Even if you managed to make the lines, then you would need to sort those lines, another hard task without proper topology or sorted starting data.
Imo, try to firstly close your input curves, fix all gaps.
Closed curves would at least give “regions” of what is the road and what is not-the-road:
then, this task is still hard:
see Extract Centreline of polylines - #6 by laurent_delrieu
or
Old Town Roofs - #44 by laurent_delrieu