Take a listen to this episode of the Freakonomics Radio Podcast, on parking.

The episode begins with Stephen Dubner talking to parking guru Donald Shoup, a professor of urban planning at UCLA and author of the landmark book The High Cost of Free Parking. In a famous Times op-ed, Shoup argued that as much as one-third of urban congestion is caused by people cruising for curb parking. But, as Shoup tells Dubner, there ain't no such thing as a free parking spot.