Really, how hard would it be to make the freeways one way out of town until the exodus is over?
Update: The governor did, at least some of them:
Texas Gov. Rick Perry (R) took the unprecedented step of reversing traffic flow on the inbound lanes of several major Houston area freeways so that stalled drivers could move inland. He also ordered gasoline tankers moved to the evacuation routes to give fuel to stranded motorists.
Second update Apparently the “counterflow lane” idea just led to worse tie-ups and had to be abandoned.