Every year millions of car tires are worn down on our highways, yet the roads are not all black from the rubber, neither are the sides of the roads black. Where does all the rubber go?
First, "all that rubber" is really a very small quantity when spread out over all the road surfaces. Second, you sometimes do see rubber marks on the road. This is especially true on concrete roads where the surface is light colored. Asphalt is dark, so much of the rubber markings are not obvious.
Since so little rubber gets deposited per time on a normal road under normal use, most of it gets washed away by rain or blown away by wind, then dispersed so much that we don't notice it. The sides of roads are more dusty places than a few meters further from the road.
Again though, in most cases the total quantity of tire rubber in any one place is so small that we don't notice it.
The rubber which wear's out from the tire's are very small in size and yes they are in very small quantities and it blow's way in he wind and goes away on a world wide trip
If you want see the wearing of the tire's and accumulating on the road the skid mark's are good example and you want to see even more then watch the starting points of the track of drag races where the racer's do the burnout you can see the weard-out rubber and if they allow you on the track you can event take them on your finger tip's.