Fundamentally, this is about short-circuiting the regular road network and establishing a managed packet network that can bypass congestion. Interestingly, that's also the value proposition of public transit, though it also runs into issues of cost, and too low of a population density make it unfeasible.
I still think we haven't fully leveraged the potential of busses. In most cities, they are slow because they combine the disadvantages of road traffic with the disadvantage of time tables. But what if busses operated on their own dedicated network? Bogota deployed a public transit system made with busses but with a UX of a train[1]. This is a genius idea that could work in many US cities, which have a lot more space to spare.
But back to the original idea, I think we might see in the future a "managed" road network, reserved to self-driving cars which are driven by some central management system, optimising routing for the whole network so as to prevent congestion. This won't require tunnels, just gates, dedicated roads and lots of software.