You know those strange traffic jams that appear to come out of nowhere, with nothing causing them, and then suddenly end? As Wired reports, a team of M.I.T. mathematicians calls them “phantom jams” or “jamitons,” and has found mathematical equations to describe them, similar to those that describe detonation waves from explosions. Phantom jams, the mathematicians found, can form when a single driver slows down (to take a sip of coffee or talk on the phone) on a road with too many cars on it. They hope the new equations will lead to roads engineered to keep traffic below the density where a jamiton can form. [%comments]
Ghost Jams
TAGS: traffic
and 
. You can also watch it on 
I’m with Tracey. I have called it the Slinky effect. Or in
Investment jargon, Gap theory…all gaps get filled. (my belief)
@assumo, I want that technology! Seriously, why are we all controlling metal boxes hurtling along a road and susceptible to the least inattention? 40,000 deaths a year attributed to automobiles. Some kind of freeway car-train seems hugely safer and more efficient.
@lee, the Highway Patrol doesn’t have to get in front of people to slow them down. Just being there in any lane reduces the top speed dramatically.
And I’m another one who tries to even out speeds instead of tailgating. Makes dealing with significant traffic jams a little less stressful.
How about rubber-necking an accident in the opposite flow? Maddening!
-1 for the smarts of MIT folks. This is not news. Anyone who observes the phenomena knows what is going on.
Don – it is “obvious” to someone who frequents this board, but you still hear people talking about “getting stuck in traffic for no apparent reason…”
Well, there was a reason and it happened 20 minutes ago 2 miles up the road.
If this new math can help us, then great.
@avi – yeah, 40,000 traffic deaths is ridiculous. we’re all driving around at speeds we’re not designed for.
@jeffrey – NASCAR is indeed more complicated than most think. Heck, last weeks race saw teams calculating their fuel consumption, and the fact that the two leaders didn’t want to risk slowing down made it very interesting. 1 & 2 ran out on the last lap… seams like another potential Freakonomics analysis!
#8: What you’re talking about is Adaptive Cruise Control, which is a system that maintains the distance between your car and the car in front, and it exists (although it hasn’t been widely available yet). Studies have shown that even if only a small fraction of cars on the road have ACC (say 10% – 20%), traffic jams are greatly reduced or eliminated. This makes intuitive sense: imagine that every 5th car or so acts as a traffic jam “shock absorber”, dampening out that chain reaction of tailgaiting cars that over-brake and cause the well-known “slinky effect”.
Of course, we can all do the same thing by simply keeping a safe following distance (shout out to #7!). I have often thought of starting a “flash mob” through Facebook, called “Leave-a-Gap Day”. I’d choose one typical commuting day and encourage as many people as possible just on that one day to “leave a gap” between their car and the car in front. If enough people do it, traffic jams will magically disappear for that one day. If the news media gets wind of it, then maybe everyone will realize what happened and people will start leaving a gap all the time and traffic jams will be a thing of the past.
Who’s with me?
@14 – The key is that only a few in the herd leave the buffer. If there are too many gaps, other, less enlightened drivers speed in to fill them. If the gap is left as a rule, we don’t have enough capacity to maintain high speeds. Of course anything is better than gridlock.
Sure this seems nothing more than “common sense,” but your “common sense” does not have the potential to actually do something about the problem.
Only by analysis can you get these models that can be used to find ways to minimize the problem.
Joe D has the right idea. We don’t need to force this on people, but something on the dashboard that uses intelligence to tell you if you are too close to the vehicle in front of you would be very helpful.