What is the primary characteristic that determines the meaning of a highway sign?

The primary characteristic that determines the meaning of a highway sign is its shape. Highway signs are designed with specific shapes to convey important information quickly and effectively to drivers. For example, an octagonal shape signifies a stop sign, while a triangular shape typically alerts drivers to slow down and yield to oncoming traffic.

Using shape allows for immediate recognition, ensuring that even at a distance or at high speeds, drivers can identify the sign's purpose without needing to read text. This visual cue is especially critical in promoting road safety and facilitating smooth traffic flow.

While color, size, and pattern are also important elements of highway signs, they serve more as secondary features that enhance the recognition and messaging established by the sign's shape. For instance, the use of specific colors can provide additional context—such as red for stop or green for go—but it's the shape that fundamentally conveys the core meaning of the sign.