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Back to Archives | Back to November 2008 Contents 

The Role of Automatic License Plate Recognition Technology in Policing: Results from the Lower Mainland of British Columbia

By Inspector Norm Gaumont, Officer in Charge, “E” Division Traffic Services; and Constable Dave Babineau, Media Relations Officer, Royal Canadian Mounted Police Traffic Services in British Columbia



he advancement of technology has definitely changed the way people live their lives. Cellular telephones, laptop computers, wireless technology, and digital music players have all affected modern society in ways unimaginable just 15 years ago. The world of policing is no different: automatic license plate recognition (ALPR) technology has the potential to have a huge impact on the future of policing in Canada.

ALPR was developed in 1992 at Cambridge University in the United Kingdom in response to terrorism. In 1993, the Irish Republican Army bombed Bishopsgate, in the heart of London’s financial district. The massive explosion shattered windows and destroyed several buildings. One person was killed and more than 40 were injured in the blast. Immediately after the attack, the U.K. government erected what it called the “ring of steel” around the city. There were roadblocks in and out of the financial district; security remained high for some time. By 1996, ALPR technology was present at every western U.K. port to read every license plate entering the country from Ireland. The United Kingdom continues to lead the way when it comes to the use of ALPR technology. There are more than 3,000 cameras, stationary and mobile, across the country. In 1999, the government made a huge purchase, supplying every police force in England and Wales (43 total) with van-based systems. In 2002, British police recognized that the most effective way of exploiting ALPR technology was to use it with dedicated intercept teams.1

At the other end of the spectrum, in 2006, the Royal Canadian Mounted Police (RCMP) in British Columbia, Canada, initiated a pilot project to assess the viability of ALPR technology in the province. Four fully marked and five unmarked police vehicles were equipped with the technology and were deployed as part of the project for use with traffic and criminal violations.

The project was originally launched in the Lower Mainland of British Columbia (Greater Vancouver) as a result of the large number of auto thefts in the area. Over the last decade the province gained the reputation of being a world leader in auto thefts per capita. The city of Surrey had quickly become known as the auto theft capital of the world,2 a reputation that the Integrated Municipal Provincial Auto Crime Team (IMPACT) wanted to change. In 2005 alone, nearly 6,500 auto thefts were reported. As a result, IMPACT wanted to look into the feasibility of ALPR technology as a tool to combat the problem.3


How Does ALPR Technology Work?

ALPR technology was designed to capture and process images of license plates and then check them against a database of known plates. The list of known license plates (called the hotlist) is updated daily at the beginning of each shift. The information comes from the Canadian Police Information Centre (CPIC) and the British Columbia Motor Vehicle Branch (ICBC). A hotlist consists of the following information:

  • Stolen license plates

  • Plates associated with stolen vehicles

  • Plates associated with prohibited drivers

  • Plates associated with unlicensed drivers

  • Plates associated with uninsured vehicles

Plates associated with persons of interest are not yet available but are coming soon. This information will include wanted persons, sex offenders, charged persons, known criminals, and so on. When necessary, data can be entered manually for AMBER Alerts.

ALPR uses video cameras in combination with infrared (IR) illuminators that are capable of capturing the image of the front or the rear of a vehicle that passes through its field of vision. Each ALPR vehicle is equipped with two or three camera systems and an onboard computer. Each camera system consists of two cameras: one captures an image of the license plate, and the other captures an image of the vehicle (see figure 1). Each camera system is IR supported, enabling the cameras to capture images in low light, adverse weather conditions, and even total darkness.
Figure 1
Figure 1. ALPR cameras mounted on top of a patrol car
Photo by Corporal D. A. Reichert, “E” Division Traffic Services

The technology has the potential ability to capture up to 3,000 license plates per hour. The number of plates actually captured ultimately depends on traffic volume and road design. It stands to reason that the more vehicles are on the road, the more images the system can capture. Road design may play an even bigger role than traffic volume. ALPR technology has the capability to photograph vehicles that are on both sides of as well as to the front and the back of the police car to which the cameras are attached. However, the cameras can take pictures of only those vehicles that are in the lanes directly beside the cruiser. This can create problems on multilane highways or lanes that are separated from the camera by a median.

