In 2018, there were a total of 64,285,009 km of any kind of roads in the world. These were shared between 411,853 km of expressways and 63,873,156 km of normal roads (paved and not paved).
If you want to know more, please go here. This data was sourced from the book Transportation and the Belt and Road Initiative, in which more data as well as the original primary sources of the data are available.
