I remember reading those comments on FR and being totally flabbergasted that the highways were clear after it was obvious that evacuation was the only sane response.
Sure a lot of folks couldn't leave; any number of reasons, more or less valid. But with half a million people warned, the roads should have been jammed by early Sunday morning. And by Sunday dinnertime the roads should have been all one way: outbound.
The figure given, 80 percent of NO evacuated, does sound suspicious.
Texas has how many evacuated here? I think the Houston area alone has nearly 10% of the equation. Hope somebody is keeping tally of this figuring.
About those jammed roads... last I remember, I-10 and the Ponchratrain bridge (which I never saw opened to "one-way traffic only") were at a dead-pan stop. I have been looking for valid info stating/showing those roads were cleared by the time Katrina hit.