[aspenmayer]

That just made me appreciate how much greater value still might be unlocked by simply building as few as 3 stations in metro areas that don't currently have any at all, and then expanding from there. That would be an interesting study if it hasn't been done: what is the MVP of underground subway networks? How many stations do you need for a given area is probably a budgetary concern as much as a passenger capacity concern.

Have any metro areas built entirely new subways where there were none before in recent times? I know a lot of places are looking at light rail too, so have there been any greenfield light rail deployments in USA either?

It seems like a uniquely American problem, which leads me to believe that there just isn't political will to overcome the massive car lobby in most places, which is all the more reason to advocate for it, in my view.

[throwaway2037]

"Have any metro areas built entirely new subways where there were none before in recent times?" China is the easiest one to study. The number of kilometers of heavy rail metro lines built since the year 2000 is simply mindboggling. (Specifically, I am not talking about high-speed train lines.) In the same two decade time range, look at Korea, Taiwan, Hongkong, and Singapore. I guess multiple systems have doubled or tripled in size (length or stations). Remember that Korea has two major systems: Seoul and Busan; and Taiwan has Taipei and Kaosiung.

I am not an urban planner but the north-south & east-west initial two-line style seems very popular. In my experience, the trick to quickly increasing ridership on new lines is closely coordinate with private developers. Be transparent about line planning, then team-up with private developers who can build (large) residential or office buildings with subway entrances in their basement. I've never seen a city do it better than Tokyo. My assumption is that the Elizabeth Line in London will spur similarly spectacular levels of redevelopment.

Light rail: Silicon Valley opened their system in Dec 1987.

About "unlocking value": Two massive upgrades come to mind. East Side Access in Manhattan will allow LIRR trains to enter Grand Central Station. The construction photos online are like something from science fiction. And look at last 30 years of Tokyo metro tightly integrating with private suburban rail lines where trains enter same station, but opposite sides of same platform. Everything is timed to the minute, so transfers are seamless.

[ashtonkem]

> Have any metro areas built entirely new subways where there were none before in recent times?

None that I can think of in the US, but Madrid is generally pointed to as the stellar example of rapid and cheap subway expansion. They added an unbelievable amount of track and stations at really low cost.

> Between 1995 and 2007, the Spanish capital swiftly and cost-effectively upgraded its subway system, building more than 150 new stations over 120 miles at costs far below New York City rates. First, in just four years, Madrid designed, constructed, and opened 39 new metro stations and laid 35 miles of rail, 23.5 miles of which required new tunneling. The expansion was unprecedented for its low costs (about $65 million per mile of rail) and speed. Then, between 2000 and 2003, Madrid built Metro Sur, a 28-station, 25-mile circular subway line that connects the densely populated municipalities south of the city. Simultaneously, Madrid completed a direct metro line from the city’s central business district to its airport, now a 12-minute train ride away. Finally, between 2004 and 2007, commuters in the Madrid region gained an additional 80 new metro and light-rail stations, at a cost of $6 billion.

Just like high speed rail, this was less of a revolution in public works, and more a series of unglamorous minor improvements that added up to something greater than the sum of its parts. The government aimed for speed above all else, with the understanding that delays and financial uncertainty are the doom of any large project. So they would hire multiple teams to bore tunnels at once, and pit them in friendly competitions to bore faster. They negotiated with local land and business owners over more interruptions over a shorter period of time to reduce lawsuits (a big issue in NYC subway expansion), and they designed all the stations to be modular so that they wouldn't waste a ton of time designing and constructing bespoke stations. The sum is that they got it done really fast and really cheap.

Ironically, it looks a bit like the way that we construct our highways.