Drive straight through on I-75. I-285 is a much longer distance, and the traffic can be just as bad. Also, trucks are not allowed on 75 inside the perimeter (285) unless the truck has a local delivery to make). Therefore, 285 is filled with trucks, and 75 will have significantly fewer. If there is more than 1 of you in the car, then get in the HOV (high occupancy vehicle) lane (far left lane) and stay in it until it ends. You are not likely to have any problems at 1 or 2 in the afternoon.