Tunnels are our Transportation Future
https://austinvernon.eth.link/blog/tunnels.html
It is mostly focused on The Boring Company. It has details about how costs can be reduced, for example by boring the tunnels at an angle from the surface and by putting stations above ground. Then there is the "synergy" with electric vehicles. One "big idea" in the article is that in theory tunnels turn ROWs from scarce rival goods into plentiful goods that can be built as needed, but this was always kind of obvious, and the big problem was always cost.
The Las Vegas tunnel project numbers are good:
The LVCC project included 2 miles of tunnel, two above-ground stations, and one underground station. If we use the calculator numbers, the estimate range is $50-$80 million, right in line. The Boring Company completed the project and verified the capacity in June 2021.
2 miles of tunnel for 100M CAD of tunnel would make all sorts of projects profitable. The "mobilization" cost was $2.5M US. I wonder if that could be brought down. In theory, all sorts of small tunnels could be built around cities to weave together ROWs.