Yes. Police departments across the United States use license plate scanners, and they use them heavily. About 40 percent of U.S. law enforcement agencies operate some form of automatic license plate reader, or ALPR, and a single vendor, Flock Safety, contracts with more than 5,000 police departments.1NBC News. Flock Police Cameras Scan Billions per Month, Sparking Protests The cameras sit on highway overpasses, traffic poles, and the roofs of patrol cars, and if you drive in a city of any size, your plate is almost certainly being read many times a day without your knowledge.
How the Scanners Work
An ALPR pairs a high-speed camera with character-recognition software. The camera photographs a passing plate, and the software turns the image into a text string of letters and numbers. Most cameras use infrared light so they can read plates in rain, at night, and at highway speeds. The software then checks the plate against law enforcement “hot lists” that flag stolen vehicles, wanted persons, and vehicles tied to active investigations. If there’s a match, the officer gets an alert within seconds.2Congressional Research Service. Automated License Plate Readers: Background and Legal Issues
Along with the plate number, most systems record the date, time, GPS coordinates, and a photo of the vehicle and whatever is around it. Newer cameras also capture the vehicle’s make, model, and color, which officers can search on their own even when a plate number is only partially readable.3NPR. Why Some Cities Are Canceling Flock License Plate Reader Contracts
Fixed Cameras
Fixed ALPRs are mounted on poles, gate arms, overpasses, and other permanent structures. They run around the clock with no one on-site, scanning every car that passes.4EMCI Wireless. Mobile vs Fixed LPR Systems: Which Is Right for You? Because they never move, they’re especially useful at chokepoints: highway on-ramps, bridge approaches, city borders. A single busy intersection can generate thousands of reads in a day.
Mobile Cameras
Mobile ALPRs ride on patrol cars, usually on the roof or trunk. Some departments use unmarked vehicles with cameras hidden behind the grille or inside a light bar. These systems scan plates in real time as the car drives through neighborhoods, parking lots, and traffic, and a single patrol car can read thousands of plates in one shift.4EMCI Wireless. Mobile vs Fixed LPR Systems: Which Is Right for You?
What the Scans Are Used For
The most straightforward use is recovering stolen vehicles. When a car is reported stolen, its plate goes onto a hot list, and the next ALPR that reads it pings the nearest officer. The same mechanism drives Amber Alerts, missing-person cases, and warrant hits.
The second use is historical. Detectives working a hit-and-run, a robbery, or a homicide can query stored ALPR data to find out which vehicles passed through a particular intersection at a particular time. That after-the-fact search capability is where the technology gets powerful, and it’s where most of the legal fight is happening.
How Much Data Gets Collected
The volume is enormous. Flock Safety’s network alone scans more than 20 billion license plates per month across the United States.1NBC News. Flock Police Cameras Scan Billions per Month, Sparking Protests Digital Recognition Network, owned by Motorola Solutions, has accumulated more than 15 billion vehicle sightings over the past decade and adds roughly 250 million more every month.5WIRED. License Plate Readers Are Creating a US-Wide Database The overwhelming majority of those scans are of ordinary drivers with no connection to any crime.
Who Can See Your Data
Many ALPR cameras aren’t owned by police at all. Companies like Flock sell the hardware and cloud storage as a subscription and then let their police customers query a nationwide pool of data that reaches well beyond any single city. Flock says each customer has “sole authority” over whether to share its data with other agencies. In practice, some city officials have found out after the fact that federal agencies, including U.S. Border Patrol, had been searching their local ALPR data without the city’s explicit approval.3NPR. Why Some Cities Are Canceling Flock License Plate Reader Contracts
Federal immigration enforcement has also contracted directly with private ALPR vendors. ICE agents can load up to 2,500 plates onto a single alert list and be notified in real time whenever any of those plates is spotted anywhere in the vendor’s network.6Georgetown Law Immigration Law Journal. U.S. Immigration and Customs Enforcement Use of Automated License Plate Reader Databases A plate captured by a small-town camera can trigger an investigation hundreds of miles away. That reach is what has pushed several cities to cancel their Flock contracts or pull out of shared data networks.
