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Hendon Publishing

Advancements in Automated License Plate Recognition Systems

Today’s law enforcement community is being inundated with technology. It is not just the technology that is overwhelming. The sheer pace with which the technology advances makes it very difficult to keep up. Just look at what is out there: mobile computing software, computer-aided dispatch software, records management software, AVL/GPS mapping software, in-car camera systems and, of course, automated license plate recognition or automated license plate reader (ALPR) systems.

ALPR systems are somewhat new to front-line policing, but they have been used in other areas and other countries for many years. Areas like ground border crossings, tolling, congestion charging, access control, traffic monitoring and automated site security solutions, military, airports, parking lots, highways and many others.

ALPR typically consists of several cameras mounted on the roof of a vehicle, usually in three “pods,” one center, one right, and one left. In a pod, there may be one infrared (IR) camera to read the plate and a color camera to capture the vehicle. Some of the newer systems offer more cameras as they are now much smaller. Some new cameras are slim enough to fit between the lightbar and the roof of the vehicle.

The first generations of ALPR were large, difficult to install, difficult to conceal and not very accurate. Today, infrared camera technology and a major reduction in camera size have allowed for some very cost-effective, high-quality systems. Infrared illuminators provide a light source for the IR cameras. This allows the cameras to take plate images day or night and in almost any weather conditions. IR allows the cameras to see even when there is sun glare and other difficult conditions.

After the picture is taken, the system’s processor takes the computer-readable text and runs it against one or more “hot lists” (lists of plates of target or stolen vehicles) stored in the vehicle’s trunk-mounted processor. Hot lists are generally downloaded to each ALPR police vehicle either wirelessly or manually at the beginning of each shift.

The system usually returns a “hit” within seconds, and most systems have some type of display that shows the plate for confirmation along with an overview of the target vehicle. All hits are commonly stamped with GPS location and time / date. Audible responses are also common, with voice confirmation of a hit, repeat of the plate, type of hit, and location relative to police vehicle. The efficiency of these systems is nothing short of remarkable, some capable of reading 3,000 plates per hour.

Some unexpected benefits exist with ALPR systems. Consider the issues around arbitrary detention or racial profiling. The ALPR system tells the officer which vehicle to stop based on random scanning of plates that produces lawful information allowing the officer to form grounds for the stop. ALPR doesn’t see race or ethnicity, so racial profiling claims should be reduced, if not eliminated. Also, when an Amber Alert is issued, ALPR can be deployed in high-probability areas, scanning plates with far greater efficiency than regular patrol units.

Significant differences exist between ALPR manufacturers. When looking at various systems, one should be careful to understand exactly what these differences are. Some claim to read 95% of the plates accurately, but that is only the plates they read, and doesn’t take into account all the plates that passed by their camera unread. The better test is to see how many plates (of a known quantity) the system reads, and then how many of those it got right. There can be a massive difference in overall accuracy.

The ALPR systems are not cheap. The average system costs about $20,000. Adding cameras or functionality will increase costs accordingly. As with any technology, the next few years of ALPR development will see these systems get smaller, less expensive and fully integrated into existing police technology. As cameras get smaller and higher quality color / IR lenses are combined in single housings, the possibility of embedding ALPR into existing lightbars is probably not that far off.

As with any law enforcement technology advancement, there are always skeptics who believe that the more police can see, the greater the infringement on their right to privacy. Those concerned with their privacy should consider what’s being developed in Australia. An ALPR camera that can be concealed in a road stud has been developed by a company called Astucia Traffic Safety Systems ( and is being tested on Australian highways.

The traffic surveillance camera can take pictures of the license plates of cars speeding by at up to 150 miles per hour. The traffic surveillance camera protrudes from the road surface only 5 millimeters. It is linked to a computer that can read and decode license plates written in either italic or cursive scripts. The camera is so sensitive that it can tell if your tires are balding as your car moves by at speed. The road stud measures the speed of the vehicle, as well. It can flash the car license plate and speed on a display at roadside, warning the driver to slow down. That will sure raise a few eyebrows when they start putting them in our highways!

Brad Brewer is a sergeant with the Vancouver Police Department. He can be reached at

Published in Law and Order, Jun 2009

Rating : Not Yet Rated

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