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Traffic jam mystery solved by mathematicians from PhysOrg.com
Mathematicians from the University of Exeter have solved the mystery of traffic jams by developing a model to show how major delays occur on our roads, with no apparent cause. Many traffic jams leave drivers baffled as they finally reach the end of a tail-back to find no visible cause for their delay. [...]

While traffic engineers have known this for a while (did these folks pay any attention to the MUTCD?), I don't think that there has been an equation to this effect that would allow for the calibration of automated devices for individual vehicles.  Why does this matter for TDM?  A couple of reasons...

First, smoother flowing roadways mean less congestion in general, regardless of how many people are in the vehicle or what type of lane they're in.  If there are preferential carpool lanes, these devices could help with controlling lane conflicts from delay associated with a slower moving lane next to the carpool lane.  It would require designated access points, but I believe this is coming to most areas in the near future anyway associated with broader tolling schemes.

Second, in my opinion, the less personal control over the driving experience that the system user (i.e. driver) is allowed to have in order to maximize the use of the system, the more likely they are to consent to a shared travel experience with others in their conveyance.  This, of it's very nature, is an encouragement to HOV travel.  Admittedly, this could be more of a boost to the personal rapid transit crowd, but I can't see that level of separate infrastructure being created any time soon, and I see more emphasis on efficient use of existing infrastructure.

Chris Simmons, TDM Corridor Implementation Planner, WSDOT

simmocw@wsdot.wa.gov

Comments

[Jeremy]

I also saw this article (after having encountered this EXACT scenario leaving a meeting in Washington DC a few weeks ago) linked to on FARK.com and found it pretty fascinating. I think quantifying TDM's impact on the inputs into this equation can be a powerful tool to support our efforts. There's often a big push to measure our impact, this could provide another way to do that in the larger metro areas.

On a secondary note, while I agree with your comment that systems flow better when drivers exercise less personal control, I would be cautious about using terms like "allowed to have." The cornerstone of automobile culture in the U.S. is the perceived sense of freedom that drivers have, to the extent that many - if not most - are willing to idle in traffic for hours to indulge that sense. Framing the goals of TDM as "not allowing" that personal control runs the danger of butting up against that deeply ingrained sense and raising the specter of a Nanny State taking your driver's seat. Of course, I would also argue that there's very little freedom to be had in spending a significant part of one's day sitting on the freeway breathing everyone else's exhaust when one could be home playing with the kids or doing something constructive; much less than zipping along in a train, bus, or carpool, but the battle against the SOV attitude will best be fought with language that invokes drivers making smart choices and expanding their control rather than reducing it.

-- Jeremy