Kart racing or karting is a road racing variant of motorsport with open-wheel, four-wheeled vehicles known as go-karts or shifter karts. They are usually raced on scaled-down circuits, although some professional kart races are also held on full-size motorsport circuits. Karting is commonly perceived as the stepping stone to the higher ranks of motorsports, with most of Formula One champions including Sebastian Vettel, Nico Rosberg, Ayrton Senna, Max Verstappen, Lewis Hamilton, Michael Schumacher, Kimi Räikkönen, and Fernando Alonso having begun their careers in karting.