Interesting discussion of HSR in The Transport Politic discussing my interview posted yesterday.
But Mr. Levinson fails to address the fact that investment is needed in both intercity and intracity corridors. Claiming that we should not fund high-speed rail because urban transit is more important is equivalent to saying that federal subsidies to air travel and non-urban highways should simply end, because metropolitan areas need more investment and travel between cities is less important.
Perhaps such subsidies should end. I am not going to be a modalist and support subsidies for mode A because mode B gets them, or even suggest any mode should get subsidies (unless a good economic rationale justifies it). Transportation, especially intercity transportation, is an economic activity foremost that should justify itself on economic grounds. There are of course social aspects to this as well, but going down that path to justify multi-billion dollar systems is indeed a slippery slope.
An argument could be made about strengthening intercity linkages to refashion the current metropolitan system into a megalopolitan system, where people more regularly interact between cities. (Switzerland writ large). If the division of labor is limited by the extent of the market, and transportation can be used to expand the market, the division of labor can therefore increase (i.e. be more specialized), which should have some positive effects for the economy (akin to agglomeration economies). The magnitude of this is uncertain (and certainly location-specific), but I think presents the best case that can be made in favor of HSR in the US.
That said, remember that real HSR (not the short term improvements to get to 90 or 110 MPH, which may or may not be a good thing, but is certainly not HSR) is a long term deployment, so it needs to be compared with cars 10 or 20 or 30 years hence, and the air transportation system over the same period. Cars are getting better from both an environmental perspective and from the perspective of automation technologies. The DARPA Urban Challenge vehicles need to be bested to justify HSR. Cars driven by computers should be able to attain relatively high speeds (though certainly not HSR speeds). Further they may move less material per passenger than HSR (trains are heavy), and so may have net less environmental impact. This really waits to be seen.
The table that Mr. Freemark assembled (link above) is interesting and is a useful way to arrange a comparison (user time, negative externalities) being two of the major considerations. Operating costs and capital costs would be good to include as well. But the table is a bit harsh on aviation. Convenience is in how the system operates, and while the security theater we face now, especially in older large airports, is a disaster, it is not necessarily what we will face 20 years from now. Airports will be closer for many people (especially in multiple airport cities like SF, LA, DC, NY) than downtown train stations, though certainly not for all.