Some interesting takes in this thread... Could do without all the personal battles and arguing about qualifications, but whatever.
The lines that got me we along the lines of "nobody" does the speed limit.
Interestingly, my employer collects that data for the state I reside in, and it shows that under non-weather impaired driving conditions, for roads with a speed limit over 45 mph under our jurisdiction, that between 30 and 40% of drivers actually do the speed limit or below. 1/3rd of the traveling public is more than nobody...
The data also shows that the 85th percentile speed for nearly all road types is less than 10 mph over the posted speed limit. (The exception is 60 mph divided highways, mostly found in our urban areas, where the 85th percentile speed climbs to 13 mph over the posted speed limit). If you want to make the arguement that speed limits are set based on 85th percentile speeds, that is true except where state laws cap speeds in some circumstances - which is the case for most of the roads in our jurisdiction. The big point here is that 85% of drivers are traveling at speeds less than 10 mph over the speed limit.
If we are talking about speed limiting, then if a reasonable buffer is applied on top of the speed limit, say 20 mph, the reality is that less than 15% of the driving public is being affected by such a limitation.
I'm amused by the lines of of you have to keep up with traffic, etc... Its the same logic family uses when they tell me how fast they drive to the same places I go, and that they'll get run over if they go slower. And yet I get there too, and it sure doesn't feel like I'm getting run over and regularly pass other drivers. Reality is some people just like to drive fast - and that is one way of justifying their own behavior.
I drove cars in a previous employers work fleet that were capped at the maximum speed limit in Minnesota.... and survived to tell about it. If the traveling public isn't willing to police themselves, and law enforcement is unable or unwilling to reign that in, then this is the next logical place to look.