It seems crazy, but there's also some appeal in the idea of opting out of all the legacy infrastructure. If we could rebuild our roads from scratch today to serve a vehicle for the 21st century, what would we build? Probably something like this - standardized vehicles on automated roadways with built in electric connections that enable unlimited long-distance high-speed travel (though we'd just build this into cars instead of using 'carriers').

But it does seem pretty far out that we'd have tens of levels of tunnels for all this underground traffic. Hyperloops seem more plausible.