License plate scanners: Useful tools, but what about all that data?

Police around the country have been making increasing use of automatic license plate recognition (ALPR) systems, which combine optical character recognition with database storage and matching to help catch criminals, solve crimes and finding missing people.

In fact, their use is becoming so widespread that some organizations are raising privacy concerns.

ALPRs use a camera and OCR to read and photograph license plates as a police car travels down the road or cruises a parking lot. A computer compares the information collected with a national database; when a match is found the officer receives an alert on his/her computer, which shows the vehicle owner and nature of the potential problem.

The devices can use existing closed-circuit television, road-rule enforcement cameras, infrared cameras or cameras specifically designed for the task. Some can store a photograph of the driver, noted a Wikipedia entry.

ALPRs are also known by various other terms, including automatic vehicle identification (AVI); car plate recognition (CPR); license-plate recognition (LPR); lecture automatique de plaques d'immatriculation (LAPI) and automatic number plate recognition (ANPR).

The cameras were designed to help locate stolen cars, wanted criminals and vehicles involved in Amber or Silver alerts. They are also used as a method of toll collection.

Police have been enthusiastic about the technology, which is becoming more widespread as prices for the devices drop. Two of the latest to install the technology are police in Des Moines and Sioux City, Iowa, reported the

Police in Sioux City will begin using the technology in about a month; Des Moines will be adding it in the fall. The program debuted in Iowa in Polk County police vehicles last year.

“We’re just trying to make it right for everyone on the street,” said Polk County Sheriff’s Deputy Jeff Rullman in the article. “The number of plates this thing will read on a daily basis compared to what an officer can -- it’s no comparison. It’s not uncommon to have this thing run 6,000, 7,000 plates” during an eight-hour shift on a busy Des Moines street, he added.

Polk County obtained the devices gratis via a nearly $26,000 grant from the Justice Department. The police department will probably apply for additional funds for more equipment, said Rullman.

Large cities have been using the technology for a while. In Washington, D.C., for example, a network of ALPRs collects 1,800 images per minute, which are added to a database of people’s movements around the city, the Washington Post has reported.

The storage of those images is what has gotten the attention of the American Civil Liberties Union. The ACLU is questioning whether these gadgets will be used in a way that will create an Orwellian state.

In late July, ACLU affiliates in 38 states sent requests to local police departments and state agencies, asking how they will be using the readers to track and record Americans’ movements. In addition, the national organization and the ACLU of Massachusetts filed Freedom of Information Act requests with the Justice, Homeland Security and Transportation departments to learn how the federal government is funding the use of ALPRs and how the agencies themselves will be using the technology.

“When used in a narrow and carefully regulated way, ALPRs can help police recover stolen cars and arrest people with outstanding warrants. Unfortunately, law enforcement agencies are increasingly moving towards a ‘keep everything, share widely’ formula concerning ALPR data,” with many police departments storing location information of millions of motorists, not just those suspected of criminal activity,” the ACLU said in a recent blog on the topic.

“Only two states (New Hampshire and Maine) have passed legislation barring the retention of ‘non-hit’ plate data for extended periods,” the ACLU said. “On the other hand, we know for certain that some departments are eagerly engaging in this surreptitious data collection. As license plate location data accumulates, the system ceases to be simply a mechanism enabling efficient police work and becomes a warrantless tracking tool, enabling retroactive surveillance of millions of people.”

But are these popular yet controversial devices more effective than current methods? According to a blog post at, a 2010 study by George Mason University's Center for Evidence-Based Crime Policy found that "[o]ver a third of large police agencies have already adopted [license plate recognition]" even though there's been little discussion of its use or of community concerns, and "the question still remains as to whether this technology is more effective in reducing, preventing or even detecting crime."

Even Polk County’s Rullman conceded that he doesn’t really know how many law breakers have been identified using the technology.

Interestingly, the concern of the ACLU -- storing information on non-criminals for indefinite periods -- appears to be seen as a bonus by law enforcement. Des Moines police spokesman Christopher Scott noted that if a license plate is later tied to a child abduction, database information on the plate could be used to potentially track the abductor.

“People get freaked out about running plates and having banks of information,” he said in The Des Moines Register. “What we’re doing is basically putting in our storage bag a license plate, and if we search for it we can find that information. If we’re not searching for it, we’ll never find that information.”

About the Author

Kathleen Hickey is a freelance writer for GCN.


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