It isn't that I assume they'd use existing lines, it is just that most of the good mountain passes are already taken. Furthermore, the existing alignments show how difficult it is to cross those mountains in the first place. Hell, there are many places in the US where even the Interstate network couldn't find a better route - like along the Colorado River east of Grand Junction.
A lot of politicians and advocacy groups like to point to existing lines as a solution to crossing mountains and getting through cities. This is rather short-sighted as rail lines in the US are designed for slower moving heavy-tonnage and don't take advantage of the differences HSR alignments have.
When you want to run an HSR line, your requirements are quite different. Regular (read: freight) lines require easier grades and can take sharper curves due to their slower speeds and heavier tonnage. The busiest mountain passes typically have no more than 2-2.5% ruling grades, using curves to lessen the steepness. HSR can use much steeper grades (5%) but requires extremely gentle curves, which then demands a lot of expensive tunnel and bridge work.
When you want to take an HSR rail line across a series of mountains like the Tehachapi range, you run into a major problem. The change in elevation is extremely sudden and drainages are short, curvy and have steep walls. The end result is that you have to do many cuts, fills, bridges and tunnels to get up the grade. The expense is astronomical compared to a regular highway, yet most proposals don't actually take that into account.
However, the man who designed the map is at least a bit more realistic about the cost (several trillion). I do firmly believe that HSR is actually quite viable in the US in many places, it just isn't something we can draw on a map and say "here we go!"
We have to solve the problem of topography vs. budget. If we want a truly national network like shown in the map, we have to accept that the cost will be enormous - likely many times that of the interstate system (in today's dollars). If the people are willing to take that cost, then it should be built, but we should be careful what we propose to make sure it is truly viable.
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It isn't that I assume they'd use existing lines, it is just that most of the good mountain passes are already taken. Furthermore, the existing alignments show how difficult it is to cross those mountains in the first place. Hell, there are many places in the US where even the Interstate network couldn't find a better route - like along the Colorado River east of Grand Junction.
A lot of politicians and advocacy groups like to point to existing lines as a solution to crossing mountains and getting through cities. This is rather short-sighted as rail lines in the US are designed for slower moving heavy-tonnage and don't take advantage of the differences HSR alignments have.
When you want to run an HSR line, your requirements are quite different. Regular (read: freight) lines require easier grades and can take sharper curves due to their slower speeds and heavier tonnage. The busiest mountain passes typically have no more than 2-2.5% ruling grades, using curves to lessen the steepness. HSR can use much steeper grades (5%) but requires extremely gentle curves, which then demands a lot of expensive tunnel and bridge work.
When you want to take an HSR rail line across a series of mountains like the Tehachapi range, you run into a major problem. The change in elevation is extremely sudden and drainages are short, curvy and have steep walls. The end result is that you have to do many cuts, fills, bridges and tunnels to get up the grade. The expense is astronomical compared to a regular highway, yet most proposals don't actually take that into account.
However, the man who designed the map is at least a bit more realistic about the cost (several trillion). I do firmly believe that HSR is actually quite viable in the US in many places, it just isn't something we can draw on a map and say "here we go!"
We have to solve the problem of topography vs. budget. If we want a truly national network like shown in the map, we have to accept that the cost will be enormous - likely many times that of the interstate system (in today's dollars). If the people are willing to take that cost, then it should be built, but we should be careful what we propose to make sure it is truly viable.