Maryland drivers have received more than 1 million speeding tickets from work zone speed cameras over the past three years, and many of those tickets were issued even though no one was working in those zones at the time.

The controversial cameras raked in $18.9 million in 2011, adding to the $30.7 million they generated in their first two years of operation. The cameras have now issued more than a million tickets, according to data from the Maryland State Highway Administration.

At $40 per ticket, drivers have been irked by the cost, but also by the circumstances: The work-zone cameras nab speeders even though no workers are present in the work zone, including on legal holidays. Critics say that means the cameras are about revenue, not safety.

"Although motorists aren't as apt to break the posted speed limit when they sense speed cameras are present, they are also clearly bothered by the fact that they can be slapped with a speeding citation while driving through a work zone during the hours when no workers are present on the site," AAA Mid-Atlantic's John Townsend said. "Based upon a previous study, 63 percent of the work zone tickets were issued when workers were not present in the work zone."

But state officials say the program has slowed drivers down, cutting by half the number of drivers who go more than 10 mph over the speed limit in the zones.

Work zone cameras on the Beltway caught 30,886 speeders in just the last five months of 2011. In August the cameras caught 12,001 violators; in November they only caught 3,963, and in December, 5,569.

Maryland lawmakers are set to take up the issue this week. The state Senate will debate a bill that would allow speed cameras to track drivers only when workers are present in the work zone.

But that same bill failed last year, and the General Assembly has a history of supporting the use of speed cameras. Maryland legislators approved seven camera traffic enforcement programs in the last seven years, AAA Mid-Atlantic noted.