Imagine what it was like when those college kids decided to get line up 3-4 deep in every lane and do the speed limit. They had traffic at a standstill in Chattanooga!
Best time I ever made getting out of Atlanta was two days before Christmas, 80,100 pound gross, loaded with peanuts, rolled right through, then got on 75 and doing 50 with the high dollar lane clear. Got out there with another guy and we didn't back it down til we hit the curve in Chattanooga.
Things would work better if they didn't keep the trucks pinned over in the two lanes next to the ramps. And if you really want to reduce congestion, separate all through traffic from the local traffic. Not like Chicago, where they open 3 lanes into 8, and let cars fly ahead, and jam things up even worse when the 8 lanes drop back down to 4.