[trebuchet03]

Originally Posted by tjts1

A good read on the subject.
http://www.usroads.com/journals/aruj/9709/ru970901.htm



And another one.
http://www.azdot.gov/highways/traffic/Speed.asp

How the Germans deal with speed limits.
http://www.gettingaroundgermany.info...tm#speedlimits

That seems to confirm that lowering the limit increases capacity...

From second link

Traffic Volume

At some point, the volume of traffic affects its flow and forces motorists to slow. This factor is important because:

* Traffic volume is often used as a reason to lower speed limits.
* Peak volume occurs at certain times and for certain durations.
* Merging volumes, densities of traffic, and increased speeds all affect drivers' abilities to merge and change lanes.
* Each highway section has a certain carrying capacity.

While it doesn't specifically say capacity increases with lower speeds (it just says lower speeds are used when volume is high) - its last point doesn't link carrying capacity with speed.

And in the third link - limits are set in areas of heavy congestion....

This is actually rather interesting - I wonder if there's a Bernoulli like model for this.

..... researching......

So it looks like Metro was right...
http://www.vtpi.org/tdm/tdm96.htm

Vehicle density and vehicle flow (vehicles per hour per lane) increase in a nonlinear fashion as speed reduces. That is, maximum traffic volume (capacity) is higher for slower moving traffic.