One of the things I like best about normative signs is the variety of ways of saying the same thing. Look at this trio of signs, for example, posted at a hospital parking lot in Toronto:
All three of them embody the same message, the same request: “Slow Down.” But none of them actually says that.
The first is a pictogram, depicting speed bumps, effectively warning you that failure to slow down will do damage to your car. Buyer beware.
The second merely (?) describes the present neighbourhood as being of a certain kind. This is a “traffic calmed” (not “calmed traffic”?) neighbourhood. In other words, this is the sort of neighbourhood where a certain kind of behaviour — namely, driving calmly or slowly — is obviously appropriate.
And the third sign indicates that the speed limit (not legally binding, I think, because it’s private property and the sign is in yellow) is just 20 kilometres per hour.