Cop Car License Plate Scanners: Understanding Mobile ALPR Technology and Privacy Implications

Automated License Plate Readers (ALPRs) are sophisticated surveillance systems employing high-speed cameras and computer technology. These systems are designed to automatically capture license plate numbers of vehicles. While you might commonly see them mounted on street poles or traffic lights, a significant deployment of this technology is through Cop Car License Plate Scanners. These mobile ALPRs, attached to police vehicles, are transforming law enforcement’s ability to monitor and track vehicle movements, raising important questions about privacy and civil liberties.

These cop car license plate scanners are not just about reading plates; they record the location, date, and time of every scan. This vast amount of data, including images of the vehicle and sometimes even occupants, is then uploaded to a central server, creating a detailed record of vehicle movements.

Vendors of these systems, like Vigilant Solutions, highlight the benefits for law enforcement, asserting that the collected information can help trace a vehicle’s past locations to determine its presence at crime scenes, identify travel patterns, and even link vehicles of interest. Furthermore, law enforcement agencies have the option to share this data with a wide network of other agencies, amplifying the reach and scope of this surveillance.

However, the aggregation of ALPR data paints a comprehensive picture of a driver’s life, potentially chilling activities protected by the First Amendment. The technology of cop car license plate scanners can be used to monitor individuals visiting sensitive locations such as healthcare facilities, immigration support centers, gun stores, union halls, protest sites, or places of worship.

Given that drivers are legally obligated to display license plates, the use of cop car license plate scanners to track the movements of millions of ordinary citizens, the vast majority of whom are not suspected of any wrongdoing, is a matter of growing concern.

Types of Cop Car License Plate Scanners and How They Operate

While the term “cop car license plate scanner” immediately brings to mind mobile units, it’s helpful to understand the broader landscape of ALPR technology, which can be categorized into three main types, with mobile ALPRs being directly relevant to police vehicles.

Stationary or Fixed ALPR Cameras

Alt text: Stationary ALPR cameras mounted on traffic light, monitoring vehicle traffic.

Although not directly related to cop car license plate scanners, stationary ALPR cameras provide context to the wider ALPR ecosystem. These cameras are permanently installed at specific locations like traffic lights, utility poles, facility entrances, or highway exits. They primarily capture license plates of vehicles moving within their field of view.

Strategically placed stationary ALPRs along roads enable tracking vehicle direction and speed. A network of these cameras allows for real-time vehicle tracking. Stored data reveals historical travel patterns, potentially indicating a driver’s residence or workplace. Smaller communities sometimes use these at town entrances and exits, creating a digital checkpoint where every vehicle entering or leaving is recorded. Interestingly, some police departments camouflage ALPRs as ordinary objects like traffic cones or even cacti to maintain covert surveillance.

These fixed ALPR systems are frequently integrated with red-light and speed enforcement systems and are also used for automated toll collection on roads and bridges.

Mobile ALPR Cameras: The Core of “Cop Car License Plate Scanners”

Alt text: Mobile ALPR system mounted on top of a police car, capturing license plates while patrolling.

Mobile ALPRs are the embodiment of cop car license plate scanners. Mounted on police patrol vehicles, these systems empower law enforcement to gather license plate data as officers conduct their patrols throughout a city or region. Typically, these cop car license plate scanners are activated at the start of a shift and remain operational until the shift concludes, continuously collecting data.

Beyond capturing plates of moving vehicles, cop car license plate scanners are highly effective at recording license plates of parked cars. A patrol car equipped with a mobile ALPR can drive through a parking lot and capture hundreds of license plates in just minutes, amassing significant data quickly.

Police utilize cop car license plate scanners for “gridding,” a practice involving systematic driving through every street in a neighborhood to gather intelligence on residents. This blanket surveillance approach, enabled by cop car license plate scanners, raises concerns about mass data collection and its implications for privacy.

Furthermore, private vendors like Vigilant Solutions also deploy mobile ALPRs to collect license plate data, which they then sell to law enforcement agencies and other entities. This commercial aspect of ALPR technology further expands the scope of data collection beyond public law enforcement operations.

ALPR Trailers

Alt text: ALPR trailer unit deployed by police department, used for temporary surveillance in specific areas.

ALPRs are also available as towable trailers, offering a flexible deployment option. Police can position these ALPR trailers in specific locations for extended periods. Functionally similar to fixed ALPRs, ALPR trailers collect data without requiring permanent installation. The Drug Enforcement Administration (DEA) has utilized these systems, disguised as speed enforcement trailers, particularly in areas along the U.S.-Mexico border to monitor vehicle movements. Additionally, police have deployed trailers or vehicles equipped with ALPRs near gun shows and political rallies, indicating their use in monitoring specific events and gatherings.

