[ars]

If the particles were coming from the road then roads would wear in very visible ways.

But we don't actually see that kind of wear. Roads don't typically have grooves on them where the cars go that are lower than the middle which doesn't have tires driving over it.

[kungtotte]

Come to Sweden sometime.

I've driven down highways where you don't have to steer because the ruts are so deep.

[hammock]

If you look it's actually p clear where on a road (e.g. highway) cars are driving , wear patterns can definitely be seen.