Speedway racing takes place on a level oval track consisting of two straights joined by two semicircles. Tracks must be between 260 and 425 metres (853 and 1394 ft) in length, this is measured at a distance of 1 metre (3.3 ft) from the inner boundary. ~ Wikipedia
Origins of Speedway
"The origin of this sport is questionable, though most believe that arose in Australia in the second decade of the twentieth century."
Speedway is widely believed to have begun in Maitland, near Newcastle, NSW, in December 1923.
"Johnnie Hoskins was the first promoter to put up a cash reward for the winner at West Maitland, and from the huge turn-out this novel event generated, speedway began to form in Maitland with a cinder track, rules and regulations, and the broadsiding of bikes in the corners. No previous event inspired such a metamorphosis as this." Ian Hoskins, son of John Hoskins and the world's first motorised mascot, 20/03/06.
The discussion continues with another chap, who appears to have done considerable research, refuting that claim. There is considerably more on the subject, this one from the horse's mouth.