Regarding evacuation on Interstates, I-16 will be westbound only (contraflow, normal eastbound lanes will be dedicated to westbound traffic for coastal evacuation) from Savannah to Dublin starting Saturday at 8AM.
Details here:
http://www.dot.ga.gov/AboutGeorgia/Pages/GDOTAnnouncementDetails.aspx?postID=355
I was just on I-95 north in the Jax area. Heavy traffic going only 45-60 MPH. Seems the big deluge of evacuees has started.