Texture over Roads?

Is there a way to add a texture on top of roads? Or do I need to texture the road (spline) itself. I am trying to have a portion of the road with a layer of sand like it's been blown across the road by the wind. I tried adding a layer above the route and that didn't work. I suspect this is something that can't be done (at least not easily).

It could be done by raising the terrain level just slightly above the road level. The road level spline height would have to be fixed on each side of the "sand drift".