At least once per year, we drive N-S and S-N through the Atlanta area. If we happen to hit the narrow windows when traffic is light, then everything goes nicely. But the rush hour seems about four hours long each morning and evening, that can be horrendous. Last year we took over 4 hours to get from abeam Stockbridge to abeam Kennesaw on I-75, and that may not be the worst we've had. Using I-285 around the city actually seems worse- longer distance but no better speed.
Obviously, the best trick is to avoid the rush hours. But if that's not possible, are there any back road routes around the city that save time during the rush hours? Going around the west side via Calhoun-Rome-Cedartown-Carrolton-Newnan-Griffin looks possible, but I'm not sure it would actually save any time.