Police are getting sneaky in Prince George County, Md. County officials expect to raise $12 million in fines this year using mobile speed cameras disguised as mailboxes, the Washington Examiner reported.

The county purchased nearly five dozen cameras, increasing its number of speed cameras by a factor of four, and projected $28 million in income for 2013. The movable, disguised cameras will replace fixed-pole cameras, which some say only cause drivers to slow down and then speed up again after passing the camera.

The new cameras are battery powered and don't require underground wiring. More than 349,000 citations were issued in the first nine months of the program, which began in September.

"Using [mobile cameras] on a rotating basis at various locations along the same section of roadway and on nearby roadways, we have almost created a series of enforcement zones around the city," said Michael England, director of the Rockville City Police Department's Special Operations Bureau, reported the Washington Examiner. "As a result, motorists are changing their driving habits and slowing down."