Behind the camera (and in the industry) of license plate readers


If you hear this while driving, chances are you’ve passed an automatic number plate reader.

ALPRs are cameras mounted on police vehicles or streetlights that scan license plates and feed this information into databases. But with more surveillance come bigger questions about who should be using this technology and for what purpose.

Rachel Levinson-Waldman is executive director of the Liberty & National Security program at the Brennan Center for Justice. She said this technology is different from cameras that can catch motorists caught in speed traps or at red lights because ALPR is not designed to issue tickets. The following is an edited transcript of her conversation with Kimberly Adams.

Rachel Levinson-Waldman: Basically, they literally scan a car’s license plate, they log the date and time of each scan, the letters and numbers on the license plate, the GPS coordinates – so there’s this location information – and then pictures of the car. This is then fed back into a database and usually compared to a hot list. So that could include anything from stolen cars [to] Yellow warnings of pending arrest warrants, subject to police department policy and any state laws in effect.

Kimberly Adams: To be clear, if you are in a community that uses these ALPRs, your license plate and information could be captured right now every time you drive past a police vehicle.

Levinson-Waldman: That is exactly right. And I think that addresses a really important point, which is that it has nothing to do with suspicion. Despite this, they indiscriminately scan all this data and keep it for anywhere from a few seconds to several years depending on the applicable policy and law.

Adam’s: I imagine many people are unaware that this technology is even being used in their communities. How common is it in the United States?

Levinson-Waldman: So we don’t have current numbers. but what we have suggests that they are used fairly frequently. As of 2013, over 90% of police departments in cities and urban areas with a population of more than one million – that is 16 cities and urban areas – were using their own ALPR systems. And police departments often integrate this type of technology into so-called real-time crime centers. So [they] could combine license plate data with surveillance footage from cameras, be it police cameras, school cameras, traffic cameras, gunshot detection systems or even social media surveillance. And a number of cities have real-time crime hubs, so we’re talking cities like New York, DC, Austin [Texas]Miami – a number of cities across the country.

Adam’s: Police departments use ALPR as you just pointed out. Who else implements this technology?

Levinson-Waldman: So we know that ICE, Immigration and Customs Enforcement, an arm of the Department of Homeland Security, accessed ALPR data. And there is also a significant private industry. As a result, many police departments contract with vendors that give them access to private databases of scans, even from other law enforcement agencies. So you see, sometimes this disk data is able to traverse quite significant networks of sharing.

Adam’s: What privacy concerns are associated with this type of monitoring?

Levinson-Waldman: The Supreme Court has ruled fairly clearly that because vehicles are heavily regulated, which includes having a number plate affixed, and because vehicles on public roads can be seen by any member of the public, there is simply no expectation of privacy associated with license plates. We also see police departments regularly sharing ALPR data with each other. And a number of states simply don’t have laws governing how police departments can share this data, leaving it at the discretion of individual departments. And there were real concerns about how these devices could be used to invade privacy and interfere with the exercise of constitutional rights.

Adam’s: What concerns are there about how this tip might be used in a post-roe? [v. Wade] Vicinity?

Levinson-Waldman: The police don’t need a search warrant to get this kind of information. And that’s how you can map many travel patterns to license plate data, right? It depends on how extensive a license plate reader network is or if you combine that license plate data with other information. Like cell phone tracking information, information passed to the apps that people have on their phones, things like that. Especially with the incredibly restrictive laws we see criminalizing so many of these related activities, having license plate reader data in hand becomes really dangerous.

Levinson-Waldman co-authored a Brennan Center white paper on ALPR. In it, they advise police departments to implement more transparency and oversight so third parties can assess how responsibly this technology is being used.

Following the Supreme Court decision in Roe v. Wade, many tracking technologies come under closer scrutiny. But unlike an app or website, you can’t necessarily delete, avoid, or unsubscribe from the ALPR network.

Wired has a story on how these systems could be used to track those who want abortions and more details on the network of data sharing between law enforcement and private systems, such as a homeowners association setting up ALPRs in the neighborhood.

Flock Safety, a private company with systems in about 1,500 cities, issued a statement to Wired that it does not sell or share data with third parties.

“While we cannot speak for other providers, we have never and will never sell data to collection companies or third party organizations, including anti-abortion groups.”


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