http://www.click2houston.com/news/18252031/detail.html Vid of people driving there...
When it does freeze and snow that far south they aren't as prepared for it. It's not like in the north where they have all of the equipment and people ready every year.
The big thing about H-Town are the bridges. "Everything is bigger in Texas". This means bridges as well. There's tons of them, and they're huge. It's not the snow that gets ya, it's the black ice.
Best thing to do when it freezes there, stay home, build a fire, drink heavily. That always worked for me.