Note: police officer example is based on Belgian traffic laws, only three signs allowed:
(article 4.2 of the Belgian traffic code, translated by deepl:
4.2. In particular, orders are considered to be :
1° the arm raised straight up, which means stopping for all road users, except for those who are at an intersection and who must clear it;
2° the arm or arms outstretched horizontally, which means stopping for road users approaching from directions indicated by the arm or arms;
3° waving a red light transversely, which means stopping for the drivers to whom the light is directed;)
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So yeah, in theory road rules are trainable IMO.
In practice we will see challenges, I agree, but I think they can be overcome. (but it will take many years)