How do license plate scanners work

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Skip to Content. Automated License Plate Recognition. Facebook LinkedIn Twitter. What does ALPR look like? How does it work? What is a hot list? License plates that are in poor standing can fall into one or more of the following categories: Plates that belong to a driver with a suspended license Plates associated with stolen vehicles or that are reported stolen or missing Plates that have been suspended Plates with expired validation tags Plates associated with persons with outstanding Canada-wide warrants or who are reported missing For a complete list of reasons, please read the IPC's report.

What is a hit? A hit happens when a scanned license plate matches a license plate on the hotlist. The information you enter will appear in your e-mail message and is not retained by Phys. You can unsubscribe at any time and we'll never share your details to third parties. More information Privacy policy. This site uses cookies to assist with navigation, analyse your use of our services, collect data for ads personalisation and provide content from third parties. By using our site, you acknowledge that you have read and understand our Privacy Policy and Terms of Use.

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Several companies operate independent, non-law enforcement ALPR databases, contracting with drivers to put cameras on private vehicles to collect the information. These data are then sold to companies like insurers, but law enforcement can also purchase access to this commercial data on a subscription basis.

Law enforcement agencies will often pre-load a list of license plates that the ALPR system is actively looking for—such as stolen vehicles and vehicles associated with outstanding warrants. Police officers can also create their own hotlists. If the ALPR camera scans a plate on the list, the system sends an alert to the officer in the squad car if it's a mobile reader or the agency if it's a fixed reader. Some hotlists include low-level misdemeanors and traffic offenses. Some agencies use these hotlists to generate revenue by stopping citation scofflaws.

ALPRs collect license plate numbers and location data along with the exact date and time the license plate was encountered. Some systems are able to capture make and model of the vehicle. They can collect thousands of plates per minute. One vendor brags that its dataset includes more than 6. When combined, ALPR data can reveal the direction and speed a person traveled through triangulation.

With algorithms applied to the data, the systems can reveal regular travel patterns and predict where a driver may be in the future. The data also reveal all visitors to a particular location. However, law enforcement officers can use other databases to connect individual names with their license plate numbers. A privacy impact assessment report indicates that the photographs may even include bumper stickers, which could reveal information on the political or social views of the driver.

ALPR data is gathered indiscriminately, collecting information on millions of ordinary people. Without ALPR technology, law enforcement officers must collect license plates by hand. This creates practical limitations on the amount of data that can be collected and means officers must make choices about which vehicles they are going to track. ALPR technology removes those limitations and allows officers to track everyone, allowing for faster and broader collection of license plates with far reduced staffing requirements.

Licenses plates are often added to hot lists because the vehicle is stolen or associated with an outstanding warrant. Officers may also add a plate number to the list if the vehicle has been seen at the scene of a crime, the owner is a suspect in a crime, or the vehicle is believed to be associated with a gang.

Hot lists often include low-level offenses, too. Since ALPRs typically collect information on everyone—not just hot-listed vehicles—officers can use a plate, a partial plate, or a physical address to search and analyze historical data. For example, an officer may enter the location of a convenience store to identify vehicles seen nearby at the time of a robbery.

The officer can then look up those plate numbers to find other locations that plate has been captured. Training materials, policies and laws in some jurisdictions instruct officers that a hot-list alert on its own may not be enough to warrant a stop. Officers are instructed to visually confirm that a plate number is a match.

Failure to manually confirm, combined with machine error, has caused wrongful stops. Law enforcement claims that ALPR data has been used to, for example, recover stolen cars or find abducted children.