In some of the western states, where 70 - 75 mph limits are posted,typical speeds are well in excess of the limit.
On the basis of very limited observation, I've tentatively concluded people tend to exceed the speed limit-no matter how high you set it.
The reason people are going 70-75 on the freeway now that you have a 65mph limit, is that the artificial 55mph limit and its excessive fines exerted downward pressure on the overall speed of traffic that has been somewhat relieved by the 65mph speed limit. People are driving closer to the safe design speed of the roadway because they're no longer threatened with half a dozen points on their license and three years of exhorbitant insurance rates for doing so.
If the speed limit were set to 70-75, or even repealed entirely, a variety of traffic engineering studies indicate that the overall speed of traffic would settle in at the safe speed for the road, rather than increasing in 10mph increments over the posted limit.
I don't know about that. The Autobahn in Germany still has many stretches with no speed limit at all. Most people seem to like to drive at around 130 km/h (approx- 78 mph). There's always the BMWs that are driving in excess of 100 mph but for the most part it seems that around 130 km/h is a speed that most people like to drive- myself included.