You may not be familiar with Dr. Elbert Dysart Botts, but if you have driven in California, Nevada, Texas or other areas with little or no snowfall, you have probably encountered one of his inventions. He may have even saved your life or prevented grievous injury.
Dr. Botts was working at the California Department of Transportation on research to improve the visibility of highway lane markings, particularly in the rain when traditional painted markings were hard to see. After experimenting with numerous types of paints, in 1954 he hit upon a new solution: a truncated hemispherical raised lane marker. He found that this type of marker was visible from more than 100 meters, even in the rain.
Unfortunately, securing these new markers to various types of road surfaces proved a daunting tribological challenge. At first his team experimented with drilling a hole through the top of the dome and securing the marker with metal spikes. While this worked well initially, the markers could break or work loose, resulting in a sharp metal protrusion in the road that would damage tires. It took Botts and his team until around 1960 to develop a viable solution, a quick-setting epoxy adhesive that would hold the marker to the roadway. Testing indicated that the new adhesive could hold the markers in place for up to 10 years. They were, however, susceptible to damage by snowplows, limiting their use to warmer areas.
Sadly Dr. Botts passed away in 1962, four years before California mandated his invention be used for all Los Angeles freeways. It is estimated that hundreds of millions of these raised lane markers are now in use worldwide. While properly named hemispherical raised pavement markers, they are much more commonly known as Botts’ Dots.
As often happens with truly great inventions, Botts’ Dots had an unexpected benefit. In addition to making lane divisions more visible, a motorist who departs from a lane receives immediate auditory and tactile feedback from the tires encountering the dots, often resulting in the driver returning to the designated lane. As a result, many highways have Botts’ Dots not just between lanes but also along the edge of the pavement, potentially saving the lives of drivers who have become distracted or sleepy by alerting them before they drive completely off the road!
What started in California also may have begun to end there. The California Department of Transportation has decided to begin phasing out Botts’ Dots. Newer types of raised pavement markings are proving to be easier to see, especially for autonomous (self-driving) vehicles.