Well, it really depends - safety is highly compromised when you are driving at such speeds, due to reduced reaction time and other possible imbecilic drivers on the roads who might not be as attentive as they should be. (Well, it's really not a racing track, and it is indeed a public thoroughfare, shared by young/old/incompetents alike...)

I once was upgraded by Sixt at HAM some years ago to an awesome A6 turbo quattro Avant, where I reached 300 kmph (as per the speedometer - not sure if calibrated) at times (slightly downhill on this section back to HAM), but did not feel very safe going that fast, and continued at 270-280 kmph.

Only a double-lane on this stretch, at daybreak, only a few cars on the road, but *very* dangerous - as you never know if the car in the slow lane might simply pull out in front of you, with no shoulder to go to/space to react - you are basically dead meat if something should happen.

It was definitely a thrill, but my cautious side came into play and I had to tone it down, despite being slightly late for my flight!