For our area, the evacuation route will flow North and West. Lane reversals are possible and should be expected during an evacuation. Evacuation routes can be found at https://www.scemd.org/prepare/know-your-zone/.
Again, if you able to leave early, it is a wise decision to reduce traffic congestion and personal frustration and you will also have freedom to travel the route you choose. Once, an evacuation is underway, you will most likely have to take the route which the officers are directing you.