Automated patent plate reader (ALPRs) space high-speed, computer-controlled camera equipment that space typically mounted on street poles, streetlights, highway overpasses, mobile trailers, or attached to police squad cars. ALPRs immediately capture all license plate numbers that come right into view, along with the location, date, and also time. The data, which contains photographs that the vehicle and also sometimes its driver and passengers, is climate uploaded to a main server.

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Vendors say that the information accumulated can be used by police to find out whereby a bowl has remained in the past, to determine whether a vehicle was at the step of a crime, to recognize travel patterns, and even to find vehicles that may be associated with each other. Law enforcement agencies can pick to re-publishing their details with thousands of other agencies.

Taken in the aggregate, ALPR data have the right to paint an intimate portrait that a driver’s life and also even chill very first Amendment defended activity. ALPR an innovation can be used to target motorists who visit sensitive areas such as health and wellness centers, immigrant clinics, pistol shops, union halls, protests, or centers of spiritual worship.

Drivers have actually no regulate over even if it is their car displays a license plate since the federal government requires every car, truck, and also motorcycle vehicle drivers to display license key in public view. So it’s particularly disturbing the automatic patent plate readers are offered to track and also record the activities of millions of ordinary people, even though the overwhelming bulk are not associated to a crime.


How ALPRs Work

 Automated license plate readers can be broadly divided into two categories.

Stationary ALPR cameras 

Photo by Mike Katz-Lacabe (CC BY)

These are set up in a fixed location, such together a website traffic light, a phone call pole, the entrance of a facility, or a freeway departure ramp. These cameras generally record only vehicles in activity that happen within view. 

If multiple stationary ALPR cameras are mounted along a solitary thoroughfare, the data have the right to reveal what direction and also what speed a car is traveling. If the data room stored end time, they have the right to reveal every time a certain plate has passed a offered location, permitting the government to infer the the driver likely lives or works close by.

Stationary cameras have the right to sometimes it is in moved. For example, monitoring vans or truck trailers have the right to be outfitted through ALPR systems and then parked at strategy locations, such as gun mirrors or politics rallies. 

ALPR cameras are often used in conjunction through automated red-light and speed enforcement systems, and likewise as a method of assessing tolls top top roads and also bridges. 

Mobile ALPR cameras

Photo through Mike Katz-Lacabe (CC BY)

These are regularly attached to police patrol cars, allowing law enforcement policemans to catch data from license plates together they drive roughly the city throughout your shifts. In many cases, this cameras room turned on at the beginning of a transition and not turned turn off again until the end of the shift. Also, private sellers like Vigilant Solutions capture plate data through mobile ALPRs and also then sell that data to police agencies and others. 

In addition to recording images of pass vehicles, cell phone ALPR cameras are reliable at catching license bowl of parked cars. For example, a patrol vehicle may drive around a windy parking lot catching hundreds the vehicles’ plates in minutes. 

ALPR Databases 

Most the this ALPR data is save in databases for prolonged periods that time—often as lot as 5 years. The databases may be maintained by the police departments, however often lock are kept by exclusive companies such as Vigilant Technologies. Regulation enforcement agencies there is no their very own ALPR solution can access data gathered by other legislation enforcement agencies through local sharing systems and also networks operated by these private companies. Number of companies operate independent, non-law enforcement ALPR databases, contracting with motorists to put cameras on exclusive vehicles to collect the information. These data are then offered to companies favor insurers, but law enforcement can also purchase access to this advertising data on a subscription basis. 


Law enforcement agencies will frequently pre-load a perform of patent plates the the ALPR system is proactively looking for—such as stolen vehicles and also vehicles linked with superior warrants. Police police officers can likewise create their very own hotlists. If the ALPR camera scans a bowl on the list, the system sends one alert come the officer in the squad auto (if it"s a mobile reader) or the agency (if it"s a solved reader). Part hotlists incorporate low-level misdemeanors and traffic offenses. Part agencies usage these hotlists to generate revenue by preventing citation scofflaws. 

