What is a common feature of regulatory signs?

Regulatory signs play a crucial role in traffic management and safety as they are designed to inform drivers of the laws and regulations they must follow. Typically, this type of signage indicates specific actions that are required or prohibited, such as speed limits, stop signs, yield signs, and no parking zones. These clear instructions help to ensure that drivers understand their responsibilities on the road, promoting safe driving behavior and order on the highways.

While some regulatory signs might have specific shapes or colors to enhance visibility or communication (as suggested in other options), the defining characteristic of regulatory signs is their function in conveying enforced laws and regulations. This is why their primary purpose is to indicate mandatory actions or restrictions for drivers.