> Which geometric shape is commonly used for stop signs?And the answer: octagon.Photo credit: public domain.While the earliest stop signs were square-shaped,they've had the eight sides of an octagon since at least 1954. The unique shapehelps drivers coming from the other direction, as well as those driving atnight, to easily recognize the sign."Motor City," as Detroit, Michigan, would come to be known, was home to the veryfirst stop sign. In the early 1900s, the design for the stop sign was verybasic: a simple white square with "STOP" in black lettering. As the 20th century progressed, however, the public appetite for the automobilegrew insatiably. Coupled with a steep rise in the number of roadway constructionprojects, the need to establish a set of uniformed roadway signage standardsbecame paramount. Throughout the century, the design changed several times. Before its trademarkred coloring, the stop sign was several variations of yellow and white. Finally,in 1954, it evolved into the design with which we're all familiar. This standardoctagonal shape and red coloring has made its way around the world as a commonroadside marker, finding its way from Egypt to France to Iran. In fact, stopsign usage became regulated at the UN Vienna Convention on Stop Signs during theCold War (yes, we promise it's a real thing).