What is the Cat's Eye in Road Construction?

At night or in low visibility conditions, road peephole studs are one of the key facilities for ensuring driving safety. It provides drivers with clear lane boundaries and direction guidance through reflective or active lighting technology, reducing the risk of traffic accidents at night. Next, NOKIN will systematically disassemble this common yet often overlooked road safety device, the cat's eye stud, from its definition, history, technical principles to practical applications.

What is A Cat's Eye Road Stud?

Road peephole studs, also known as road studs or reflective studs, are reflective safety devices embedded or fixed on the road surface. Their core function is to guide the direction of vehicle travel in low visibility scenarios such as at night, in rainy or foggy days. From daily observations, "cat's eye road studs" are usually distributed on the road surface in small block forms, and their colors are mostly white, yellow or red. Different colors correspond to different functional zones of the road.
 

Cat's Eye Road Stud Working Principle

The core value of the "cat's eye road stud" lies in "visibility", and its working principle revolves around "how to enable drivers to clearly see it in low visibility", mainly divided into two technical paths: passive reflection and active lighting.
 

Passive reflection:

This is the core technology of traditional cat's eye road studs. The principle is similar to that of a "reverse mirror" - through the built-in prism or glass lens, the light from the vehicle's headlights is reflected back to the driver's eyes in the original direction. This "return along the original route" feature enables cat's eye road studs to appear particularly bright at night, and it does not require an external power supply, with low cost and simple maintenance.
 

Active lighting:

Modern high-end cat's eye road studs integrate solar panels and LED lights. During the day, the solar panels store electrical energy, and at night, the LED lights (mostly yellow or white) automatically turn on to provide active lighting guidance. Solar-powered cat's eye road studs perform better in extremely low visibility scenarios such as heavy rain and thick fog. Their visible distance is 2 to 3 times longer than that of passive types, making them suitable for installation on critical sections of highways, tunnel entrances and exits, etc.
 

Cat's Eye Road Studs Common Types and Colors

Note: The uses of green and blue cat's eye road studs vary by region. For instance, in some Chinese cities, green is used to mark the boundaries of bus lanes, while in Europe, blue is commonly used to mark bicycle lanes. Specific regulations should be followed by local transportation authorities.
 

Cat's Eye Road Studs Materials, Manufacturing and Durability

"Cat's eye road studs" are exposed to the outdoors for a long time and need to withstand tests such as vehicle rolling, high-temperature sun exposure, and rain immersion. Therefore, the material selection directly determines their service life and safety.
 

A Comparison of Common Materials of Cat's Eye Road Studs

Engineering plastics (such as PC, ABS) :

Their advantages include light weight, strong weather resistance (able to operate normally from -30℃ to 70℃), and low cost. The drawback is that it has a medium compressive strength and is prone to cracking after long-term rolling. It is suitable for urban side roads or roads with low traffic volume.
 

Ceramic:

Its advantages include extremely high compressive strength (capable of withstanding the pressure of wheels weighing over 10 tons), wear resistance, and UV resistance (not prone to fading). The disadvantages are high cost and great brittleness (prone to breakage under the impact of heavy vehicles), making it suitable for sections with a high density of heavy vehicles such as highways and freight channels.
 

Glass encapsulation:

Mostly used as the reflective core (lens part) of cat's eye road studs, it adopts high-transparency tempered glass, which has a high reflectivity and is not easy to wear. However, it should be noted that if the glass lens is damaged, it will directly affect the reflective effect and needs to be replaced in time.
 

Metal base (such as aluminum alloy) :

Mainly used for the outer shell of active cat's eye road studs, with the advantages of being pressure-resistant and corrosion-resistant; The disadvantages are that it is heavy and costly, and is usually used in combination with ceramics or engineering plastics.
 

Cat's Eye Road Studs Compressive Strength and Weather Resistance Requirements

The durability requirements for cat's eye road studs vary significantly among different roads:
 

Expressways:

They need to withstand frequent high-speed wheel impacts (at speeds of 80-120km/h), so the compressive strength of cat's eye road studs should be ≥10 mpa, and their wear resistance should meet the requirement that "the reflectivity does not decrease by more than 20% after being rolled over 1 million times".
 

Urban main roads:

Heavy traffic but low vehicle speed (30-60km/h), compressive strength requirement ≥8MPa, and at the same time, it must have oil resistance (to prevent oil leakage from vehicles from corroding the base).
 

