Why do these vehicles usually race only on oval tracks?

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American motor racing started on oval trotting tracks used for horse racing in the 19th century and the custom has developed from there. The oldest motor race track in the world may be the one mile oval at Milwaukee which started horse racing in 1875, it had its first motor race in 1905 and is still in use today. © Cranfield University

American motor racing started on oval trotting tracks used for horse racing in the 19th century and the custom has developed from there.

The oldest motor race track in the world may be the one mile oval at Milwaukee which started horse racing in 1875, it had its first motor race in 1905 and is still in use today.