Retro-reflective material: how does it work?

Reflective surfaces are everywhere, from road signs and safety clothing to the number plates on your car. The type of material used is known as ‘retro-reflective’ because it bounces back light from another source. But exactly how does this work?

Light relief

As we hinted in the opening paragraph, reflective material is all about light and what happens to it when it hits a surface. Most reflective materials rely on one of two concepts, one being glass beads, the other microprisms.

Glass beads are usually found in things like road markings where they are mixed in with the paint on white lines. Microprism material is used on signs and the reflective tape used on vehicles. In either case, the basic principle is the same, light hits the bead or microprism and bounces back. However, because microprisms have a larger area and it’s more evenly sized, it is able to reflect back more light.
The effectiveness of reflective surfaces can be adversely affected by factors like moisture. Microprism surfaces avoid this by having a smooth plastic surface allowing water to run off and therefore minimising the effect of rain on the effectiveness of the reflector.

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Reflectors in the real world

We’ve already mentioned some of the places where you can see retro-reflective material at work. Anyone who uses the roads will encounter it on a regular basis. Road signs, for example, are reflective so that they can be clearly seen in your headlights at night or in bad weather.

Similarly, vehicles make use of reflective material. Lorries have had to carry reflective markings on the rear in the UK since the 1970s, and reflective number plates on all new vehicles became compulsory in 1975. From 2010, HGVs have to have reflective markings on the side of the vehicle too, so as to be visible in all circumstances.

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Vehicles that work on the roads, from police cars to maintenance vehicles, have liveries using reflective markings to help them stand out and ensure that they can operate safely, for example, Chapter 8 chevrons such as those supplied by https://www.vehiclechevrons.com/.

Vulnerable road users like cyclists and motorcyclists often use reflective jackets or belts to make themselves more visible too. European law requires that people who work on the roads must have reflective material on their uniforms too.