> If you look at a map of all airline flights there are many thousands of short-range flights. Replacing them all with trains would be interesting.

Replacing “them all” is to set the bar unnecessarily high. I suspect there’s an 80/20 rule in effect here, and we should aim to replace the most popular short haul routes, not all of them. That’s why I specifically called out SF->LA. Major population centers within a few hundred miles of each other are prime HSR targets, and in countries with HSR we see a lot of passengers preferring rail for these exact types of trips.

There’s no reasonable world where every single small town gets a high speed rail running to it, but we shouldn’t set that as our goal. Don’t let the perfect be the enemy of the good. In particular there are nice stretches of good density along the coasts of the US that seem like prime targets for high speed rail, that would make travel more ecologically sound and comfortable for a large chunk of the population.

> Just the right-of-way property transactions would be daunting. Look at California as a lesson in how this can't be easily done.

And yet right of way transactions regularly pass for highway and highway expansions. Not without difficulty, but they get done. Letting rail projects grind to a halt while forcing road ones through is a political choice, not a law of nature.

> The other thing is, people move around. Airlines can change flights easily to map to demographic changes; that's a major strength of air travel. Not as easy to rip up tracks and start over.

This is only kind of true. Changing routes is easy only to a point. Expanding and refitting airports to handle increased traffic can be incredibly expensive and slow. LA is going to spend a huge amount of time and money trying to fix not just their airport, but also the transit to their airport which is currently overwhelmed.

My city is probably well on its way to its airport being incapable of handling the recent population growth. Expanding that airport and improving transit to it will be massively expensive, and require the eminent domain of a lot of property.

Secondly, while people do move around, it’s not like they’re throwing darts at the map and moving there. The places Americans are moving to are easily predictable; they’re moving to cities. You’re not going to wake up one day to discover that America has moved to the middle of nowhere Kansas.

Generally the cities that would make the best HSR targets are also the least likely to totally collapse in population too. NYC isn’t going anywhere, neither is Boston or Philadelphia. One would be forgiven not predicting the rise of say, Denver, but that doesn’t mean we shouldn’t at least be aiming for HSR to the obvious targets.

And thirdly, transit availability and where people move is a two way process. People like and care about access to transit options, and the quality of the local airport (and cost of flights) is already one thing that people consider when they move to a new location. There’s no reason to believe that access to HSR wouldn’t be the same. Especially since it’s possible to put HSR stations in far more convenient locations, given the lack of turbine noise to piss off the neighbors.