Pretty much as per the title - with the addition of the exhaust fumes (which is nice) there is a problem in that if you stand in the flyover at Reading as a HST (for example) passes underneath, the exhaust appears through the floor and up into the ceiling of the building. I was too slow to get a screenshot sorry.
Well you would kinda need to add smoke colliding with absolutely everything in order to 'fix' this. Might not be worth the trouble, especially considering how smoke is not very realistic overall and effort spent on making smoke physics work would be better off spent making smoke look better since 99% of the time smoke doesnt clip through anything.
Been that way for years in TS.Some smoke just looks more realistic.Not really dense enough to worry about.
I have a screenshot where it is black smoke. Just when i started accelerating. Look at my screenshot in my spotting topic