For someone who has never been to NYC before, what mjm is talking about here is that in most subway stations, the entry points onto the platform are these little turnstiles that are very easy to get luggage entangled in (and I see many non-New Yorkers having problems swiping the flimsy plastic MetroCard at just the right speed for the turnstile to accept it).

The wheelchair door is a larger gate where you could walk through carrying your luggage. I don't think I've ever used this gate for entry like this, but I thought that you had to ask the person in the booth to let you use. I didn't know that you could swipe at the adjacent turnstile to use it. The only times I've used it is when the I swiped at the turnstile with a student or unlimited card, had some sort of problem, and then couldn't use my card again right away. I asked the person at the booth to let me through.