Raised pavement marker

M9 motorway in Carlow, Ireland with cat's eyes on the road surface and retroreflectors on barriers

In almost all European countries, such markers will include reflective lenses of some kind. Most appear white or gray during daylight; the colors discussed here are the color of light they reflect. Because of their inconspicuousness during the day, they are always used in conjunction with painted retro-reflective lines; they are never seen on their own.[4]

• White markers — for lane markings. When used on dual carriageways, motorways or one-way roads, they may illuminate red on the reverse, to indicate drivers are traveling the wrong way.
• Yellow or amber markers — These are found next to the central reservation (US: median) on motorways and dual carriageways and, in the Republic of Ireland, are also used on hard shoulders.
• Red markers — These are found by the hard shoulder on motorways and at the edge of the running surface on other roads. They are also occasionally used to indicate a no-entry road and when travelling down the wrong way of the motorway/dual carriageway.
• Green markers — These are used where slip-roads (US: off-ramp) leave and join the main carriageway on dual carriageways. In some countries, they are also used across the entrances of minor roads or accesses onto major single carriageway roads or lay-bys.
• Blue markers — Are used to indicate the entrance to police reserved slip-roads (these do not lead anywhere, they are to allow police to park and monitor motorway traffic).

The exception to the above rules are:

• Fluorescent yellow markers — These are used to indicate temporary lanes during roadworks on major roads[5] and are glued to the road surface; they are never embedded in it. Any painted markings will be removed from the road surface if they contradict the markers. They are fluorescent yellow in color, so they stand out in the day, but reflect white light at night. Where used, they are much more numerous and dense than standards markers, as they are not used in conjunction with painted lines. They also appear yellow on the edges but reflect red on the left side or amber on the right

A white retroreflective raised pavement marker (Stimsonite design)

A blue raised pavement marker (for marking the location of fire hydrants)

• White markers — for lane markings or to mark the right pavement edge.
• Yellow or orange markers — These separate traffic moving in opposite directions, or mark the left pavement edge on one-way roadways.
• Blue markers — Usually placed in the center of the roadway to mark the location of fire hydrants on the shoulder or at the curb.
• Green markers — Usually used to indicate that emergency vehicles can open gates to enter a gated community.
• Red markers — Usually indicate areas that are closed to traffic.

Colors can also be combined, with a different color facing each direction:

• White and red or yellow and red — white or yellow for normal use in one direction, and red to indicate "do not enter" or "wrong way" in the other direction. Red-Clear Markers are primarily used to warn motorists they are going the wrong way; most people have never seen these because they show clear when approached in the correct direction, and only appear red to wrong-way drivers.[6]
• 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 do not apply.

The current trend for lane markings is to intersperse retroreflective paint lines with reflectors as seen on the majority of American highways.

A red raised pavement marker

A yellow raised pavement marker used to mark a stop valve

While Australian designs generally follow those in the US, the colors generally follow European usage. Differences from European usage include:

• Blue — Usually used to mark the location of fire hydrants, as in North America
• Yellow — In addition to marking the median of freeways, in Victoria single yellow reflectors are used with broken yellow lines to denote tram tracks on which motorized traffic can drive, and double yellow reflectors are used with solid yellow lines to denote tram tracks on which motorized traffic may not drive other than to cross.

Retroreflective spheres set into a cat's eye in the UK

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 invented in the United Kingdom in 1933 by Percy Shaw and patented in 1934 (UK patents 436,290[7] and 457,536),[8] and the United States in 1939 (US patent 2,146,359).[9] On March 15, 1935, Shaw founded Reflecting Roadstuds Ltd, which became the first manufacturer of raised pavement markers.

The plastic markers now used widely throughout the United States and elsewhere did not appear until more than two decades later. They were originally invented by American engineer Sidney A. Heenan in the course of his employment with the Stimsonite Corporation in Niles, Illinois.[10] Heenan filed an application for a patent on October 23, 1964. Patent No. 3,332,327 was subsequently granted on July 25, 1967.[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.[13] For six years, 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). The company (based in Ennis, Texas) changed its name to Ennis Traffic Safety Solutions and now markets the Stimsonite product line and descendants under the Stimsonite brand. Other manufacturers of retroreflective raised pavement markers sold in the United States under various designs include 3M, Apex Universal, Volume, and Ray-O-Lite.