This road-sign always puzzled me when I was little. I couldn't understand why they would actually put up a sign to tell us about these "concealed driveways". I mean, surely they'd been concealed for a reason? Wouldn't their owners be a bit annoyed that someone was going around putting up signs alerting everyone to their existence, when they'd tried so hard to hide them? (I've always been a rather literal thinker.)
These signs still baffle me a bit, to be honest, although for a slightly different reason. I presume their purpose is to warn us that people might unexpectedly be turning out of these concealed driveways - but surely it's the responsibility of the motorist doing the turning to make sure that the road is clear before they pull out into it?