building underground is much more expensive (developers like to say 10X more, but that's probably a gross exaggeration to make us feel sorry for those poor deve

building underground is much more expensive (developers like to say 10X more, but that's probably a gross exaggeration to make us feel sorry for those poor developers), but i'm all for building parking underground in urban areas, even potentially for single family homes. put a good chunk of powered transportation underground and you could create more green space (for people and pets, to walk, exercise, play, bike, etc.). to make that happen, cities should price in the cost of street parking (one of the externalities that developers try to take advantage of, in their arguments about the high cost of parking ordinances). for instance, require every car parking on the street to have a neighborhood permit (many municipalities do this, but not widely). price the permits progressively. make each additional permit per household more expensive. use the funds to maintain both roads and public green space. as LA did in the 50's(?) in downtown bunker hill, on major thoroughfares, you could have two levels of streets, one at ground level and one underground. underground streets could have direct access to underground parking structures. in higher density areas, you could even build single family homes on top of mixed-use, multi-story buildings. it wouldn't be quite the same, but for many, it would be the best of both worlds. ps - i saw the japanese zoning article the first time around and thought it was intriguing.