Obviously a static sign is not aware of your current state, so it's message can only be interpreted as relevant to your likely state... i.e. the posted speed limit.

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recursive 10 hours ago | parent [-]

If you should slow down relative to the posted speed limit why not change the speed limit to reflect that directly?

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estearum 8 hours ago | parent [-]

Usually the reason is the "slow down" portion is very small, and it's confusing to shift down the actual speed limit for a 200 foot stretch of road then increase it again.

	▲	Dylan16807 6 hours ago \| parent \| next [-]
		There are signs for that. Advisory speeds that don't change the actual limit. https://wisconsindot.gov/PublishingImages/doing-bus/local-go... Much better to be specific than a vague "slow down". There's a road near me with two tight turns a couple blocks apart. One advises 25mph and the other advises 10mph.
	▲	recursive 7 hours ago \| parent \| prev \| next [-]
		FWIW, it seems less confusing to me than longer speed limits, but with "Slow Down".
	▲	alistairSH 7 hours ago \| parent \| prev [-]
		Except we do that all the time in school zones... normally 35+, but from 7am-9am and again from 2pm-4pm the limit drops to 25mph (which is still to fast if the kids are actually crossing the street or walking alongside en masse).