One of the oldest forms of motorsport and invented in the United States in the early 20th century, dirt speedway racing involves vehicles racing each other round dirt-surfaced lightly-banked oval tracks. Originally stock car and Indycar racing were varieties of this, but diverged with the development of hard-surfaced superspeedways.
Whilst there are several categories of vehicles raced, the most prestigious category of dirt speedway racing is that of sprintcars. Sprint cars are purpose-built racing machines, with a body design somewhere between a dune buggy and an open-wheel racer. They are powered by large, modified V8 engines producing around 600 horsepower (450 kilowatts) mounted directly ahead of the driver. They are fitted with large tyres. As the cars lack a differential and always drive around the speedway in a counterclockwise (check?) direction, the left tyre is usually considerably smaller than the right tyre. They are also fitted with huge, asymmetrical wings on their roof designed to create downforce mainly on the outer-facing right side, both to reduce rollovers and increase cornering speed).
Unlike bitumen racers, the fastest cornering technique on a dirt speedway involves inducing a controlled slide to bring the rear of the vehicle around the bend, then using the power of the engine and counter-steering to balance the sprintcar on corner exit. These visually spectacular cornering, combined with close, aggressive racing, frequent crashes, the small tracks making night racing common and setting up a track cheap and easy, make speedway a popular form of motor racing in some areas.
As well as its home in the U.S., speedway racing is found in Australia and (where else?)
Motorcycles are also raced on dirt speedways.