Rural roads:

The traffic volume is small, but they may be exposed to ice, snow and water immersion. Therefore, the cat's eye road studs need to have frost resistance (not brittle at -40℃) and water resistance (IP67 level or above water resistance).

Cat's Eye Road Studs Installation and Construction Key Points

The installation quality of "cat's eye road studs" directly affects their service life and reflective effect. The construction must follow strict procedures and avoid common problems at the same time.
 

Pre-construction Inspection

Before installing cat's eye road studs, three key inspections of the road surface need to be carried out:

Road surface flatness: The undulation of the road surface in the installation area should be ≤2mm; otherwise, the cat's eye road studs are prone to uneven force and damage.

Drainage situation: The installation point should avoid areas with accumulated water on the road surface to prevent rainwater from seeping into the base and causing bonding failure.

Paving materials and temperature: If the road surface is asphalt, it must be cooled for at least 24 hours after the asphalt is laid before construction. If it is a cement pavement, it is necessary to ensure that the pavement strength meets the design requirements (≥C30) to avoid pavement cracking during drilling.
 

Installation Steps

Positioning: According to the design drawings, mark the installation positions of the cat's eye road studs on the road surface with chalk or a positioning instrument (usually the spacing is 10-20 meters, and it can be shortened to 5-10 meters at curves).

Milling grooves/drilling: Use a dedicated milling machine (for asphalt roads) or a drilling machine (for cement roads) to dig grooves at the designated points - the size of the grooves should match the base of the cat's eye road studs (usually 10-15cm in diameter and 5-8mm in depth).

Base curing: Apply epoxy adhesive or asphalt adhesive at the bottom of the groove. The thickness of the adhesive should be uniform (about 2-3mm) to ensure that the cat's eye road studs are closely bonded to the road surface.

Embedding/Fixing: Insert the cat's eye stud into the groove, gently press it to make it adhere to the adhesive, and adjust the levelness at the same time to avoid tilting.

Maintenance/Inspection: After the construction is completed, the road surface should be closed for 2 to 4 hours (the specific time depends on the type of adhesive). Once the adhesive is fully cured, test the reflective effect with vehicle headlights at night to ensure uniform brightness.
 

Common Construction Mistakes and Their Avoidance

Weak adhesion:

This is often due to incomplete road surface cleaning (with dust or oil stains), or uneven application of the adhesive. Avoidance method: Before construction, rinse the road surface with a high-pressure water gun and wipe the grooves with alcohol to ensure there are no impurities.
 

The reflective surface is covered:

During the construction of asphalt pavement, if cat's eye road studs are installed before the asphalt has completely cooled down, the asphalt will stick to the reflective mirror plates, blocking the light. Avoidance method: Strictly wait for the road surface to cool down to the specified temperature (usually ≤50℃).
 

Position deviation:

During positioning, the center line or markings of the lane were not combined, resulting in the misalignment of the cat's eye road stules with the markings, which affected the guidance effect. Avoidance method: Before installation, use the road surface markings as the reference and calibrate the position with a positioning instrument.
 

Drainage was not taken into account:

The installation point was located in a low-lying area of the road surface, and long-term immersion by rainwater caused the base to rust. Avoidance methods: Before construction, check the slope of the road surface, install the cat's eye road studs at a slightly higher position, or reserve small drainage holes at the bottom of the groove.
 

Cat's Eye Road Studs Maintenance and Replacement

The core of maintaining "cat's eye road studs" is to "promptly identify failed individuals and replace them" to prevent the interruption of lane guidance due to the damage of a single cat's eye road stud.
 

Daily Inspection Contents

Daily inspections should focus on the following four indicators:
 

Night visibility:

When driving a vehicle at a speed of 40-60km/h at night, observe the reflective brightness of the cat's eye road studs. If the brightness of a certain individual is significantly lower than that of the surrounding area (dropping by more than 50%), or it does not reflect light at all, it needs to be marked and replaced.
 

Color fading:

Check if the surface color of the cat's eye road studs has faded (such as red turning to pink or yellow turning to white). Fading can cause functional confusion and should be replaced in a timely manner.
 

Physical damage:

Check for any cracks in the base, broken lenses, or tilting of the raised cat's eye road studs. Damage can affect the compressive strength and reflective effect.
 

