Back to the Future Part II was a classic '80s movie in part because it was an escape. From the harp plucking and the optimistic-sounding French horn in the first scene, it's obvious that you're going to get a picture of the future that is probably closer to Star Trek than Big Brother.

So when you're watching the movie and you see that every car's license plate is a barcode, it's easy to think, "Sure, easy scanning. Very convenient." It's also easy to imagine why, in a movie released at the peak of one of the strongest periods of economic growth in the U.S., one of the most recognizable symbols of commerce – the Universal Product Code – was picked for plates.

Spoiler alert for those who haven't yet looked closely at a car in 2015: We don't have barcode license plates. But the reality is in some ways more impressive and more concerning. Instead of codes that usually need to be scanned with the help of a laser, license plate recognition cameras are being used all over the country to constantly record traffic. And we're often keeping all of that data for uses we haven't yet realized.

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The "haven't yet realized" part worries Kade Crockford, director of the Technology for Liberty project at the Massachusetts American Civil Liberties Union (she also writes the Privacy Matters blog). In the last decade, the practice of collecting and storing traffic data has become widespread but mostly unregulated, she says.

The barcode plates of Back to the Future Part II and the plate-scanning practices of the real world do have something in common: They're both about making information machine-readable. Barcodes were invented to make it easy to attach data to products that could be organized by computers. LPR technology, also called Automatic License Plate Recognition, does the same thing, either by reading a plate and attaching metadata in a matter of milliseconds, or sending a constant stream of photos to a server farm where the data is read and stored. These cameras usually capture not only the plates but an image of the car as well.

Technology now being used across the U.S. began as an invention of British law enforcement in the 1970s. It gained popularity there in the 1990s as a weapon against terrorism, following bombing attacks by the Irish Republican Army. LPR seems to have crossed the pond as computing power, storage, and camera technology became cheaper. By some estimates, LPR usage by police departments in the U.S. has nearly quadrupled, going from 20 percent to 71 percent between 2007 and 2012.

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The problem, says Crockford, is that there is little oversight or even an understanding of how LPR technology is actually being used. Private companies like Digital Recognition Network and Vigilant Solutions "Hoover up" billions of data sets, she says, and sell them to both law enforcement and private repo companies. Even though the technology has been in America for over a decade, the first real federal scrutiny of it seems to have occurred last May, via a task force created by the Justice Department.

States are just starting to lay out rules about the collection and storage of data. In the last two years, around 30 pieces of legislation have been written, but only a handful have gone into effect. Of the bills in place, those that endeavor to make police departments clear data after a certain amount of time has passed or try to prevent private companies from using LPR technology are already being challenged in the courts.

Here's one last bit that wasn't imagined in Back to the Future Part II but could become a reality: The Center for Investigative Reporting recently found what it says are documents that suggest Vigilant wants to create a massive data collection system that combines LPR, public records, and facial recognition. Almost makes you wish for silly barcode license plates.

This post originally appeared at Marketplace Tech