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License Plate Recognition Systems Extend the Reach of Patrol Officers

Plate readers help shorthanded departments spot stolen cars and other criminal activity.

Being caught on camera comes with the territory in the UK, where license plate recognition systems are well established. But now the technology is taking root in the United States.

U.S. police are seeing spectacular results from license plate recognition systems, which extend the reach of police, providing functionality much like an extra officer. Nearly 400 of the 1,800 police agencies in the United States now have at least one license plate reader, and as the word of its potential spreads and prices fall, that number is expected to grow.

Since 1991, Britons have watched as the number of cameras used to keep an eye on the public has grown to more than 4 million. There are more than 200,000 in London alone, and by some estimates, Britons are filmed more than 300 times a day.

In the United States, the technology emerged on toll roads where radio frequency identification (RFID) transponders are used instead of human toll collectors. License plate recognition technology records the identity of motorists who blow through toll plazas without a transponder. Now police departments -- such as those in Los Angeles and Sacramento, Calif. -- use the technology to locate stolen vehicles, and others use it for surveillance.

License plate recognition systems typically consist of cameras mounted on police squad cars or in fixed locations. The cameras are linked to an optical character recognition (OCR) processor that reads the data and compares it to one or more databases. In the event of a "hit" on a license plate in a stolen vehicle database, for example, an alarm alerts officers of the match.

Agencies using the technology say it dramatically increases their ability to spot stolen vehicles, and it may prove even more valuable for other investigative tasks. But the systems aren't cheap -- it's upward of $20,000 to equip a single police cruiser. And privacy advocates worry about what police will do with the license plate data they collect, as agencies ponder its use for everything from catching tax cheats to rounding up parking scofflaws.

Early Adopters
The California Highway Patrol was the first to adopt automated license plate recognition (ALPR) systems, according to Brian Shockley, vice president of marketing for PIPS Technology, which manufactures and distributes ALPR technology. "A lot of West Coast agencies are adopting the technology, and there are pockets in Texas, Chicago, Florida, Ohio and New York state."

Without license plate readers, police drive around and type license plate numbers into a laptop or mobile data terminal (MDT), waiting for a hit on a stolen vehicle. Automating that process allows agencies to check many more vehicles, and it frees officers' hands in the process.

And ALPR systems can help in the investigation of more serious crimes too.

In 2005, a trooper on the Pennsylvania Turnpike was alerted by his ALPR of a stolen vehicle. The trooper confirmed the vehicle was stolen and that the three occupants were also wanted for kidnapping and attempted murder. The ALPR system was only in use for a week.

In 2007, in San Jose, Calif., an officer was alerted of a stolen vehicle by his ALPR system. The officer investigated and soon found the vehicle was used in the kidnapping of a 12-year-old girl days earlier. The girl had escaped, and because of the ALPR, the suspect was arrested and charged with kidnapping and forcible child molestation.

That same year in Roseville, Calif., witnesses to a hit-and-run that killed a 76-year-old man offered police a partial license plate number. Police used their ALPR system to query the back-office software on the partial plate and the location of the hit within a 10-mile radius. They came up with a few results, one of which led to a felony hit-and-run arrest.

Dramatic Results

I'm still amazed by it," said Mark Bateson, senior solution architect of the Sacramento Police Department, which has deployed two ALPR units. "In real time, the computer is evaluating live video from three cameras, and all the while -- with every frame that goes by -- it's looking for a license plate."

When the camera locates something similar to a license plate, it isolates that image and performs OCR on the plate. The data is immediately compared against a local database of stolen vehicles or other violations.

If there's a match, the ALPR notifies the officer in a computer-generated voice. The officer's laptop or MDT screen shows a picture of the plate, the vehicle and the reason for the hit. The officer can then contact dispatch to make sure the information is correct.

The systems can sometimes be fooled by wording on the sides of vehicles and are affected by dirt on a license plate and other obstructions. But it's a far cry from an officer manually typing in a few dozen plate numbers during a shift, waiting for a hit. An ALPR system can run thousands of license plates during a typical shift -- it's a breakthrough for understaffed police departments.

"The systems that get used regularly recover four to five times the number of vehicles an officer would recover," said Charlie Beck, chief of detectives and commanding officer of the Detective Bureau at the Los Angeles Police Department, which has 12 vehicles equipped with ALPR systems. "A good, efficient running system is the difference between fishing with a line and fishing with a net -- it's that dramatic."

ALPR systems are relatively new with few in use, so concrete statistics aren't available that point to an increase in stolen-vehicle convictions. But in Los Angeles, officers running an ALPR sometimes get two or three hits in a shift, whereas they'd previously get that many in a month.

"The issue is, we have a limited number of [systems]," Beck said. "We have a dozen, but we run 1,500 black-and-whites. It's really a drop in the bucket, but it will change the way we do things."

The Pennsylvania Auto Theft Prevention Authority was created in 1996 to combat a runaway auto theft problem. Thefts have dropped from 53,000 in 1996 to 28,000 in 2007. Pennsylvania equipped 13 squad cars with license plate readers, and with the hope of continuing that decline in stolen vehicles, began using the technology in earnest in 2007.

"It would be nice to have them set up on those roads where we know they're transporting stolen cars," said Michelle Staton, executive director of the Pennsylvania Auto Theft Prevention Authority. "New York City is not far from the upper end of our state, and they're stealing from there and transporting through our state. If we could pick up on those cars, it would be great."

