Gotthard is impressive, but it took the Swiss 17 years to build it. Nearby, Brenner Base Tunnel is under construction between Italy and Austria, and it is expected to take 25 years to complete.

I can't imagine how long would it take to tunnel through the Rockies. Look at the map, they are far wider than the Alps. Getting through the Rockies is like getting from Denmark to Croatia.

Use the Army Corps of Engineers, Navy Sea Bees, something like that. Look at https://en.wikipedia.org/wiki/Seikan_Tunnel going between islands under the Japan Seas in an earthquake area.

Think BIGGRRRR! (Aggressively so, instead of sissying around!)

edit: also not to forget about 'Nuclear Tunnel Boring Machines/Subterrene' https://havacuppahemlock1.blogspot.com/2015/06/nuclear-power...

cf. "Trans-Planetary Subway Systems

A Burgeoning Capability

by Robert M. Salter

February 1978"

https://www.rand.org/pubs/papers/P6092.html

Better get started soon then! Once you make a tonnel, it stays there forever, it's a good investment

Indeed, if we want tunnels to make a rail network cross the Rockies, we had really better get started, since you'd need 5 east-west routes to make trains practical ("less impractical"?) to cross the Rockies. No one is going to take an additional 1000 mile (7+ hour) diversion north-south to pass through a tunnel to repeat that north-south diversion on the other side.