'Botts Dots' Make a Friendly Bump in the Night

It’s a dark night, it’s drizzling and you’re approaching a foreboding curve with various looming undulations of landscape on both sides of the road. Your eyes focus on the brightly shining reflectors running along the centerline of the narrow highway. If the reflectors weren’t there to catch your headlight beams, if they weren’t evenly spaced to mark the coming route like stitches on the planet’s crust, you’d probably feel uneasy. Without them to point the way, you could find yourself hurtling off the dark asphalt.

Botts Dots, as these pavement reflectors are fondly called, have been the driver’s friend since the 1960s, first in California and now virtually everywhere.

Millions of Botts Dots are repeated on highways, city streets and parking garages across the U.S. They are named after their inventor, Elbert Dysart Botts, whose clever development passed into the public domain for everyone’s benefit.

Mr. Botts was born in rural Missouri in 1893. After obtaining a doctorate in chemistry from the University of Wisconsin in 1924, he accepted a teaching job at San Jose State University in California. There he remained for 16 years until the outbreak of World War II, when he went to work for the federal government as a chemist. In that capacity, he joined the California Department of Transportation — today known as Caltrans — in 1950.

Assigned to research and development, Mr. Botts took charge of developing a reflective paint that could withstand the wear and tear of road surfaces. The reflection had to be visible at night and in weather-obscured conditions. Caltrans came up with a durable paint to apply to road surfaces, but whenever a film of water covered the painted lines, as it often does, the reflective quality was diminished because of the light’s refraction by the water’s surface.

So Mr. Botts decided to develop markers that protruded from the coarse surface. The ceramic modules he produced, which he called RPMs for Reflective Pavement Markers, were an immediate success in terms of reflectivity under negative conditions, and they were later improved with the addition of glass reflectors.

However, getting the RPMs to stay put was a big problem. The early models were fastened to the roadway with spikes. Once the ceramic body broke loose, the spikes became tire hazards.

former student of Mr. Botts named Herb Rooney came up with the solution: an extremely tough epoxy that also was fast-drying. Epoxy resolved the problem of exchanging one road hazard for another, and tests continued through the 1950s.

Mr. Botts retired in 1960 and died two years later. He never saw the full-scale application of his invention. But his name lives on. The first highway to receive Botts Dots was Interstate 80 in Solano County, Calif., in 1966. Highway 99 near Fresno was next to be adorned with the three-dimensional markers.

As their use grew wider, highways became a little safer. An unintended benefit of having the reflectors protruding slightly from the road surface was that a vehicle’s tires audibly drum against them, warning drivers when they are drifting into the centerline or onto the shoulder.

For the full story, see the Dec. 28 print edition of Transport Topics. Subscribe today.