[banach2]

Not sure about this. I drove through Europe last year, including through several cities in Germany and encountered a lot of unrestricted autobahns. There are some areas where they gradually decrease the speed limit (often for roadworks) but I never came across any section for which the the speed limit was altered for, effectively, less than 8 seconds. As someone living in the UK, the missing presence of 40/50mph average speed regions for tens of miles was quite welcome.

[cm3]

There really aren't long stretches of unlimited road and frequent limit fluctuation is risky both from an accident and ticketing perspective. If you want to slow it down, keep it at 80km/h, but don't do a circus of jumping up/down.