The orange markers seperate opposing traffic lanes. A cat's eye (also known as a Botts' dot or a raised pavement marker) is a device used in some countries for road construction. A safety device, it consists of one or more small retroreflectors built into a sturdy housing, capable of surviving as vehicles pass over it. They are placed along road markings, as they serve to highlight these markings at night. They are particularly useful when lighting is poor and in addition to reflective road markings.
Cat's eyes were invented in 1933 by Percy Shaw of Yorkshire in England. The name "cat's eye" comes because the inventor was inspired when he saw light reflecting from cat's eyes. They became popular in Britain during World War II, in the era of blackouts. The Government realised that drivers needed to see where they were going, even in the midst of a blackout. Cat's eyes use a system where the light is reflected from the car's headlights, thus allowing a limited amount of light. There are now some self-illuminated versions, either wired to a power supply or using solar power. These increase visibility range. An unexpected benefit of cat's eyes is the typical thunk sound made when driving over the device, warning a driver that they have started to leave their lane.
Local practice
Various types of cat's eye exist. In Britain, white cat's eyes are used for the centre of a road, lane markings, or soft traffic islands. Red cat's eyes are placed along the hard shoulder of a motorway, and orange cat's eyes are placed along the edge of the central reservation. Green cat's eyes denote joining or leaving slip roads at junctions, and blue cat's eyes are used for police slip roads. In Ireland, usage is similar, but yellow cat's eyes are used on all hard shoulders, including motorways (red cat's eyes are not used, nor are blue). In addition, standalone retroreflector batons are often used on the verge of Irish roads.
In the many parts of the United States, Botts' dots, named after Dr. Elbert Botts, a California Department of Transportation (Caltrans) engineer credited with inventing the epoxy used to attach the markers to the road, come in two varieties, rounded white markers used for lane dividers, and square, colored, reflective markers used for other situations. White markers are used for 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 markers were developed in the 1950s and 1960s as a replacement for painted lane lines for several reasons, mainly due to painted lines becoming invisible during rain and because painting the lines exposed Caltrans workers to dangerous traffic situations.
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