Skip to content
October 4, 2013 / Jim Fenton

Automated License Plate Readers

The Police Department in my city, Los Altos, California, and many others nearby were recently  given Automated License Plate Readers (ALPRs) as part of a grant from the Department of Homeland Security. Having heard about this in the local newspaper, I decided to learn more about ALPRs and to participate in public discussions about their use.

For those who aren’t familiar with them, ALPRs are cameras that are either attached to vehicles or fixed that can automatically take a picture of the license plate of a passing car, perform optical character recognition on it, query a database to see whether it is wanted, and keep a record of the encounter for future use. I first became aware of ALPRs when I read an article a year or so ago about their use in Minneapolis. One of the local newspapers in Minneapolis had submitted a public records request for automated license plate reader data on the Mayor’s car, which was retained for up to a year.  The newspaper obtained that data, resulting in calls for making that data private and for shortening the retention period for the data.

In our city, compelling justifications for the license plate reader were provided. By not requiring the driver of the police car to individually type in and check license plates, more cars with warrants could be stopped. And by recording the cars leaving a crime scene, there was a higher chance of catching a fleeing criminal. Neither of these uses requires much retention of the data. But the data would be also shared with law enforcement agencies at the county and regional levels (and perhaps higher; that was never quite clear to me) and would be retained for a minimum of one year. The data would only be used for a valid law-enforcement purposes.

The retention period for the data is critical. The one-year retention is based on a California law requiring minimum retention periods for public records by cities, and license plate data is considered to be a public record. But with longer retention periods, there is a greater opportunity to discern patterns of activity of individuals, which may be subject to misinterpretation. Fortunately the California Highway Patrol is not subject to that particular requirement, and keeps ALPR data for only 60 days. A few other municipalities also haven’t applied the one-year public record rule to ALPR data, such as Tiburon, although they are notable for their use of ALPRs on all traffic entering the leaving their city.

I was very happy that the Los Altos City Council took up this issue, providing an opportunity for public discussion and policy making. It was also an opportunity for our Chief of Police, who had obviously studied the ALPR issue extensively, to educate all of us on their use of ALPRs and their data. One of the issues that surfaced was that the county, where our ALPR data would be stored, hadn’t set a retention policy for the data and it wasn’t clear when they would do so. The Council decided to approve the use of a single ALPR for one year with an understanding that the data retention issue needed to be settled by then.

While this public process around police-collected ALPR data worked well (even though I would have preferred that we seek a shorter retention period), private companies operate ALPRs as well, with no oversight. The most common private users of ALPRs is auto repossession companies, who find it them to be an efficient way to identify target cars. But their data have no restrictions on their use and retention, and companies like , and companies like MVTRAC have been successful at blocking efforts to limit their retention of data. This unrestricted data can be used by data brokers and others to do the same activity pattern analysis that is of concern when done by the government, and is available to virtually anyone willing to pay for the data. If it is the government that one is concerned about, remember that they could use private companies as a loophole to obtain data that they aren’t legally able to collect themselves.

I thank our Chief of Police, Tuck Younis, for several informative discussions on this subject.


My public comment to the City Council:

To: Los Altos City Council
From: Jim Fenton
Date: September 15, 2013

I’d like to thank the Council for considering the topic of Automated License Plate Readers in Los Altos.

The report from Chief Younis and coverage in the August 7 Town Crier point out a lot of good reasons for Los Altos to have a license plate scanner. The uses described for the scanner emphasize those that require little or no data retention: checking vehicles quickly for active warrants or observing those leaving a crime scene. But the scanner will also record the images it collects, along with the associated date, time, and GPS coordinates and upload them to a database. The question for me is how long is that data retained, with what agencies is it shared, and how may it be used by all of those agencies?

My biggest concern is the sharing of collected information with other agencies, such as the County and the Northern California Regional Intelligence Center. What are their policies on use, retention, and further sharing of the information? If Los Altos wants to restrict the retention and use of that data, will they comply?

There is also the question of privately-operated ALPRs. These collect license plate data with no restrictions on the use or retention of that data. Should that be permitted in Los Altos?

The vast majority, over 99%, of data collected by ALPRs will be of law-abiding citizens. With such a vast amount of information that can reveal personal habits and associations, the potential for abuse is there. While I trust our local police department and want them to have the best tools to keep Los Altos safe, I hope we consider the consequences and potential harms of broad tracking of our citizens.

Jim Fenton

Image Credit: California_license_plate_ANPR.png by Wikipedia user Achim Raschka used under Creative Commons license.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: