A cat’s eye road stud is a reflective device designed to enhance lane visibility and guide traffic during low-visibility conditions such as nighttime, fog, or heavy rain. It provides clear lane delineation and helps improve vehicle guidance and road safety. Invented in the 1930s by Percy Shaw in the UK, these reflective markers have since become a standard safety feature on highways, city roads, and other transport infrastructures across the world.
What is a Cat’s Eye Road Stud?
A cat’s eye road stud is a reflective road marker embedded in the pavement to indicate lanes and road edges. Named for its resemblance to the bright, reflective nature of a cat’s eyes in the dark, this device reflects vehicle headlights back to drivers, offering guidance and enhancing visibility, especially during nighttime, fog, rain, or dust storms.
Components of a Cat’s Eye
Typically, a cat’s eye road stud consists of:
- Reflective Lenses: Usually made of glass or high-quality plastic, placed within the stud to reflect light from vehicle headlights.
- Housing/Casing: Made of durable materials like cast iron, aluminium, or toughened plastic to withstand vehicle loads and environmental conditions.
- Rubber Dome (Optional): Some types include a flexible rubber dome that compresses under vehicle load to help self-clean the reflectors.
- Adhesive or Anchoring Mechanism: Used to fix the stud securely to the pavement.
Also, Read: Traffic Islands: Types and Functionality
Colour Coding and Meaning
| Colour | Meaning | |
|---|---|---|
| White |  | Marks lane lines or road centerlines. |
| Red | | Indicates the left edge of the road or no-entry zones. |
| Yellow/Amber | | Separates opposing traffic or marks medians. |
| Green | | Marks permissible crossovers or access points. |
| Blue | | Often used to identify locations of emergency services or fire hydrants. |
Placement of Road Studs
Proper placement of road studs is critical to ensure road safety and user guidance. They are installed:
- Along lane lines: To define lanes, especially at curves and intersections.
- On centerlines: To separate opposing traffic flows.
- On road shoulders: To guide drivers and warn of the road edge.
- At roundabouts, pedestrian crossings, and merging lanes.
- Before speed breakers or rumble strips: To warn drivers in advance.
Installation Tips:
- The surface must be clean and dry.
- Adhesive or epoxy must be properly applied.
- Correct orientation of reflectors should be maintained.
- Cure time (usually 1–2 hours) before traffic is allowed.
Also, Read: Sight Distance in Highway Design
Spacing of Road Studs
The spacing of road studs depends on the type of road, curvature, traffic speed, and visibility conditions. Below are common guidelines based on international and Indian road standards (e.g., IRC 79, MoRTH):
a. Straight Roads:
| Road Type | Spacing |
|---|---|
| Urban Roads | 3 to 5 meters |
| Highways | 6 to 9 meters |
| Expressways | 9 to 15 meters |
b. Curves and Intersections:
| Road Feature | Spacing |
|---|---|
| Sharp Curves | 2 to 3 meters |
| Roundabouts | 2 to 3 meters |
| Approaches to Intersections | 3 to 4 meters |
c. Hazardous Zones / Speed Breakers / Pedestrian Crossing:
- Spacing: 1 to 2 meters for a clear warning.
- Colour: Often yellow or red to attract the driver’s attention.
*** Note: For solar studs may be spaced at longer intervals (up to 20 m), due to their superior visibility. ***
BOQ Specification
Item Description For Plastic
Supplying and fixing of plastic road studs made from ABS or polycarbonate material, approximate dimensions 100 mm × 100 mm × 20 mm, equipped with two-way retroreflective lenses (polycarbonate/micro-prism type), capable of withstanding vehicular load up to 20 tons. Reflectivity shall be ≥ 100 mcd/lux/m² (white), and studs should be installed using epoxy adhesive as per the manufacturer’s instructions. The rate shall be inclusive of all materials, labour, adhesive, transportation, and installation. Complete in all respects and to the satisfaction of the Engineer-in-Charge.
Item Description For Metal
Supplying and fixing of metal road studs made from cast aluminium alloy (minimum weight: 800 g), dimensions approx. 100mm × 100mm × 20mm, equipped with two-way retro-reflective lenses (polycarbonate or tempered glass), capable of withstanding a compressive load of ≥ 40 tons. The studs shall have a reflectivity of ≥ 100 mcd/lux/m² and be fixed using a two-component epoxy adhesive as specified by the manufacturer. The surface shall be cleaned, dried, and prepared before installation. All tools, materials, labour, and adhesive to be included. Complete in all respects as directed by the Engineer-in-Charge.
Technical Specification
The fixing of plastic and metal road studs can be done in two different ways. This should be described by the engineer responsible for preparing the specification. Usually, the fixing mechanism is as follows:
- With adhesive glue: This shall include cleaning and applying adhesive glue on the surface of the road stud and the pavement surface.
- With screed fixing: This shall include the embedding of the screew in the pavement surface and fixing the road stud to the pavement surface.
Measurement Unit:
The measurement unit for each item can be “Each or No“.
Mode of Measurement:
Counted per piece of plastic or metal road stud fixed in position as per specifications and approved by the Engineer-in-Charge.
Standards and Codes
Road studs should comply with relevant standards to ensure quality and durability:
- ASTM D4280 – Retroreflective raised pavement markers.
- BS EN 1463-1 & 2 – Road marking performance standards.
- IRC:79-1981 – Recommended guidelines for the use of reflective road studs in India.
- MoRTH Specification Clause 804 – Specification for road marking and stud placement.
FAQs:
Q: What is the distance between two cat’s eye road studs?
Answer: The distance between two cat’s eye road studs is
References:
- Indian Roads Congress. (1981). IRC:79-1981: Tentative guidelines for the design of high embankments. Indian Roads Congress. https://law.resource.org/pub/in/bis/irc/irc.gov.in.079.2019.pdf
- ASTM International. (2021). ASTM D4280 – Standard specification for extended life, type I retroreflective pavement markers. ASTM International. https://www.astm.org/d4280
- British Standards Institution. (2009). BS EN 1463-1: Road marking materials — Retroreflecting road studs — Part 1: Initial performance requirements. British Standards Institution. https://www.bsigroup.com
- Road studs – Types, requirement, and placement. (2020, March 28). theconstructor.org. https://theconstructor.org/others/road-studs-types-requirement-placement/38724/
