When driving at night or in foggy, rainy conditions, have you noticed the bright ‘glowing dots’ lining the roadside along the carriageway? These battery-free, non-electrically powered dots are reflective road studs. But how do they ‘glow’ in the dark? This article will gradually unravel the mystery of their working principle.
Retro-reflective road studs address the critical issue of poor night-time visibility associated with traditional road marking paint. They clearly delineate lane boundaries for drivers, with data indicating they can reduce night-time lane departure accidents by 30%-50%. Understanding their operational logic deepens our appreciation of their irreplaceable value in traffic safety.
This article caters to three groups: road maintenance personnel (optimising product application), drivers (enhancing trust in the product), and engineering procurement teams (supporting selection decisions). It also explains the technical principles in accessible language for curious general readers.
(1) Ordinary Reflection: Light Scatters in All Directions
When ordinary objects (such as white walls) reflect light, it scatters in every direction, with only a fraction reaching the observer's eyes. This explains why roadside objects are difficult to discern at night without illumination – most reflected light is lost.
(2) Retroreflection: Light ‘returns by the same path’
Retroreflection operates entirely differently: light striking the object reflects back along the incident direction, as if the light ‘returns home by the same route’. For reflective studs, this means the light emitted by vehicle headlights is largely reflected back into the driver's eyes, creating a clear light point visible even from hundreds of metres away.
(1) Step One: Light Capture
The stud's reflective layer (embedded with retroreflective material) actively ‘captures’ light from vehicle headlights. Its surface is optimally angled to maximise reception of forward-facing light, preventing loss due to misalignment.
(2) Step Two: Light Refraction and Reflection
Upon entering the retroreflective material, light undergoes multiple refractions and reflections to adjust its direction. Whether utilising glass microspheres or microprism structures, the light is ultimately ‘guided’ towards the incident direction, preparing it for the next stage of reflection.
(3) Step Three: Light Transmission to the Driver
The redirected light is then reflected back along the headlight's path into the driver's field of vision, forming a bright spot. A continuous sequence of studs creates a ‘light band’, clearly delineating the lane's trajectory.
(1) High-Refractive-Index Glass Microspheres
Structure: Tiny glass beads (0.1–0.5 mm diameter) embedded within a transparent resin layer, featuring a refractive index of 1.9–2.2 (significantly higher than ordinary glass at 1.5).
Function: Light first passes through the resin layer into the glass bead, where it refracts before striking the aluminium reflective coating on the rear surface. After further refraction, the light exits the bead and returns along its original path towards the headlight source.
Advantages: Low cost and stable performance, suitable for most standard road conditions.
(2) Microprism Film
Structure: Manufactured from highly transparent polyester material, its surface features a three-dimensional prism structure measuring 50–100 micrometres, resembling countless miniature ‘reflector arrays’.
Functionality: Light entering the prism undergoes total internal reflection across three prism surfaces, with the reflected light emerging parallel to the incident beam for highly efficient return to the light source. Its reflectivity is 3-5 times that of glass microspheres.
Advantages: High reflectivity, strong penetration in foggy conditions, service life of 7-10 years, suitable for high-standard applications such as motorways and mountainous roads.
Function: Applies a transparent, scratch-resistant, UV-resistant coating to the retroreflective material surface. This shields the material from damage by vehicle碾压 and dust accumulation while ensuring unimpeded light transmission, maintaining optimal reflectivity.
Material Properties: Light transmittance ≥90% (virtually unobstructed light transmission), abrasion resistance withstands 1 million tyre passes, and UV resistance prevents yellowing and ageing.
Material: Manufactured from high-strength ABS plastic or aluminium alloy, with a load-bearing capacity ≥50 kilonewtons (≥100 kilonewtons for motorway-specific models), preventing deformation under vehicle pressure.
Shape Design: Slightly convex top protruding 5–10 mm above road surface (prevents coverage by standing water or debris); reflective surface angled 30–45° to road surface, precisely matching vehicle headlights' 1–2° downward beam angle to maximise light capture.
Light Source: Vehicle dipped headlights (most commonly used night lighting), with an illumination range of 10-100 metres.
Functionality: The retro-reflective material captures the dipped beam light, reflecting it back to the driver's eyes, with a visible distance of 200-300 metres. Continuously arranged studs form a ‘light band’, enabling drivers to anticipate lane direction in advance.
