https://en.wikipedia.org/wiki/Tunnel#Cut-and-cover
https://en.wikipedia.org/wiki/Saint-Michel_station_(Paris_M%C3%A9tro)
https://en.wikipedia.org/wiki/Cit%C3%A9_station#Platforms
https://en.wikipedia.org/wiki/Downtown_Seattle_Transit_Tunnel
https://en.wikipedia.org/wiki/University_Link_tunnel
https://en.wikipedia.org/wiki/University_Link_tunnel#Stations
https://en.wikipedia.org/wiki/Tunnel_construction#Enlargement
https://dailyhive.com/vancouver/skytrain-canada-line-rebuilding
The very small scale Canada Line was only built with 50 m tunnel stations when they should have been at least 3 times as long. It was deliberately designed to be so small that it can't even accommodate 4-5 car trains. It can only be expanded from a 2 car joke of a train upto a 2.5 car train.
https://globalnews.ca/news/5778392/canada-line-10-year-anniversary
"We paid a Rolls-Royce price for a Volkswagen system," said Stephen Rees, a transportation critic and a B.C. Green Party candidate in the spring provincial election.
"The problem with this system is it can't be expanded easily. The stations are short, there's long sections of single track, and both of those limit the amount of additional capacity you could add in the future," Rees told CBC News Monday." https://www.cbc.ca/news/canada/british-columbia/canada-line-opening-draws-long-lineups-1.799296