When the Scanners Get It Wrong
ALPRs are not perfect readers, and the consequences of a bad read fall on the driver. Flock Safety says its cameras read plate characters and issuing state correctly “in the high 90 percentiles.” At a 2025 Iowa city council meeting, a Flock representative put the accuracy rate at around 90 percent; the company later said the employee misspoke. Independent testing by the research firm IPVM found that Flock cameras misidentified the plate’s issuing state about one in ten times and regularly misclassified vehicle type and make.7Business Insider. Flock Safety’s AI Cameras Misread Plates
Even at 95 percent accuracy, billions of scans a month produce millions of wrong reads. When a misread happens to match a stolen vehicle or a wanted person’s car, an innocent driver can end up on the wrong end of a felony stop. A Business Insider investigation documented at least a dozen incidents where ALPR errors led to people being stopped at gunpoint, handcuffed, arrested, or attacked by police dogs for crimes they had nothing to do with. In Toledo, Ohio, a Flock camera misread a “7” as a “2,” and the driver was hospitalized after a police dog attack and jailed on charges that were later dismissed.7Business Insider. Flock Safety’s AI Cameras Misread Plates
The Ninth Circuit Court of Appeals has ruled that an unconfirmed ALPR hit, by itself, may not be enough to justify a traffic stop. Officers who rely blindly on an alert without independently verifying it could violate the driver’s Fourth Amendment rights.8Electronic Frontier Foundation. New Ninth Circuit Opinion Calls into Question Blind Reliance on License Plate Camera IDs Many officers still treat an ALPR hit as automatic grounds for a high-risk stop, which is how innocent people end up facedown on the pavement.
How Long the Data Is Kept
Every scan, whether it hits a hot list or not, typically gets uploaded to a central database. That means the system is storing location records for millions of vehicles that have nothing to do with any investigation. How long that data sticks around depends on where you live. Eight states have enacted laws limiting how long non-hit ALPR data can be kept, and the periods vary widely, from as short as 48 hours in some proposed bills to 180 days or longer in others. When ALPR data becomes relevant to a criminal investigation, court order, or subpoena, it can be preserved indefinitely regardless of any general purge schedule. Most states have no ALPR-specific retention limit at all, leaving the decision to individual agencies or the private vendor holding the data.
What the Law Says
The Fourth Amendment is the main legal battleground, and the law is still catching up to the technology. Courts have generally held that reading a license plate displayed on a public road is not a search, because the plate is in plain view and you have no reasonable expectation of privacy in it. Federal courts have mostly distinguished ALPR data from the cell-site location information at issue in the Supreme Court’s 2018 decision in Carpenter v. United States, which required a warrant for historical cell phone location records. The reasoning has been that ALPR data, as currently used, is not yet “remotely comparable” to the detailed tracking cell-site data provides.2Congressional Research Service. Automated License Plate Readers: Background and Legal Issues
That consensus is cracking. In 2024, a Virginia circuit court ruled in Bell v. Commonwealth that the Flock camera network covering all of Norfolk was so comprehensive that accessing its stored data without a warrant violated the Fourth Amendment. The judge compared the system to a GPS tracker and wrote that “a person does not surrender all Fourth Amendment protection by venturing into the public.”9GovTech. Virginia Judge Rejects ALPR Evidence Without Warrant The ruling isn’t binding outside Virginia, but it signals the direction some courts may go as networks get denser.
What You Can Do
You can typically submit a public records request to your local police department or the state agency that operates ALPR cameras to find out whether your plate has been scanned and what the record shows. The process varies by jurisdiction. Some agencies handle these under state open-records laws, and federal databases fall under the Privacy Act, which lets you request records about yourself from federal agencies. Response times and the level of detail you get back depend on local law and the agency’s own policies.
If you’re stopped by police based on an ALPR hit, stay calm and follow the officers’ instructions in the moment. The Ninth Circuit has made clear that an unverified ALPR alert may not amount to reasonable suspicion, which means a stop based solely on a misread plate could form the basis of a Fourth Amendment claim afterward.8Electronic Frontier Foundation. New Ninth Circuit Opinion Calls into Question Blind Reliance on License Plate Camera IDs If you believe you were stopped, detained, or injured because of an ALPR error, write down everything you can: the time, the location, what the officers said, any injuries. Then talk to an attorney about possible civil rights claims. Lawsuits on exactly these facts are already being filed around the country.