Today the ACLU is launching a nationwide effort to find out more about automatic license plate readers (ALPR). By snapping photographs of each license plate they encounter—up to three thousand per minute—and retaining records of who was where when, license plate readers are fundamentally threatening our freedom on the open road.

You may have seen the recent New York Times op-ed that admonished us to start referring to our mobile devices as “trackers” instead of “phones.” Perhaps as ALPR technology spreads we should start saying “tracker” in place of “car,” too. We need statutory protections to limit the collection, retention, and sharing of our travel information.

And we need to find out more about this technology.

Unfortunately, we don’t have a comprehensive sense of how this technology is being implemented nationwide. But, here’s some of what we do know:

• License plate tracking is a big business, and growing. As with so many other cutting-edge surveillance and identification tools, the Department of Homeland Security, Department of Justice and even the Department of Transportation have dished out many millions of dollars to state and local law enforcement for the purchase of ALPRs. Just a couple of years ago an ALPR unit cost about $22,000; market demand has already pushed the cost down to as little as $12,000 per unit, and it’ll likely dive further. The technology is flying off the shelf, and police couldn’t be more thrilled about what it enables, not least the retroactive, nationwide tracking of our every motoring move.

• The Drug Enforcement Administration is planning to install a network of plate readers on major highway systems nationwide. The Department of Homeland Security clocks every car that enters the country. Local and state police departments operate many thousands of ALPR systems nationwide—how many and to what extent, we aren’t sure. Together these programs form a network of data points that can tell the government a lot about our lives.

• Only two states in the nation have statutes on the books to regulate ALPR use, New Hampshire and Maine. The former’s legislature all but banned ALPR; as in Maine, no private deployment is allowed, but in NH the government can use it only to monitor critical infrastructure like bridges. Maine’s statute requires that police delete data after 21 days, allowing investigators access to information that could help solve murders or robberies after the fact while aiming to prevent the kind of society-wide tracking we privacy advocates warn against.

• New Jersey has implemented statewide guidelines, but they do not go nearly far enough to protect the privacy of motorists in the state, allowing police departments to retain data for up to five years—well beyond what’s reasonable and required in order to make good use of the tool.

• Various state and regional surveillance centers are pooling the collected ALPR data from various cities or counties into mega-databases, allowing local, state and federal law enforcement to track ordinary motorists’ movements without any kind of judicial oversight—all with the click of a button.

• The federal government is giving out big money to state and local police to buy the technology, but local communities are rarely consulted about what commonsense privacy protections should be implemented, if they are notified about introduction of the new surveillance tool at all.

It’s not an exaggeration to say that in ten years there will be ALPRs just about everywhere, making detailed records of every driver’s every movement, and storing it for who knows how long. In some cases, we know that the worst-case scenario—vast databases with records of movements of massive numbers of people—is already happening.

To avoid this fate we need to convince the nation and our lawmakers to take action on this serious threat to our liberty. And to make a convincing case, we need to know a lot more about the problem as it stands.

Last year, most people didn’t know why we should call our mobiles “trackers” instead of phones; there was very little public information on how police departments were using our phones to track our location. The ACLU stepped in and spearheaded a massive public records project, bringing together affiliates from every part of the country, obtaining documents that showed how police nationwide were getting access to our intimate information without judicial oversight. This led to a press storm, spurring Congressman Ed Markey’s inquiry to cell providers and leading to a truly astonishing New York Times headline earlier this month. We haven’t yet witnessed the passage of the GPS Act, but we are closer because of that work, and awareness of the issue is now widespread.

Now we are tackling location tracking via ALPR. Today, ACLU affiliates in 38 states are filing public records requests to their state and local law enforcement agencies to find out how widespread ALPR deployment is and whether there are commonsense privacy protections in place. We are also filing federal Freedom of Information Act (FOIA) requests with the Department of Justice, Department of Homeland Security, and Department of Transportation to learn about how these agencies are funding ALPR expansion nationwide, how they are using the technologies themselves, and how they are accessing state, regional and local databases.

Stay tuned for more information on how license plate trackers are being deployed in your state, and for concrete actions you can take at the state and local level to ensure that police don’t go too far with ALPR.