What Is It?

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Automated license plate readers (ALPRs) are computer-controlled, high-speed camera systems that automatically record and store images of vehicle license plates that pass into the camera’s view. Some models can photograph up to 1,800 license plates every minute, and every week, law enforcement agencies across the country use these cameras to collect data on millions of license plates.

ALPRs are typically attached to vehicles, such as police cars, but can also be mounted on street poles, traffic lights, highway overpasses, or mobile trailers. These camera systems may be stationary (mounted in fixed locations) or mobile (attached to mobile vehicles like police patrol cars). Stationary cameras can be attached to non-stationary posts like a trailer that can be hitched to a police vehicle to be positioned at strategic enforcement locations at particular times.

ALPR cameras use optical character recognition (OCR) technology to convert license plate numbers into alphanumeric characters and automatically record the location, date, and time of the scan, and sometimes log the make and model of the vehicle. ALPRs may also capture images of the vehicle itself, the vehicle’s driver, passengers, and its surroundings. That data is then uploaded to a central database that is routinely searched by law enforcement and shared across multiple jurisdictions across the nation. An investigator can search the historical travel patterns of a single vehicle, generate a list of vehicles that were seen near particular locations, identify cars seen in proximity of each other, or add a vehicle to a "hot list" to get near-real-time alerts.