[groar]

In France some local speed limitations are lowered from time to time with the first goal of making the traffic with less waves and jams.

I do not have the numbers for these specific points, but these are mainly points where speed differences are important between slowest and fastest cars and so generate "waves", slowing down the traffic. By slowing down the max speed, you lessen the speed differences and diminish the waves which accelerates the mean speed.

An excellent document is here : SCIENCE HOBBYIST: Traffic Waves, physics for bored commuters

In Germany several experiments (no reference, from memory) on highways showed that the more people are using cruse control, the faster is the traffic. The explanations were confirming the trafficwaves.org document.

Have fun,

Denis.