Samenvatting
The permissive and prohibitive traffic symbols as proposed by the U.N. are described. The prohibitive is drawn inside a red circle with a red diagonal slash through the symbol. The permissive symbol is surround by a green ring. The purpose of the study described is to determine the extent to which the slash might obscure a symbol on the prohibitive signs. Results seem to indicate that the slash to indicate prohibition does interfere with perception of the symbol.