page_title: Botts' dots
section_title: History
hierarchical_section_title: Botts' dots / History
caption_attribution_description: English: Northbound traffic on Farm Hill Boulevard in Redwood City. Note the use of round nonreflective raised pavement markers (Botts' dots) for dividing lanes going in the same direction (the white dots) and lanes going in the opposite direction (the double line of yellow dots). Note also that Stimsonite reflective raised pavement markers (appearing orange in the photo) are placed in the lines of yellow Botts' dots at regular intervals. This makes the lines more visible at night, while costing less than if the lines were formed entirely of Stimsonite markers.
context_page_description: Botts' dots are round non-reflective raised pavement markers. In many parts of the US and other countries, Botts' dots are used, along with reflective raised pavement markers, to mark lanes on highways and arterial roads. They provide tactile and auditory feedback to drivers when moving across designated travel lanes, and are analogous to rumble strips.
  Botts' dots are named after Elbert Dysart Botts, a California Department of Transportation engineer credited with overseeing the research that led to the development of the markers.
  Botts' dots are most commonly white but may be yellow when used to substitute for the yellow lines that divide opposing directions of traffic in North America. The dots are made of various ceramic materials or plastics such as polyester.
  On some roads, lanes are marked only with a mix of Botts' dots and conventional reflective markers, eliminating the need to repaint lane divider lines. Botts' dots are rarely used in regions with substantial snowfall, because snow plows damage or dislodge them.
context_section_description: Caltrans engineers may have studied the concept of raised pavement markers as early as 1936.  However, the department did not commence research in earnest until 1953, when the postwar economic boom resulted in an alarming increase in the number of cars and car accidents in California.  Painted lines tended to become invisible during rain.
  The initial dots were made of glass and were attached to the road by nails or tacks, as suggested by Botts. The nails were soon abandoned: his team discovered that when the dots popped loose under stress, the nails punctured tires.  Contrary to a common myth, the published record does not make clear whether Botts invented the famous epoxy that solved the problem; some sources indicate that one of his protégés was responsible for the epoxy. In September 1966, the California State Legislature mandated that Botts' dots be used for lane markings for all state highways in all non-snowfall areas.
caption: Botts' dots replace the painted median stripes. Reflective Stimsonite (darker orange) markers are spaced at regular intervals for increased visibility at night.
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