The algebraic method of computer highway capacity is a non-starter. Consider my recent drive from Chicago to Milwaukee: work zones, traffic jams, accidents, off ramps, bad weather left lane grannys... None of these allow for the two second rule and 55-65mph driving. The realistic average speed for that whole trip was nowhere near 65mph, and quite a lot of it was crawling past accidents, waiting to merge for road work, stoplights at on ramps...
Consider the Top Gear races where Clarkson drives a massively overpowered car and Hammond/May are forced to take public transit the whole way. While this is a parody of real lift, it illustrates just how limited drivers in something like a Nissan GTR or Mustang GT350 are despite being quite nimble and powerful.
I was quite disappointed with the entire CAHSR effort, but HSR and HrSR will play a relevant role in the future. Traffic in the really large metroplexes is just getting to be too heavy.
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