Braess's Paradox - 42nd Street in NYC

The New York Times: "What If They Closed 42nd Street and Nobody Noticed?"

In 1990, they closed 42nd Street in NYC on Earth Day. 42nd Street is one of the busiest roads in NYC, and people thought the closing would create "historic traffic jams." Wrong. Traffic actually got better. This is an example of Braess's paradox (in reverse). The removal of this resource eased congestion on the streets connected to it, improving traffic.

The article says that "adding a new street probably makes things worse at least half the time." Interesting.