I wish we had more trains where it's still possible to route them in shallow tunnels that are cheap to build by excavations, say, in many parts of Brooklyn. (The 2nd Avenue extension had to pierce rock at rather serious depths.)
The problem is political not technical. People don'tewant thair streets block by construction for a couple years and so make up reasons against it. New york is easy as nothing archeolorical evists to worry about (north america generally lacks minerals to make things of interest from they used things that decayed long ago.
