Okay here is the restriction on having to use I285 around Atlanta, this information comes from GA Department of Public Safetey. Note restriction does not apply motorcoaches so you can legally take whichever route you like.
(O.C.G.A. 40-6-52)
A "truck" is defined as any vehicle equipped with more than six wheels except buses and motorcoaches
(O.C.G.A. 40-6-51)
Truck traffic is not allowed inside the perimeter of Atlanta. All trucks traveling on I-75,
I-85, or I-20 must take I-285 around the city, except for the following reasons:
1. Pick up or delivery to or from a shipper physically located inside I-285;
2. Going to or from the carrier's terminal facilities physically located inside I-285;
3. Going to or from a repair facility for service which is physically located inside I-285;
4. A driver going to or from his residence located within the perimeter.