A Quad is any four-wheeler with solo or tandem seating, a handlebar for steerage and off-road style knobbies all around. Though they aren't street legal, some will outfit their quad ATV with street tires and use it as a neighborhood stoplight-burner. Displacement runs much the same range as motorcycles with machines in the couple hundred range up to two liters plus. Quads were developed after three-wheeled ATVs were outlawed in the '80s because of their inherent instability and the series of accidents that highlighted the danger. They can be of the Homeowner Jane sort to be used as a beast of burden for medium-duty gardening activities, a hunter's best friend, a fun trail machine, and of course, they lend themselves to racing quite well.