Sharp-eyed drivers have spotted what appears to be an unmanned mower cutting the grass on the Garden State Parkway.

Their eyes aren't deceiving them.

There are six lawn care versions of a Roomba robot vacuum cleaner cutting the grass on the Turnpike and Garden State Parkway, and each one costs $83,000.

The mower, known as a TRAXX-RF, is manufactured by Texas based Alamo Industrial and deployed in areas that are deemed too hazardous for a mower operated by a person, said Thomas Feeney, a spokesman for the New Jersey Turnpike Authority which runs both highways.

They're used on terrain where a conventional riding mower could be in danger of rolling over, he said.

"They are used in retention basins, catch basins, and on steep embankments where conventional mowing may be unsafe - that is, in areas where conventional mowers don't fit or where the slope of the terrain is too steep," Feeney said . "The Authority has been using them since 2014."

The Turnpike Authority joins contractors in North and South Carolina, which also use remote controlled mowers to cut lawn and brush on rough terrain on the sides of highways. The mower is operated by a maintenance worker who uses a remote control with joysticks to control speed and steering, according to the company's website.

The Alamo Traxx remote control mowers aren't cheap because they roll on treads similar to a bulldozer, rather than on tires. The purchase price for one mower is $83,856 and the authority bought four for $335,424 in 2014 and contracted in February to buy two more for $178,764, according to authority documents.

Larry Higgs may be reached at lhiggs@njadvancemedia.com. Follow him on Twitter @commutinglarry. Find NJ.com on Facebook.