How could one avoid detection by ANPR cameras? Hypothetically, of course.

August 28, 2012 1:06 PM

An article about ANPR cameras in the paper today had a quote from a policeman saying that a particular driving style could prevent detection. I am curious about what he meant by that, any ideas?

This is the article in question. The relevant section:

DS Neil Winterbourne, in charge of the ANPR cameras for Scotland Yard's counter-terrorism command, told the tribunal criminals could evade the cameras by adopting "a particular driving style", which he did not describe.

"I will not go into the conduct of such tactics herein," he said, "but it is true to say that a properly trained driver can adopt a particular driving style that will greatly reduce the chance of the vehicle being detected by ANPR.

"These tactics are only effective in the short term, when in close proximity to a camera, and it would be impracticable for anyone to permanently drive around in such a fashion."

posted by gregjones to Travel & Transportation (2 answers total)

Best answer: The possibilities I've heard are (1) driving straddling two lanes, ie, on the dotted line between the lanes rather than in the lane itself or (related) switching lanes just at the spot the cameras would take the photo, which might throw off the cameras if they are calibrated to look for license plates when the car is in a certain part of the lane, (2) tailgating and/or having another vehicle tailgate you, which might physically block the license plates from the camera's point of view, and (3) continuously altering speed and direction, which throws off the software that uses predictions about your speed/velocity to stack several (typically noisy) photo frames of your license plate to get one frame that is a lot clearer.

Any of those might fit the description given in the article, but here is a bit of support for method #3 that seems to be from someone who knows about how the systems work. #3 certainly fits the description in that a sudden deceleration/swerve might throw off detection of any particular plate, particularly if lighting conditions aren't that great, but driving that way all the time really is impractical.
posted by flug at 1:51 PM on August 28, 2012 [1 favorite]

flug nailed all the things I can think of. I've used a few different types of ANPR cameras, and they tend to have quite a narrow field of view, such that the licence plate fills as much of the image as possible - so they are aimed at the center of a lane. This means flugs (1) seems most likely to me.
As pixel count and processing speed go up I expect it's already possible to to cover a much wider field of view and process multiple lanes, but probably too expensive for the moment.
posted by samj at 1:57 AM on August 29, 2012