Every time I go through Atlanta I have to go around the city on the 285 loop. Yesterday I missed my exit onto 285 so I went straight through downtown on 75.
I'm not sure if it's technically illegal or just very strongly discouraged. I know if you're picking up or delivering within the loop (which I have at least once, at Coca Cola) then you're allowed inside, but otherwise they want you to take the loop around the city
