The Acela is capable of lower-end TGV speeds, and if you look at how they are developed one could call them cousins on the rails. The Acela's speed is held back by the curvy nature of the NEC. Most TGVs are running at 187mph, (300KPH) in revenue service. My point is that there are already trains on the shelf that can run at or above 150 mph. The next generation of TGV is supposed to capable of 200-225mph in revenue service. They are capable of much higher speeds.
The reason most TGVs are only running about 186 MPH in revenue service is the level of vision the French had when they constructed their track 30 years ago. The next generation trainsets are still going to have to run at 186 MPH on the curvy sections of the older TGV alignments for the forseeable future.
There's an important lesson here: the French experience suggests that whatever you pick as your top speed when building the track is going to limit the top speed for the next several decades or perhaps even much longer than that. If the speeds the trainsets are capable of creep up each decade, you'll only be able to take advantage of that if the track was designed for that possibility.
Umm the 350mph concept was straight off of your comment if I'm not mistaking, if I am I apologize and perhaps I misinterpreted your statement. I was merely pointing out that it would be far too costly to develop a train to run that fast when one could just purchase a system that is tested and proved- like Spain did with its AVE which is a TGV and South Korea with its KTX, another TGV. Russia is slated to begin constructing its own high speed line using German ICE trains.
I'd said ``This probably also requires a speed of about 350 MPH for most of the route'', and I was talking about the top speed, not the average speed. I don't think it would be meaningful to talk about an average speed if we were talking about the speed for most and not all of a route.
There's some question of whether it's really possible to buy a proven-elsewhere trainset for use in the US anyway, since their crashworthiness tends to not meet US standards, and the California HSR trains do need to run on some track that does need to be shared with freight service near San Francisco.
You mentioned that the Acela runs at about half the TGVs average speed. OK let's talk average. Then why does Amtrak command more than half of the market share BOS-WAS? Because Acela is fast enough to attract and keep customers. In normal non-recession times its expensive by most people's standards to ride Acela. The Acela proves one thing: It doesn't have to go all that fast to get customers. Like I said, current Acela-TGV speeds would be fast enough to get the customers. So when you're building your CHI-NYP high-speed line remember, the faster you go the more it will cost if not up front at purchase and construction, then later in maintenance, (a very weak link in the Amtrak chain). I don't know the specifics but I recall reading that 200-225mph was about the threshold for wheels and rails from a cost perspective.
I've not heard about wheels and rails having cost issues above 200-225 MPH. Do you have a link?
But even if the steel parts do wear out faster, who cares? It's not like we have a shortage of the raw materials or willing underemployed labor domestically to deal with it. We should be far more concerned about petroleum, something which airplanes do not make terribly efficient use of.
I thought it was just New York City to Washington DC where Amtrak had more than 50% of the market share, and that's a segment that the Acela does cover in less than the magic three hours. Amtrak certainly doesn't have 50% of the trips for the BOS to WAS city pair, but there's no reason why HSR couldn't eliminate most or all of the current air service on that route.
(I also tend to think the reason Amtrak doesn't have even more of the New York City to DC market share is a lack of seats on Amtrak's existing rolling stock. It's certainly the case that if Amtrak sold 50% more tickets than they do today on the New York City to DC corridor and didn't reallocate equipment from other routes, they wouldn't have seats for all the passengers.)