Extending the subway line, which currently terminates underneath Times Square, is considered a linchpin of redeveloping the Hudson Yards area. The neighborhoods around the MTA's West Side rail yards currently are not served by mass transit. "The redevelopment of the Hudson Yards has been talked about for decades, but with the expansion of the number 7 line, its potential will finally be realized," says Mayor Michael Bloomberg in a statement.

One of the boring machines has already started mining north of the station cavern toward 42nd Street, where the 7 line currently terminates, while the other is being pulled through the cavern and will begin mining in a few weeks. Since the 7 extension will run under the tracks of the Eighth Avenue Subway lines as well as Amtrak and New Jersey Transit tunnels, excavation and underpinning of the Eighth Avenue Subway line is under way. This is to allow the new tunnels to tie into the existing 7 Line tail tracks at Times Square.

Tunneling is scheduled to be completed next spring, according to a release from the city. When the tunneling is done, work will commence on station entrances and finishes, along with support facilities such as ventilation and traction power substations. The new service is scheduled to open in December 2013.