When flagging at night, which property ensures visibility to drivers?

• A. Fluorescent.
• B. Luminous non-retroreflective.
• C. Non-visible.
• D. Retroreflective.

Answer: (D)

Night visibility for flagging hinges on materials that send light back toward the driver. Retroreflective surfaces do exactly that: they reflect light back to its source, so when vehicle headlights shine on the flagger or signs, the light returns to the driver and the flagger becomes highly conspicuous. This makes retroreflective gear the most reliable way to be seen at night, regardless of the viewing angle.

Fluorescent materials can look bright in daylight, but they don’t reliably return headlights back to the driver, so visibility at night isn’t as strong. Non-visible obviously wouldn’t be seen at all. Luminous non-retroreflective surfaces might emit light, but without reflecting headlights back toward the driver, their visibility under actual vehicle illumination is poor.

So, the retroreflective property is the key to ensuring nighttime visibility for flagging.