From “Where Do All the Cabs Go in the Late Afternoon?” in the January 11, 2011 New York Times:

The hour from 4 to 5 p.m. has long been considered a low tide of taxi service, the maddening moment when, in apparent violation of the laws of supply and demand, entire fleets of empty yellow cabs flip on their off-duty lights and proceed past the outstretched hands of office workers seeking a way home.

To my total delight, I stumbled upon this shift change at the BP gas station at Houston and Lafayette. It’s quite fun to watch. If you love NYC, add this to your bucket list.