> For example, the Dutch railways deploy a mush of sand, potato fibers and iron particles on top of the mush to give trains the necessary grip when they brake

> For example, the Dutch railways deploy a mush of sand, potato fibers and iron particles on top of the mush to give trains the necessary grip when they brake That sounds like Sandite, which is definitively in use on the UK rail network. But I think the cleaning effect of that is still relatively limited, and the adhesion improvement only lasts a certain number of trains, after which the material needs to be re-applied again to the track.