Friday, February 12, 2010

Bloomberg's Experiment and Braess on Broadway

According to The New York Times, the New York Traffic Experiment Gets Permanent Run!

The road closure(s), which banned vehicles on Broadway from 47th to 42nd Streets and from 35th to 33rd Streets, was pitched last February as an innovative way to fight congestion. It quickly became a fascination for tourists and New Yorkers alike, drawn to the curious sight of a pedestrian mall, complete with picnic tables and folding chairs, under the neon lights.

The article states that Mayor Bloomberg was more trusting of separate data collected from GPS devices in yellow cabs. Those numbers encompassed 1.1 million Midtown taxi trips taken between Fifth and Ninth Avenues in Midtown. Of those trips, northbound travel times improved by 17 percent, and southbound trips slowed by 2 percent, but a street-by-street breakdown could not be calculated.

This network redesign, if I may call it, was discussed on the Traffic panel that I was part of last June in New York City as part of the World Science Festival, which was tremendous fun. The above graphics were prepared for that panel.

The closure of that segment of Broadway would be representative, as I depict above, of the reverse of the Braess paradox (in which the addition of a road makes all travellers worse off in terms of travel time due to selfish or user-optimizing, as opposed to system-optimizing behavior). You can read up on the paradox and Professor Braess on the Virtual Center for Supernetworks site.

Of course, one has to realize that midtown Manhattan and its streets are subnetworks of a much larger transportation network with multiple origin/destination pairs of associated demands which vary dynamically over the day and the night.

Nevertheless, this initiative by Mayor Bloomberg demonstrates how the science of traffic flow and associated congestion management tools can be implemented in the real-world and what could be more dramatic than doing this right in the heart of NYC!