[Catherine Crump][1]:

> Automatic license plate readers are the most widespread location tracking technology you’ve probably never heard of. Mounted on patrol cars or stationary objects like bridges, they snap photos of every passing car, recording their plate numbers, times, and locations. At first the captured plate data was used just to check against lists of cars law enforcement hoped to locate for various reasons (to act on arrest warrants, find stolen cars, etc.). But increasingly, all of this data is being fed into massive databases that contain the location information of many millions of innocent Americans stretching back for months or even years.

I’ve long known about these readers, but I had no clue they were saving the data and amassing a database. I like these readers because they are actually a very effective tool.

The scenario that has always been described to me is either during an amber alert and a fugitive situation: cars equipped with this tool can effectively drive around large swathes of areas quickly and be alerted if the license plate they are looking for is driven by. So think about there being an amber alert, one cop car could vet and entire mall parking lot in minutes. That’s pretty great.

However, if license plate data is being stored? That’s shady.

> The primary law enforcement use of these systems is to take pictures of plates to make it possible to check them against “hot lists” of cars of interest to law enforcement. This can be done virtually instantaneously. While plates that generate a “hit” may need to be stored for investigative purposes, *there is no need to store plates for months or years* to achieve this purpose.

Agreed.

[1]: http://www.aclu.org/blog/technology-and-liberty-national-security/police-documents-license-plate-scanners-reveal-mass?utm_medium=App.net&utm_source=PourOver