The traffic jam seemed unending. Kate and Ed were traveling home from an early dinner and the road leading to their home was so congested with other cars that they barely seemed to move at all. Eventually, Kate spotted the problem up ahead – the left lane was closed for roadwork, meaning all cars had to shift into one lane. When the pair finally passed the delay, Ed observed that the workers were repainting the yellow and white lines on the road. “That’s great…” Ed said in a sarcastic tone. “There was nothing wrong with the old lines. Why couldn’t they paint the new lines in the middle of the night when fewer people are using the road?”

The chemistry of traffic paint is intended to create stronger paint for outdoor exposure.
Image courtesy of Ennis Flint.

The work that goes into preparing the highways and byways of this country is substantial and often complicated. From planning and clearing the right-of-way to bringing in road base and pouring concrete, the construction of streets and roads from coast to coast is quite an undertaking. Once construction is complete, the real work of keeping travelers safe begins. Aside from traffic signals and speed enforcement, the most important ongoing aspect of road maintenance and management comes in the form of painting lines and arrows to guide drivers safely to their destination. Most often, these markings can last for years despite ongoing exposure to dirt, rain, heat, and sunlight. So what is it that makes road paint so durable and strong? What goes into the actual paint process to ensure the paint lasts a long time and reliably directs drivers safely along the way?

Traffic paint is usually acrylic in base, but the most important difference between traffic paint and other exterior paint is that traffic paint includes an often-scarce chemical compound called methyl methacrylate. Methyl methacrylate is used as a hardening cement for everything from PVC pipe construction to human joint replacement. This compound gives traffic paint exceptional strength and adhesion so the paint can withstand everything from tires driving over it to high temperatures, and from sunlight to rain, snow, and dirt. A surprisingly small number of companies manufacture methyl methacrylate, which means that any interruption in production of this compound creates a further disruption down the line as a lack of traffic paint means new roads can’t be completed.

After the base acrylic is manufactured, reflective flakes or beads are added to make the paint more visible at night. When the paint is shipped to the paint companies and crews responsible for painting the roads, application is surprisingly efficient, but also time-consuming. A single gallon of paint can paint 16 standard stripes in a parking lot and a mere 16 gallons are needed to paint a one mile long, four inch wide stripe on a road. Furthermore, most traffic paints will dry completely within an hour. The time-consuming part of application actually has little to do with the paint itself, but rather the road surface to be painted. Traffic paint should not be applied until the road surface or substrate’s final layer has set up for at least a month. The extra strong adhesion of traffic paint means that the paint can contract upon the surface and pull the asphalt or concrete apart if it’s not properly cured when the paint is applied. Herein lies the secret to traffic paint: extra strength of adhesion prevents harsh elements and wear and tear from separating the paint from the asphalt or concrete. In fact, rainwater even serves to keep the paint clean enough to be effective.

The next time you see a road crew refreshing the paint on a road or adding new road signage, remember the steps taken to make the completed paint job a reality. From the chemist in the paint lab to the professional painters applying the coating after waiting weeks for the surface to be readied, the paint industry plays a vital role in the safety and maintenance of our roadways. Any product that can withstand such harsh elements for such a long time is clearly built to last! Click here to learn more about paint chemistry and how special types of paint can create some unusual paint results!