Unlimited Potential

The Los Angeles Police Department would like to have more readers too, but they're not cheap. A unit for a police vehicle ranges from $20,000 to $25,000, depending on the manufacturer, of which there are several.

ALPR units, such as those manufactured by PIPS Technology, include a computer processor and OCR software that's mounted in the vehicle's trunk, cameras that are typically mounted on the car's light bar, and a graphical interface that officers view on an MDT or laptop. Then of course there's the back-office software that connects the system to the lists of stolen vehicles and arrest warrants.

Law enforcement officials say spotting stolen vehicles is just the start of what ALPR technology can do.

"As an investigative tool, it has unlimited potential," Beck said. "That will be its strongest use. It's always going to be great for the black-and-white to be driving down the street and find stolen cars rolling around,

and they are more effective at doing that. But the real value comes from the long-term investigative uses of being able to track vehicles --where they've been and what they've been doing -- and tie that to crimes that have occurred or that will occur."

In Pennsylvania, where crime rings transport vehicles they've stolen and runners transport drugs, that investigative ability is promising. "The hope is to take all the readings and put them into one database for when you've got another jurisdiction or state looking for a car that may have shown up here," Staton said. "There are a lot of possibilities; we've just scratched the surface. If a bank robbery happens at lunchtime and the guys running license plate reader detail could say, 'Here are the plates we read at that location. It's possible one of those cars was the bank robbers' car."'

Los Angeles is beginning to use license plate readers as a tool for parking checkers -- those little Department of Transportation vehicles with workers who drive around, mark tires and hand out parking tickets.

With a GPS piece that can be purchased with an ALPR unit, the process of marking tires can be eliminated. The system tracks which cars have been parked for more than an hour. "It's a big boon for them," Beck said. "But the investigative boon for us is they will collect all this data from the cars that were parked, so you have this huge advantage. If you have a rape, burglary or some other crime in the area, the detectives can search the system to see if there's any data involving the cars that were parked there."

Shockley said there's also an increased use of ALPR systems for scofflaw enforcement, including parking enforcement and finding tax cheats. One Pennsylvania municipality was looking into purchasing a system and using it to issue parking tickets and spot unregistered vehicles, according to Staton. "It could be a generator of revenue for the city," she said.

It's the Data, Stupid
But the data collection potential that has law enforcement so excited has privacy advocates concerned.

"The real potential for danger is collecting a tremendous amount of information, which can then be used, very inexpensively, to do speculative data mining based on searches to target people for various kinds of extra-judicial harassment," said Andrew Blumberg, a Samelson postdoctoral fellow at Stanford University.

Most agencies are keeping the data for extended periods because of the investigative factor and because storage of the numerical data is easy. Blumberg said it would be better if the information expired after a few days, but that won't happen.

"It's so easy to make copies of things. How could you possibly assure a hygienic information trail?" he asked. "Look at the E-ZPass [electronic toll] data; it's being subpoenaed in civil court to be used in evidence in divorce cases."

Blumberg said the issues of how cameras are used and what happens to the data they produce deserve serious consideration. "All I really want is for there to be a national debate and for people to acknowledge that this is what's happened. Then we can make informed decisions about what the law ought to be and what reasonable expectations are, or how private people should be when using a car and public access."

As the devices get cheaper, they could theoretically be put on every street corner to track everyone's movements. "That's what makes me uncomfortable," Blumberg said of a proliferation of license plate readers. "There will be a post on every corner and it's recording all of the license plates that go by, and that can be used to track everybody all the time without anybody ever knowing it's happening."

There can be a compromise that protects people's privacy and still gives authorities the information they need to protect the public, police say.
"This is the future, and we can either figure out good ways to use it, put good restrictions on it, make sure it's used by people who have a reason and authorization to use it, or it will grow wildly on us," Beck said. "And that's not what we want."

Either way, Beck said license plate reading technology is here to stay. "This is as plain and as obvious a use in policing as the two-way radio was 50 years ago," he said. "There's just no way that this won't be the future of policing. It's just too exactly on point."

One of the biggest challenges now, he added, is for police agencies to share the ALPR data they're capturing.

"The systems work fine," Beck said. "A lot of it depends on how expensive you want to go, with the cameras, with infrared or not. The biggest issue as more and more police departments become equipped with this is data sharing. We've got a bunch of stovepipe, stand-alone systems saving data throughout California right now, but they don't mesh. We've been sharing data for years, but this is new."

Police budgets are tight everywhere, and there's no indication it will change anytime soon. Nearly all police agencies need more officers than they will get, and license plate reader technology, serving as an extension of the police officer, will help.

"That is the promise of technology in law enforcement. It can make up for our limited resources. Cops are getting more expensive all the time; there is tremendous competition in the job market and they take a lot of time to hire," Beck said, adding that it takes time to hire and train officers and have them ready to function on their own, and the process doesn't keep up with the numbers of officers who leave the force.

"From the day you give me money to buy an officer, which would buy many of these systems, I'm at least a year or year and a half from having an officer who's even on the street and probably three years from having one who can function independently. It's a hard fact that this is technology I can immediately buy and leverage resources with, whereas no matter how much money you dump on me, I can only hire so many cops."