The safest speed to drive is the speed of traffic, because the thing that's most likely to cause accidents is changing lanes or speed. Traffic is almost always moving faster than the speed limit, so the speed limit actually reduces safety. If they were designed based on the speed people feel comfortable driving then they'd be reasonable and safe, but that's not how they were decided. Speed limits are bad.
The reason traffic moves at above the speed limit is that people see the speed limit and go slightly above it because it feels fine.
Speed limits are absolutely necessary in residential areas, and still a good thing on highways. High speeds are insanely fuel inefficient and they do also endanger people more.
My country has been debating putting a speed limit on highways that previously didn't have one so I've heard quite a lot about this topic.
Because literally everything is made to pressure you, every demand is just slightly more than what you can achieve if you follow all the rules. By design.
Speeding is just a simple easy way for them to remind you. To teach you that youre prey.
Because I don't want too. Without taking the time to dig up resources John Oliver put it best that speed limits were decided on not by science or safety standards but what appears to be random guessing.
That said I follow rules, 10 over on low traffic interstate and highways, 5 over on low traffic main roads, speed limit everywhere else.
And pretty sure I read outside of impaired or distracted driving the thing that kills or injures most drivers is trying to make the yellow, not speed.