1993 Buick Regal Owner's Manual - Page 133

Shape of Road Signs The shape of the sign will tell you something, too. An OCTAGONAL (eight-sided) sign means STOP. It is always red with white letters. A TRIANGLE, pointed downward, indicates YIELD. It assigns the right-of-way to traffic on certain approaches to an intersection. ST0 P I ' I . \ F b A DIAMOND-shaped sign is a warning of something ahead - for example, a curve, steep hill, soft shoulder, or a narrow bridge. I PASSING 4 0 A TRIANGULAR sign also is used on two-lane roads to indicate aNO PASSING ZONE. This sign will be on the left side of the roadway. 121