On Fri, 1 Feb 2008, Doug Henwood wrote:
> I mean inexplicable in the sense of no accident blocking traffic, or
> rush hour. Bumper-to-bumper traffic at 1 PM on a Wednesday in
> Hawleyville, Ct., seems weird.
http://blogs.zdnet.com/emergingtech/?p=778
The traffic jam mystery finally solved
When you're caught in a traffic jam, you probably don't know why. Is
there an accident ahead of you? In most of the cases, the answer is no.
And all the electronic devices installed in your car can't help you.
You're stuck for a while -- until the traffic gradually improves. Now,
European mathematicians have solved the traffic jam mystery.
<snip>
This mathematical model has been developed by Dr Gábor Orosz of the
Dynamical Systems & Control research institute of the School of
Engineering, Computing and Mathematics at the University of Exeter, UK.
Orosz, who also maintains a personal homepage, worked on this project
with Gábor Stépán of the Department of Applied Mechanics at the
Budapest University of Technology and Economics (BUTE) and who leads
the research group on `Dynamics of Machines and Vehicles.'
Here is a description of what the two mathematicians did. "The team
developed a mathematical model to show the impact of unexpected events
such as a lorry pulling out of its lane on a dual carriageway. Their
model revealed that slowing down below a critical speed when reacting
to such an event, a driver would force the car behind to slow down
further and the next car back to reduce its speed further still. The
result of this is that several miles back, cars would finally grind to
a halt, with drivers oblivious to the reason for their delay. The model
predicts that this is a very typical scenario on a busy highway (above
15 vehicles per km). The jam moves backwards through the traffic
creating a so-called `backward travelling wave', which drivers may
encounter many miles upstream, several minutes after it was triggered."
<snip>
For more information, this research work has been published in the
Proceedings of the Royal Society A under the title "Subcritical Hopf
bifurcations in a car-following model with reaction-time delay" (Volume
462, Number 2073, Pages 2643-2670, September 8, 2006):
http://publishing.royalsociety.org/index.cfm?page=1086