Automated License Plate Recognition (ALPR)

ALPR technology uses a combination of cameras and computer software to scan the license plates of passing vehicles.

These computer-readable images of license plates allow the police to compare plate numbers against plates of wanted vehicles and vehicles associated with wanted persons and missing persons.

ALPR cameras are positioned at fixed locations in Palo Alto to capture rear license plates only and are not designed to capture images of vehicle occupants or utilize facial recognition technology.  To derive maximum benefit with the fewest cameras needed, cameras are typically placed at strategically-selected locations based on several factors: crime statistics, common vehicular ingress and egress points, and traffic volume.

ALPR technology is used by the Police Department to solve all sorts of crime.  Recent years have seen regional increases in catalytic converter thefts, auto burglaries, vehicle thefts and organized retail thefts.  And, although still rare, the community has experienced several brazen armed robberies.

Those responsible for such crimes commonly use a vehicle to travel to and flee from the crime scene. Moreover, such offenders often engage in a series of criminal offenses involving multiple jurisdictions and victims, and commonly arrive in a stolen vehicle, a vehicle bearing stolen plates, or a vehicle that law enforcement has previously connected to verified criminal activity.

Identifying stolen or wanted vehicles, via ALPR technology installed at fixed locations, as they enter a target area provides law enforcement an opportunity to intervene before additional crimes are committed, and potentially apprehend wanted persons or recover stolen property.  ALPR data also provides investigators with an additional technique to identify, locate and apprehend offenders once a crime has already occurred.

The use of ALPR technology provides several benefits, including crime deterrence, real-time alerts to police when stolen or wanted vehicles enter an area, and enhanced investigative capabilities when a crime has already occurred.

• Deterrence: Even if officers are unable to locate and stop the vehicle in question, suspects may see the police response and be deterred from further criminal activity. Indeed the mere presence of the ALPR cameras, visibly mounted on public infrastructure and potentially accompanied by signage, may act as a deterrent. Police personnel have reported to staff that some criminals will intentionally target jurisdictions without ALPR technology to increase their chances of successfully avoiding detection while committing crimes.

• Real-Time Alerts: When a real-time ALPR alert occurs, notifying police of the presence of a wanted or stolen vehicle, officers can respond to the area to search for the vehicle. If officers locate the vehicle, prior to making an enforcement stop, they visually confirm the plate number and manually check it against law enforcement databases to confirm the accuracy of the ALPR information and the legal justification for the stop.

• Solve Crimes Already Committed: In addition to providing opportunities to prevent crime and apprehend wanted persons via real-time alerts, ALPR data is used by investigators to solve crimes that have already occurred.  Commonly, by the time a crime is reported to police, the suspects have already fled the area, and it is the job of police to identify and locate the suspects at a later time.  While victims and witnesses can often provide responding officers with a description of the vehicle used by a suspect, those descriptions are frequently incomplete (e.g., a partial license plate number, vehicle type and color only) or consist of a license plate number that corresponds to a stolen vehicle or a stolen plate.  Investigators can turn that imperfect or incomplete information into actionable leads by querying the ALPR database.

• Regional Coordination: ALPR data sharing among local law enforcement partners allows agencies to collaboratively investigate, identify and apprehend multi-jurisdictional offenders, or those who commit crimes in one jurisdiction but reside in another.

• Expanded Searchable Data Set: Private entities (e.g., homeowners associations, shopping centers, individual retailers) utilizing ALPR cameras can also elect to share their data with local law enforcement, to include real-time alerts when wanted or stolen vehicles are captured.  Multiple such entities exist in Palo Alto, including the City’s largest shopping center, the Stanford Shopping Center.  This is a one-way share of information; a private entity that shares its ALPR data with law enforcement does not gain access to law enforcement data in return.  The investigative usefulness of an ALPR system is greatly enhanced as its searchable data set increases, whether from other law enforcement contributors or private entities.

The system captures the following information:

• Date, time, and location
• License plate (including the state, the plate number or partial plate number, or the absence of a license plate)
• Vehicle characteristics (the make, model, type, and color)
• A photo of the rear of the vehicle showing the license plate

The system is not intended to capture images of vehicle occupants (ALPR cameras would photograph passing vehicles from the rear).

The system does not use facial recognition technology.

