There is no single nationwide retention period for automated license plate reader (ALPR) data in the United States. How long a plate read is kept depends on the applicable state and local rules, the agency’s written policy, the vendor and system configuration, and whether the record is preserved for an investigation or legal process. Examples include Maine’s 21-day limit for certain covered records, Palo Alto’s stated 30-day practice, and Flock Safety’s published seven-day default. Those examples have different scopes and are not a national range or average.
Why ALPR retention periods differ
ALPR systems capture license plate reads and may retain associated information. The exact data fields and what counts as a retained record—such as images, metadata, or derived information—depend on the applicable law and system documentation.
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For any particular camera network, check both the rules that govern the agency and the actual written policy and configuration. A vendor’s default is not necessarily the agency’s active setting or the legally controlling limit. Contracts or data-sharing arrangements may also affect retention of copies.
- Law: State statutes and local requirements can limit or condition retention.
- Agency policy: A police department may adopt a specific routine retention period.
- System and contract: Vendor defaults, customer-selected settings, and contract terms can differ.
- Preservation: Investigations, evidence needs, or legal process can result in particular records being kept longer than routine, unflagged reads.
Examples from laws, local policy, and vendor terms
| Source and scope | Stated period or rule | What it means |
|---|---|---|
| Maine statute: covered ALPR data | No more than 21 days | The cap has exceptions for specified intelligence and investigative records and commercial motor-vehicle screening data. Maine statute, 29-A M.R.S. §2117-A |
| Washington statute: specified retention circumstances | Allows retention under qualifying warrant, subpoena, court order, or specified evidentiary circumstances | The cited provision does not set one general fixed period for every ALPR record. Washington statute, RCW 46.63.170 |
| North Carolina statute: data preserved after a request | Destruction under the custodian’s own retention policy after one year from the initial preservation request, unless another request arrives in time and resets the period | This applies to data preserved after a request, not the everyday default for all plate reads. North Carolina statute, §20-183.31 |
| City of Palo Alto: local police practice | The city says its Police Department believes 30 days is sufficient | This describes one local policy, not California statewide law. City of Palo Alto ALPR information |
| Flock Safety: published vendor policy | Seven-day default; approved extensions may reach one year, subject to jurisdictional law | A vendor policy can change and may not match every customer’s contract or configuration. Flock Safety Evidence Policy |
| Flock Safety: Washington contractual provision | 21 days, or a shorter period selected by the customer | This term applies to the stated jurisdiction and customer relationship; it is not a universal Flock setting. Flock Safety Washington law-enforcement terms |
When a record may be kept beyond the routine period
A routine deletion schedule does not necessarily settle the retention of a specific record. A statute may permit preservation for an investigation or evidence, or in response to a warrant, subpoena, or court order. The details vary: Maine excludes specified categories from its 21-day cap, Washington addresses particular legal and evidentiary circumstances, and North Carolina sets a preservation rule measured from the initial request, with a timely further request able to reset that period.
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These are different legal mechanisms, not interchangeable extensions to a general retention deadline. For a specific read, the governing provision and the agency’s preservation procedure determine what applies.
How to find your local department’s retention period
- Identify the operator. Find the police department or other agency responsible for the camera network; a city, county, or state agency may operate different systems.
- Check current law. Review the current state statute and any applicable local rule. State summaries can help locate issues, but use the statutory text for a specific legal claim. The National Conference of State Legislatures overview describes differing state approaches; it is not a complete substitute for checking current law.
- Find the agency’s written policy. Look for an ALPR, surveillance technology, or data-retention policy, and distinguish routine plate-read retention from rules for records flagged or preserved as evidence.
- Check the system terms and settings. Identify the vendor, default, customer-selected retention setting, relevant contract terms, and any data-sharing arrangements that could create separate copies.
- Ask about the specific data type and exception. Clarify whether the stated period covers reads, images, metadata, or exports, and whether an investigation or legal process has preserved the record.
Why old surveys do not establish today’s national practice
A 2013 survey by the American Civil Liberties Union and the International Association of Chiefs of Police reported responses from 40 law-enforcement agencies. The reported approaches ranged from 30 days or less to multiple years and indefinite or capacity-based retention, alongside policies in development and unknown or unanswered responses. Those historical respondents do not establish current practice across U.S. agencies or a national average. The 2013 survey report is useful as evidence that practices varied, not as a current estimate.
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