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Why are police scanning millions of license plates?

Molly Wood Aug 17, 2012

Why are police scanning millions of license plates?

Molly Wood Aug 17, 2012

The American Civil Liberties Union is filing information requests with nearly 500 police departments in 38 states having to do with License Plate Reader cameras, or LPRs. 

Tens of thousands of them are being used around the country, according to Cyrus Farivar who wrote about LPRs for Ars Technica.

Cyrus Farivar: These are cameras that are optically scanning at very high speeds your license plate. The camera just needs to be able to see you for kind of a split second. It doesn’t need to be right on you, it happens very very fast.  So fast, in fact, that many of these cameras can scan 60 plates per second.

Moe: And these cameras are constantly on, they’re constantly scanning?

Farivar: That’s right. And these cameras can be mounted above the street, they can be mounted on buildings, they can be mounted  on law enforcement vehicles. If a police officer has one of these on his car, and he’s driving around his town, then he’s just constantly scanning all plates that he can see, that includes cars driving past him, in front of him, cars parked on street – whatever, and basically what the camera is doing is scanning the license plate itself, so the letters and numbers, against what is often referred to as a hot list.

That’s a list of cars that may be wanted by the police. Officers can then pull them over.

Catherine Crump, staff attorney at the ACLU, what’s the problem?

Catherine Crump: The problem comes when police departments don’t just look to see if a car is for example stolen, but starts storing people’s license plate data for long periods of time, and increasingly local police departments are storing people’s plate data for months or years on end and even sharing it with other regional or national databases.

Moe: So, these are license plates that, if I walk out on the street here, I could see a bunch of license plates, I could write them down, what’s the problem with reading, storing, even swapping around something that has already been made public?

Crump: Because license plate data when it’s aggregated, and you’re talking about millions of hit data going back years, ends up painting a really detailed picture of where people are going and what they are doing and what their activities are. You have to remember these license plate scanners aren’t just attached for example to bridges. They can go through church parking lots to see who’s attending services, through the parking lots of NRA gun conventions and so forth. And when you add all of that together, you often get a very detailed picture of people’s lives.

Very few laws govern this new technology. Some police departments keep their records indefinitely; others dump them after 30 days.

The cameras are inexpensive.

Crump: Even a very small town can afford a license plate scanner, but there’s not that much known about how the technology is actually being deployed.


I can’t stop looking at this map of the U.S. that blogger Renee DiResta made. She went to Google and for each state asked ‘Why is that state so’ — then looked at the autofill answers, put ’em on a map. Those answers are what Google users wonder about that state.

Example: I live in Minnesota. People wonder why Minnesota is so liberal, so windy, so humid, so awesome. And why is New Jersey so bad, hated, expensive, and corrupt?

DiResta noticed that people want to know why both Pennsylvania and Connecticut are so haunted.

Renee DiResta: It turns out there’s a number of tourist tours that you can take in Connecticut and Pennsylvania, various old, haunted

Moe: The ghost industry is big in those states.

DiResta: Apparently. Apparently you can take ghost tours there.

Most of the states had four attributes. Missouri had one. Were there any questions for Missouri beyond why is it so humid?

DiResta: There weren’t or they were not served to me.

Find your state.

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