Some jurisdictions store the information in a large networked database; others retain it only in the memory of each individual reader's computer, then delete it after several weeks as new data overwrite it.
A George Mason University study last year found that 37 percent of large police agencies in the United States now use license plate reader technology and that a significant number of other agencies planned to have it by the end of 2011. But the survey found that fewer than 30 percent of the agencies using the tool had researched any legal implications.
With virtually no public debate, police agencies have begun storing the information from the cameras, building databases that document the travels of millions of vehicles."
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