seems the key move was to close on- and off-ramps. the problem with traffic
in many cases is merging. seems drivers, pursuing individual success over
the success of the whole operation, merge "uneconomically."

i've seen a model that shows how drivers, if all are civil and merging is
zipper-like (each car lets in one car ahead of it) flows, well, like a
zipper. if drivers "disobey" and don't allow merging regularly, the whole
flow shuts down and a jam is created.

can't find the model offhand. but there is a wealth of traffic data and
modeling and other info at

and there's a book called, i think, Micro Behavior and Macro Effects that
addresses the issue as well.


> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
> Krist van Besien
> Sent: Wednesday, August 29, 2001 9:46 AM
> Subject: Traffic Jam paradox..
> To the west of the Amsterdam city centre lies the A10-West freeway. This
> freeway has three lanes northbound and southbound, and in in places a
> fourth lane for entering-exiting traffic. Speed limit is 100kph. The
> road is frequently jammed, with stop-and-go traffic the norm during rush
> hour.
> The A10-West needed an overhaul, and the public works department decided
> to do this over a 6 week period in July-August. During this period
> almost all on- and off ramps were closed of, the number of lanes reduced
> to just two narrower ones nortbound and southbound, and the speedlimit
> reduced to 70kph. This speedlimit was strictly enforced by the local
> police and as a result well observed.
> Almost everybody expected huge traffic jams. But strangly thes didn't
> materialise. For the entire six weeks the A10-West was traffic jam free.
> Als on roads leading to the A10-West traffic volume apeared to have
> dropped.
> When the roadworks were finished, and everything brought back to normal
> last monday the traffic jams returned, both on the A10-West, and on the
> other roads leading to it.
> This episode got policy makers and public commentators alike a bit
> puzzled. Most people subscribe to the view that more roads will lead to
> less traffic jams, and thus less roads to more traffic delay. But here a
> reduction in the amount of "road" available led to an even greater
> reduction in demand, and less traffic delays. This is counterintuitive
> to most people.
> I think that what this case shows is that common conceptions about the
> causes of traffic jams are wrong. In the political debate the right will
> tell you that we need more roads, the left that we need to reduce car
> usage.
> The real cause in my opinion is that traffic jams are just the way
> supply and demand meet on the freeway. The amount of delay you
> experience at a particular time is the "price" you pay for access. Some
> people (like me) will find this price to high and travel outside rush
> hour, or take the train. Traffic jams apear when the "market clearing"
> price entails delays that are not possible while maintaining smooth
> traffic patterns...
> What happend on the A10-West was that the authorities increased the
> price for using the road (by lowering the speed limit), and reduced its
> utility (by the closing of ramps), and as a result demand for the road
> was lowered. For six weeks many people used other routes, or other means
> of transportation. The amazing thing is that demand dropped far enough
> that traffic delays disappeared.
> Anyone willing to comment on this? Any pointers to information in teh
> economics of traffic jams are welcome...
> Krist

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