The Endangered Species of Road Signs

Brennan Edwards

October 27, 2022 | 10:04 PM

Everyone knows them. The big green signs that hang above the lanes when driving on the freeway. They’re an unforgettable, indispensable part of American highway infrastructure, not to mention one of the most well known features of it. Many people just know them and move on with their lives. They see it, read it, and then disregard it in favor of their GPS directions. But, If you’re anything like me, relying almost solely on these for navigation (which, by the way, is possible, even though not a lot of people do this), you may have noticed, on a road trip, drive to the store, or even your daily commute, that maybe one or two of the signs on the freeway look different, and if you live in the city of Los Angeles, a lot of them do. Some of them may appear to be a darker green, or may appear to have little rhinestone-like imprints in the white legend.

So, why the inconsistency? The answer to that question is simple: the signs containing rhinestone-like reflectors (called “Button Copy” signs) in the legend are older and the DOT forgot to replace them in that area. How did we get here, though? Why didn’t we use the super shiny ones to begin with if they work so well today?

Where did all of these different versions come from?

So dive with me here as we talk about the sign technology of the 50’s forward! It all started in California, where just as the rest of the country was beginning to build their freeways, California already had many miles of freeway that needed to be signed, as we did not have the navigational tools we have today. California was way ahead in the 50's! Because at this time there were no standards on how to make the signs, California used black signs with white legend. This was done to increase visibility, and it worked well. However, studies were done on what color is most optimal for a background, and green was chosen as the federal standard in the 1960's. ADOT still holds by this standard, claiming that while the color is not only less surprising, it also stands out and the contrast is perfect.

White on Green, when put up against all the others, and eventually the at-the-time standardized White on Black, was found to be more visible at night than any of the others tested. So, the old white and black signs were eventually ordered to be replaced with white on green by a federal mandate. So, California hung up the new ones and illuminated them with uplights. However, one light may not be too bad. But when you have potentially several per sign, on thousands of sign bridges across the state, things get expensive fast. But, on their own, these signs could not be seen at night with a vehicle’s headlight alone. Eventually, a solution was found: Place small retroreflective dots in the legend so that when the light from a vehicle’s headlamp hits the sign, the dots glow in the direction of the driver so that the sign can be seen at night.

Many created in the mid 1970’s, these button copies lasted for several decades. Some of the ones that still stand today are over 50 years old. However, around 20 years ago, new technology was invented to integrate the retroreflectivity previously found in the buttons into the sheeting they use on the sign panels today. This makes the entire sign super reflective at night, often being able to reflect the entire sign back rather than just the legend. This makes the entire sign super reflective at night, often being able to reflect the whole thing back rather than just the legend. It has even found its way onto smaller signs such as stop signs, varieties of yellow warning signs, and much more. It often works without external lighting, such as the lights used on the old painted signs, too.

These signs in north Carolina are so powerful that they reflect during the day. | I-77, Charlotte, North Carolina

California is the dream of these people - they’re still holding onto their old button copies because, especially in the older generation, they made them with porcelain enamel (a reinforced glass-like substance used as a substitute for metal) because they would supposedly last (at time of fabrication) at least 60 years and they’re going to get the whole lifetime out of them. In other states, though, there are small populations of people here and there who go and try to find the ones remaining.

So, why is this important? At the end of the day, the signs will always be there in some form, and will always improve to give better guidance information on every iteration, so why does it matter? As I said before, everywhere somewhere there is someone who finds value in these old relics. I consider myself to be one of these people. I’ve found that knowing the history behind the older signs has given me an appreciation for the amount of detail that goes into road and freeway design, and a realization that it’s an incredibly complex combination of mathematics and civil engineering. I think it’s sad that people don’t realize the sheer amount of work that goes into planning and designing a freeway when they get into their car for the morning commute. Just through signs alone, the differences in technologies are huge and I think that seeing that gives us a more appreciative lens for the world we live in, not only for the future, but for the past as well.

Why am I qualified to talk about this?

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