Here is a sample ALPR image:

Data captured by ALPR technology is automatically purged after 30 days, unless a specific record has been identified as relevant to a specific criminal investigation.

Many law enforcement agencies already employing ALPR technology choose to store all data for up to one year or longer.  The Police Department believes that a retention period of 30 days is sufficient in Palo Alto.

The Police Department is mindful of privacy concerns that some community members may have about ALPR technology and the data that it collects.  The Police Department took those concerns into account when proposing how the use of ALPR technology could be implemented in Palo Alto, and City Council discussed those concerns and our responses to them prior to authorizing our use of the technology.

• The use of ALPR technology is specifically regulated by California Civil Code §1798.90.5, et seq., and is also subject to the City’s Surveillance Technology ordinance, Palo Alto Municipal Code §2.30.620, et seq.  The Department's policies and training satisfy the requirements of all of these statutes.
  
  
• The Police Department has ensured that ALPR cameras are positioned at fixed locations in Palo Alto to capture rear license plates only and are not positioned to capture images of vehicle occupants or utilize facial recognition technology.  To derive maximum benefit with the fewest cameras needed, cameras are typically placed at strategically-selected locations based on several factors: crime statistics, common vehicular ingress and egress points, and traffic volume.
  
  
• Data captured by ALPR technology is automatically purged after 30 days, unless a specific record has been identified as relevant to a specific criminal investigation.  Many law enforcement agencies already employing ALPR technology choose to store all data for up to one year or longer.  The Police Department believes that a retention period of 30 days is sufficient in Palo Alto.
  
  
• Data obtained from ALPR technology is only accessible to properly trained staff with a legitimate law enforcement need, and all queries are logged and subject to audit.  This is consistent with decades-long legal standards of access to other law enforcement computer databases, like driver license information, vehicle registration information, and criminal history records.  Unlawful use of law enforcement computer databases is against state law, and subjects personnel to civil and criminal liability as well as discipline up to and including termination.
  
  
• ALPR data is transmitted in an encrypted format and stored remotely by our contracted third-party vendor, Flock Safety, consistent with industry-standard Criminal Justice Information System (CJIS) security protocols.  The Police Department accesses the data via a secure web-based platform.
  
  
• To view the policy governing our use of ALPR technology, visit our Police Policy Manual page, download the manual, and navigate to Policy §462. 

Didn't you already have ALPR technology installed in patrol cars?

• The Police Department has one patrol car equipped with a mobile ALPR unit.  It has had this unit for over ten years, and has recovered stolen vehicles and located wanted criminals as a result.  The limitation of a single mobile ALPR was that alerts and data collection only occur when that vehicle is being operated by an officer, which is limited by staffing, calls for service, and other duties.  Data is also limited to the route and distance traveled by the single patrol vehicle.

• In April 2023, City Council authorized the Police Department to contract with Flock Safety to install fixed ALPR cameras at strategically-selected locations in Palo Alto based on several factors: crime statistics, common vehicular ingress and egress points, and traffic volume.

Who within the Police Department can access the data?

• Data obtained from ALPR technology is only accessible to properly trained staff with a legitimate law enforcement need, and all queries are logged and subject to audit.  This is consistent with decades-long legal standards of access to other law enforcement computer databases, like driver license information, vehicle registration information, and criminal history records.  Unlawful use of law enforcement computer databases is against state law, and subjects personnel to civil and criminal liability as well as discipline up to and including termination.

Are neighboring police agencies using ALPR technology?

• Other local communities are currently using fixed ALPR technology, including Menlo Park, Atherton, Los Altos Hills, Saratoga, Campbell, San Jose, Los Gatos, Gilroy, Morgan Hill, Milpitas, and Santa Clara, with several other local jurisdictions in the process of implementing the technology.  These jurisdictions anecdotally report that, since the deployment of fixed ALPR, they have experienced a marked increase in the recovery of stolen vehicles, as well as investigative success stories attributable to ALPR data.

Where in Palo Alto are the ALPR cameras located?

• To derive maximum benefit with the fewest cameras needed, cameras are placed at strategically-selected locations based on several factors: crime statistics, common vehicular ingress and egress points, and traffic volume.  As the ALPR cameras are a law enforcement investigative tool, the Police Department does not provide their locations on this website. If criminals are made aware of the location of the devices in advance, they could take measures to avoid detection by the system.

