One of my neighbors left early Thursday from Houston, for refuge with family in Memphis. They made it there in reasonable time and had no gas troubles... simply by staying OFF the evacuation routes. Another neighbor left for Austin on Friday, the day AFTER the traffic gridlock, and at a time when we were being instructed to stay put, and hunker down. Again, they sailed through with no trouble.
Sometimes it's better to NOT follow the "official" instructions.
Or go the same way as the rest of the herd. I was suggesting to anyone who listened to go southwest to Laredo or the Valley. There would have been less traffic and a better chance to find an available room. Beats driving to New Mexico.