WHY?

About six weeks after they "darned the worst holes" these signs appeared.

We are, here, just about at the geographic centre of a Housing Estate, all of which is a designated 20 m.p.h. zone with some rather "outstanding" sleeping policemen; in a town, the centre of which is, well guess?

I couldn't clearly see any other patches in camera range; and one of them is on the footpath, hence the marking(s).