The cat's eye is a retroreflective 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 have proven to be 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 realised that he'd been using the polished strips of steel to navigate. The name "cat's eye" comes from Shaw's inspiration for the device: the eyeshine reflecting from the eyes of a cat. In 1934, he patented his invention (patent No. 436,290 and 457,536), and on 15 March 1935, founded Reflecting Roadstuds Limited in Halifax to manufacture the items. The name Catseye was their trademark. The reflective lens had been invented six years earlier for use in advertising signs by Richard Hollins Murray, an accountant from Herefordshire.

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 car 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 amber 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.

Solar powered cat's eyes, showing a red or amber LED to traffic, are being introduced on roads regarded as particularly dangerous. However, shortly after one such installation in Essex in the Autumn of 2006 the BBC reported that the devices, which flash almost imperceptibly at 100 times a second, could possibly set off epileptic fits and the Highways Agency had suspended the programme.

Flashing blue LED cat's eyes were demonstrated on the TV show Accident Black Spot, aired on Channel 4 on 2000-12-19, which alert the driver to potential ice on the road when a low enough temperature, provisionally set at 3 °C, is reached. Proposed enhancements, for an "intelligent cat's eye" of the future, will see the standard white light change to amber for four seconds after the passing of a vehicle, or red if the following vehicle is too close or traffic ahead is stationary.

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 , since they do not sink into the road when driven over and frequently break free of the road surface when driven over, especially by trucks. 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.

Hazard

On 25 April 1999 on the M3 motorway, Hampshire, UK, a passing lorry dislodged the steel body of a cat's eye, which flew through the windscreen of a following car and killed a passenger, the disc jockey known as "Kemistry". Investigators acknowledged that the cat's eye bodies occasionally came loose, but added that such an accident was previously unheard of. A review of the "long-term integrity" of various types of road marker was ordered.

References

External links

• Reflecting Roadstuds (Shaw's company)
• Shaw's patent
• Cat's Eyes at the Design Museum, London