In the 2022-2023 financial year, Australia had a total of 21.2 million registered vehicles. This included passenger vehicles, light commercial vehicles, and other types of motor vehicles. (According to Google)
The average length of an Australian car is 4.9m. (According to Google)
Putting them end to end, they would stretch 2½ times around the equator - and sure as hell someone would pull out and try to overtake.
