![]() When the flow of traffic reached an unacceptably low velocity on a given road, that road was deemed dysfunctional and removed from the model.īy repeating this process in a recursive fashion, the investigators discovered that a massive cascading failure of the urban transportation system occurred in a sudden and discontinuous fashion, much the way a phase transition occurs suddenly when ice melts or water boils.Īuthor and project leader Dingding Han said, "We used publicly available maps for the Yangpu District in Shanghai and identified four roads that serve as major commuting thoroughfares. The traffic load on each road was converted to a velocity. To simulate the effect of commuting, we increased the population of bordering regions," author Yu-Gang Ma said. "The urban area is an open system where, in addition to intraregional flows, there is also an exchange of flows between external regions. They generated trips between various population centers, assigning those trips to roads that provided the shortest travel distance. In constructing their model, the investigators considered the existing road network and population distribution in Shanghai. When liquid flows through a network of pores, it is occasionally blocked in much the same way the flow of vehicles through roads can be blocked. ![]() The model uses a modified form of percolation theory, widely used to understand flow of liquids through porous media, such as soil and gels. This research sits at the intersection of physics and information science and is an innovative model involving the study of smart cities. They describe their approach in Chaos, by AIP Publishing, and show that their model can be used to find previously unknown bottlenecks that could lead to failure of the entire road network. Scientists from Fudan University and Shanghai University of Electric Power in China developed a modeling technique to study urban traffic flows and verified it with real-world data from Shanghai.
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