Wednesday, August 21, 2013
Just Take Me Home
My husband and I were in a traffic event recently. The traffic guy in the helicopter told us it would be stop and go through exits that were at least ten miles down the road. My Washington State Department of Transportation app showed the freeway in black (meaning the color beyond the transition from green to yellow to red). Every once in a while we sped up and we thought we were through the worst only to hit a wall of brake lights again. I have learned that there is a name for this: Phantom Traffic Jam. According to my new favorite smart people a Phantom Traffic Jam is "...a jam that arises in the absence of any obstacles." The smart people that explain such phenomena are an international research team from the University of Alberta, KAUST, McGill University, MIT and Temple University. (KAUST is the King Abdullah University of Science and Technology located in Thuwal, Saudi Arabia.) Their work was supported by the National Science Foundation, I expect in the hope that better understanding of the effects of too many cars on the road would lead to better traffic management. In the case of our event, there were no obstacles - no wreaks, nothing interesting happening on the shoulder, no blocked off ramps. The research team also have a name for the momentary openings that sucker me into thinking I can resume highway speed. These false promises are Jamitons, travelling waves of traffic instability. They compare traffic waves, jamitons, to detonation waves: "In the language of detonation theory, such traffic roll waves are very similar to roll waves in shallow water flows....on long periodic roadways, final states can arise that consist of multiple jamitons." You can read a short report of their theories and conclusions here. Make a copy to read the next time you are in a Phantom Jam.