I will reiterate what HookD said as well. U.S. roads, once upon a time, were the backbone of our automotive society as well as the roads that kept the nation moving economically and industrially. They may not be able to handle as many cars as an interstate, but are often far less traveled and can provide a nice alternative in a bad situation...they are often far more scenic than the interstate yet allow you to get out faster to a safer location than a clogged interstate will.

Routes heading north out of the Gulf coast include U.S. 45, U.S. 43 (Alabama), U.S. 31, U.S. 29, U.S. 231, U.S. 331 (last four Florida-->Alabama), U.S. 49, U.S. 51 (last two Mississippi), and U.S. 61/65 (Louisiana). Head east or west just a bit on U.S. 98 or U.S. 90 (or, in portions of the coastal area, U.S. 84) to get to one of these roads if not nearby.

Also consider state roads in larger locales, but always carry a map. One of the smartest purchases you can make is the $5 Rand McNally atlas at Wal-Mart. It's not only handy in times like this, but in planning road trips as well. Plus, you can't beat the price. By taking U.S./state highways, you'll not only reduce the stress and time to evacuate for yourself, but for others who do stick to the interstates as well.