Loosening condition:

Gently push the cat's eye rail stud with your hand. If there is obvious shaking, it indicates that the bonding has failed and it needs to be re-reinforced or replaced.
 

Recommended Maintenance Cycle

The maintenance cycle needs to be adjusted according to the road grade. Refer to industry practice:
 

Urban roads (branch roads/community roads) :

With low traffic volume and slow wear and tear, it is recommended to conduct a comprehensive inspection once a year and replace them in batches every 2-3 years (even if they are not completely ineffective, the reflectivity will decline with usage time).
 

Urban main roads:

With heavy traffic volume, it is recommended to conduct inspections every six months, replace the faulty ones annually, and carry out a comprehensive assessment every three years to determine whether to replace them in bulk.
 

Highways/freight channels:

There are many heavy vehicles and they wear out quickly. It is recommended to conduct an inspection every three months (a dedicated road inspection vehicle can be used). Replace any failed individual within 24 hours and replace them in batches every two years.
 

Quick Troubleshooting Checklist

 

Cat's Eye Road Studs Regulations, Standards and Compliance

The installation and use of "cat's eye road studs" must comply with local traffic regulations and industry standards. The requirements vary among different countries/regions, and the core norms are mainly concentrated in three dimensions: "color, spacing, and compressive strength".
 

China:

You can refer to "Technical Conditions for Anti-corrosion of Steel Components in Highway Traffic Engineering" (GB/T 18226) and "Glass Beads for Road Marking" (GB/T 24722), which have detailed regulations on the materials, reflectivity and installation spacing of cat's eye road studs.
 

United States:

Referring to the "Roadway Lighting and Signing Handbook" issued by the Federal Highway Administration (FHWA), it is required that the LED brightness of the active cat's eye stud should not be less than 200cd/m², and it should have a light control function (automatically turn off during the day);
 

Europe:

In accordance with the EN 1463-1 standard, strict requirements are imposed on the weather resistance (cyclic test from -40℃ to 70℃) and wear resistance (weight loss ≤5% after being rolled 1 million times) of cat's eye road studs.

It is recommended that engineering personnel directly consult the official website of the local road management department before construction to obtain the latest local standards and avoid compliance risks caused by non-compliance with standards.
 

Common Misconceptions and Q&A (FAQ)

Q1: Can cat's eye road studs completely replace road markings?

No, the two are in a "complementary relationship" rather than a "substitution relationship". Road markings (such as white lane lines and yellow divider lines) are highly visible during the day, while cat's eye road studs have more obvious advantages at night and on rainy days - the reflectivity of cat's eye road studs on rainy days is 3 to 5 times that of road markings (as rain reduces the reflective effect of the markings). In practical applications, cat's eye road studs need to be used in conjunction with road markings to achieve all-weather guidance.
 

Q2: Why are cat's eye road studs more useful on rainy days than during the day?

The core reason is the "adaptability of the reflective principle". During the day, when sunlight shines directly on the road surface, the passive reflection of the "cat's eye road studs" will be masked by strong light and appear less obvious. On rainy days, there is a thin layer of water accumulation on the road surface. On the one hand, the water accumulation reduces the interference of stray light on the road. On the other hand, the lens of the cat's eye road studs can precisely reflect the light from the vehicle's headlights back into the driver's eyes. At the same time, the raised cat's eye road studs can rise above the water surface, avoiding being covered by water accumulation. Therefore, the visibility of the cat's eye road studs is actually stronger on rainy days.
 

Q3: Will installing cat's eye road studs affect the wear of tires on expressways?

No, the design has fully taken into account the issue of tire wear. Firstly, the embedded cat's eye road studs are flush with the road surface. When wheels pass over them, there is almost no jolt and they will not increase tire friction. Secondly, the raised cat's eye road studs are designed with elastic rubber or an arc-shaped surface. When wheels pass over them, they provide a certain degree of buffering, and the contact area is small (only 1-2cm² at the top), causing negligible wear to the tires. Actual tests show that the service life of vehicle tires on roads equipped with cat's eye road studs is not significantly different from that on ordinary roads.

Although the cat's eye road studs are small in size, they are the "invisible guardians" of driving safety at night. It provides precise guidance solutions for different road scenarios through mature reflective technology, diverse material options and clear color standards. Meanwhile, reasonable installation, maintenance and cost planning can maximize its safety benefits and reduce the risk of traffic accidents at night.