By simply passing vehicles on a highway, a city street or in a parking lot, car-mounted cameras can record up to 3500 license plates a minute. A computer then saves and tags the plate picture with the date, time and location it was taken.
"Most people don't know that this is happening," said Mike Katz-Lacabe.
Until Katz-Lacabe requested pictures from his local police department, he had no idea officers had stored 100 plate photos of his family's cars around town over a two-year period. He was surprised to see himself in one photo, and another shot captured his children in his driveway.
"I was shocked. It's very powerful information," he said.
Private companies, car repossession agents, and according to one report, more than 37 percent of large law enforcement agencies across the country are all scanning plates.
Some police departments keep their own plate databases. But some law enforcement agencies and repo firms send it to private companies, like MVTRAC, a leading plate recognition system seller that maintains a massive national license plate photo database.
"It's perfectly legal. It's not infringing on anyone's rights," said Scott Jackson of MVTRAC.
It is perfectly legal to shoot and store video shot in public. But Katz-Lacabe and national privacy advocates want this plate storing practice to yield, and want to know how long photos are being kept, how they are being used and who has access to them.
"There's no law that would impact how the different municipalities and states would implement this, and therefore the potential for misuse or unintended use is extraordinarily high," said Mary Ellen Callahan, former chief privacy officer.
An International Association of Police Chiefs survey shows some agencies keep the plate information indefinitely, while others delete data after a few months. The association says it's critical to crime fighting and police keep the info secure.
"We don't know of a single instance where automated license plate recognition data has been misused or abused," said David Roberts with the International Association of Police Chiefs.
But Katz-Lacabe says even though he's no criminal, he's still not comfortable with his daily activities being caught on camera and stored.
"That sort of thing frightens me," he said.
More than two dozen law enforcement agencies in Los Angeles County alone are using license plate recognition technology. That includes the Los Angeles Police Department and the Los Angeles County Sheriff's Department. It is not known if they supply the information they gather to companies like MVTRAC.