Originally Posted by Fruit'n'nut

This is going to sound like teaching people to suck eggs, but IMO if you come round a bend and are going too fast to slow down for a change in speed limit, then you're also going too fast to stop in an emergency.

Other cues act as warnings for speed limit changes, or the possibility that something will be in your path; for example in that ^ picture the speed limit sign may normally be obscured but there's the junction warning sign (a junction on or just after a bend) and there are rooftops visible over the hedges in the near-distance. The location sign looks as though it's brown, usually associated with "attractions." Those are three warning signs that you should perhaps slow down in case of dawdling or turning traffic, and should also expect a change in speed limit.