As I understand it, most of the NYC subway was built by basically just closing of major chunks of streets and excavating them, sticking the subway in and then c

As I understand it, most of the NYC subway was built by basically just closing of major chunks of streets and excavating them, sticking the subway in and then covering it back up. Compared to boring underground tunnels, you can imagine how much less involved it is to simply dig a hole from above. I'm not sure why they don't do that anymore, though I can imagine it's some combination of where the new routes are (maybe they aren't following the street grid?) and higher impact of year-long closures of streets. The NYP has a good article comparing the methods of construction then and now: https://www.nypl.org/blog/2015/05/04/subway-construction-then-now https://www.nypl.org/blog/2015/05/04/subway-construction-the...