 What kinds of Data ALPRs Collect

ALPRs collect patent plate numbers and also location data together with the precise date and time the patent plate was encountered. Part systems room able to capture make and also model the the vehicle. They have the right to collect hundreds of plates every minute. One merchant brags the its dataset includes more than 6.5 exchange rate scans and grows in ~ a rate of 120-million data points each month.

When combined, ALPR data deserve to reveal the direction and also speed a human traveled v triangulation. In accumulation over time, the data can reveal a vehicle’s historic travel. V algorithms applied to the data, the systems deserve to reveal consistent travel patterns and predict where a driver might be in the future. The data also reveal all visitors to a details location. 

The data usually does not incorporate the driver’s name. However, law enforcement officers have the right to use various other databases to connect individual names v their patent plate numbers. 

In enhancement to capturing license plate data, the photographs have the right to reveal photos of the vehicle, the vehicle’s drivers and passengers, and its prompt surroundings—and even human being getting in and also out of a vehicle. A 2009 privacy influence assessment report suggests that the photographs might even include bumper stickers, which can reveal information on the political or social see of the driver.

How legislation Enforcement supplies ALPRs

A time-lapse visualization of the data accumulated by Oakland Police room vehicles mounted with patent plate readers


ALPR data is gathered indiscriminately, collecting details on numerous ordinary people. By plotting auto times and also locations and tracing past movements, police can use save on computer data to paint a very certain portrait the drivers’ lives, determining previous patterns the behavior and also possibly also predicting future ones—in spite of the reality that the vast bulk of world whose patent plate data is built up and stored have not also been accused the a crime. Without ALPR technology, law enforcement officers need to collect patent plates by hand. This creates useful limitations on the lot of data that deserve to be collected and way officers have to make choices around which vehicles they room going to track. ALPR modern technology removes those restrictions and allows officers to track everyone, allowing for quicker and broader collection of license plates v far decreased staffing requirements. 

Law enforcement has two basic purposes for utilizing license bowl readers. 

Real-time investigations

By including a license plate come a “hot list,” officers deserve to use ALPR to immediately identify or track particular vehicles in actual time. Licenses plates are often added to warm lists due to the fact that the vehicle is stolen or connected with an exceptional warrant. Officers might also include a plate number come the list if the car has been checked out at the scene of a crime, the owner is a suspect in a crime, or the auto is thought to be connected with a gang. Hot lists often include low-level offenses, too. 

Historical investigations

Since ALPRs typically collect details on everyone—not simply hot-listed vehicles—officers can use a plate, a partial plate, or a physical deal with to search and analyze historical data. For example, one officer may go into the location of a convenience keep to determine vehicles seen adjacent at the moment of a robbery. The officer can then look increase those plate numbers to discover other locations that plate has actually been captured. 

Training materials, policies and laws in some jurisdictions instruct officers that a hot-list alert on its own may not be enough to warrant a stop. Officers are instructed come visually confirm that a bowl number is a match. Failure to manually confirm, combined with maker error, has actually caused wrongful stops. 

Law enforcement claims that ALPR data has actually been offered to, for example, recoup stolen car or find abducted children. However, police have likewise used ALPR data for mass enforcement of less serious offenses, together as looking for uninsured vehicle drivers or tracking down people with date court fees.

The ACLU estimates that less than 0.2 percent of bowl scans are attached to criminal activity or automobile registration issues. Countless law enforcement agencies store ALPR data because that years, and also share it v other legislation enforcement agencies and federal agencies. 

The size of time that ALPR data is maintained varies from company to agency, indigenous as quick as mere days come as long as number of years, although part entities—including personal companies—may maintain the data indefinitely. 

Who selling ALPR Technology

Vigilant Solutions and also ELSAG space the biggest ALPR vendors.

Vigilant Solutions" subsidiary Digital acknowledgment Network, together with MVTrac, room the two key companies hiring home builders to collection ALPR data throughout the country. The service providers then re-publishing the commercially-collected data not simply with legislation enforcement but likewise with auto recovery (aka "repo") companies, banks, credit reporting agencies, and also insurance companies. Data built up by personal entities walk not have actually retention limits and also is not subject to sunshine laws, or any kind of of the various other safeguards that space sometimes uncovered in the federal government sector.

