I wish they would have put money into a feasibility study for the Hyperloop, which would have followed the existing highways, thus did not require obtaining additional rights of way, not to mention the LA-SF time was one hour as opposed to the three hours (which is probably still too optimistic), they are talking about now.
The Hyperloop is a vactrain, a sort of system proposed every now and the for the last half century at least. It has daunting technical challenges, and it would take a LOT of R&D to get it working safely. For instance, its entire tube would have to be evacuated, and stay evacuated reliably. A leak anywhere would shut down the whole line. Also, crossovers would be awkward.
Let's see what it has to do.
SF - LA HSR distance: 463 mi / 746 km (detours into the Central Valley and Antelope Valley)
SF - LA highway distance: 386 mi / 622 km
SF - LA great-circle distance: 349 mi / 561 km
Will use 400 mph / 640 km/h / 180 m/s
Acceleration distance = (speed)
2 / (2* (acceleration))
For an acceleration of 0.1 g (1 m/s
2), this is 16 km or 10 mi.
The acceleration time penalty is equal to the time to travel the acceleration distance at full speed, so it's not very great here.
Now for following highways. They usually have lots of curves in them, and I will use design standard to estimate the centrifugal acceleration for going around them. I'll use
NJDOT Roadway Design Manual -- that's the New Jersey highway department. "The suggested minimum radius for a freeway is 3000 feet in rural areas and 1600 feet in urban areas." Also, "Every effort should be made to exceed the minimum values. Minimum radii should be used only when the cost or other adverse effects of realizing a higher standard are inconsistent with the benefits."
That's about 1 km for full cruising speed.
Centrifugal acceleration = (speed)
2 / (radius of curvature)
For a 1-km curve, the sideways acceleration is
Car (60 mph / 100 km/h / 28 m/s): 0.78 m/s
2
High-speed train (186 mph / 300 km/h / 6.9 m/s): 6.9 m/s
2
Hyperloop (400 mph / 640 km/h / 180 m/s): 32 m/s
2
Minimum radius of curvature, to be consistent with car standards:
High-speed train: 9 km
Hyperloop: 41 km
So the Hyperloop line won't be able to follow highways.
It will likely be built on a viaduct or extended bridge, two tubes about 16 ft / 5 m across. Expect the NIMBY's to howl with outrage at the prospect of seeing that. The California HSR system has already gotten a lot of NIMBY objections, like between San Francisco and San Jose, and this system would be even worse.