Know when to glow!

You may have seen road and construction workers dressed in hard hats, vests, or other apparel in fluorescent colors, with strips of shiny reflective banding. This apparel is often referred to as “high-visibility” or “hi-vis.” 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 clothing seems to glow?

I spy with my little eye…

Our eyes respond best to bright colors, but fluorescent colors are particularly visible, because they contain special pigments that absorb and reflect invisible ultraviolet (UV) light. This makes them appear unusually bright, as though they were “glowing,” when an ultraviolet light source (like sunlight) is present.

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.

Reflecting on safety

Fluorescent safety gear literally makes workers more visible, especially in low-light hours such as dawn or dusk. These 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 shiny strips made from what is called “retroreflective” material.

When light shines on most objects, it bounces and disperses in various directions. The amount of light reflected back to our eyes is what we see. Retroreflective banding contains tiny crystalline beads that reflect light directly back toward its source – so when a light is shined on a vi-vis vest that contains this material, it appears very bright, almost glowing.

ANSI standards

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. Depending on what job you do, you may be required to wear a certain class of ANSI-approved clothing.

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.

Hi-vis is for everyone

Even if you’re not working on the roadway, it’s a really good idea to wear hi-vis apparel if you’re out walking or biking, especially in low light conditions. Each year, cyclists and pedestrians are killed by motor vehicles. In addition to biking and walking defensively, increasing your visibility means you’re less likely to be overlooked by a distracted driver.

So get that hi-vis gear… and GLOW ON!