Botts' dots are raised markers used along roadways all over the United States, and especially in California. They were developed by Dr. Elbert Dysart Botts, an engineer who was employed by the California Department of Transportation (CalTrans) in the middle of the twentieth century. Botts refined the design of the markers as well as the epoxy used to attach them, and in 1966 they became standardized markers on highways all over California.
The design may be round or square, depending on how Botts' dots are being used, and they may be white, yellow, blue, or red. The markers are used instead of or in addition to painted lines in the road. Reflective dots are easier to see at night than painted lines, which can become obscured by heavy rain, fog, or mud. In addition, the raised pavement markers are used in so-called “rumble strips,” to alert motorists to the fact that they are drifting out of their lane or off the road.
White Botts' dots are used as lane dividers, delineating different lanes on freeways or the edge of the road. The yellow versions indicate a roadway split, typically between two way traffic, while red markers indicate that a motorist is going the wrong way. Blue Botts' dots are used on roadways around fire hydrants. The pavement markers may be reflective or not, with non-reflective dots being interspersed with reflective versions for better visibility.
The need for some kind of raised highway marker was recognized as early at the 1930s, and several different versions were developed. Botts' invention was unique for several reasons. The first was the materials used, as previous highway markers tended to fade and degrade quickly. Botts also developed a strong epoxy to attach the markers to the road, a safe alternative to nails, which were used to attach other types of lane markers previously.
Over time, the epoxy will ultimately wear away, and cars will dislodge Botts' dots from the road. Some people have raised concerns about the safety of Botts' dots as a result, since they can be thrown at very high velocity into passing traffic. CalTrans has responded to this concern by researching the safety of Botts' dots and potential alternatives, but the organization seems satisfied with Botts' dots, and tells motorists that “they'll be with us for a long time.”
In areas with heavy snow, these dots are not typically used, because they would be dislodged by snow plows. If they are installed, they will be placed into divots in the road, ensuring that the top of the marker is level with the roadbed so that it will not interfere with snow plows.