Which of the following is NOT one of the five basic requirements for traffic control devices?

The requirement for traffic control devices to be visually attractive is not considered one of the five basic requirements. The primary focus for traffic control devices is their functionality and effectiveness in managing traffic safely and efficiently. They must fulfill a specific need to address traffic conditions, convey clear and simple meanings so that drivers can easily understand them, and provide adequate time for drivers to react to the information being presented. While visual appeal may enhance the overall design, it does not constitute a fundamental requirement for traffic control devices, which should prioritize clarity, visibility under various conditions, and effective communication of important information to ensure safety in work zones.