Raised pavement marker
From Wikipedia, the free encyclopedia
A raised pavement marker is a safety device used on roads. These devices are usually made with plastic, ceramic, or occasionally metal, and come in a variety of shapes and colours. Many varieties include a lens or sheeting that enhance their visibility by reflecting automotive headlights. Some other names for raised pavement markers include: Botts' dots, delineators, cat's eyes or simply reflectors.
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[edit] Reflective Raised Pavement Markers
Common in the United States, Canada, as well as Australia these plastic devices with two angled edges facing 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 snowplowable markers to be placed directly on the surface without any embedding. In areas with little snowfall, reflective raised pavement markers are applied directly to the road surface rather than being embedded into the surface.
The device's reflective surface enables the device to be clearly visible at long distances at night and in rainy weather. The devices come in multiple colors including:
- White markers — for lane markings. These sometimes have a reflective red lens 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 designs now used widely throughout the United States are based on the invention of 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 worldwide 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. Other brands of reflective raised pavement markers sold in the United States under various designs include 3M, Apex Universal, Hi-Way, and Ray-O-Lite.
[edit] Non-Reflective Raised Pavement Markers (or Botts' dots)
[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 channelize traffic. These are a form of raised pavement marker but unlike most such markers, delineators are not supposed to be hit except by out-of-control or drifting vehicles. Unlike their smaller cousins, delineators are tall enough to impact not only a vehicle's tires but the vehicle body itself. 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 markers in a "T" shape. They can also be used to indicate lane closures as in cases where the number of lanes is reduced.
The name delineator is also used for reflective devices attached to other objects which are technically not pavement markers.
[edit] Cat's eyes
Cat's eyes were invented in the United Kingdom in 1933 and patented in the United Kingdom in 1934 (UK patents Nos. 436,290 and 457,536), and the United States in 1939 (US patent 2,146,359).
[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.
