# Math Model May Decrease Phantom Traffic Jams

More traffic-related stories here. The ‘phantom’ traffic jams in the title are those where there is no apparent cause. These traffic jams typically occur when there are a lot of cars on the road and some small irregularity—one driver hitting the brakes hard, for instance—starts a chain reaction of driver reactions that blows up back through the line of cars and into a full-fledged stoppage. The “chain reaction” and “blows up” language turns out to be appropriate here. Recently a team of MIT researchers looking at the equations that describe these traffic jams—equations that had been unsolved since the 1950s—made a breakthrough when they realized that the equations were very similar to solved equations describing the detonation of explosives! The story’s combination of cars and explosions was catnip to the media, of course, with the story appearing among other places at MSNBC and Wired and overseas at the Telegraph.

And in another traffic story coming down the pike, another researcher, Morris Flynn at the University of Alberta, has proposed that outfitting cars with some kind of ‘interactive GPS’ could help decrease traffic density and thus decrease the occurrence of these phantom jams. Flynn’s idea was number 39 of Discover’s Top 100 Stories of 2009. Minnesota has used special stoplights at entrance ramps to great effect to do the same thing, as described in Numbers Rule Your World: The Hidden Influence of Probabilities and Statistics on Everything You Do, a recent book by Kaiser Fung.

And finally, to complete this math and traffic pile-up, we have another story featuring Morris Flynn which has an interesting psychological angle. Instead of solving the governing traffic equations, Flynn has been using computers to ‘kick the tires’ of various different mathematical models for traffic flow, and one of the models he investigated looked at those who abide by traffic rules assiduously, the rule-abiders, versus drivers who are willing to bend the rules every now and then, the rule-breakers. Not surprisingly, when rule-breakers rule the road traffic typically doesn’t flow well, since it’s impossible to ‘go with the flow’ if you don’t have a good idea of what the other drivers are going to do. Somewhat surprisingly, rule-abiders don’t do so well by themselves either: when a group of them gets into jams they are in a jam for a good long time. Most surprisingly, traffic works best with a mix of both. In fact, according to Flynn’s calculations a 60%/40% mix of rule-abiders vs. rule-breakers is just about ideal. This story appeared in “A Cure for Traffic Jams: Rule-Breakers” at ABC News.