Whenever you are driving your car at night, glass beads present on road markings act as tiny reflectors which send the light from the headlight back to the driver so that he or she can clearly see the road. Without glass beads, most of the light would just travel in the forward direction making night time driving dangerous. It is very important that the glass beads are of spherical shape to give maximum retroreflection as shown in the diagram.
Though different countries have different size specifications for road marking glass beads, they can be broadly divided into 2 types:
a) Intermix Glass Beads: As the name suggests, it is intermixed with the road-marking paint premix and then laid on the road.
b) Drop-on Glass Beads: Again as the name suggests, it is dropped on to the road marking paint as it is being laid. Due to this form of application, drop on glass beads give instantaneous refection.
The road marking glass beads types are further described in literature with their size specifications.