"The technology has reached the point where it's very good now. It puts a tool in the hands of police officers out in the street to help fight terrorism," said Reardon, who works in his department's homeland security unit.
The readers will scan the license plate of every vehicle that zooms by and run the numbers through federal criminal databases and terrorist watch lists, Reardon said. Maryland, Virginia and the District could plug in additional databases.
When the machines get "hits," they instantly notify police or other law enforcement officials. The devices can typically read hundreds of plates an hour.
Civil liberties advocates say the tag readers are the latest sign of how surveillance programs are expanding in U.S. cities, driven by terrorism fears and rapidly developing technology. New York officials said last week that they plan to scan the license plates of all cars and trucks entering Manhattan as part of a new security system that also involves thousands of closed-circuit cameras.