This study has some interesting data, but more interesting is the conclusions they draw...
Within a year after the Federal Government ended any role in setting speed limits, 23 states raised their rural Interstate speed limits to 70 or 75 mph. Many studies showed that this increased fatalities. One study compared changes in the number of fatalities for the same distance of travel for states that increased their limits to states that kept their limits at the then prior limit of 65 mph. The states that increased speed limits to 70 mph experienced a 35% increase in fatality rate, and the states that increased speed limits to 75 mph a 38% increase.
This is not based on any reputable studies. Speed limits across the US have been going up and traffic fatalities by any measure are going down. There were all kinds of protests and news articles about how dangerous it was to increase Ohio's speed limit to 70mph a few years ago before it went into effect. It went up, fatalities have gone down (but not significantly), and now all of them are back again to protest proposals to raise it again to 75mph.
But I digress on the speed limits... Their figure 9-1 (inconveniently not included in the text version) cannot be verified and they do not cite the source of this data and note that it only included drivers from one organization in 3 states. That screams to me cherry picked data to match their conclusion. Similar to all the citations from insurance institutes for high speed limit dangers. Insurance companies make a lot of money off speeding tickets raising people's rates, they would hate to see that venue stream dry up. The National Highway Traffic Safety Administration has done several studies and their findings have primarily been that people ignore speed limits and thus they were unable to conclude anything about higher and lower speed limits.
I don't deny that some people who go to the track drive like assholes. But then plenty of people drive like assholes that think they are race car drivers. I agree that there is no way to conclusively judge a person's driving ability and habits. However, my point is still that insurance companies make no attempt to measure these things other than bullshit "defensive driving" courses. The reason they don't is because it serves them no financial interest. Why would they collect more data and do extra analysis to reduce rates for highly trained drivers or well maintained cars?