What makes signs and pavement markings appear to glow in the dark?
The material or “sheeting” used on traffic signs is Retroreflective. “Retroreflectivity” means that when light strikes the surface, it is reflected back to the source. When your vehicle’s headlights shine on a sign, it is reflected back to the driver. The retroreflectivity is caused by tiny spherical glass beads imbedded in the sign sheeting. The same effect for pavement markings is achieved by dropping the tiny glass beads onto the wet paint as it is applied to the surface of the road.
