Yield sign
History
A black triangle (within the standard down-arrow-shape of stop signs) was a symbol of "stop for all vehicles" from about 1925 in Germany. The triangular yield sign was used as early as 1938 when it was codified in Czechoslovakia in a blue-white variant without words and in 1939 in the Protectorate of Bohemia and Moravia which adopted the current red-white variant.
Yield sign-3