The scientists tracked anonymized information from more than 680,000 Boston-area drivers over three weeks. The engineers used commuters’ cellphone signals to locate the position of individual drivers. The study identifies the origin or “home” districts of the drivers according to the hours and locations of the calls. For the purposes of the study, a trip is occurring when the same mobile phone user is observed in two distinct zones within one hour.
What’s true at a single intersection turns out to apply on a larger scale: It’s just a few drivers, relatively speaking, who jam things up for the rest of us.