Any road where you have a big differential between speeds by various road users is just inherently dangerous. If everyone would be doing 250km/h, it'd be safe. Same if everyone would be doing 120km/h. But when you mix 250 and 120 on the same road, it's inherently dangerous.
The issue with ground based traffic is that you have a lot of non-moving objects around you, like trees, walls, animals, etc. So even if all cars drive at 250 km/h, those non-moving objects still remain there and pose an ever increasing risk with increased speed. Furthermore, curves are more dangerous at higher speeds.
Due to topography, Autobahn roads can still be very curvy. The Albaufstieg [0] is an extreme example but not the only one. Notice the sign at 3:04, it's limited to 60 kmh. Weather can make those curves even more dangerous, e.g. rain or ice. As for objects, they still occur. One example is prior accidents. Another example is the end of a traffic jam. These are an especially bad problem for trucks [1], that actually drive way slower than 130 kmh even. The problem here is driver attention, but too fast speed can also contribute [2].
I know that A8 part. It’s pretty cool. The speed limit there is most likely due to how steep it is. Trucks are pretty slow there. The ICE goes around that mountain as slow as the traffic on the Autobahn.
The higher your speed, the higher your speed differential with the road and guard rail. A car nudging another at 250 km/h can cause the other to violently roll over, while a car nudging another at 40 km/hr can't. Speed differential between cars is not the only factor in safety.
I agree, and if we had decided to create an autonomous car only line where the speed gets controlled by a central computer, this would apply.
You still shouldn't ignore that the higher the speed, the more likely larger speed differences can appear. At some point external force will slow down cars significantly faster than the brake of the vehicle behind.
Any road where you have a big differential between speeds by various road users is just inherently dangerous. If everyone would be doing 250km/h, it'd be safe. Same if everyone would be doing 120km/h. But when you mix 250 and 120 on the same road, it's inherently dangerous.