The Extensive ALPR Databases

The data collected by cop car license plate scanners and other ALPR systems is typically stored in databases for long durations, often up to five years. These databases can be managed by police departments themselves or, frequently, by private companies like Vigilant Solutions or Flock Safety. Law enforcement agencies lacking their own ALPR infrastructure can access data collected by other agencies through regional sharing systems and networks operated by these private companies. Notably, several companies operate independent, non-law enforcement ALPR databases, contracting with individuals to install cameras on private vehicles for data collection. This commercially collected data is then sold to various businesses, such as insurance companies, but law enforcement can also subscribe to access this data, further broadening their surveillance capabilities.

Hotlists: Targeted Surveillance with Cop Car License Plate Scanners

Law enforcement agencies commonly preload “hotlists” into their ALPR systems. These hotlists contain license plate numbers of vehicles of interest, such as stolen vehicles or those associated with outstanding warrants. Officers can also create their own hotlists for specific investigations. When a cop car license plate scanner detects a plate on a hotlist, the system immediately alerts the officer in the patrol car (for mobile ALPRs) or the relevant agency (for fixed ALPRs). Some hotlists even include vehicles linked to minor offenses like misdemeanors and traffic violations. Agencies sometimes use these hotlists to generate revenue by targeting individuals with outstanding citations.

Data Collected by Cop Car License Plate Scanners and ALPR Systems

Cop car license plate scanners and ALPR systems collect a rich dataset beyond just license plate numbers. They capture location data, along with the precise date and time each license plate is recorded. Some advanced systems can also identify the make and model of the vehicle. These systems are incredibly efficient, capable of capturing thousands of plates per minute. One vendor boasts a dataset exceeding 6.5 billion scans, growing by an astounding 120 million data points each month, demonstrating the sheer scale of data collection.

By combining ALPR data, it’s possible to determine a vehicle’s direction and speed through triangulation. Over time, aggregated data reveals a vehicle’s complete travel history. Algorithms applied to this data can identify regular travel patterns and even predict future locations. The data also reveals all vehicles that have visited a specific location, providing detailed insights into traffic patterns and points of interest.

While ALPR data typically doesn’t include driver names directly, law enforcement can use other databases to link license plate numbers to individual identities.

In addition to license plate data, the images captured by cop car license plate scanners and ALPR systems can reveal images of the vehicle itself, the driver and passengers, and the immediate surroundings. Some systems even create “vehicle fingerprints,” including details like vehicle color, make, model, physical damage, and bumper stickers, further enriching the collected information.

Law Enforcement Applications of Cop Car License Plate Scanner Technology

A time-lapse visualization of the data collected by Oakland Police Department vehicles mounted with license plate readers.

ALPR data collection is indiscriminate, capturing information on millions of ordinary individuals. By analyzing vehicle times and locations and tracing past movements, police can utilize stored data to construct detailed profiles of drivers’ lives, identifying past behavior patterns and potentially predicting future actions. This occurs despite the fact that the vast majority of individuals whose license plate data is collected are not suspected of any crime. Before ALPR technology, officers manually recorded license plates, a process that limited data collection and required officers to selectively choose which vehicles to track. Cop car license plate scanners and ALPR technology remove these limitations, enabling the tracking of everyone and facilitating faster, broader data collection with reduced manpower.

A 2021 EFF report analyzing data from 63 California law enforcement agencies revealed that only 0.05% of the data collected by ALPRs was relevant to a public safety interest at the time of capture. This stark statistic underscores the vast amount of irrelevant data collected on law-abiding citizens.

Law enforcement primarily uses license plate readers for two main purposes:

Real-time Investigations Using Cop Car License Plate Scanners

By adding a license plate to a “hotlist,” officers can use cop car license plate scanners to automatically identify or track specific vehicles in real time. License plates are frequently added to hotlists for stolen vehicles or vehicles associated with outstanding warrants. Plates might also be added if a vehicle was seen at a crime scene, if the owner is a suspect, or if the vehicle is linked to gang activity. Hotlists can also include vehicles associated with less serious offenses.

Historical Investigations Leveraging ALPR Data

Since ALPRs, including cop car license plate scanners, collect data on virtually everyone, officers can search and analyze historical data using a plate number, partial plate, or physical address. For instance, an officer investigating a convenience store robbery could enter the store’s location to identify vehicles present nearby at the time of the incident. They can then trace those plate numbers to uncover other locations where those vehicles have been recorded.

Training materials and policies in some jurisdictions advise officers that a hotlist alert alone might not justify a vehicle stop. Officers are instructed to visually confirm the plate number match. Failures in manual confirmation, coupled with machine errors, have led to wrongful stops.

