Sorry for taking so long to reply. I got caught up in real life again :)

SafeZones are just places that were designated free of radiation by the Lowley Rails, and they are often packed to the brim with people and cities. SafeZones span about 20-40 square miles on average, and they are not given specific names, because they are often taken over by a single, powerful city. As of late, there are 178 known SafeZones.