Isn't it interesting to think about though? If you could built a coast to coast—or even half way—high speed transit option that isn't a bus or car, what would i

Isn't it interesting to think about though? If you could built a coast to coast—or even half way—high speed transit option that isn't a bus or car, what would it look like? If you could use existing infrastructure with perhaps minor changes, what could you build or think of? It's really a domain that presents insane constraints to work in/on. Infrastructure currently costs tremendous amounts to build and maintain, the distance is extremely vast, the terrain is rugged, the climate varies wildly, the population is low and spread out. What sort of impact could it have on future urban development?