Having lived in the south most of my life I can add an explanation here. Much of the country side around Atlanta is rolling hills with large rivers, such as the Chatahoochee, snaking through it. Fog forms on the water (warm fronts push over cold water) and from one hill to the next you can go from a clear view to a split pea soup. Seems crazy that 50-100 cars could pile up but Georgia drivers are notorious for speeding and once into the fog, it's too late to slow down. These conditions are typical in several southern states.
