Can I defeat automatic license plate readers?

July 13, 2019 8:59 PM

So I read this story about Palantir's massive surveillance database and decided I don't want to play. One of the creepiest things is automatic license plate readers (ALPR). Do infrared shields like SunFlexZone's actually work?
posted by Johnny Wallflower to Technology (9 answers total)

Yes, they really do work. You don't even need the shield as there are clear coat spray treatments that also work. Another option is IR lights that shine around the plate and obscure it. You don't even really need a fancy countermeasure since some carefully painted on dark mud can be enough to make these systems fail at properly reading individual characters on the plate.

ALPR isn't that hard to defeat, but you run into other problems:

- It may be illegal for you to attempt to defeat it. In Canada (where I live) it is illegal to obscure a plate by any means and that includes clear shields or sprays. That means if the police catch you doing this they are going to doubly ticket you. You may have more luck in your specific jurisdiction.

- Even if you do defeat the ALPR it is just going to flag your plate to be checked by a human. In the case of parking enforcement cars it means they stop and enter it themselves. They might even ticket you, depending on the rules of the lot. Police will just pull you over and do whatever they are going to do.

The better way may be to use a car share system instead of having a car specifically associated with you. Viability of this as a way of obscuring your movements depends on how many different car share vehicles you have available to you and how many other people are using them. The car share company will have the data on who booked which vehicle when, so it is still possible it could be linked to you. You would want to select a car share company with a good privacy policy that doesn't share their data unless court ordered.

Don't forget to leave you smart phone at home! Even if you have location services turned off it is still tracking your movements by scanning the SSIDs of any wifi networks it encounters. Assuming you trust that those settings really do turn things off entirely.
posted by forbiddencabinet at 9:25 PM on July 13, 2019 [12 favorites]

In NYC those plate filters are highly illegal. As is anything that even partially obscures a plate, including the popular rubber shock bumpers and even technically a dealer plate frame (they don’t seem to care about those however).

Which is why only cops — and a lot of cops — have them on their personal vehicles so they don’t have to pay tolls, which is also illegal, but the laws don’t apply to them.

They’ll write you a large ticket for having one.
posted by spitbull at 9:38 PM on July 13, 2019 [7 favorites]

A buddy of mine is in the LAPD, and when he did patrol he loved loved loved to find people who had modified their license plate in some way in order to “defeat” radars or cameras or whatever. If he saw a car a half mile up the road with a plate didn’t reflect light correctly, he race up to pull it over and fuck with the driver and make fun of them for their gimmick.

Of course, many people doing stuff to their plates had reasons to trying to escape the eye of the police, but often it had the opposite effect.
posted by sideshow at 12:04 AM on July 14, 2019 [5 favorites]

Yeah giving the cops an always-on pretext to pull you over is not my idea of better privacy.
posted by spitbull at 8:15 AM on July 14, 2019 [6 favorites]

Another way to protest the database would be to fill it with junk and false-positives. The plate-scanners don't try to identify the actual vehicle, they just scan anything that looks like a plate, hundreds of times a second. A monitor or tablet in a house street-facing window could generate the display of hundreds of random plates a second.
A lawn-sign with (retro-reflective) plate-like printouts will insert your car (and/or your friend's cars) into that location every time a scanner passes by, etc.
posted by anonymisc at 1:12 PM on July 14, 2019

Four months ago I was ticketed because my Walt Disney World license plate frame covered the serifs on top of the N and J of New Jersey. It was a major bummer, so I wouldn't try it if you're planning on visiting my lovely Garden State.
posted by kimberussell at 6:14 AM on July 15, 2019 [1 favorite]

I doubt these work. Mythbusters did fairly extensive testing.
posted by Kalatraz at 10:53 AM on July 15, 2019

Response by poster: Thanks, everyone. I decided to get them anyway. No issues so far.
posted by Johnny Wallflower at 12:24 PM on August 13, 2019

Response by poster: A woman after my own heart: The fashion line designed to trick surveillance cameras (Alex Hern, Guardian)

To human eyes, Rose’s fourth amendment T-shirt contains the words of the fourth amendment to the US constitution in bold yellow letters. The amendment, which protects Americans from “unreasonable searches and seizures”, has been an important defense against many forms of government surveillance: in 2012, for instance, the US supreme court ruled that it prevented police departments from hiding GPS trackers on cars without a warrant.

But to an automatic license plate reader (ALPR) system, the shirt is a collection of license plates, and they will get added to the license plate reader’s database just like any others it sees. The intention is to make deploying that sort of surveillance less effective, more expensive, and harder to use without human oversight, in order to slow down the transition to what Rose calls “visual personally identifying data collection”.

posted by Johnny Wallflower at 8:17 PM on August 14, 2019