A computer model of the London Underground predicts trains that travel too fast will compound overall congestion levels when key locations outside the city center, where travelers switch to another mode of transport, become bottlenecks.
In comparison, the New York City subway system, which is more centralized, gives rise to downtown congestion that would be improved by faster trains.
The researchers found London's system would best operate with trains traveling about 1.2 times faster than the average speed on the roads, making optimum train speed about 13 mph, compared to the current average of 21 mph.
The study reflects the increasing interconnectedness of transport networks and a trend toward multimodal trips, which Marc Barthelemy, a statistical physicist at the CEA research center in Saclay, France, says are unavoidable in large urban centers.
Once models of the London and New York road and subway networks were complete, the researchers linked them based on the proximity between streets and subway stations. "We create these connections, and then we make an assumption, which is: when someone wants to go from A to B, they look for the quickest path--whatever the mode," Barthelemy notes.
The study is theoretical, as the model includes no passenger data from the transport system itself.
From BBC News
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