Which of the following shapes is NOT a regulatory sign?

Regulatory signs are designed to inform drivers of the laws and regulations that must be followed on the road. These signs typically have specific shapes associated with particular meanings.

In the context of the shapes mentioned, round signs are often used for speed limits and other important regulations; inverted triangles indicate yield; octagonal signs are universally recognized as stop signs. Each of these shapes has a clear, established purpose in communicating important traffic rules.

On the other hand, square signs are primarily used for guide signs and informational purposes, not regulatory ones. They provide information about directions, distance, or other general guidance rather than enforceable rules of the road. This distinction is crucial for understanding traffic sign categorization and contributes to maintaining safety on the road by effectively communicating the necessary instructions to drivers.