In my experience driving (in the US), I don't think I've ever seen an attentive driver going consistently 5-10% above the speed limit as a prime safety issue.

In my experience driving (in the US), I don't think I've ever seen an attentive driver going consistently 5-10% above the speed limit as a prime safety issue. Far more often the issues I see are (1) distracted drivers (e.g. on their phone) or (2) aloof/aggressive drivers (e.g. abrupt lane changes, tailing cars, switching lanes without checking blind spots, blatant speeding, driving significantly slower than surrounding traffic, etc). I do think a warning system for exceeding the speed limit can make sense, but it needs to have the right threshold and mitigations to avoid being ignored, a distraction, or (worse yet) putting the driver in a more dangerous situation. The right threshold is clearly not at 1km/h above the speed limit. I think a more reasonable one would be 10mph/15km/h over the posted limit. EDIT: I'll add that I think a looser threshold would still hit the low hanging fruit of egregious speeders, but without burning public goodwill towards car safety features. Let the features demonstrate value first, then discuss whether the thresholds should be tighter.