Key point: The reflector angle is specifically optimised for low beams, preventing glare and ensuring clear visibility.
Challenges faced: Rainwater covering the road surface renders road markings ineffective, while fog scatters light, making traditional markings nearly invisible.
Adaptive Mechanism:
The slightly raised stud body rapidly drains water, preventing the reflective layer from becoming submerged;
The microprism material concentrates reflected light, minimising the impact of fog dispersion. Even in dense fog with visibility reduced to 50 metres, it maintains a visible distance of 80-100 metres (compared to approximately 30-50 metres for glass bead variants).
Requirements: Vehicle speeds of 60–120 km/h necessitate extended reaction distances, requiring earlier detection of road studs.
Performance enhancements:
Microprism material increases visibility to 300–500 metres, affording drivers ample reaction time;
Reduced marker spacing to 5-8 metres creates denser ‘light bands’, aiding rapid identification of lane changes, bends, and gradients.
Misconception 1: ‘They emit light like LED lights’
Fact: Reflective markers possess no active light-emitting capability, relying entirely on reflecting external light sources (e.g., vehicle headlights). Without illumination, they become indistinguishable from ordinary stones – fundamentally different from battery-powered solar LED studs.
Misconception 2: ‘Brighter headlights yield better reflection’
Fact: Excessively bright lights (e.g., modified high-intensity lamps) cause glare, impairing drivers' ability to discern stud reflections. Optimal performance is achieved when standard dipped headlights or main beams align with the reflector's angle of incidence – brighter is not necessarily better.
Misconception 3: ‘All reflective studs operate on the same principle’
Fact: Glass bead studs function via ‘refraction-reflection’, while microprism studs operate through ‘total internal reflection’ – fundamentally different mechanisms. This results in microprism studs offering higher reflectivity, superior fog performance, and suitability for more demanding conditions.
Principle difference: Marking paint relies on diffuse reflection, wasting most light; reflective studs use retroreflection, maximising light utilisation. During rainfall, road marking paint becomes covered by water and loses its reflective capability, whereas the convex design of studs avoids pooling water and maintains normal operation.
Reliability Difference: Solar studs rely on battery power and cease functioning during prolonged overcast or rainy periods due to depleted charge. Reflective studs require no electricity and operate whenever illuminated by headlights, eliminating the risk of ‘power failure failure’ and offering greater reliability.
Reflective Efficiency Gap: Traditional cat's eye studs, made from ordinary glass without retroreflective design, offer visibility of only 50-100 metres. Modern reflective studs (especially microprism types) provide 2-3 times greater visibility, delivering superior performance.
Regular cleaning: Monthly high-pressure water jet washing of stud surfaces to remove oil, dust, and fallen leaves, preventing light obstruction.
Avoiding damage: During roadworks, shield studs with protective barriers to prevent crushing by heavy machinery. Immediately replace studs with scratched or peeling reflective layers.
Angle Check: Conduct inspections every six months. If studs tilt due to vehicle impact, this causes deviation in light capture angles, necessitating readjustment or replacement.
Height Check: Ensure studs protrude 5-10 millimetres above the road surface. Studs set too low risk being obscured by debris, while those set too high risk damage from vehicle scraping.
Glass bead studs: Replace every 5-8 years. Resin layers and glass beads degrade over time, reducing reflectivity.
Microprism studs: Replace every 7-10 years. Prolonged UV exposure degrades prism structures, impairing total reflection.
The operating principle of reflective studs is straightforward: utilising retroreflective materials (glass beads/microprisms) to reflect light back along its original path. Combined with optimised structural design and protective coatings, this achieves a ‘self-illuminating’ effect without electricity. This simple yet highly effective design makes them the ‘guardians’ of night-time road safety.
Requiring no electricity, featuring low maintenance costs, and adapting to diverse road conditions, reflective studs offer exceptional value as traffic safety infrastructure. Particularly in night-time and low-visibility scenarios, no other signage can fully replace them.
Should you require road safety upgrades (such as optimising urban or motorway markings) or bulk procurement of reflective studs, please contact us. We supply products compliant with international/national standards including EN 1463-1 and GB/T 24725, ensuring reflective efficiency meets specifications. We also provide on-site installation guidance to guarantee each stud functions reliably, safeguarding every journey.
