Always wondered if you could solve housing issues by high speed rail, like Sacramento-Bay area (not a local so I could be completely wrong)
If I was going to spend a few trillion on infrastructure, I'd look into build massive housing blocks on the distant outskirts of the most expensive cities and connect them via fully automated high speed rail lines. Eventually the areas around the housing blocks would become cities in and of themselves if you put them out far enough.
That reminds me of book the way you put that with automated high speed rail.