Why do school zone signs use that distinctive loud, bright, fluorescent yellow-green color

You are the driver. This means that you subscribe to the rules and regulations of the road – and are expected to follow them. That is, unless you want to risk paying fees, losing your license, and going to jail. But you know the screw it and go to jail option is useless, so you obey the speed limit, deliberately avoid colliding with other motorists, and keep an eye out for school buses, their flashing lights, retractable stop signs and, of course, their precious cargo.

However, it’s not just school buses – it’s school zones that warn you to slow down and pay attention. And what happens to all those school zones? A set of bright yellow-green school zone signs that might lead you to question whether you’re color-blind. Now, you might be thinking, “Oh, they’re a shade of alien spacecraft-signaling color because it’s more visible.” And, to some extent, you would be right. But the thing is, smart guy, there’s a lot more to it than glitter and visibility.

Believe it or not, the standardized school zone signage you probably see all the time hasn’t always existed on American roads. The rules for traffic control signage, set out in the Manual on Uniform Traffic Control Devices, were not published until 1935. This was 27 years after the paradigm-changing Ford Model T and its simple look began rolling off the line and electrifying the country. Nevertheless, a standard for school zone signage was not included in the MUTCD until its third edition in 1948. And those guidelines essentially called for school zone roads to be marked with a sign that said “SCHOOL” in black letters on a yellow background. Hardly ground breaking. Worse, those signs were not required to be reflected and were not required to be shown after the school year.

So, what about that specific color? Well, the shade we’re referring to here is fluorescent yellow-green (FYG), and it didn’t come out in big numbers until the 1990s. During the last decade of the millennium, injuries and deaths among pedestrians were increasing. To counter this trend, the Federal Highway Administration (FHWA) made its move and withdrew its reserved-yet-undetermined FYG. In 1993, the FHWA conducted a study to determine how effective fluorescent paint was in reducing incidents. Two years later, the organization concluded that signage in FYG had significantly reduced the incidence of pedestrians being struck by vehicles.

OK, so why FYG specifically? There are a lot of bright, noticeable colors out there, right? Why not red or pink? After all, red is the shade of choice for both stop signs and stop lights. or orange? Orange is one of the colors chosen for those high-visibility marker balls on power lines, along with brighter shades of aviation yellow and white intended to contrast with terrain and background and to alert pilots. Regarding red stop signs, early iterations were not noticeable enough in low-light conditions such as night. In some areas of the US, add-on lights and glass buttons are used to reflect oncoming headlamps and boost visibility. Frankly, the glass bead stop sign looks like some pretty garage art. But, by 1954, stop sign manufacturers could rely on fade-resistant porcelain enamel.

FYG, on the other hand, got a chance to prove itself against other colors in the 1990s. And after testing by 57 jurisdictions, the highlighter-esque yellow-green color was found to reduce vehicle-vs-pedestrian incidents. In the 1990s, FHWA conducted a study with the National Park Service to test the effectiveness of fluorescent yellow-green paint. This proved to make the signals more visible from greater distances than yellow signals.

According to the 2009 edition of the MUTCD, the eye-catching FYG is the required color for school warning signs, including supplemental signs such as school zone speed limit signs and bus offloading signage. This also makes sense. Despite slight deviations, American road signs use the same font, size, and style wherever possible to make things easier for the oncoming driver.