I had never seen or heard that these signs exist and so it was quite a laugh when I read about them this week.
Trying to find more information on these is not easy because you end up with pages from funny signs web sites ;-)
From what I see they exist in Romania, Thailand, South Africa.
This was funny 'Officials of 'Pecica', a village located in the country's west about 13 miles from the Hungarian border, have had enough of drivers running over drunken citizens minding their own business late at night in the middle of the street, struggling to cross or simply having a well justified nap. So 10 bright red signs reading "Drunk Citizens" have been ordered and manufactured in an attempt to save some lives.'
Original Article: http://www.taalblad.be