So, there’s a balance. If you don’t build enough room to do anything but drive slow to be safe, the moment someone is fast, the chances of a crash are very high.
If you build a road that has too much clearance, you end up with people driving faster, which is okay because there’s more room for people to be out of the way, likely reducing the amount of crashes. The drawback to this is, if people drive faster, the fewer crashes that do occur are at higher speeds, which are more deadly.
So the ratio of number of crashes to severity of crashes is what the end result is.
Granted, I live in the US where single lane country back-roads will have people in trucks going down at 50MPH randomly, so I don’t know if Europeans drive more cautiously. I know their driving tests are more comprehensive for sure.