The problem is a cultural one. Most people interpret a speed limit of N as "I should go N+10" (or something like that). If we remove speed limits, the majority of people would end up driving at unsafe speeds. People will always break speed limits unless they are set at that unsafe level.
Make roads narrower. Add more bends and lateral shifts. Plant trees along the road to obstruct sight lines. Build roads so that only speeds below the speed limit are safe on them and people will travel below the speed limit.
I come from the position that on a dry, well-maintained, and straight road, with no traffic, I think even 100 mph is a safe speed. I assume people like you that even consider 80 mph to be unsafe are assuming there's significant traffic on curved roads that might not have the best maintenance. I also assume you're driving a large truck or SUV which has abysmal handling, whereas I'm used to the tighter handling of my Subaru BRZ.
Generally, I don't think speed causes crashes, it just makes crashes worse. So if I'm coming from assumptions above, then crashes basically won't happen.
Add some traffic? Then the safe speed depends on their discipline. Are drivers keeping right except when passing? Or is some asshole playing "traffic cop" and camping the left lane at the speed limit, or even below it?
If if the conditions actually require it, that’s when I brake. Not because a sign told me too when I may not actually need to. I feel that’s probably the most economical option.
[[citation needed]]
(particularly section 2 "Limitations of the 85th Percentile Rule for Setting Speed Limits")
I'll admit that "the majority" could be an overstatement, perhaps I should have said "enough people to be dangerous"
I would be totally fine fine with speed limits being actual, enforced, no wiggle room limits, IF the actual limits were reasonable in the first place. This would mean most interstates outside of built up areas being posted at 80-90mph, say .