A cat's eye or road stud is a
retroreflective safety device used in
road marking and was the first of a range of
raised pavement marker
''Raised'' is the third studio album by American country music, country artist Hailey Whitters. It was released on March 18, 2022, via a partnership between Big Loud and her own imprint, Pigasus.
Background
Heavily inspired by her Midwestern upb ...
s. The cat's eye, when illuminated by the lights of an approaching car, becomes very visible as a marker.
Description
The cat's eye design originated in the UK in 1934 and is today used all over the world. The original form consisted of two pairs of
retroreflectors set into a white rubber dome, mounted in a
cast iron
Cast iron is a class of iron–carbon alloys with a carbon content of more than 2% and silicon content around 1–3%. Its usefulness derives from its relatively low melting temperature. The alloying elements determine the form in which its car ...
housing. This is the kind that marks the centre of the road, with one pair of cat's eyes 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 largely resistant to damage from
snow ploughs.
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.
History
The inventor of cat's eyes was
Percy Shaw of
Boothtown,
Halifax, West Yorkshire
Halifax is a town in the Metropolitan Borough of Calderdale, in West Yorkshire, England. It is in the eastern foothills of the Pennines. In the 15th century, the town became an economic hub of the old West Riding of Yorkshire, primarily in woo ...
, England. When the
tram-lines were removed in the nearby suburb of Ambler Thorn, he realised that he had been using the polished steel rails to navigate at night.
[
] 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 (patents Nos. 436,290 and 457,536), and on 15 March 1935, founded
Reflecting Roadstuds Limited in
Halifax to manufacture the items.
The name ''Catseye'' is their trademark. The
retroreflecting lens had been invented six years earlier for use in advertising signs by Richard Hollins Murray, an accountant from
Herefordshire
Herefordshire ( ) is a Ceremonial counties of England, ceremonial county in the West Midlands (region), West Midlands of England, bordered by Shropshire to the north, Worcestershire to the east, Gloucestershire to the south-east, and the Welsh ...
and, as Shaw acknowledged, they had contributed to his idea.
The
blackouts of
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
(1939–1945) and the shuttered car
headlight
A headlamp is a lamp attached to the front of a vehicle to illuminate the road ahead. Headlamps are also often called headlights, but in the most precise usage, ''headlamp'' is the term for the device itself and ''headlight'' is the term for t ...
s 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
A ministry of transport or transportation is a ministry responsible for transportation within a country. It usually is administered by the ''minister for transport''. The term is also sometimes applied to the departments or other government a ...
committee led by
James Callaghan
Leonard James Callaghan, Baron Callaghan of Cardiff ( ; 27 March 191226 March 2005) was a British statesman and Labour Party (UK), Labour Party politician who served as Prime Minister of the United Kingdom from 1976 to 1979 and Leader of the L ...
and
Sir Arthur Young. Eventually, their use spread all over the world.
In 2006, Cat's eyes were voted one of Britain's top 10 design icons in the Great British Design Quest organised by the
BBC
The British Broadcasting Corporation (BBC) is a British public service broadcaster headquartered at Broadcasting House in London, England. Originally established in 1922 as the British Broadcasting Company, it evolved into its current sta ...
and the
Design Museum
The Design Museum in Kensington, London, England, exhibits product, industrial, graphic, fashion, and architectural design. In 2018, the museum won the European Museum of the Year Award. The museum operates as a registered charity, and all fund ...
, a list which included
Concorde
Concorde () is a retired Anglo-French supersonic airliner jointly developed and manufactured by Sud Aviation and the British Aircraft Corporation (BAC).
Studies started in 1954, and France and the United Kingdom signed a treaty establishin ...
,
Mini
The Mini is a very small two-door, four-seat car, produced for four decades over a single generation, with many names and variants, by the British Motor Corporation (BMC) and its successors British Leyland and the Rover Group, and finally ...
,
Supermarine Spitfire
The Supermarine Spitfire is a British single-seat fighter aircraft that was used by the Royal Air Force and other Allies of World War II, Allied countries before, during, and after World War II. It was the only British fighter produced conti ...
,
K2 telephone box,
World Wide Web
The World Wide Web (WWW or simply the Web) is an information system that enables Content (media), content sharing over the Internet through user-friendly ways meant to appeal to users beyond Information technology, IT specialists and hobbyis ...
and the
AEC Routemaster
The AEC Routemaster is a Front-engine, rear-wheel-drive layout, front-engined double-decker bus that was designed by London Transport Executive, London Transport and built by the Associated Equipment Company (AEC) and Park Royal Vehicles. The ...
bus.
