Many police departments use gadgets called automated license plate readers, or LPRs, to scan tons of license plates throughout the day. These tools can help them spot stolen vehicles and collect helpful information to solve cases, but they also pose a huge privacy concern.
Scanning license plates of random cars isn't that concerning on its own. But, what departments do with that information is a bit more worrying. The Oakland Police Department has over 4.6 million scans from the past several years and it's unclear exactly how long they hold to that information. The scarier thing is anyone could possibly access that information using a public information request.
Neither the Oakland City Council nor the OPD has ever imposed a formal data retention limit, though OPD has deleted older LPR data as needed to make room for newer data. As LPR devices and storage prices continue to fall, it's likely the volume and rate of such data collection will continue to rise, and its retention time can become longer.
Why is the collection of license plate data concerning? Ars Technica got a hold of Oakland's collection of scans to show how they could be used to compromise your privacy.