Sign Shapes- an in-depth look at the differences and what they mean.

Traffic signs appear in many shapes, like octagons and pentagons, diamonds and trapezoids. Uniformity seems to be sacrificed in favor of a mix-and-match system – and that’s because each shape sends a different signal to the brain. When we see signs of different shapes, our brains notice a pattern and the message conveyed is easily recognized. Shapes with smooth curves, for instance, like circles and ovals, suggest a friendlier message than do the jagged edges and sharp points of the octagon and the diamond.

The Department of Transportation is accordingly very particular about the individual and varying shapes for each street sign. The DOT’s Manual on Uniform Traffic Control Devices actually defines the symbology of shapes. For example, the octagon is a sort of cross-breed between a square and circle, suggesting both power and complexity. Similarly, it is no surprise that the MUTCD mandates that the STOP Sign, arguably the most important traffic sign, is not only an octagon, but also blood-red. The bold combination of the two immediately alerts the brain to something dangerous enough to warrant a STOP.

Similarly, the points on triangular or diamond-shaped signs are, as mandated by the MUTCD, used to indicate warning and danger, and reflect instability and conflict. These signs are usually bright yellow or red, for visibility and to underscore the strident nature of the shape.

Meanwhile, circle and ovals lack jagged points; these shapes are soft on the eyes and are used in community crime watch signs and the like. With no end or beginning, they classically signify wholeness, security, and comfort. It is no wonder, then, that circular signs indicate community and security, while the slightly square circles (meaning, ovals) are generally used for friendly, polite notices.

Rectangles and squares are simple shapes with right angles, embodying order, familiarity, and security. The traditional shape also allows for flexibility: while the MUTCD designates these shapes for all kinds of regulatory and guide signs.

Different shapes impact our brains uniquely. Perhaps unconsciously, human brains perceive the depth and forms of shapes in strange ways. Each shape imparts a different feeling and communicates a different message. By aligning these perceptions with traffic and safety signs, people are better able to comprehend the sign’s message from the shape alone. By recognizing these patterns, people can become subconsciously more aware of how to interact with their surroundings, and gain an innate understanding of traffic flow on the road.

Shape	Indication	Emotion Elicited	Common Signs
Octagon	Stop	Fear	Stop Sign
Diamonds, Triangles	Warning, Hazard	Caution	Yield Sign, Voltage Sign, Warning Sign
Oval, Circles	Welcome	Comfort, respect	Welcome Sign , Community Sign
Squares, Rectangles	Miscellaneous	Familiarity	Parking signs, Direction Signs, Notice Signs