What is a requirement for any sign used at night?

For any sign used at night, it is essential that it must be fully reflectorized or illuminated. This requirement ensures that signs remain visible and legible to drivers during nighttime conditions or low-light situations. The purpose of reflectorization is to enhance the sign’s visibility by reflecting light from vehicle headlights, making it easier for drivers to see and react to the information displayed on the sign.

Illuminated signs additionally aid in visibility without relying solely on the external light provided by vehicle headlights. Proper visibility is critical in work zone safety since it helps prevent accidents and informs drivers of potential hazards, detours, or instructions that are crucial for safe navigation through work areas.

While brightly colored signs can aid in visibility, and larger sizes can improve readability, these factors are secondary to the necessity for signs to either have reflective properties or be illuminated at night.