What colors are most commonly used for regulatory signs?

Regulatory signs are crucial for maintaining safe traffic flow and providing direction to drivers. These signs are designed to inform road users of specific laws, regulations, and prohibitions that must be followed. The colors most commonly associated with regulatory signs are white, black, and red.

White serves as the background for most regulatory signs, providing clear visibility and contrast against black text or symbols. Red indicates prohibitive actions such as "Stop" or "Do Not Enter," making it critical for conveying important restrictions. The combination of these colors helps ensure that the signs are easily recognized and understood by drivers, which is essential for safety on the road.

The other color combinations provided do not align with the standard color scheme used for regulatory signs. For example, yellow is typically used for warning signs rather than for regulatory purposes. Therefore, the selection of white, black, and red is consistent with the established standards in traffic operations and safety.