I was listening to a local Emergency Management official on WWL 870 AM early this morning.
He said something about a new "50 hour" rule in reference to evacuating the New Orleans area.

April 13, 2005 -- According to today's FEMA National Situation Update, a new hurricane evacuation plan was demanded by Governor Kathleen Blanco after Hurricane Ivan when a traffic snarl that stretched from New Orleans to Baton Rouge lasted upward of 12 hours. The plan was put together by state police and the DOTD and includes evacuation routes for not only New Orleans and points south, but Lake Charles, Lafayette and the Houma-Thibodaux area. Under the new plan preparing for evacuations would begin at least 72 hours in advance. One of the problems during Ivan was the time required to get barriers, people and other material in place to allow lane reversal on highways.

Beginning 50 hours in advance, evacuations south of New Orleans would be ordered, public offices and schools would be closed, but traffic would remain along normal routes.

At 40 hours, evacuation south of the Mississippi River, including the West Bank of New Orleans, would be ordered.

In Phase 3, if the storm is a category 3 storm or higher, contraflow would be triggered.
Problems that slowed traffic last time ran the gamut from signs that were too hard to read, forcing drivers to slow excessively, to breakdowns. Under the new system tow trucks will be stationed along the routes and new signs will be installed. The new hurricane evacuation plan also requires a number of new ramps to be added or widened, new crossovers and other items at a cost of $7.5 million.
http://www.emforum.org/news/05041301.htm