Raised pavement marker
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A raised pavement marker, also known as a Botts' dot, delineator, Stimsonite Markers, or simply a reflector, is a safety device used on roads in the United States, Australia as well as other countries.
Some countries are using Botts' dots to detect and cite speeders and others are using the devices to illuiminate roadways.
Stimsonite markers
Most regions of the United States use plastic devices with two angled edges facing the drivers with a corner reflector strip. They are placed in a small indentation in the pavement in areas where snow plowing is frequent. Later improvements have allowed for on surface snowplowable markers.
The devices can be seen from a great range and come in multiple colors including:
- White markers — for lane markings and the shoulder. These sometimes have a red strip on the opposite side to notify drivers of their incorrect direction of travel.
- Yellow markers — found on the left signifying the traffic direction change, or a median. They are also sometimes used on the shoulder.
- Blue markers — Usually used to mark the location of fire hydrants.
- Green markers — Usually used to indicate that emergency vehicles can open gates to enter a gated community.
- White and red — white for marking lane divisions in one direction, and red to indicate 'do not enter' in the other direction
- White and black — white for marking lane restrictions (such as an HOV diamond) in one direction on a roadway that has 'reversible' traffic flow, and black in the other direction when the markings don't apply
The design now used widely throughout the United States was invented by engineer Sidney A. Heenan in the course of his employment with the Stimsonite Corporation in Niles, Illinois. Heenan filed an application for a patent on October 23, 1964. Patent No. 3,332,327 was subsequently granted on July 25, 1967.
Stimsonite went on to become the leading manufacturer of raised pavement markers in the United States and was acquired in the mid-1990s by Avery Dennison Corporation. For about a decade, Avery sold Stimsonite's line under its Sun Country brand. In 2006, Avery sold its raised pavement marker division to Ennis Paint, one of the largest manufacturers in the world of paint for pavement markings (particularly lane markings). Ennis Paint (based in Ennis, Texas) now markets the Stimsonite product line (and descendants) under its Stimsonite brand. Another manufacturer of Stimsonite markers is 3M.
Cat's eye
Cat's eye (road) is a similar device invented in the United Kingdom and patented in the United States in 1939 [link].
Botts' dots
In many U.S. states Botts' dots are used to mark lanes on highways and many arterial roads and to create rumble strips across travel lanes. Botts' dots are named after Dr. Elbert Dysart Botts, a California Department of Transportation (Caltrans) engineer credited with overseeing the research that led to the development of the markers and the epoxy used to attach them to the road.
Botts' dots come in two varieties: rounded markers used for lane dividers; and square, colored, reflective markers used for other situations. Of the square markers, white markers are used (between clusters of the round markers) to indicate lane lines (often with red "wrong way" reflectors on the back side), yellow markers to separate traffic directions, and blue to locate fire hydrants. The round markers are made out of clay, plastic, or polyester, while the square markers are made out of plastic. The round dots are generally yellow or white in color.
Botts' dots are rarely used on freeways in regions where it snows because snow plows scrape them off.
Some roads have lanes only marked with Botts' dots eliminating the need to replain lane divider lines.
History
According to journalist Mark Stein, Caltrans records indicate that its personnel may have been speculating about 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[#endnote_stein]. Painted lines tended to become invisible during rain creating a saftey issue during rainy weather.
In September of 1966, the state Legislature mandated that Botts dots were to be used for lane markings for all state highways except in areas where it snowed in the winter[#endnote_stein].
Today, there are more than 25 million Botts dots in use in California[#endnote_haldane].
References
↑ Cave, Kathryn. "State lab in fast lane of high-tech road gadgets." The Orange County Register, 21 October 1991, sec. A, p. 1.
↑ Haldane, David. "Dots' Demise Denied." Los Angeles Times, 7 March 1997, sec. B, p. 1.
↑ Martin, Hugo. "Behind the Wheel: The Botts Dot's Future May Hit a Bump in the Road." Los Angeles Times, 23 October 2001, sec. B, p. 2.
↑ Richards, Gary. "It May Be End Of Road For Noisy Botts Dots." Contra Costa Times, 18 January 1997, sec. A, p. 3.
↑ Rubenstein, Steve. "Caltrans Plots To Erase Lots Of Botts Dots." San Francisco Chronicle, 18 January 1997, sec. A, p. 13.
↑ Stein, Mark A. "On the Button: The Quest to Perfect Botts' Dots Continues." Los Angeles Times, 11 August 1991, sec. A, p. 3.
External links
- [Caltrans Botts' Dots fact sheet]
- [Ennis Paint - the leading manufacturer of raised pavement markers]
- [Article on Botts dots to catch speeders]
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