Of course it would be a good candidate for HSR, or at least "fast frequent" corridor service. I've driven I-35 many times between Dallas/Ft. Worth and San Antonio, and the traffic is pretty similar to that of I-95 in the Northeast. The main difference is that there aren't large intermediate cities to enrich the ridership. Between New York and Washington you have Newark, Philadelphia and Baltimore. Between Dallas and San Antonio you have Austin, and then smaller places like Waco and Temple. The average trip ride length in the Northeast Corridor is 164 miles (Rail Passengers Association). 30% of trips are less than 100 miles and 40% of trips are 200-300 miles. A Dallas-San Antonio corridor would have to find ways to increase the ridership of the 200-300 mile trips to make up the presumable smaller number of less than 100 mile trips (due to the fact that intermediate stops serve smaller markets than in the northeast). There also isn't the same network of commuter rail that they have in the northeast to feed suburban passengers to the main stations.