[Aditya]

All you need to know about Road Studs (Cat's Eyes)

Driving along a dark road, you might have seen occasional flashes of light emitting from some devices that have been installed on the road. These devices are called road studs, or cat's eyes (due to their design) or Raised Pavement Markers. These objects include a lens or sheeting that enhances their visibility by reflecting the light from headlights of vehicles and make the road visible to the drivers. They are bonded or anchored within the road surface for lane marking and delineation for night-time visibility.


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History

Road studs were invented British inventor Percy Shaw in 1933 and patented in the UK in 1934. In 1935. They were designed in order to help drivers follow the road in darkness or fog. The idea came to his mind after observing the manner in which cars' headlights reflected off road signs. Shaw founded a company called Reflecting Roadstuds Ltd., which was first manufacturer of road studs.

Description

Road studs come in different sizes and are available in aluminum, rigid ABS plastic or glass. They are built to be able to withstand heavy loads and severe impacts. They can have reflectors on either one, both or all sides. The reflectors can be or various colours depending upon their intended use. The most common ones we get to see in India are white, yellow and red.

Of late, more advanced road studs have been introduced. These feature solar-powered LEDs instead. They can run on a single charge for many days. Of course, these are also more expensive than the regular reflector version.

Types of Road Studs

Aluminium Road Studs:

As the name suggests, aluminium road studs have aluminium casings with reflective objects installed within them. These are strong and durable. They are suitable to install in the middle of the road.


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Plastic Road Studs:

Plastic road studs are made of plastic and have reflective materials. They are not as strong as aluminium road studs and less durable as well. They can be used on the centre line of a road, sides of a highway and bridges.


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Glass Road Studs:

Solid glass road studs are made of hardened safety glass. The bottom of the reflector is covered with a coating, providing the reflective effect. The incoming light is bounced back by a reflector in the exact same direction from which it came, for 360 degrees. This means the reflector reflects the light of vehicles from every angle back to the road users.


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LED Road Studs:

LED road studs come with a solar panel on the top and a battery they gets charged by sunlight during the daytime. At night their LEDs start emitting light. They may or may not have small reflectors, but because of the bright LEDs, they are a lot more visible. They can easily be viewed from a longer distance than other types of road studs.


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Reflective Materials

Reflective sheet and Plastic Reflectors:
These are suitable for short term projects as they have a short life-span and lose their reflective properties with time. Reflectors with these materials are more suitable in places where road works are carried out on a more frequent basis compared to others.

Glass Beads:
Glass Beads are more durable than reflective sheets and plastic reflectors. They require less frequent replacement and are more suitable for long term projects.

Purpose

Road studs are among the most important devices in preventing cars from running off the road or their lanes and making our roads safer. They reflect the light from a car's headlights to allow the driver to observe the curves and corners of the road from a distance. Even in the dark, the driver is easily able to see the road alignments, ends, and corners of the road and judge where to turn, what lane of the road to adopt and in turn, drive safely. This makes studs extremely useful on poorly lit roads. They provide effective night guidance even under adverse weather conditions.

Additionally, these studs serve as lane markers. When a car runs over them, bumps are transmitted into the cabin which the occupants will always notice. That means that if the car is drifting from one lane to another, the driver will be alerted and can take corrective action.

You will also find road studs installed at pedestrian crossings. These give the driver of an approaching vehicle a clear indication of the pedestrian crossing.


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The rules of distance to be maintained between two reflective road studs varies from country to country. In India, the distance between two reflective cat's eyes on the road is determined by the type of road. On highways, it is usually 9 m - 18 m and depends on the radius of the horizontal/vertical curve of the section of the road.

Pros of Road Studs

• They act as guidelines telling the drivers where and how the road turns.
• They work and provide visibility during the day or night, regardless of the weather.
• They tell the driver that his car is drifting into another lane by providing audible and tactile feedback.
• Road studs on the edge of the road highlight and help drivers judge the boundaries of the road. This reduces the chances of vehicles running off the road.
• They do not need electricity. They have either reflectors or solar-powered LEDs, which means there is no electricity consumption.
• They act as speed breakers. Elevated road studs are installed to reduce or control the speed of vehicles, particularly on city roads.

