"In Italy most autostrade (the Italian for motorways, or freeways) are toll roads. Major exceptions are the beltways around some larger cities (tangenziali) which are not part of a thoroughfare motorway, and the section of the A3 motorway between Salerno and Reggio di Calabria which is operated by the government-owned A.N.A.S. S.p.A.. Both are toll free." [Wikipedia]
If "strada" also means "path" and "libera" also means "clear" then saying to someone "the path is free" or "clear" is proper english even if you're saying it to a driver.
Actually, it is better English than the answer provided in DUO "the street is free." In reality, unless you're saying that the street costs nothing, "the street is free" is somewhat of an incomplete sentence as in "the street is free" "of what" exactly or "from what" exactly.