Photograph of Eighth Avenue traffic by Danny L. on Flickr

Besides trying to figure out whether taxi drivers cheated passengers out of fares (or just made a mistake), know what else taxi cabs' GPS systems are good for? Giving urban planning geeks a glimpse into Manhattan's traffic flow. The NY Times has details on a study where "officials tracked the routes of tens of millions of taxi trips over the past two years. The result: a database of speeds and travel routes that can be broken down by minute, month and neighborhood."

Besides offering up a graphic of the average daily speed of taxis during the week—Wednesdays are the slowest at 9.3 MPH, while Sunday is the fastest at 11.5 MPH—here are some other details:

• "Thursday, Nov. 13 was the slowest weekday of the year studied, with an average speed of 7.5 m.p.h. — about the speed of the typical jogger in Central Park. Excluding holidays, the fastest weekday: Monday, Sept. 28, at a speed of 11.7 m.p.h." Also, as expected, U.N. General Assembly week turned traffic "to sludge."
  
• "The four fastest days to drive in Manhattan, in order of average speed: New Year’s Day, Christmas, Memorial Day and July 4."
  
• "On a typical Tuesday night, about 13,000 cabs travel south from the Upper East Side to a destination between 14th Street and Canal Street; on Saturdays, about three times as many cabs (38,000 on average) make the trip."

Unlike other cities, Manhattan's streets stay pretty congested between morning and evening rush hours, which officials chalk up to commercial deliveries. Department of Transportation consultant Bruce Schaller points out the obvious, "Walk around downtown San Francisco at 11 o’clock in the morning and there’s not much going on. You go to SoHo, and it’s really busy."