Yet the more usual cause is simply too many people wanting to be in the same place at the same time. Limitations in the road system or minor inconsistencies in the behavior of drivers can then compound to cause torturous slowdowns. Past methods of predicting traffic patterns relied on statistical models that treated traffic as a homogeneous fluid, ignoring differences between individual drivers. Sections of transportation networks were often analyzed in a vacuum, without regard for the interactions between the components. Refinements in the mathematical treatment of complexity, however, coupled with hugely greater computing power, have revolutionized traffic analysis.
Traffic lies in the middle.
It goes beyond physics to a human scale. On the physical side are the stunning variety and number of vehicles and road systems, each contributing its own peculiarities, as well as the weather and other environmental factors. To understand the forces acting on traffic flow, transportation planners must analyze the many possible outcomes from this snarled network of decisions. As a further complication, seemingly logical solutions to traffic problems can have counterintuitive consequences. One instance is known as Braess's paradox, named for the German operations researcher Dietrich Braess, who in 1968 first noticed the phenomenon.