Are ALPR cameras located in my neighborhood?

• The Police Department will not install ALPR cameras permanently in residential neighborhoods.  However, if faced with a specific crime trend in a particular neighborhood, the Police Department could temporarily relocate an ALPR camera into that neighborhood long enough to address the crime trend.

How many cameras are there?

• Thirty.  These adequately cover key areas of Palo Alto and provide the flexibility to temporarily relocate cameras if necessary to address a specific crime trend.

How long do you store the data?

• Data captured by ALPR technology is automatically purged after 30 days, unless a specific record has been identified as relevant to a specific criminal investigation.

Does ALPR technology use facial recognition software?

• No.

Does ALPR technology capture my picture while I drive my car?

• ALPR cameras are not designed to capture images of vehicle occupants or utilize facial recognition technology.  They are positioned at fixed locations designed to capture images of rear license plates only.

Does ALPR technology provide constant surveillance of members of the public?

• No.  ALPR technology only provides authorized law enforcement personnel with information about a vehicle located on a public roadway for a single moment in time at a single location.  This information is only used by law enforcement to provide potential leads to support criminal investigations.

Does the Police Department share its ALPR data with other local police agencies?

• Yes.  ALPR data sharing among local law enforcement partners allows agencies to collaboratively investigate, identify and apprehend multi-jurisdictional offenders, or those who commit crimes in one jurisdiction but reside in another.  Individual data sharing agreements between the Police Department and each other local police agency with which Palo Alto ALPR data is shared are signed prior to the sharing of any data.
  
  
• As of April 2026, the Police Department has signed data sharing agreements with the following agencies:  Menlo Park Police Department, East Palo Alto Police Department, Los Altos Police Department, Stanford Department of Public Safety, Sunnyvale Department of Public Safety, Belmont Police Department, Concord Police Department, Gilroy Police Department, Burlingame Police Department, California Department of Corrections, Redwood City Police Department, Milpitas Police Department, Santa Clara Police Department, Campbell Police Department, Town of Los Gatos, San Jose Police Department, San Bruno Police Department, Colma Police Department, Hillsborough Police Department, Foster City Police Department, San Mateo Police Department, Fremont Police Department, Hayward Police Department, San Leandro Police Department, Union City Police Department, Newark Police Department, Pleasant Hill Police Department, Pleasanton Police Department, Dublin Police Department (as serviced by the Alameda County Sheriff's Office), Livermore Police Department, Tracy Police Department, Stockton Police Department, Walnut Creek Police Department, Benicia Police Department, Clayton Police Department, Danville Police Department, Albany Police Department, El Cerrito Police Department, San Pablo Police Department, Oakley Police Department, Marin County Sheriff's Office, Mill Valley Police Department, Monterey County Sheriff's Office, Monterey County District Attorney's Office, Oakland Police Department, Sacramento District Attorney's Office, Turlock Police Department, Vacaville Police Department, Vallejo Police Department, Lincoln Police Department, Salinas Police Department, Watsonville Police Department, Capitola Police Department, Carmel Police Department, Seaside Police Department, Dixon Police Department, West Sacramento Police Department, Rohnert Park Department of Public Safety, Elk Grove Police Department, Citrus Heights Police Department, Roseville Police Department, Fairfield Police Department, Suisun City Police Department, San Francisco Police Department, Santa Rosa Police Department, Central Marin Police Department, Folsom Police Department, the San Mateo County Sheriff's Office, the Alameda County Sheriff's Office, the Napa County Sheriff's Office, the Solano County Sheriff's Office, the San Joaquin County Sheriff's Office, the West Valley Mission College District Campus Police, and the California Highway Patrol. 

Does the Police Department share its ALPR data with out of state or federal police agencies?

• No. Police Department policy only permits the sharing of data with local law enforcement agencies in California, pursuant to individual data sharing agreements.
  
  
• For more information, see the accordion below entitled "February 2026 Update - Flock in the News."

Is ALPR data used for immigration purposes?

• No.

How much does ALPR technology cost?

• The total estimated costs of our three-year contract with Flock Safety to provide ALPR technology is approximately $165,900 (which includes $61,900 for the balance of FY23 and all of FY24, plus $52,000 annually for FY25 and FY26).

What research did the City do prior to implementing ALPR technology?