Cons of Road Studs

• They are expensive to install and replace. Painting lines to mark lanes and the edges of the road is cheaper.
• Poor installation of road studs can make them loose, which may cause accidents.
• Road studs with bright blinking solar-powered LED can create a flickering effect that is picked up by the brain and causes photosensitive epilepsy.
• Vehicles create a noise when they go over road studs. This can be annoying for occupants of the vehicles and other road users.
• Road studs cannot be installed on unpaved roads.

Here's a video showing how road studs are installed:

https://www.youtube.com/watch?v=DbsHIpVUbn8

Sources: NK Roadstud, Civil Engineering Bible, 3M India

[Aditya]

Thread moved out from the Assembly Line.

[ashis89]

I have always wondered about the shape and design of these studs (and those scientific speed breakers). They're small in size, couple of inches in height and yet, they make their presence felt.

As far as I know, even with the best suspension setup, a car can't mask the jerk created with driven over these studs. They serve the purpose to warn the driver of lane discipline

Edit:
A particular stretch of road that I always remember and have loved doing the stretch at night - Vijayawada - Hyderabad. Due to these studs and well demarcated lanes, it is a bliss to cover this stretch at night and they also reduce road fatigue.

[Researcher]

Thanks for sharing this. Road studs and I have a strange relationship. I hope I am not driving on them when they are present. And I surely miss them when they are absent.

On a serious note, more often than not, I have observed the reflective strips to be missing on these road studs in many parts of our country. This makes it a bit less purposeful, especially at night during the rains.

Specific to two-wheelers, I have always taken extra care not to ride over the road studs (or reflective paint) on two-wheelers as I have always felt the vehicle to be losing balance slightly. This is as per my personal experience on Activas and Accesses I have had the chance to ride, so the experience may be different with wider tyres.

[Emvi]

Very informative thread!
I personally find these bright reflectors bit intrusive especially in the ghat sections of highways, more so when the roads are narrower than usual.

[papr23]

Cat eyes are normally used as road and pavement markers. However, in Hyderabad they are used as speed breakers
Usually cat eyes are lined along the boundary of crosswalks. Here the entire crosswalk is filled with cat eyes and make an annoying sound when you go over them.

[TrackDay]

Nice article and well written

Would also like to add the color in which these come about and what they denote. Kindly note that the following is for roads outside India and might be subject to change as per our road rules.

There are four main colors: red, green, white and amber - plus a green/yellow that appears on occasion.

The most common lights you'll see will be the standard white as these mark the lanes or the middle of a road. On a regular three-lane wide motorway you'll see two rows of these.

Amber cat's eyes appear on the far side of the road to mark the central reservation - and to stop you mindlessly changing lane to the right.

By contrast, red lights denote the left edge of the road - before you hit barriers or drift onto the hard shoulder.

The least common of the regular cat's eyes are green which appear to break up the red strips on the inside.

Green tells you that this part of the motorway can be driven over as there's a slip road, lay-by or - on some A-roads - a bus stop.

A blue reflector next to a yellow triangle points to a fire hydrant and are useful for vehicles attending a fire because they can quickly locate a source of water.

Source: https://www.nk-roadstud.com/news/new...lor-means.html
https://www.thesun.ie/motors/2158920...t-in-the-dark/

I prefer cat's eyes rather than those old school huge dots called Botts' dots. As a kid I used to think those were idlis on the road Botts' dots makes your vehicle jump around like someone was kicking from below the car.

Also any idea how these markers/cat's eyes affect a car's tyre life ? Also is there any risk/implications of driving low profile tyres over them ?

[Aniket Verma]

Originally Posted by TrackDay

Also any idea how these markers/cat's eyes affect a car's tyre life ? Also is there any risk/implications of driving low profile tyres over them ?

Informative Post on the colours of Cat Eyes.

A true Cats Eye should recede in it's housing when it comes in the contact with a tyre. I have not encountered such housing in India, rather they are fixed on the surface.