While law enforcement emphasizes the use of ALPR data in recovering stolen vehicles or locating abducted children, police have also used ALPR data for widespread enforcement of minor offenses, such as identifying uninsured vehicles or tracking down individuals with unpaid court fees. This expansion of ALPR use beyond serious crimes raises concerns about mission creep and disproportionate impact on certain communities.

Data retention policies for ALPR data vary widely among agencies, ranging from just a few days to several years. Some entities, particularly private companies, may retain data indefinitely, further amplifying privacy concerns.

Vendors in the Cop Car License Plate Scanner and ALPR Market

Vigilant Solutions (a subsidiary of Motorola Solutions) and Flock Safety are leading vendors of ALPR technology in the United States. Other notable vendors include Rekor, Elsag, Axon, Perceptics, and Jenoptik.

Vigilant Solutions, through its sister company Digital Recognition Network, provides access to privately collected data obtained through partnerships with repossession companies, who passively collect ALPR data using their vehicles. Flock Safety has established similar partnerships with numerous homeowners associations, gaining access to data from neighborhood ALPR systems that is then shared with law enforcement. Both Vigilant Solutions and Flock Safety offer data-sharing capabilities, enabling law enforcement agencies across the country to access and exchange ALPR data.

Privacy and Civil Liberty Threats Posed by Cop Car License Plate Scanners and ALPRs

ALPR, especially cop car license plate scanner technology, represents a potent surveillance tool with the potential to infringe upon individual privacy and violate the rights of entire communities.

Abuse of this technology by law enforcement agencies has been documented. Examples include police in New York electronically recording license plates of vehicles parked near a mosque and police in Birmingham, UK, targeting a Muslim community with surveillance while misrepresenting the project’s nature to the public. EFF’s analysis of Oakland Police Department ALPR data revealed a disproportionate deployment of ALPR-equipped vehicles in low-income communities and communities of color, raising concerns about discriminatory surveillance practices.

Furthermore, individual officers have misused law enforcement databases, including license plate information. Instances of officers abusing access to license plate data for personal gain, such as extortion and stalking, underscore the risks of insider misuse.

Beyond intentional misuse, ALPR systems are prone to errors in plate reading, leading to serious consequences. Cases of individuals being wrongly pulled over, handcuffed at gunpoint, and even having their vehicles searched due to ALPR errors highlight the potential for misidentification and the significant impact on innocent individuals. While some court rulings have addressed the issue of stops based solely on technology error, vulnerabilities remain.

The aggregation of ALPR data over extended periods makes it increasingly invasive and susceptible to misuse and data breaches. Even well-resourced agencies like Customs & Border Protection have experienced data breaches involving ALPR vendor systems. Implementing sensible data retention limits, clear access policies, and robust audit processes are crucial to mitigate these risks. One of the most effective privacy safeguards would be for police to discard data immediately when a vehicle does not match a hotlist, minimizing the collection and storage of data on innocent individuals.

Cop car license plate scanners and ALPR technology can also be used to target vulnerable communities, such as immigrant communities and individuals seeking or providing reproductive health services, raising concerns about the use of surveillance to monitor and potentially intimidate these groups.

EFF’s Advocacy and Legal Work on ALPR Technology

The Electronic Frontier Foundation (EFF) has been actively investigating and challenging the privacy threats posed by ALPR technology through public records requests, litigation, and legislative advocacy since 2012.

ALPR Litigation Efforts

EFF, in collaboration with the ACLU of Southern California, has pursued legal action against law enforcement agencies to increase transparency and accountability regarding ALPR data. Their lawsuit against the Los Angeles County Sheriff’s Department and the Los Angeles Police Department sought access to ALPR data, challenging the agencies’ claims that these records were exempt from public records laws. The California Supreme Court ultimately ruled in favor of EFF and ACLU, emphasizing the public’s right to access this information.

EFF and the ACLU also litigated against the Marin County Sheriff’s Office for unlawfully sharing ALPR data with out-of-state agencies, including Immigration & Customs Enforcement (ICE), in violation of California law. A settlement was reached, preventing further unlawful data sharing.

Beyond California, EFF has filed amicus briefs in cases in other states, challenging excessive ALPR data collection and advocating for stronger privacy protections for drivers.

Promoting ALPR Accountability and Transparency

EFF has actively promoted legislative reforms to enhance ALPR accountability and transparency. In California, EFF advocated for S.B. 34, a bill that mandates data protection measures, access logs, public meetings for ALPR programs, usage and privacy policies, and restrictions on data sharing.

EFF has also coordinated volunteers to gather and analyze ALPR policies across California, exposing agencies failing to comply with the law. Through projects like Data Driven and Data Driven 2, EFF has utilized public records requests to shed light on how agencies use ALPR data.

In 2019, EFF successfully advocated for a California State Audit of law enforcement agencies’ compliance with S.B. 34, resulting in a critical report substantiating EFF’s concerns about inadequate policies and excessive data sharing.