Less is more: Braess' Paradox

Like many counterintuitive anomalies, it needs the right combination of conditions to actually pop up in real life; but it has been observed empirically in real transportation networks — including in Seoul, Korea, where the destruction of a six-lane highway to build a public park actually improved travel time into and out of the city (even though traffic volume stayed roughly the same before and after the change)

http://www.cs.cornell.edu/home/kleinber/networks-book/networks-book-ch08.pdf