During the evac during Katrina all the traffic was routed to the interstates going north. Once you were away from the city some of the smaller towns blocked the exits into their towns and blocking access to the back roads. If you want to travel the back roads you need to leave early. There are possible advantages of being on the interstate, there are a lot of people to help if there is a problem, I saw more than one person shareing gas. One of the problems on the interstate is there are a lot of people on the interstate that can cause problems thankfully I didn't see any problems of this kind.