Local practice
United Kingdom and Hong Kong

In the United Kingdom, different colours of cat's eyes are used to denote different situations:
* White is used to indicate the centre line of a single carriageway road or the lane markings of a
dual carriageway or
motorway
A controlled-access highway is a type of highway that has been designed for high-speed vehicular traffic, with all traffic flow—ingress and egress—regulated. Common English terms are freeway, motorway, and expressway. Other similar terms ...
.
* Amber and red cat's eyes denote lines that should not be crossed under normal circumstances. Amber is used for the right-hand side of dual carriageways and motorways, delineating the central reservation. Red is used for the left-hand side of the same and may be crossed in order to access a hard shoulder in emergencies.
* Green indicates a line that may be crossed, such as a slip road or lay-by.
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. These are typically day glow green/yellow so they are easily visible in daylight as well as in darkness; they can then 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 known as solar road studs and showing a red or amber
LED
A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...
to traffic, have been introduced on roads regarded as particularly dangerous at locations throughout the world. However, shortly after one such installation in
Essex
Essex ( ) is a Ceremonial counties of England, ceremonial county in the East of England, and one of the home counties. It is bordered by Cambridgeshire and Suffolk to the north, the North Sea to the east, Kent across the Thames Estuary to the ...
in the autumn of 2006 the
BBC
The British Broadcasting Corporation (BBC) is a British public service broadcaster headquartered at Broadcasting House in London, England. Originally established in 1922 as the British Broadcasting Company, it evolved into its current sta ...
reported that the devices, which flash at an almost imperceptibly fast rate of 100 times a second, could possibly set off
epileptic fits and the
Highways Agency
National Highways (NH), formerly Highways England and before that the Highways Agency, is a government-owned company charged with operating, maintaining and improving motorways and major A roads in England.
It also sets highways standards u ...
had suspended the programme. The suspension appeared to have been lifted by 2015, when LED cat's eyes began to be installed along newly re-paved sections of the A1 and A1(M) in
County Durham
County Durham, officially simply Durham, is a ceremonial county in North East England.UK General Acts 1997 c. 23Lieutenancies Act 1997 Schedule 1(3). From legislation.gov.uk, retrieved 6 April 2022. The county borders Northumberland and Tyne an ...
and
Tyne and Wear
Tyne and Wear () is a Ceremonial counties of England, ceremonial county in North East England. It borders Northumberland to the north and County Durham to the south, and the largest settlement is the city of Newcastle upon Tyne.
The county is ...
.
Flashing blue LED cat's eyes were demonstrated on the TV show ''Accident Black Spot'', aired on
Channel 4
Channel 4 is a British free-to-air public broadcast television channel owned and operated by Channel Four Television Corporation. It is state-owned enterprise, publicly owned but, unlike the BBC, it receives no public funding and is funded en ...
on 19 December 2000, which alert the driver to potential ice on the road when a low enough temperature, provisionally set at , is reached. Proposed enhancements in 2013 were to change the standard white light 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 Ireland yellow cat's eyes are used on all hard shoulders, including motorways (neither red nor blue cat's eyes are used). In addition, standalone reflector batons are often used on the verge of Irish roads. Green cat's eyes are used to alert motorists to upcoming junctions. There are limited installations of actively powered cats eyes, which flash white light, on particularly dangerous sections of road such as the single carriageway sections of the N11.
United States
The closest equivalent in the United States is the Stimsonite retroreflective raised pavement marker, a fixed marker without the rubber self-cleaning property. Stimsonite markers are made out of plastic, not metal, and were invented in 1963.
New Zealand
In New Zealand, roads are generally marked with white reflective cat's eyes every 10-metres along the centreline, occasionally on high volume roads; both
Botts' dots
Botts' dots (turtles in Washington and Oregon or buttons in Texas and other southern states) are round non-reflective plastic and ceramic raised pavement markers. In many parts of the US, Botts' dots are used, along with reflective raised ...
and cat's eyes are used (typically there is one cat's eye followed by three Botts' dots places in every ten-metre stretch of highway). The colour pattern on New Zealand roads is white or yellow cat's eyes along the centre of the road (yellow indicating overtaking is not permitted), and in certain places red dots along the hard shoulder or left edge of a motorway. Single blue cat's eyes are used to indicate the location of fire hydrants. In rural settings and along
State Highways
A state highway, state road, or state route (and the equivalent provincial highway, provincial road, or provincial route) is usually a road that is either Route number, numbered or maintained by a sub-national state or province. A road numbered ...
, these markings are augmented by retroreflective posts along the edge of the road (white reflectors on the left, yellow reflectors on the right when on a left turning bend). Bridges are similarly marked with retro-reflective markings in diagonal bands of white and black (to the left) and yellow and black (to the right).
