Raised pavement marker
These devices are usually made with plastic, ceramic, thermoplastic paint, glass or occasionally metal, and come in a variety of shapes and colors.
When a speeding vehicle runs over the raised road lines, it produces a strong warning vibration to remind the car driver of deviation from the lane.
[1] Perpendicular to driving directions, these marking lines are used for settled mainline toll plaza, ramp entrances, mountainous areas, continuous sharp turns, downhill sections and the end of the highway (intersection of highway exit and the plane of the common roadway), gates and entrances of enterprises, institutions, and school.
In the United States, Canada, Mexico, some countries of South America, Thailand and Australia, these plastic devices commonly have two angled edges facing drivers and containing one or more corner reflector strips.
[2] In areas with little snowfall, reflective raised pavement markers are applied directly on top of the road surface.
In 1965 San Diego Police Motorcycle Officer Kenneth Grant Maine, improved upon and applied for a patent on the white epoxy-resin reflective raised pavement marker.
There are a number of types, ranging from a single LED point source RPMs, with limited daytime visibilities, (road studs), to multi-LED linear type RPMs, visible in all full sunlight and nighttime applications.
Some lit linear visual aids / RPMs, melt snow, without needing any additional heating elements, as such, these types or self-cleaning RPMs are more energy-efficient compared to those that need additional heating elements to melt snow so are NOT self-cleaning.
Linear visual aids can also be used for creating in-pavement signs and messages such as lit merge arrows.
Cat's eyes made out of metal were the earliest form of retroreflective pavement markers, and are in use in the United Kingdom and other parts of the world.
They were originally invented by American engineer Sidney A. Heenan in the course of his employment with the Stimsonite Corporation in Niles, Illinois.
[11] Stimsonite went on to become the leading manufacturer of retroreflective raised pavement markers in the United States[12] and was acquired in 1999 by Avery Dennison Corporation.
Other manufacturers of retroreflective raised pavement markers sold in the United States under various designs include 3M, Apex Universal, Vialume, and Ray-O-Lite.
[citation needed] Cat's eyes, in their original form, consist of two pairs of retroreflective glass spheres set into a white rubber dome, mounted in a cast-iron housing.
Nonreflective raised pavement markers (also known as Botts' dots) are usually round, are white or yellow, and are frequently used on highways and interstates in lieu of painted lines.
Delineators are often used in snow-prone areas in lieu of raised pavement markings as the latter can be easily dislodged from the road surface by snowplows.
