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Urban planners may soon have a new way to measure traffic jams. By putting in the different routes by which vehicles can travel between locations, researchers have developed a new computer algorithm(运算法则) that helps quantify regions of jams in urban areas and suggests ways around them.

The study published in the Journal of Physics: Complexity, used traffic speeds from taxis in New York City to demonstrate how road infrastructure(基础设施)and driver behavior can create complex road networks that differ among cities.

The team approached the issue by designing a computer algorithm to capture the topology- or relationship between the different routes between locations--of road networks. "We found that the most significant traffic bottlenecks in Manhattan seem to arise as a result of the city's structural layout," said study co-author Daniel Carmody. "For example, the fact that a bridge enters Manhattan at a range where traffic is already limited due to Central Park slows traffic in the area considerably."

The researchers performed a comparative analysis using traffic patterns in Chengdu, China, to test if the algorithm works equally well in areas with different layouts. Manhattan has a long and thin structure, while chengdu is round. There are significant differences in the way traffic moves between these two different setups, the researchers said.

"The bottlenecks in Chengdu seem to arise due to the function of the buildings in a particular area," Carmody said. "For example, it is hard to travel in and out of the central business district in Chengdu because of the large amount of traffic alone. Beltways, or faster streets around busy areas, have emerged in circles around this area, which is not surprising because this feature was intentionally built into the city."

In Manhattan, the bridges and underpasses that form the entry and exit points cause traffic slowdowns. However, in lower Manhattan where drivers seem to obey the lower posted speed limits, traffic moves more smoothly, forming a new traffic beltway with the southern end of Central Park acting as a block between lower and central Manhattan.

"It surprised us that there is an emergent beltway in such a busy area of Manhattan," Carmody said. "This indicates that, unlike in Chengdu, beltways seem to arise from driver behavior even when they aren't part of the structural plan of a traffic network."

"The researchers have imagined that this technology could give urban planners a means to quantify traffic patterns, leading to better traffic, Carmody said. "As methods of transportation develop new problems will emerge, and we hope that our tools will give planners new ways to measure what is going on with city traffic."