Most subway stations are in built-up areas and most tunnels under built-up areas.

the MTA in NY is struggling to ameliorate its service because the underlying infrastructure is subpar and eats too much into its budget.

New York has an extensive old system to maintain. However, for new projects, costs tend to climb to the sky in the USA for reasons not entirely clear to me -- the hiring of consultancies, redundant planning jobs, handed out to political clients, among them.

_{*Lunatic*, n.
One whose delusions are out of fashion.}