I’m pretty sure they grease the rails in some spots, particularly the curvy bits that are often near platforms so it would get stuck to the rails and such. Cars would put out massively more pollution but it’s more free to blow around in the wind.
I had some boxes stored in a storage cage in my apartment car park and after 6 months sitting there, they were all coated in a thick black dust. Since there was no wind or rain to move it around, it just settles and builds up.
They don't grease the cross beams on ceilings though, and those things are nasty in train stations. Same stuff you see creeping up the walls around the tracks in the subway tunnel. Not a competition though, the pollution is bad and we're all so used to it.
It is quite important to discuss exactly where the top sources of pollution are through so we can cut back on the worst sources of them to have the most impact.
I had some boxes stored in a storage cage in my apartment car park and after 6 months sitting there, they were all coated in a thick black dust. Since there was no wind or rain to move it around, it just settles and builds up.