This may be me misunderstanding the feature, however once the tunnels are entered I would expect outside weather to have minimal impact upon the adhesion function of the 1972 stock. When I have set the weather to snow on a Harlow and Wealdstone to Elephant and Castle Service, the outside portion works as expected with the reduced adhesion. However when in the underground section of line, the train still behaves as if I was driving in snow (slow to pick up power and skidding when hammering on the breaks).
I've yet to experience this myself, however, in real life I'd expect there to be a minimal reduction in adhesion when 'deep' inside the tunnels. However, when entering the tunnel from the outside there may well be contamination on the wheelsets picked up from the railhead
They mentioned this in one of the streams, apparently you'd expect there to still be some adverse affects but not as severe as outside of the tunnels. Personally I'm not entirely convinced, especially in the deeper sections, it behaves the same as going under a bridge in game rather than in a long damp but dry tunnel. Seems odd to have wheelslip coming out of Elephant and Castle for instance
