“Retroreflectivity”, try saying that 3 times! 

So, what is it and why is it important? 

Retroreflectivity is what occurs when a surface reflects light back to its source. 

As engineers, we like to harness this phenomenon in traffic signs to improve their visibility on the road. This is usually done in two ways: 

1 – Either through integrating hundreds of small glass beads into the sign, allowing light from vehicles to enter, refract, and then be reflected back to the road user. 

2 – Or through hundreds of prisms, where small reflective cube corners are built into the sign, allowing light to bounce off internal angles back to the road user. 

Newer, brighter signs typically use the prismatic system. 

Reference: https://www.3m.com/3M/en_US/road-safety-us/resources/road-transportation-safety-center-blog/full-story/~/road-signs-retroreflectivity/?storyid=328c8880-941b-4adc-a9f9-46a1cd79e63