By the current ANSI definition, ATVs are intended for use by a single operator, although some companies have developed ATVs intended for use by the operator and one passenger. The passenger is not required to have a helmet. These ATVs are referred to as tandem ATVs.
The rider sits on and operates these vehicles like a motorcycle, but the extra wheels give more stability at slower speeds. Also dirt bikes are considered to be ATVs as that they were designed for off road use only. Although most are equipped with three or four wheels, six-wheel models exist for specialized applications. Engine sizes of ATVs currently for sale in the United States, (as of 2008 products), range from 49 to 1,000 cc (3 to 61 cu in).
Royal Enfield built and sold the first powered quadracycle in 1893. It had many bicycle components, including handle bars. The Royal Enfield resembles a modern ATV-style quad bike but was designed as a form of horseless carriage for road use.
The term "ATV" was originally coined to refer to non-straddle ridden six-wheeled amphibious ATVs such as the Jiger produced by the Jiger Corporation, the Amphicat produced by Mobility Unlimited Inc, and the Terra Tiger produced by the Allis-Chalmers Manufacturing Company in the mid 1960s and early 1970s. With the introduction of straddle ridden ATVs, the term AATV was introduced to define the original amphibious ATV category.
The first three-wheeled ATV was the Sperry-Rand Tricart. It was designed in 1967 as a graduate project of John Plessinger at the Cranbrook Academy of Arts near Detroit. The Tricart was straddle-ridden with a sit-in rather than sit-on style (similar to the contemporaneous Big Wheel toy). In 1968 Plessinger sold the Tricart patents and design rights to Sperry-Rand New Holland who manufactured them commercially. Numerous small American manufacturers of 3-wheelers followed. These small manufacturers were unable to compete when larger motorcycle companies like Honda entered the market in 1969.