I-75 north through Atlanta

You did not say what you were driving, but it appears that you are not confident in you driving skills. My thoughts when driving is that I have as much right to the road as other drivers and I am entitled to my space. If some one is driving to slow, I pass them; if some one is taking up part of a second lane I move over. Going through Atlanta or any other big city is no different than any other road. In Atlanta they drive faster(even if the speed limit is 55 MPH), they will not keep a safe space between cars, and they will cut you off short. If you drive 55, you will most always have space in front of you to stop and make lane changes. By the way, I almost always go straight through in non-rush hours and stay out of the middle lane, watch for the exit only signs which gives you a heads up to prepare to change lanes.