number of arrests made by officers without ALPR systems.
The Royal Canadian Mounted Police (RCMP) had a different experience when only about 1% of stolen vehicles recovered in October 2006 came about through identification by an ALPR-equipped constable. The RCMP attributed the low identification rate to the practice of car thieves altering license plates or abandoning the vehicle after the crime was committed.
Cincinnati Police Department ALPR study
The eight ALPR-equipped cars operated by the CPD scanned 2,823,944 license plates during the 12 months from July 2008 to July 2009. The cars were operated by 30 officers during this period. Those officers made 844 “follow-up” arrests during the study period.
In this context, a follow-up arrest was one related to a crime that had been previously reported, as opposed to one where the crime was observed by the officer. During the same period, 111 officers who did not work ALPR-equipped cars made 242 follow-up arrests. The officers in the ALPR cars were almost 15 times as efficient at making arrests than those who did not have access to the technology.
The efficiency of the ALPR-equipped officers was not consistent over all types of crime. The officers with ALPR actually made fewer violent crime arrests than those without, but they excelled at arrests for property crimes.
ALPR was found to be considerably more cost-effective than traditional policing methods, even after accounting for the cost of purchasing the systems. The differences in efficiency showed that the ALPR systems amortized themselves in less than 21 days.
As with most research articles published for academic journals, this one was heavy with statistical analyses and methods. This summary details the high points, but anyone who plans on using the article to support the purchase of an ALPR system should read the original work.