Continental Europe

In almost all European countries cat's eye road studs include reflective lenses of some kind. By contrast to the UK where use of cat's eyes is widespread, in Continental Europe cat's eyes are rarely used as a permanent fixture. 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.
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 are used next to the central reservation (US: median) on motorways and dual carriageways and, in the Republic of Ireland, also on hard shoulders.

Red markers are used 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 traveling down the wrong way of the motorway/dual carriageway.
Green markers are used where slip-roads 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 are used to indicate temporary lanes during roadworks on major roads 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 colour, 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
Lebanon
In Lebanon, cat's eyes are widely used on most freeways, highways and roadways. On freeways and highways, every one (or sometimes two) white stripes separating lanes is followed by a white shining cat's eye. On the edge of the road next to the median strip, a yellow cat's eye is placed every . On the road shoulders a red shining cat's eye is placed every . On roadways separated by double yellow lines, a yellow cat's eye is placed inside the double yellow lines every . Before speed bumps, a series of cat's eyes are placed shining white to the oncoming traffic and red to the car from the opposite direction. On pedestrian crossings, blue shining cat's eyes are placed after every zebra line. On roads with traffic lights, a series of red shining cat's eyes are placed before traffic lights to make drivers slow down.
Accidents caused
On the morning of 25 April 1999 on the
M3 motorway in Hampshire, England, a van dislodged the steel body of a cat's eye which flew through the windscreen of a following car and hit electronic musician
Kemistry, who was a passenger, in the face, killing her instantly. The
coroner
A coroner is a government or judicial official who is empowered to conduct or order an inquest into the manner or cause of death. The official may also investigate or confirm the identity of an unknown person who has been found dead within th ...
recorded a
verdict
In law, a verdict is the formal finding of fact made by a jury on matters or questions submitted to the jury by a judge. In a bench trial, the judge's decision near the end of the trial is simply referred to as a finding. In England and Wales ...
of
accidental death
An accidental death is an unnatural death that is caused by an accident, such as a slip and fall, traffic collision, or accidental poisoning. Accidental deaths are distinguished from death by natural causes, disease, and from intentional homici ...
. Investigators acknowledged that the cat's eye bodies occasionally came loose, but added that such an accident was previously unheard of. A question was asked in the
House of Lords
The House of Lords is the upper house of the Parliament of the United Kingdom. Like the lower house, the House of Commons of the United Kingdom, House of Commons, it meets in the Palace of Westminster in London, England. One of the oldest ext ...
about the safety of cat's eyes in light of the incident, and the
Highways Agency
National Highways (NH), formerly Highways England and before that the Highways Agency, is a government-owned company charged with operating, maintaining and improving motorways and major A roads in England.
It also sets highways standards u ...
conducted an investigation into the "long-term integrity and performance" of various types of road stud.
In the
1957 Mille Miglia road race, while driving along a straight road at 150 mph (240 km/h) at the village of
Guidizzolo in Italy, a blowout of the left front tyre on the
Ferrari 335 S driven by
Alfonso de Portago caused the car to violently flip over and fly out of control, killing him, his navigator and nine spectators, including children.
Enzo Ferrari
Enzo Anselmo Giuseppe Maria Ferrari (; ; 18 February 1898 – 14 August 1988) was an Italian racing driver and entrepreneur, the founder of Scuderia Ferrari in Grand Prix motor racing, and subsequently of the Ferrari automobile marque. Under h ...
was prosecuted for 11 counts of manslaughter, but was acquitted in 1961 after a panel of automobile engineers told the court that the blowout was probably caused by the car striking a cat's eye.
In the 2023 film ''
Ferrari
Ferrari S.p.A. (; ) is an Italian luxury sports car manufacturer based in Maranello. Founded in 1939 by Enzo Ferrari (1898–1988), the company built Auto Avio Costruzioni 815, its first car in 1940, adopted its current name in 1945, and be ...
'' a damaged metal cat's eye cutting the tyre is blamed for the fatal accident, consistent with the Italian judiciary's official findings.
Notes
References
External links
Reflecting Roadstuds Ltd(Shaw's company)
*
ttp://v3.espacenet.com/textdoc?IDX=GB436290&CY=gb&LG=en&DB=EPODOC Shaw's patentbr>
Cat's eyes website with information about a previous patent applicationCat's eyes: How a pub trip made the world's roads safer BBC
{{DEFAULTSORT:Cat's Eye (Road)
English inventions
Road infrastructure
Road surface markings
Traffic signs
20th-century inventions