Gas explosions: A new way to study phantom traffic jams

A University of Alberta researcher has devised a new theoretical approach to studying phantom traffic jams. Normally a traffic tie-up happens when vehicles reach a bottleneck and traffic flow is reduced, or in the case of an accident, halted completely. Phantom traffic jams are created by something as simple as a single driver tapping lightly on the brakes inadvertently starting a chain reaction of over-braking by drivers in the following vehicles. Eventually a long line of traffic comes to a complete stop. On major freeways in North America, phantom traffic jams can involve hundreds of vehicles and can snarl traffic for hours.

U of A mechanical engineering professor Morris Flynn has revealed a new way to study the phenomenon.

"We treat traffic as a chemically reacting gas," Flynn said. In the research team's eyes, traffic flow is a gas and the start of a traffic jam is an explosion and that force ripples outwards engulfing everything in its path.

"Once a detonation wave begins, it keeps expanding outwards," added Flynn. "By the same token, a phantom traffic jam may start with only a handful of vehicles, but then quickly grow in scale and severity."

Flynn and researches from the Massachusetts Institute of Technology created mathematical formulas to calculate the severity of phantom traffic jams for highways with various speed limits and traffic volumes. His research was published online this week in Physical Reviews E, which is published by the American Physical Society.

Source: University of Alberta