Nobody told anyone but the immediate coastal counties to evacuate. People in Katy and Cypress and Memorial had just seen the Katrina shitshow on sensational network news ("people are eating each other in the Superdome!") and were (unreasonably) terrified of that happening here. So decided on their own to leave, often in two cars, sometimes pulling boats and RV's, and got in the way of the people coming north from the coast and it all just clogged the shit out of the roads.
Mrs CL and I were going to ride it out and both our parents kept calling every 15 minutes pleading with us to get out, and recruited other family members to call us too, so we finally did leave on Friday afternoon just to shut them up and thus began the exodus to Austin that lasted 12+ hours. By the time we got to Giddings it was clear that Rita was going to miss Houston but we had already committed and kept going. It was an enormous clusterfuck.