cat's-eye

 

gemstone that displays a thin band of reflected light on its surface when cut as a cabochon. Its name is derived from its supposed resemblance to the eye of a cat. The optical effect, known as chatoyancy, is caused by the reflection of light from very thin, closely spaced filaments in parallel arrangement within the stone. True cat's-eye, a variety of chrysoberyl from Sri Lanka and Brazil, is the most valuable, but some quartz, tourmaline, and a few other minerals that display chatoyancy are also used as gems. A golden-yellow species called tiger's-eye is a form of quartz that contains crocidolite asbestos.

The cat's eye is a safety device used in road construction and was the first of a range of raised pavement markers. It originated from the UK in 1933 and is used all over the world.

It consists (in its original form) of two pairs of reflective glass spheres set into a white rubber dome, mounted in a cast iron housing. This is the kind that marks the centre of the road, with one pair of cat's eye showing in each direction. A single-ended form has become widely used in other colours at road margins and as lane dividers. Cat's eyes are particularly valuable in fog and are remarkably resistant to snow plough damage.

A key feature of the cat's eye is the flexible rubber dome which is occasionally deformed by the passage of traffic. A fixed rubber wiper cleans the surface of the reflectors as they sink below the surface of the road (the base tends to hold water after a shower of rain, making this process even more efficient). The rubber dome is protected from impact damage by metal 'kerbs' - which also give tactile and audible feedback for wandering drivers.

The inventor of cat's eyes was Percy Shaw of Halifax, Yorkshire in England. When the tram-lines were removed in the nearby town of Bradford he realized that he'd been using the polished strips of steel to navigate.^[1] The name "cat's eye" comes from Shaw's inspiration for the device: the light reflecting from the eyes of a cat. In 1934, he patented his invention (patent No. 436,290 and 457,536), and on March 15, 1935, founded Reflecting Roadstuds Limited in Halifax to manufacture the items.^[2][3] The name Catseye was their trademark.^[4]

Development and value

The blackouts of World War II (1939-1945) and the shuttered car head-lights then in use demonstrated the value of Shaw's invention and helped popularise their mass use in the UK. After the war, they received firm backing from a Ministry of Transport committee led by James Callaghan and Sir Arthur Young. Eventually, their use spread all over the world.

James May, co-presenter of the UK automobile TV show Top Gear said this of this device: "The Catseye is what great design is all about. Simple, functional, and beautiful. And on top of that, this little block of iron and rubber has probably done more to save lives on the road than anything since."

Local practice

United Kingdom

White cat's eyes are used for the centre of a road on many roads which lack street lighting but are subject to high speeds or high volumes of traffic. They are also used for lane markings, soft traffic islands and on "double-white lines" where no overtaking is permitted. Red cat's eyes are placed along the hard shoulder of a motorway or sometimes dual carriageways, and orange cat's eyes are placed along the edge of the central reservation (median). Green cat's eyes denote joining or leaving slip roads at junctions, alternate red and green indicate intersections of motorways and blue cat's eyes are used for police slip roads.

These units are not very visible in daylight and are generally used in conjunction with traditionally painted lines. Temporary cat's eyes with just a reflective strip are often used during motorway repair work and as these are easily visible in daylight as well as in darkness they can be used on their own for lane division.

Also seen during motorway repair work are plastic traffic pillars that are inserted into the socket of a retractable cat's eye rather than being free-standing. These are often used in conjunction with two rows of the temporary cat's eyes to divide traffic moving in opposite directions during motorway roadworks.

Flashing blue LED cat's eyes were demonstrated on the TV show Accident Black Spot (presented by Penny Mallory), which alert the driver to potential ice on the road when a low enough temperature is reached. The BBC recently reported that cat's eyes utilising LEDs ( known as intelligent road studs ) could possibly set off epileptic fits: the Highways Agency is currently investigating.^[5]

The cat's eye reached the top ten in the Great British design quest run by the BBC television programme The Culture Show.

Ireland

In The Republic of Ireland, usage is similar, but yellow cat's eyes are used on all hard shoulders, including motorways (red cat's eyes are not used, neither are blue). In addition, standalone retroreflector batons are often used on the verge of Irish roads. Green cat's eyes are used to alert motorists to upcoming junctions.

United States

Botts' dots (research started 1953, compulsory in California from 1966) and other raised pavement markers perform a somewhat similar function in areas of the U.S that do not receive substantial accumulating snowfall. They seem to be less durable than Cat's eyes ^{[citation needed]}, since they do not sink into the road when driven over. For areas of the US receiving substantial accumulating snowfall and thus requiring the use of snow removal equipment (ie. snowplows), recessed markers or those encased in protective metal (like cat's eyes) are used. ^[6]

Notes

1. ^ Halifax Today online news archive accessed 29 November 2006
2. ^ Reflecting Roadstuds Ltd: official company history
3. ^ Reyburn, Ross. "Inventions that prove size doesn't matter." The Birmingham Post, 26 June 1999, p. 50.
4. ^ The History of British Roadsigns, Dept. for Transport, 2nd Edition, 1999
5. ^ http://news.bbc.co.uk/1/hi/england/essex/6226285.stm
6. ^ http://www.virginiadot.org/business/resources/bu-mat-PaveMarkCh9.pdf

External links

• Reflecting Roadstuds (Shaw's company)
• Shaw's patent
• BBC TV programme Great British Design Quest
• Cat's Eyes at the Design Museum, London

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