Katrina was THE single most successful evacuation in the history of the U.S. Over 90% of the inhabitants evacuated, which has never before been achieved for a city of this size, especially one with extremely limited transportation options. Pretty much all roads out of New Orleans pass over lakes and swamps, so there are only so many roads available. There are only 3 main roads out, and these roads are also the only evacuation route for everyone living in the surrounding area, especially the more vulnerable areas to the south. Evidence after the storm found that many of the people who died had access to transportation, but simply chose not to evacuate. Many of these people were elderly and in poor health, making evacuation difficult. Evacuation could certainly have been improved, especially for the poor and infirm, but it was still the best ever accomplished in real life in the U.S.