Gridlock Traced to Just a Few Key Commuters

Tracing driver sources in the Boston area via the road usage network. Red and yellow denote the most congested roads. CREDIT: Dr. Pu Wang View full size image

Canceling some car trips from just a few strategically located neighborhoods could drastically reduce gridlock and traffic jams in cities, a new study suggests.

The study, conducted amid a global trend toward urbanization, could lead to new strategies and maybe even smartphone apps to help prevent traffic congestion, the researchers said.

Nearly 5 billion people are expected to be living in cities next year. Urban road networks already are subject to severe traffic congestion, which can decrease road quality and increase fuel consumption and air pollution. In 2007 alone, the study authors noted, congestion forced Americans living in metropolitan areas to spend 4.2 billion more hours traveling and purchase an additional 2.8 billion gallons of fuel, at a total cost of more than $87 billion.

To learn more about traffic congestion in the hope of finding ways of relieving it, an international team of scientists analyzed road use patterns in the San Francisco Bay area and the Boston area. They used mobile phone information from more than 1 million users over the course of three weeks to map out where drivers were concentrated on roads. (The data was rendered anonymous before the investigators looked at it, the study authors noted.)

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Based on their analysis, the researchers suggest that certain neighborhoods in these urban areas were home to drivers that caused major congestion. The scientists found that canceling just 1 percent of trips from these neighborhoods could drastically reduce travel time that was otherwise added due to congestion.

"In the Boston area, we found that canceling 1 percent of trips by select drivers in the Massachusetts municipalities of Everett, Marlborough, Lawrence, Lowell and Waltham would cut all drivers’ additional commuting time caused by traffic congestion by 18 percent," said researcher Marta González, a complex-systems scientist at the Massachusetts Institute of Technology. "In the San Francisco area, canceling trips by drivers from Dublin, Hayward, San Jose, San Rafael and parts of San Ramon would cut 14 percent from the travel time of other drivers."

The location of these neighborhoods apparently makes it easy for them to impact their cities. "Being able to detect and then release the congestion in the most affected arteries improves the functioning of the entire coronary system," González  told TechNewsDaily.

There are many ways people might reduce the number of drivers hitting the road from these key neighborhoods, the scientists said. For instance, the authorities might encourage alternatives "such as public transportation, carpooling, flex time and working from home," González said. Mobile phone apps that connect people using the same roads might help them coordinate carpooling, she added.

In compiling their data, the researchers did not need complete GPS information from all the travelers. "People are very repetitive in their travel patterns, and the number of data points only from billing information is vast," said González. "This is enough to make good statistical estimates, despite not everyone using the phone all the time. With a good sample and analysis of long-time observations, we could calculate the trends of road usage."

Since mobile phones are now used worldwide, the research strategy that González and her colleagues used for Boston and San Francisco could potentially help relieve traffic in nearly every urban area. The scientists are currently studying road use in the Dominican Republic, France, Portugal, Rwanda and Spain.

"In many cities in the developing world, traffic congestion is a major problem," González said. "So the detailed methodology we developed for using cellphone data to accurately characterize road network use could help traffic managers control congestion and allow planners to create road networks that fit a population's needs."

The scientists detailed their findings online today (Dec. 20) in the journal Scientific Reports.

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