ALPR-equipped police vehicles are deployed on public streets and in parking lots, indiscriminately capturing images of both mobile and stationary vehicles that enter the camera’s field of view. The image processing software then analyzes the images and extracts only the license plate characters—discarding all other information such as jurisdiction of issue, yearly validation stickers or tags, logos, flags, and the like (see figure 2).

Figure 2
Figure 2. License plate as photographed by an ALPR camera (left) and after extraneous information has been removed (right)
Photo by Corporal D. A. Reichert, “E” Division Traffic Services
The captured license plate characters are checked against the hotlist of known license plates in the onboard computer. If the plate in the image is found in any of the hotlists, the system emits an audible alarm, alerting the operator. Appropriate action can then be taken.

The system stores the images and the exact global coordinates of the location of the hit. All of the data collected by the ALPR system are uploaded to a secure server. The hits are stored for two years in accordance with the Privacy Act, and the nonhits are kept for 90 days. Following the respective time periods, the data are purged automatically.


ALPR Technology in Canada

ALPR technology has been in use in Canada for some time. The Canada Border Security Agency has been using a stationary application to read license plates of vehicles as they approach border guard booths. This allows guards to read pertinent information on the vehicles approaching the booths as well as their registered owners prior to having face-to-face contact with the drivers. This type of system is also used in Toronto for toll collection purposes.

The RCMP in British Columbia is the first police agency in Canada to evaluate the feasibility of ALPR technology for traffic and criminal code enforcement. To test its effectiveness, four unmarked police vehicles were equipped with ALPR technology and were deployed between October 10 and October 31, 2006, in the city of Surrey. The four cars were on the road seven days a week, approximately 22 hours a day. They were each assigned a specific corridor for the entire week. In total, 177,985 plates were read by the four police vehicles. Most of the plates were read during the day shift. Overall, 1,642 plates were read by each car per shift, an average of 149 per hour. This number is much lower than the estimated ALPR capability of up to 3,000 plates per hour. The lower rate in this study is most likely due to the road design in Surrey.4

Of the 177,985 plates read during the initial study, 3,873 were hits. The average number of hits for each of the four ALPR-equipped test vehicles was evenly distributed. In this phase, 1.5 percent of all the plates read resulted in a hit, an average of 3.6 hits per hour during a day shift and one hit per hour at night. Looking at the hit rates or how many cars were photographed before getting a hit reveals that there was not a significant difference according to shift type. The average hit rate for the day shift was one hit per 67.9 plates read and 65.6 at night. The collection of baseline data relating to hit rates was extremely important in measuring the future success of ALPR technology. The ability to compare hit rates over a period of time is vital. A significant reduction in the number of hits would show that the ALPR program is working to deter auto-related offenses.5

In this phase of the program, collected data were related to four types of hits: unlicensed drivers, uninsured vehicles, prohibited drivers, and stolen vehicles (see table 1 for breakdown). It showed that about 70 percent of the hits were for unlicensed drivers, about 20 percent for uninsured vehicles, about 8 percent for prohibited drivers, and less than 1 percent for stolen vehicles. Most of the plates that were read incorrectly by the ALPR systems were from stolen vehicles. It is believed that the reason for this is that once auto thieves have stolen a vehicle, they will do something to alter the plates’ appearance, perhaps partially covering them or obscuring the characters with dirt. This, obviously, makes it much more difficult to identify a stolen vehicle and explains the low percentage of overall hits on stolen cars.

Table 1

ALPR Applications

ALPR is being used at sobriety road checks in British Columbia. Officers park the ALPR vehicle a short distance away from the check and scan the license plates of vehicles as they approach the check stop. If a hit is registered, officers at the check are advised and the driver is confronted. This application has resulted in the recovery of stolen vehicles and other property, the execution of warrants, and the apprehension of unlicensed and prohibited drivers, to name a few. Covert vehicles equipped with ALPR systems can also be used by surveillance teams to target suspect vehicles. Using ALPR-equipped vehicles in this way can help avoid pursuits, eliminate damage, and prevent injury or death as a result of a collision.


