I could live with this. Imagine that every street had a car tunnel under it; it means the space that's taken up by streets today could just be a pleasant park. There would be benches. Kids would be playing catch in them. Instead of loud honking because traffic moving slowly, there would be sunflowers and tall grass everywhere. I'll take it!
It would basically remove cars from cities, without actually removing cars from cities. Seems like a reasonable compromise to me.
They started building this kind of thing around London Walk after the war - rather than more tunnels the cars are at ground level and the walkways above. Best seen at the Barbican and in a newer flavour around JP Morgan’s new office nearby.
I think we just repurpose storm drains for that. Always bring a ladder with you in the trunk of the car!
(I'm kidding. Chicago has a mildly extensive two level street system, and there are just doors in the "basements" of buildings that open up to the subterranean streets. I always thought it was neat, but was also afraid to walk around on the lower level. Also, the top level wasn't parks, it was just more car lanes.)
It would basically remove cars from cities, without actually removing cars from cities. Seems like a reasonable compromise to me.