They are off-road vehicles only, unless your individual state has a certain law passed pertaining to them.
Alabama 01/01/2012 any road except interstate highways (effective 01/01/12) 25 mph (effective 01/01/12) mini-truck (effective 01/01/12)
Alaska no state law
Arizona no state law
Arkansas 07/30/09 roads with a posted speed limit of 55 mph or less excluding interstate highways and controlled access highways if vehicle is being used exclusively for farm purposes 55 mph mini-truck
California 01/01/07 natural islands larger than 20,000 acres with a population greater than 4,000,000 no autoette
Colorado no state law
Connecticut no state law
Delaware no state law
District of Columbia no law
Florida 06/16/09 roads with a posted speed limit of 35 mph or less 35 mph mini truck
Georgia no state law
Hawaii no state law
Idaho 01/01/09 local option no utility type vehicle (UTV)
Illinois 08/31/07 roads with a posted speed limit of less than 35 mph if allowed by local ordinance 25 mph neighborhood vehicle
Indiana no state law
Iowa no state law
Kansas 07/01/08 public roads except interstate, federal or state highways; within corporate city limits if allowed under local ordinance no micro utility truck
Kentucky no state law
Louisiana 08/15/08 roads with a posted speed limit of 55 mph or less except interstate highways, controlled access highways, or multi-lane divided highways with partial or no control of access no mini-truck
Maine est. 9/09 roads with a posted speed limit of 35 mph or less 25 mph low-speed vehicle
Maryland no state law
Massachusetts no state law
Michigan no state law
Minnesota 08/01/09 local option local option mini truck
Mississippi no state law
Missouri 08/14/08 local option 45 mph utility vehicle
Montana no state law
Nebraska 01/01/11 any road except interstate highways, freeways or expressways no minitruck
Nevada no state law
New Hampshire 9/11/10 roads with a posted speed limit of 35 mph or less located within 25 miles of the registrant's home or place of business no low-speed utility vehicle
New Jersey no state law
New Mexico no state law
New York no state law
North Carolina no state law
North Dakota 08/01/07 any paved road except highways with a posted speed of more than 65 mph 55 mph off-highway vehicle
Ohio no state law
Oklahoma 11/01/08 any road except interstate highways no mini-truck
Oregon no state law
Pennsylvania no state law
Rhode Island no state law
South Carolina no state law
South Dakota no state law
Tennessee 07/01/08 streets where the posted speed limit is less than 40 mph; a county or municipality may prohibit the operation of medium-speed vehicles on any road under its jurisdiction if the governing body of the county or municipality determines that such a prohibition is necessary in the interest of safety 35 mph medium-speed vehicle
Texas no state law
Utah 10/01/08 any road except an interstate freeway; limited access highway; street within a county of the first class; municipality that is within a county of the first class; or municipality with a population of 7,500 or more people 45 mph off-highway vehicle or street-legal all-terrain vehicle
Vermont no state law
Virginia no state law
Washington no state law
West Virginia no state law
Wisconsin no state law
Wyoming 01/01/08 any road except interstate highways if a multipurpose vehicle is incapable of achieving the maximum speed allowed on the specific highway, it shall be operated on the extreme right hand edge of the roadway multipurpose vehicle