Benefits of ALPR Technology

Improved Performance and Efficiency: There is no comparison between the number of plates an officer on patrol entering license plate information manually into an onboard computer and the number that automated ALPR technology can handle. With the potential ability to read up to 3,000 plates an hour, this technology cannot help but improve productivity. Not only does the system read plates rapidly, but hits are collected only on vehicles displaying license plates that match the desired criteria and appear in the database. Lawabiding citizens are not targeted or negatively affected in any way. Data collected in the United Kingdom showed that ALPR hits accounted for 56 percent of the vehicles stopped and generated 54 percent of the arrests. Of those arrested, 55 percent had previous criminal records. Data from the United Kingdom further suggest that ALPR-enabled intercept teams achieve an arrest rate 10 times greater than the national average.6 Because the ALPR system can check many more plates than an officer can manually, officers will make many more roadside stops, thus enhancing the level of police visibility within their communities, which in turn can increase public confidence in the police.

Increased Crime Detection: The substantially larger number of vehicles pulled over as a result of ALPR technology in patrol cars means that officers will come face to face with more criminals, generating more arrests. U.K. data suggest that the national deployment of 365 APLR teams would generate 219,000 additional arrests per year. Officers attached to ALPR teams make 10 times more arrests than non-ALPR members. Arrests that are the result of ALPR stops are primarily for vehicle crimes, robbery, theft, burglary, and drug offenses. It is well known that car thieves steal cars not just to go for a drive but to help them commit other crimes such as breaking and entering, robbery, home invasion, and drug trafficking. In this way, ALPR technology can be valuable in preventing or solving many types of crime plaguing society.


Privacy Impact Assessment

The use of ALPR technology is presently a pilot project in the Lower Mainland of British Columbia. The RCMP is finalizing a Privacy Impact Assessment document that will be reviewed by the federal and provincial privacy commissioner, who will provide feedback as to any privacy concerns. Once these concerns have been addressed, the ALPR program will be expanded to include the entire province.


Conclusion

Research shows that ALPR technology offers several benefits to law enforcement agencies in the province of British Columbia. The ability to scan a large number of license plates in a short period of time is no doubt the number one benefit. There is simply no way that an officer working manually could ever come close to keeping up the pace set by ALPR cameras. The end result is increased police efficiency, higher productivity, more arrests, more convictions, and hopefully a greater deterrent to those committing crimes. The use of ALPR technology should improve officer safety, as it eliminates the need for officers to enter plate information manually into the onboard computers, allowing them to focus their full attention on driving.

There could, however, be limitations when it comes to the use of this technology. The increased number of hits could prove to be overwhelming for officers who respond to them. It would substantially increase officers’ workloads and could reduce their ability to respond not only to ALPR hits but to other calls for service as well. Because this is very likely to happen, agencies using ALPR cameras must develop a strategy that enables their officers to prioritize their responses.

Once the Privacy Impact Assessment is complete and the technology is in use across the province, there is no doubt that ALPR technology will have a very positive impact on all criminal and motor vehicle offenses in the province of British Columbia. Car thieves, prohibited drivers, and unlicensed drivers should beware. ■

Notes:


1U.K. Home Office/Association of Chief Police Officers, Engaging Criminality: Denying Criminals Use of the Roads (PA Consulting Group, October 2003), 6, https://www.paconsulting.com/NR/rdonlyres/8BEBFD54-94DC-4274-8283-EE1A66D0E09E/0/ANPR_report_24_Oct.pdf (accessed October 10, 2008).
2Ineke Schuurman, “An Examination of the Feasibility of Automated Licence Plate Recognition Technology for Parking Lot Deployment” (master’s thesis, University College of the Fraser Valley, Abbotsford, B.C., 2007).
3In 2007, IMPACT won the IACP Vehicle Theft Award of Merit for multiagency task forces; see http://www.theiacp.org/awards/2007vehtheft.pdf for details.
4Irwin M. Cohen, Darryl Plecas, and Amanda V. McCormick, “A Report on the Utility of the Automatic Licence Plate Recognition System in British Columbia” (unpublished, School of Criminology and Criminal Justice, University College of the Fraser Valley, 2007), 7. Note that none of the roadways in Surrey have three lanes traveling in the same direction.
5Ibid., 8–15.
6U.K. Home Office/Association of Chief Police Officers, Engaging Criminality, 2.

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From The Police Chief, vol. LXXV, no. 11, November 2008. Copyright held by the International Association of Chiefs of Police, 515 North Washington Street, Alexandria, VA 22314 USA.








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