“This is a rectangular sign telling you to reduce speed now. There’s a number of reasons why that might be. It might be a temporary thing with road works, it might be a junction, it might mean that you’re coming to a roundabout or a bend of the road, anything significant in the distance and this is a warning for you to reduce speed now.
Actually, that’s a little bit dubious though isn’t it? If you’re doing 60 miles an hour on a country lane at the national speed limit, you might reduce speed to 59 miles an hour, but that’s not really what it means, is it?
It means you’ve got to check your speed and get down to the right speed and yes, that will involve reducing speed.”
