The term "most interurban" can be challenging to find antonyms for as it is quite specific in meaning. However, if we break it down, we can find some antonyms. "Most" refers to being the greatest in amount, size, or degree. Therefore, antonyms for "most" would include "least," "smallest," or "nearly none."
Interurban, on the other hand, refers to the transportation system that connects urban and suburban areas. So, its antonyms would include "rural," "remote," "isolated," or "inaccessible." Combining these antonyms, we could say that the opposite of most interurban is least rural, smallest remote, or nearly none isolated.