[dpark]

I don't understand what issue you think this solves. You're describing houses that abut each other and are 3 stories tall. This would be a multi level apartment building if you didn't insist on making everyone stretch their living space across three floors and you didn't assume people want most of their housing to be in a basement. I don't think neighbors "driving across your roof" is a selling feature for most people, so I don't know who you think would prefer this over multi level apartments. Or perhaps more comparable, row homes.

From what I understand here, your proposal boils down to "make the lots half as big, build the houses directly adjacent to the street, and dig a basement that extends under the street to get some interior square footage". Yes, you could do this, or you could lift the whole thing up one level so the basement isn't really a basement (though I doubt it saves you anything since it's got to be a beefy structure to hold up to road traffic, and it's still going to feel like a basement). I just don't understand why you would do this and who would want to live in this Morlock ghetto. This sounds ugly and expensive and pointless when you could build dense housing without doing any of this.

[logfromblammo]

If you don't understand the problem, I have to assume you have never lived in a multistory walk-up apartment building with breezeway stairwells.

When I did, my wish-list was as follows.

  I wish I had...
  - a window that faced a different direction.
  - more storage space.
  - a parking space closer to my pantry, and at the same level.
  - better sound insulation between neighbors.
  - an unobstructed view of the southern sky.
  - more than one possible cable provider.
  - the option for DSL.
  - a uniquely numbered address.
  - a private outdoor space, suitable for gardening.
  - another way to get in and out of the complex.

When I moved to a freestanding house in a cookie-cutter suburban subdivision, all of those wishes were fulfilled, but I had new problems.

  I wish I had...
  - no accessible/visible lawn for the homeowners association to hassle me about.
  - a shorter/easier commute.
  - locks on my outdoor faucets, because of *that neighbor*.
  - any business at all within walking distance.
  - some sort of park within walking distance.
  - no visible ugly utility boxes.
  - lower total housing and utility costs.
  - a room that I could use as a home office.

Those are all the problems I think will be solved or reduced by my simplistic solution. Plus, there's the overall problem of cheap, dense housing that might still be accepted by Americans accustomed to typical suburban/periurban freestanding houses.