When I wanted to find out exactly how much of Greater New York's rail network I had ridden, I searched the internet for information on how big the network actually is—and discovered that no one seems to know. So I added it up. Myself. (And discovered that I've ridden 72% of it.)
As it turns out, I was about 10 miles off in my calculation of the total route miles covered by the New York City region's rail network.
I have a new (and, some would say, unsurprising) goal: to ride all 1,370 miles of passenger rail currently in service in the New York City region. That means the entire rail networks operated by the Metropolitan Transportation Authority, New Jersey Transit, and the Port Authority of New York and New Jersey.
Apparently it was necessary.