Some jurisdictions usage ALPR technology originally developed through PIPS, which to be subsequently sold to 3M. The ALPR department was much more recently obtained by Neology, Inc.

Threats posed by ALPR

ALPR is a an brickandmortarphilly.comective surveillance an innovation that have the right to be provided to invade the privacy of individuals and to violate the legal rights of whole communities.

Law enforcement agencies have abused this technology. Police officers in new York drove under a street and also electronically taped the license plate numbers of everyone parked close to a mosque. Police in Birmingham target a Muslim community while misleading the public around the project. ALPR data obtained from the Oakland Police Department verified that police disproportionately deploy ALPR-mounted vehicles in low-income communities and communities the color.

Moreover, numerous individual officers have actually abused regulation enforcement databases, including license key information and records held by motor auto departments. In 1998, a Washington, D.C. Police officer “pleaded guilty to extortion after looking increase the key of vehicles near a happy bar and also blackmailing the auto owners.” Police officers have also used databases to find romantic understand in Florida. A former female police officer in Minnesota found that her driver’s license record was accessed 425 time by 18 various agencies across the state.

In enhancement to intended misuse, ALPRs periodically misread plates, causing dire consequences. In 2009, mountain Francisco police pulled end Denise Green, one African-American city worker, handcuffed her at gunpoint, forced her to her knees, and also searched both her and also her vehicle—all due to the fact that her car was misidentified as stolen because of a license plate reader error. Her experience led the U.S. Nine Circuit Court of Appeals to preeminence that modern technology alone can not be the basis of such a stop, but that judgment does not use everywhere, leaving civilization vulnerable to similar law enforcement errors. 

Aggregate data save on computer for prolonged periods of time (or indefinitely) becomes more invasive and also revealing, and also it is vulnerable to both misuse and also data breach. Wise retention limits, certain policies about who within an agency is permitted to access data, and also audit and control procedures could aid minimize this issues. Among the much better privacy protections would be because that police to maintain no details at all when a passing auto does not match a hot list.’s work-related on ALPR has been investigating and combating the privacy risks of ALPR modern technology through public documents requests, litigation, and legislative advocacy because 2012. 

ALPR Litigation and the ACLU of southerly California sue the Los Angeles county Sheriff’s Department and also the Los Angeles Police department after the agencies refused to hand end ALPR data. The agencies asserted the records were exempt from the California Public documents Act due to the fact that they to be investigative records. This argument quantities to claiming the all Los Angelenos space under investigation, a suggest that both a lawyer because that the LAPD and a California can be fried Court justice agreed sound “Orwellian” during oral arguments. In 2017, the California supreme Court rule in and also ACLU’s favor and also ordered the case ago to the exceptional court.

Outside the California, has actually filed briefs in a lawsuit over the too much storage arsenal of ALPR data in the state that Virginia.

ALPR Accountability and also Transparency

In 2015, the California legislature happen S.B. 34, a bill that calls for ALPR individuals to safeguard data, maintain accessibility logs, host public meetings before starting an ALPR program, perform a usage and privacy policy, and maintain access logs. The law additionally prohibits public agencies from selling, sharing, or carrying ALPR data except to other public agencies. has coordinated volunteers to collection ALPR policies throughout the state of California and also to reveal agencies failing come comply v the law. has additionally independently filed public documents requests through dozens of organ to shine irradiate on their usage of ALPR data.

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ALPR Security investigated more than 100 ALPR cameras activate by legislation enforcement that were leaking data since of misconfiguration. These cameras were inadvertently publicly easily accessible through internet browsers and Telnet interfaces. After ~ disclosed these vulnerabilities, number of agencies in Louisiana and also California overhauled your ALPR networks. 

We have likewise contacted public security agencies whose ALPR data to be exposed online, frequently on websites easily accessible to anyone through a web browser, to responsibly disclose the defense vulnerabilities us found. legitimate Cases

ACLU of southern California and also v. LAPD and LASD 

Neal v. Fairfax county Police Department

For an ext Information

You space Being Tracked (ACLU)

License Plate readers for legislation Enforcement Opportunities and Obstacles (RAND Corporation)