Glow On
High-Visibility Work Zone Safety Apparel


Why do road workers wear fluorescent safety gear?

You may have seen road and construction workers dressed in fluorescent (often referred to as “high-visibility” or “hi-vis”) safety gear such as hard hats and vests. You probably know that these bright colors help flaggers and other road workers stand out in situations where their safety is at risk. But do you know why hi-vis colors seem to glow the way they do?

I spy with my little eye…

Our eyes respond best to bright colors, but fluorescent colors are particularly visible, even in dim or low light. Normally, human eyes can only detect colors whose wavelengths fall within the visible light spectrum. But fluorescent colors contain special pigments that absorb and reflect invisible ultraviolet (UV) light, making them appear unusually bright, or even as though they “glow,” when an ultraviolet light source (like sunlight) is present.

Not found in nature

Fluorescent pigments were first developed in the 1930s by a pair of California brothers, Bob and Joe Switzer, who went on to found DayGlo Color Corporation. Bob, a pre-med student at the University of California and Joe, an aspiring entertainer, were experimenting with effects for a magic act when they accidentally discovered certain chemical substances “glow” when viewed under a black light. Further experimentation led to the development of pigments that appeared to glow during daylight.

Although the colors were originally used in marketing, their potential for use in safety applications was quickly recognized.

So why is this important?

Fluorescent safety gear literally makes workers more visible, especially in low-light hours such as dawn or dusk. The eye-popping colors are used for objects found around worksites and safety garments to draw motorists’ attention to potential hazards, upcoming changes in the traffic pattern, and the presence of workers. (Hi-vis colors won’t appear any brighter in situations where UV light isn’t present, though, which is why gear worn at night must also include retroreflective elements.)

The American National Standards Institute (ANSI) created the ANSI class system to provide guidelines for high visibility safety apparel worn on the job. These garments must contain a minimum amount of fluorescent material. Fluorescent yellow-green, fluorescent orange-red, and fluorescent red are all ANSI-approved colors.

You may notice that fluorescent pink is not on this list—ANSI has determined that fluorescent pink, though bright, doesn’t provide enough of a contrast to be considered a hi-vis color.