Raised pavement marker
From Wikipedia, the free encyclopedia
A raised pavement marker, also known individually as a Botts' dot, delineator, Stimsonite Markers, or simply a reflector, is a safety device used on roads in the United States and Canada, as well as Australia and other countries.
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[edit] Stimsonite markers or reflector
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. In areas with little snowfall, Stimsonite markers are applied directly to the road surface rather than being imbeded into the surface.
The device's reflective surface allows the device to be clearly visible at increased distances at night and in rainy weather. The devices come in multiple colors including:
- White markers — for lane markings. These sometimes have a red strip on the opposite side to notify drivers of an incorrect direction of travel.
- Yellow or amber markers — found on the left signifying the traffic direction change, or a median. They are also used on the right side to indicate the beginning of 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.
Colors can also be combined, with a different color facing each direction:
- 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 current trend for lane markings is to intersperse retroreflective paint lines with reflectors as seen on the majority of American highways.
[edit] History
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 the Stimsonite brand. There are other manufacturers of Stimsonite markers.
[edit] Cat's eye
Cat's eye is a more sophisticated self-cleaning device invented in 1933 in the United Kingdom and used in their millions to the current day. Patents were taken out in 1934, manufacture began in 1935 and it became very popular in the blackouts of WWII, 1939-1945. It is patented all over the world, including in the United States in 1939.
[edit] 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 are round markers, most commonly white but also often yellow, and rarely found in black or other colors. They are made of ceramic, polyester, or another plastic.
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 repaint lane divider lines.
Some countries are using devices that look like Botts' dots to detect and cite speeders and others are using the devices to illuminate roadways.
[edit] 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. Painted lines tended to become invisible during rain creating a safety 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.
Today, there are more than 25 million Botts' dots in use in California.
[edit] Delineator
Delineators are tall pylons (similar to traffic cones or bollards) mounted on the road surface, or along the edge of a road, and are used to define lanes while discouraging exiting a lane. They usually contain one or more reflective strips. They can be round and open in the center or curved (45 degree sections) of plastic with a reflective strip. They are also used in low reflective makers usually a 'T' shape. They can also be used to indicate lane closures as in cases where the number of lanes is reduced.
Delineator manufacturer web site, with pictures.
While not a pavement marker, delineator is the name used for reflective devices attached to other objects.
[edit] 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.
