What shape primarily indicates mandatory signs that require obedience?

Round signs are primarily used to indicate mandatory signs that require obedience. These signs typically convey important regulations or commands that drivers must follow, such as speed limits or instructions to yield. The shape is distinctive and universally recognized, which helps ensure that drivers can quickly and easily understand the message conveyed without confusion.

The circular design is effective in drawing attention and often carries a sense of urgency, reminding drivers that they must adhere to the rule indicated on the sign. This characteristic makes round signs an essential part of road safety regulations.

In contrast, the other shapes serve different purposes. Triangular signs are generally used for warning purposes, alerting drivers to potential hazards ahead. Square and rectangular signs are often employed for informational or regulatory messages, such as directional signs or service signs, rather than mandatory commands. Understanding the specific functions of these shapes is vital for safe driving and compliance with road rules.