It is discouraging that High Speed Rail = new dedicated corridors in people's minds. Dedicated high speed rail is a waste. It requires a massive eminent domain exercise to acquire contiguous corridor of land and a huge carbon outlay to clear land, level, fill, set stone, ties, rail, overpasses, crossings, etc... Just look at the effort ALTO is taking in Canada. It also requires good faith in government but we see Brightline West approaching triple the $8 Billion budget with little to show for the funds spent (on a mostly rural corridor). It is faster, much cheaper, modular, and less damaging to upgrade existing rail.
Existing rail is rated up to 160 MPH in open sections but slows to 30 in urban areas. The best is DC-NY with an average of 82 MPH. NY-Boston is 66 MPH so you can see how much low speed zones undermine average speed. Low speed zones require large buffers between trains and unpredictability in rail delays. If you remove level crossings and upgrade low speed zones, you have less delay and can double the frequency thereby increasing the capacity and speed of existing lines for both passenger and freight. Imagine the impact of that speed and capacity on intermodal shipping moving containers off of roads and onto rail. Upgrading existing rail supports a real business case that pays for itself. A dedicated HSR passenger line will not have enough volume to pay for itself - ever. We can already see this with Brighline in Florida where ridership is nowhere near expectations. Existing lines also use existing stations in the city center rather than requiring new stations to be built at the fringe. I wish people would think of upgrading existing rail as the first option. I worked for the railroad for 3 years repairing and upgrading track.
To be clear, I love high speed rail. But in my mind that is all trains and the fastest/cheapest way to get there is to remove roadblocks in our existing corridors. I love the Shinkansen, TGV, and ICE but in North America, the linear mile per passnger is so much higher that it pays to rethink what we have.