This happened to me too. Several of my supply lines stopped, because civilian cars blocked the entire traffic. As far as I can determine there’s 1 crazy person that stops where they shouldn’t (in the way of trams for example) and my cobra trams stopped blocking everything. Sometimes the bugged car just disappears and everything starts moving slowly again, so apparently as clumsy my drivers are they would do OK without civilians blocking the way… looks like a bug to me. If only there was some bugtracker to report these properly.