As a German, I'd like to point out that about half of the German Autobahn network do have speed limits in place, or had in 2019 (this oscillates a lot between about 30-60%, I think).
According to a government study into Autobahn fatalities that occurred in 2018, "non-adapted speed" (defined as the appropriate speed for the traffic conditions and allowing full control of the vehicle) was the cause of death in 45% of cases overall. For stretches without a tempo limit it was 46%, for stretches with one it was 50% -- this may be a good statistical for the tempo limits, as presumably there would have been more deaths on those stretches without the limits having been set.
Overall, 70% of Autobahn deaths occur on the segments without a tempo limit for a variety of reasons.
Speed limits on the Autobahn are a frequently-discussed and controversial topic in Germany, but for what it's worth, they're quite actively managed for safety reasons.
I'm not denying any of this. I'm just observing that there's a faction in the US which seems to say "speed is a leading factor in car deaths" (which it is) and then insists on everyone never going 1mph over our often-arbitrary-and-politically-set speed limits. When what you're describing as "non-adapted speed" is exactly the actual problem . . . driving beyond one's capabilities or the capabilities of one's vehicle.
Our freeways stateside were largely built in the late 20th century to a uniform 70mph (~110km/h) speed limit engineering-wise. But after the 1970s oil crisis, speed limits became a political football that often have as much to do with driving traffic ticket revenue for local governments as actually promoting driving at a safe speed.
So the problem is that a portion of Americans commenting on our speed limits don't understand there's a difference between "what the government puts up on the sign" and "what is actually a safe speed to drive without endangering other people" as if what's on the sign is some sacred totem that shall not be questioned because We Must All Follow The Rules Like Good Little Boys and Girls.
What the government puts on the sign has significance you know. Maybe the highway was made in the 1950s vs 1970s and interchanges are too tight. Maybe its a surface road with smaller measured sightlines than you might realize. All the yellow lights are going to timed with respect to the posted speed limit and braking distance. All green waves timed with the anticipation you go the posted speed limit.
So let everyone decide to decide for themselves what a safe speed should be on any given stretch of road and see what happens? In other words, let evolution find the 'safe' speed.
Yes, though you are phrasing it negatively. Something like 90% of drivers base their speed on conditions, not on the speed limit signs. No amount of arguing that it should be exactly the opposite will actually make that happen, so we have reality to work with. We can whine on an Internet forum that terrible people are not abiding by the posted speed, or we can engineer the roads to meet our goals.
According to a government study into Autobahn fatalities that occurred in 2018, "non-adapted speed" (defined as the appropriate speed for the traffic conditions and allowing full control of the vehicle) was the cause of death in 45% of cases overall. For stretches without a tempo limit it was 46%, for stretches with one it was 50% -- this may be a good statistical for the tempo limits, as presumably there would have been more deaths on those stretches without the limits having been set.
Overall, 70% of Autobahn deaths occur on the segments without a tempo limit for a variety of reasons.
Speed limits on the Autobahn are a frequently-discussed and controversial topic in Germany, but for what it's worth, they're quite actively managed for safety reasons.
Gov source (in German): https://www.destatis.de/DE/Presse/Pressemitteilungen/Zahl-de...