From 8:00AM to 8:59 AM on an average Fall day in 2007 the NYC Subway carried 388,802 passengers into the CBD [city business district] on 370 trains over 22 tracks. In other words, a train carrying 1,050 people crossed into the CBD every 6 seconds.
Absolutely mindblowing. Now, off I go to get a bagel. [Frumination—Thanks David]