City center to city center? Last time I went from D-town Dallas to D-town Austin, I seem to recall it being about 225-250mi.
On the other hand, that *is* road distance. You're probably right about Houston, it just *seems* like 400mi.
I hear you, long drive..especially when they had those cement barriers and only 2 lanes..That was mapquest quotes so it may be shorter as the crow flies.
Click this pic on the left for a Sat loop, Rita rivals any loop I saw for Katrina.
http://www.cira.colostate.edu/ramm/rmsdsol/TROPICAL.html
Per my Rand McNally atlas, 195 road miles Dallas-Austin.
I just remember that I budget 2 hours for Waco, 4 hours to Austin and 5 hours to San Antonio from the north side of the Metroplex. Houston is 4-5 hours depending on where you are going. (5 will get you to Galveston). All times are at average traffic flow speeds and assume that the interstates are not shut down.