I haven't tested all roads but it only seems to apply correctly on two-lane roads as seen below.


From top to bottom:
Three-lane asymmetric
Two-lane one-way highway
One-lane one-way highway
Two-lane road
Four-lane road
Four-lane divided road
Edit: added a much clearer picture
I haven't tested all roads but it only seems to apply correctly on two-lane roads as seen below.
From top to bottom:
Three-lane asymmetric
Two-lane one-way highway
One-lane one-way highway
Two-lane road
Four-lane road
Four-lane divided road
Edit: added a much clearer picture