Speed is not the issue, difference in speed is the issue. Road safety actually improves when you raise the speed limit to the speed most drivers are actually driving.
The correct conclusion is that the safe speed directly depends on the present conditions, and depending on that, you can be going unsafely fast or unsafely slow (or both, if you’re drunk or inattentive).
https://www.google.com/amp/s/www.thelocal.de/20190201/are-ge...
The desire to minimize the speed at which crashes happen literally costs lives when applied in the real world because reducing the frequency of crashes is the superior option.
While I understand that minimizing crashes is important, I'd rather be faced with scenarios where we crash in a manner where people survive more often - any accidents that do happen at the higher speed is going to skyrocket the chances of a fatality.
It's too bad the civil engineers working as traffic engineers absolutely refuse to actually follow the recommendations of these studies. Honestly, I can't think of a more intellectually dishonest profession than civil engineering (specifically, the traffic engineering subset of it; the guys who build buildings and bridges are OK).
Number of accidents drop, but the number of fatalities increase when you raise the speed limit because the accidents that do happen have so much more energy in them (e=mv^2). So "safety" only improves if you have a bad definition of safety.
Do you remember where you saw the data on this?
Here's a good explanation: http://www.mikeontraffic.com/85th-percentile-speed-explained...
Basically, you set the speed limit at the speed most of those drivers are already naturally driving at, so that the people who do mind the speed limit will travel at the same speed of travel as everyone else.
And then, of course, obviously there will be outliers.