Worsening of traffic congestion in cities is an ongoing challenge in urban regions. Stories of mega-jams that last tens hours, or even days, appear not only in fiction but in reality. Associate Professor of City & Regional Planning Marta Gonzalez recently co-authored a paper in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) analyzing cell phone and vehicle GPS data to assess traffic conditions in Boston, Porto, Lisbon, Rio de Janeiro, Melbourne and the San Francisco Bay area: "Macroscopic dynamics and the collapse of urban traffic."
Although traffic dynamics is well studied in highways, its city-scale counterpart is still not well analyzed. Faculty at the National University of Colombia in Bogatá, MIT, Monash University in Melbourne, University of New South Wales in Sydney, and UC Berkeley investigated how cities recover exponentially during the morning peak hours, identifying unloading times as a metric for the congestion level of a city. Based on traffic simulations, the paper illustrators how this metric relates to actual travel demand and road supply. The authors hope these findings will open new avenues for studying empirical urban traffic with a statistical physics framework.
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