In most cities, traffic growth has outpaced road capacity, leading to increased congestion, particularly during the morning and evening commutes. One way to prevent traffic tie-ups is to have fewer cars on the road by encouraging alternatives such as public transportation, carpooling, flex time and working from home. But a new study — by Professor Marta González and researchers at Central South University in China, the University of California at Berkeley and the Austrian Institute of Technology — incorporates data from drivers’ cellphones to show that the adoption of these alternatives by a small percentage of people across a metropolitan area might not be very effective. However, if the same number of people, but from a carefully selected segment of the driving population, chooses not to drive at rush hour, this could reduce congestion significantly. Read a news release.