Admittedly, 160 was exaggerated. But on stretches where there's no speed limit and you suddenly get this 80 km/h along with Stau signs, people tend to still drive 120 if there's no visible congestion. Since those dynamic limits are not really enforced (most speed cameras tend to be in places where there's a fixed limit at all times) there's rarely a downside to drivers. Same as with driving 80 in construction sites instead of the 60 that's signed.

This is starting to change now that the polizei have started leaving mobile panzerblitzers in place for several days at a time. I've noticed in the last few months significantly more respect for changes in speed limits from the folks with local license plates.