What I remember particularly about travelling by train in the 1940s and 1950s were the windows in the doors. They had probably changed little since the early days of the railways, but that of course was outside my personal experience.
'Health and safety regulations' had not been dreamed up, and the windows in the train doors opened so that passengers could lean out. This they did, particularly when waving goodbye to people seeing them off.
There were notices pointing out that it was dangerous to lean out of the window while the train was moving, but it didn't stop anyone.
Leaning out of a train window of a moving train was a particularly enjoyable experience for children: to feel the wind rushing into one's face and through one's hair and to see the engine belching out smoke as the train rounded a bend.
A particular problem with leaning out of a train window was the smoke from the steam engine which was pulling the train. It was sooty from the partly burnt coal: it got into eyes and made faces black. So children were encouraged to 'stay inside' when out visiting; otherwise there was a quick lick and a promise from mother's handkerchief.
Irrespective of whether anyone was leaning out of the window, it was not always easy to get agreement among the passengers about how far the window should be pulled down. It could be far too draughty for passengers sitting facing the direction of travel, but not for the passengers facing them.
In the first half of the 1940s I suppose there must have been mesh stuck onto the train windows against the bomb blasts of World War Two, but perhaps this was only done for trains based in London. I only remember it for the London Underground.
Either way, any mesh was probably removed as soon as possible after the war ended, because it was so unpleasant being unable to see out of the windows.