I don't think it is a wise investment now. An interesting post at NR, and the comments thereon prompted me to post a comment of my own:
State governments collect $0.27 per gallon in gas taxes. The Feds collect another $0.18. If we are going to make an honest assessment of highway subsidies, shouldn't these taxes be subtracted to get the net? Aren't these taxes essentially user fees?
Doesn't it make more sense to work on increasing freight rail rather than passenger rail? Getting more trucks off the highways would decrease fuel use and road wear, and wouldn't require the high speeds. For some reason, people rarely discuss the question of freight transport.