"... Oversized stations are even more problematic when you consider that the MTA wants to build all of these by mining rather than using cut-and-cover, because cut-and-cover has too much disruption to surface tenants. And mining is far more expensive than cut-and-cover..."
Your response:
"... It is ALWAYS cheaper to build capacity now than to retrofit later, even inflation adjusted. ..."
The implication of your response is that on a 100-year timeline, the way that the modern stations are apparently being built (by mining) is cheaper than building them by the way the parent commenter says (cut-and-cover).
I was just curious why it's "always" cheaper. Is "mine and build big" the cheaper method only when there's a ton of density on top like Hudson Yards, or is it also the case in places with less surface density?
I think that you’re probably always better off building bigger if you expect growth in the next 100 years. How big you should build is just a matter of how much current and future traffic you expect to have.
Apologies - I may have skipped over something when reading. I was responding to the implication that a smaller station now is an appropriate cost savings.
I think what they're looking at is over-sizing rather than right-sizing. Think of it as cost=size*method. Future-proofing increases the size, not the method.
"... Oversized stations are even more problematic when you consider that the MTA wants to build all of these by mining rather than using cut-and-cover, because cut-and-cover has too much disruption to surface tenants. And mining is far more expensive than cut-and-cover..."
Your response:
"... It is ALWAYS cheaper to build capacity now than to retrofit later, even inflation adjusted. ..."
The implication of your response is that on a 100-year timeline, the way that the modern stations are apparently being built (by mining) is cheaper than building them by the way the parent commenter says (cut-and-cover).
I was just curious why it's "always" cheaper. Is "mine and build big" the cheaper method only when there's a ton of density on top like Hudson Yards, or is it also the case in places with less surface density?