The fall out of too many chase scenes and not enough real hunters. Anyone whose hunted deer or turkey knows you can't hunt by chasing -- you have to pick a good spot and wait.
The Atlanta police should have thought outside the box. The Marta transit system was a smart move on the part of Nichols. And once Nichols got to Lenox Square, he could travel unnoticed in the "green" area between Lenox road and GA 400, behind a 20 foot wall that hid him from travelers on GA 400. I'm not sure he did travel via the GA 400 route, but it was a perfect route for him to take.