Hence, I follow my Old Man's advise to avoid them, as at speed any impact will have affect on tyres.

[ScorpioYadav]

I remember these Road Studs on the then new Jaipur bye-pass on the Delhi Ajmer highway in the mid 2000s and how effortless they made the night drives.

But they seemed to have been buried under when the highways got repaved over the years, as for many years now, they are nowhere to be seen on the very same bye-pass.

They should be re-installed as they really add joy to driving in the dark & extracts more value for the money paid as toll-tax by us.

[Thermodynamics]

Amazing example of how a simple idea can have a huge impact on the way the world moves. It has saved millions of lives from getting derailed.

I hate them during the day and love them in the night as I do quite a bit of night driving. It gives a feeling that you are on a runway. Also serves as a rumble against sleepy driving.

Although Catseyes are life saving, it can also get monotonous and cause visual fatigue if used excessively. For most stretches I think reflective thermoplastic road marking paint should suffice.

[DicKy]

Thanks for sharing this! As a kid this was one thing that would trigger my OCD tendency. Just because when dad changed lanes, one side of tyres would go over the studs (Botts' dot in this case) while the other side would somehow escape hitting the studs. I would be like, "tyres on one side went tuktuktuk..I want the other side to also make it, to balance everything"

I remember getting jealous when roads in Tamilnadu got the LED road studs under one of the many Jayalalithaa regimes, while Kerala was still getting only painted lane markings. The first time I was truly mesmerized by road studs was when the first phase of Karamana-Kaliyivala stretch was opened. Especially a midnight run. Pitch black surroundings, no streetlights. The road would look like a runway!!! Ofcourse traffic wore them off and they are yet to be replaced. Could very well guess some newspapers calling them unscientific after a few two wheelers slipped on those studs.

Originally Posted by TrackDay

I prefer cat's eyes rather than those old school huge dots called Botts' dots. As a kid I used to think those were idlis on the road Botts' dots makes your vehicle jump around like someone was kicking from below the car.

Thanks for the info. I was googling 'ceramic white road studs' to no end.

For some reasons, roads in Riyadh didn't have painted lane markings. For everything; lane markings, road demarcation, road surface markings they would use the Botts' dots. Heck, it was used instead of rumble strips!!! Bone jarring. One thing I observed was when ordinary cars went over them they used to jump vertically. But when old luxobarges like my uncle's W126 or some Yank landyachts went over them, they would shimmy sideways

[raghukodali]

I very rarely (practically zero) drive on the highways in the night so I don't see them often. But we do start at Honavar back to Bangalore early in the morning while it is dark. The road from Honavar to Jog falls has these "cat eyes" very well organised and placed. It is a breeze to drive on this ghat section in the dark. This gives an excellent clarity on the curves of the ghat section as well as an indication when you are straying to the road boundary.

[s.jain1990]

This is very informative. The area where I live in Pune has installed Glass Speed Studs at edges of the road and I used to wonder what were those for.

Also, I used to think that the LED ones were connected to an electric source. Your post helped me understanding the truth.

[McLaren Roxx]

Nice informational thread.
Personally, I consider road studs more of a bane than boon. I'd rather have reflective paint used for highlighting road markings. Not only does it have a better intended effect but is also much safer for road users and lasts longer.
Not to forget one does not need to damage the tarmac by drilling into it - thus causing spots for water to seep in.

[KGS]

A very well compiled and informative post Aditya. Thanks.

In addition to what Trackday has beautifully explained in his post,
Here in UK cat eyes are an important topic while learning driving. In the theory test as well , we get 1-2 questions on the colour of cat eyes and where they are placed.

I was driving in UK on my Indian Driving License for a year and at that time I was not that aware about the colour coding used in cat eyes. But once I started preparing for Theory test for my DL. I was able to appreciate the logic behind it and how much it helps in planning our movement on the motorways.

I personally prefer having cat eyes on the motorways / highways as they are brilliant in forecasting the bends ahead and helps us keep within the lanes. A small discomfort of thud sound while changing the lane helps to keep the driver attentive while on long drive, so that can be an added benefit (If I can say so )