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ALPR: The Surveillance Tool You’ve Probably Never Heard Of

If networks of surveillance cameras and drones have you concerned, you should meet their less known but equally dangerous cousin: automated license plate recognition (or ALPR). ALPR systems track and store location data on millions of vehicles and are in regular use throughout the state of Washington. The ACLU-WA is concerned about these systems because the data they produce can provide law enforcement with a detailed map of where you have been. When that information is reviewed, it can provide police with a picture of your personal habits and routines.

ALPR systems generally consist of at least one camera mounted to either a vehicle or fixed location. The cameras photograph every passing vehicle and software then analyzes the photo to identify and extract the license plate number. With each scan, the ALPR system records the exact location and time and stores this data along with the image and license plate at a rate of one per second. The license plate is then matched against a “hotlist” of license plate numbers that has been loaded into the system. However, whether or not there is a match, the system stores the data it has collected from every passing vehicle. Over an eight-hour period, one ALPR system can capture tens of thousands of plates.

State, local and federal law enforcement agencies around the country are storing this data – often indefinitely – and uploading it to private company servers. This data is then combined with information coming in from everyone else using the vendor’s system, creating massive databases of license plate location data.

ALPR technology is uniquely concerning because it often gets rolled out unannounced and is difficult to spot. Unlike surveillance cameras which look familiar and can often be easily spotted, ALPR units don’t clearly look like anything we would recognize as a threat.  In addition, the devices are often subtly attached to police cars, making them even harder notice.  

As a result, the ACLU and other civil liberties groups have had to rely on public records requests to learn whether local law enforcement agencies are using the technology and what exactly they are recording and storing. Not all police departments have been forthcoming about the information.  For example, last week the ACLU of Southern California and the Electronic Frontier Foundation filed a lawsuit against two Los Angeles county police departments who refused to release information about their ALPR systems. That kind of secrecy about government use of a monitoring technology is alarming.

At the ACLU of Washington, we’ve had better luck gathering ALPR information from agencies around the state. In 2011 we began an investigation of ALPR use in Washington. We submitted public records requests to the Seattle Police Department and the Yakima County Sheriff’s Department. Over the course of several months, we also interviewed representatives from more than two dozen law enforcement agencies in Washington to learn about how they use ALPR technology.

The results of the investigation were disheartening. The first thing we discovered is that law enforcement use of ALPR in Washington has become relatively common and widespread.  At least 22 city police departments and county sheriff’s offices across the state reported owning ALPR systems, and we assume those numbers have only increased since 2011. The majority of those agencies had placed their systems on vehicles rather than fixed poles. 

We also learned that ALPR systems have the capability to record and maintain an extraordinary amount of data about individuals. In Seattle, for example, police department ALPR units accumulated 7.3 million license plate and location records to the department’s database during a three-year pilot project.  Of those 7.3 million records, a scant 7,244 came up as hits, for a scan-to-hit ratio of less than one tenth of one percent.  Or put another way, the Seattle Police Department photographed vehicles and recorded the exact time and location of the photo for individuals who were merely driving around in 7,369,416 instances.

That large quantity of location data provides a handy means for anyone who wishes to track others.  For example, by analyzing the ALPR data we obtained from the Seattle Police Department, we found we were able to confidently map the regular routes of ALPR operators during their shifts.  By looking at breaks in time from scanning, we were able to ascertain when and where ALPR operators prefer to take their lunch break.  By comparing this routine data to all of an officer’s data, we could identify, for instance, when an officer takes his patrol car home and where that officer lives.  In at least one instance, we discovered the SPD Detective ALPR car travelling to Portland for an overnight trip, scanning the license plates of Washingtonians and Oregonians the entire way.  Thanks to the number of scans during this trip, we were even able to calculate the officer’s average rate of speed down I-5.

If we could use the data to identify specific information about police officers, the same data could be mined to piece together a picture of each of our daily routines.

ALPR does have legitimate and valuable uses, such as helping to locate stolen cars or people with outstanding warrants. But left unchecked, these systems can put privacy at risk. We shouldn’t turn a blind eye to the dangers of government collecting this massive amount data without any restrictions on use. Large quantities of data left in the hands of government are susceptible to abuse.

Last month we sent out another series of public records request to several law enforcement agencies around the state. The information we gather will give us an up-to-date picture of the prevalence of ALPR in Washington.  We then hope to use all the data we uncover to push authorities to create better use and data management policies that will ensure our privacy rights are protected.

We shouldn’t have to live in fear that our travels and lives are being recorded indefinitely by the government. Look for more information on our findings on the ACLU-WA website in the coming months.  


A vehicle  license plate should be used to indicate that the vehicle is licensed for use on public roads, and nothing more.  Making it serve double-duty as a publicly-visible identifier just facilitates dragnet investigations.  If a police officer has no reason to suspect me of wrongdoing, he shouldn't be investigating me or the vehicle in which I am traveling.

I disagree that "ALPR does have legitimate and valuable uses"!

This is a great article, but I disagree with its statement that "ALPR does have legitimate and valuable uses"!

While it might well be valuable to help enforce some laws against actual dangerous people, consider the wisdom of the principle, "the ends do not always justify all means". It is neither necessary nor justified, to create a situation where no one can get around without being tracked, in order to help gather more evidence for crimes people most people would agree about. It really, really doesn't. Please stop and think about that. I would also say that I do not want to live in a society that wants to create a situation where even the people we really do want to catch, have to exist in a world that has been made so threatening by our government! It starts making our government itself much more threatening and nasty, and that not only makes our government a perpetrator, but it can also rightly provoke action against it.

It is a very very bad idea.

Furhtermore, the fact that it has been done without much public discussion, is sneakily tyrannical.


Great, now not only are those particular officers that are guilty of abuse and stalking, can now be empowered to have their buddies and theselves stalk easier with state and federal approval...which explains my problems being followed to drs and trying to find attorneys et al, i have been very surprised at how this system is built to bully the victims and keep knocking us down while enabling the most deviant and clever criminals that hide behind badges, medical licenses, etc


I was recently told that The

I was recently told that The state of washington DOL wants to put a chip in license plates to gather information by a radio wave wireless chip .To be replaced every 7 years

ALPR is bad as it profiles and invades Privacy  rights of Drivers .

I stand with the ACLU and  EFF to fight these atrocities against our freedoms and liberties !

ALPR surveillance

Incidentally, this is also another reason why mandatory bicycle vehicle licensing is a very bad idea.  It would not only turn what is now a right into a privelege, possibly giving police the authority to permanently impound a bicycle simply for "driving without a license"-- authority they don't currently have under most circumstances-- but also take away cyclists' right to privacy.  Even in so-called "bicycle-friendly" states, harassment and discrimination is already a huge problem.  Being subjected to constant, suspicionless surveillance could only make the problem infinitely worse.

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