• When deciding whether to employ ALPR technology, the City and Police Department did extensive background research and presented that research in public forums. The Police Department presented a study session to City Council on ALPR technology on October 24, 2022 (read the staff report for that study session here, view the presentation for that study session here, and watch the study session and ensuing discussion here). On April 3, 2023, the Police Department returned to City Council to seek their approval of implementation of ALPR technology (read the staff report here(PDF, 6MB), view the presentation here(PDF, 2MB), and watch the Council item here). Council voted 7-0 in favor of implementing ALPR technology (read the draft action minutes here(PDF, 142KB), starting on page seven).

Can I read the policy on ALPR usage?

• Yes.  To view the policy governing our use of ALPR technology, visit our Police Policy Manual page, download the manual, and navigate to Policy §462.

As of April 21, 2026, recognizing public interest on this topic, the Police Department will begin proactively posting on a monthly cadence partially redacted Flock search logs on the City’s ALPR website (see the "ALPR Search Logs" accordion below). These logs include information concerning ALPR queries performed by PAPD users, as well as queries performed by other agencies, that has not previously been released pursuant to a legal exemption. Additionally, the City continues to use best practices to secure Palo Alto ALPR data, including a 30-day limit on data retention, requiring MOUs with other agencies for data sharing, and internal policy controls.  

In late 2023, unbeknownst to many users including PAPD, Flock added a new “Nationwide Lookup” search feature. Using this feature, an out-of-state local law enforcement or federal agency could perform a broad search of data from Flock’s entire nationwide network of over 6000 cameras, including the 20 cameras then-deployed in Palo Alto. The feature did not enable targeted searches of any specific agency’s data. These searches could only be performed system-wide when a full 7-digit license plate number was known and only based on the articulation of a legitimate law enforcement purpose.   

PAPD was first made aware of this issue in December 2025 and subsequently learned that Flock had already disabled the feature for PAPD by late October 2024 and for all California law enforcement agencies by March 2025.   

While its data was included in the “Nationwide Lookup” searchable dataset during this period, PAPD has worked with Flock to confirm that no PAPD data (i.e., license plates captured by Palo Alto cameras) was actually received by any out-of-state agency or federal agency as a result of any “Nationwide Lookup” search. In other words, PAPD had no records that matched the “Nationwide Lookup” searches performed by out of state or federal agencies.  

Even though no PAPD data was shared, PAPD reviewed a sampling of the searches performed by out-of-state local law enforcement and federal agencies via the “Nationwide Lookup” feature. The searches we reviewed all appeared to be linked to legitimate law enforcement investigations (e.g., burglary, vehicle theft, assault).  Additionally, PAPD found that no searches had been performed by ICE, Customs and Border Patrol, or the Department of Homeland Security; keyword searches did not identify any searches that appeared to be associated with immigration enforcement or reproductive rights enforcement.

In January 2026, the Department added initial information on this issue to this ALPR webpage and previously updated the information in February 2026.

On February 3, 2026, the Department received a message from Flock Safety affirming its commitment to working with California law enforcement agencies on legal compliance and data security issues. To read that message, click here.

PAPD has been in contact with Flock’s executive leadership to express our concerns and, in response to PAPD’s suggestion, Flock has expressed a strong willingness to pursue third party verification that this issue has been resolved. While the City Auditor is unable to perform this task, work is underway to identify an alternate auditor. Our goal in this review would be to conduct a technical as well as operational review to confirm that Flock’s practices address the City’s expectations for security, transparency, and reporting of system features and changes. 

The Department is confident that its training, Surveillance Use Policy, 30-day data retention period, and requirement of an MOU for each agency with which it shares, meet or exceed industry standards. With that, as recommended by the City Council’s Policy & Services Committee, PAPD has discussed with the Independent Police Auditor a review of its internal policies and procedures with an eye toward areas where we may be able to do even better.   

Staff anticipates reporting to Council in early June 2026 with further updates on this topic.

Please click the link below to access all partially redacted Flock search logs since Flock went live in Palo Alto in 2023. These logs include information concerning ALPR queries performed by PAPD users, as well as queries performed by other law enforcement agencies. We initially posted these search logs on April 21, 2026, and will be updating it on a monthly basis moving forward. These search logs include information that had not previously been released pursuant to a legal exemption.

ALPR Search Logs