How many glass beads for Road marking?

When road marking there need glass beads for night-time visibility of traffic lines/signs.
Glass beads has the property of sending the incident light back to its source when it's laid in the road-marking paint.
For the best result of retro-reflection, the beads to be buried half in the film of marking medium (paint)


To obtain the best condition of reflection, premix(drop-in)beads shall require 15-20% by weight of the total marking medium.
when needs of drop-on, demanded beads Shall be 25-30 grams per 15cm(W)x100cm(L) of marking line for an optimum result. Normally 850-106 um of beads are used for roadmarking. Thesedays it, however, trends touse larger sized of beads (eg. 1.0mm-2.0mm) for improving the reflection of pavement in some advanced countries even the proce is rather higher(This is so called "LARGE BEADS")