The speed thing: there are people who are incapable at any speed, and there are cars & drivers who are capable at well over the posted limit.

The Germans have it figured out better than anyone, but also have a culture & requirements to make their deal work as well as it does.

Anyone driving through Spokane Valley on I-90: the cops use unmarked, non-typical-LEO vehicles, with hidden lights.
For a few miles, Limit drops to 60, although the freeway should still be 70; natural 95th-percentile flow is usually 70, too.
To me, that's not only "cheating", but if something doesn't present itself as law enforcement, it may not seem - or be - legit to other drivers.
There was a problem a while back where some bad guys were posing externally as LEO to get up to the cars who'd pull over.