Cat’s Eye: Reflective Road Marker
"The Cat’s Eye invented in 1933 features reflective glass spheres set inside a rubber and cast-iron housing. Each unit is complex and dynamic, its various materials engineered to serve a variety of clever functions.
The metal part of the housing protects the device while creating an audible sound when a car passes over, like Botts’ Dots. Meanwhile, a fixed rubber wiper clears off the glass when it is pushed under the road. The Cat’s Eye is also retroflective, meaning: it redirects light back toward its source with minimum scattering, optimizing visibility for cars in motion."