I’ve written about Access to the Region’s Core – the new two-track rail tunnel under the Hudson River, but today The New York Times has an extensive write-up of the project, Tunnel Milestone, and More to Come:

But the tunnels reached their peak-hour capacity in 2003 when the Secaucus transfer hub opened. So New Jersey Transit and the Port Authority of New York and New Jersey are planning to spend $7.6 billion to build a second set that will more than double, to 48 an hour, the number of trains that can traverse the Hudson.
The project, called Access to the Region’s Core, or ARC, is in some ways as monumental as the first tunnels, which cost the Pennsylvania Railroad $111 million, a price tag that included the old Pennsylvania Station and four other tunnels under the East River. (It’s about $2.5 billion now when accounting for inflation.)
If federal approval is given this summer and grants are secured later this year, construction will begin in early 2009 and take eight years. Contractors will deploy boring machines the length of football fields to drill through granite, schist and other materials, use laser-guided satellite signals to pinpoint their location, and carve a path under 34th Street so wide that commuters will be able to walk underground to 14 subway lines, and to PATH, Amtrak, New Jersey Transit and Long Island Rail Road trains.

Also see a multimedia explanation about the two different tunnels and what the Future Stewart Express Might Look Like which would utilize the new tunnels.