While rootling through the archives today, I came upon these two photos, of a single decker train and a double decker train, photoed within a few minutes of each other in Quimper, Brittany, in 2018:
On the left, a single decker train. On the right a double decker train.
Earlier this year I did a posting in which I ruminated upon the appeal of, but the disadvantages of, double decker trains. The above photos illustrate the problems of double decker trains rather well, I think.
Basically, a lot of bother, to achieve an only rather small increase in capacity.
That earlier posting was also about how much less clunky trains have become since when I was a kid in the fifties and sixties. But double decker trains must necessarily remain clunky, to support that upper deck, and to get people up to and down from it. Commenters Crozier and Jennings concurred, which was reassuring.
It’s a different story when it comes to long distance trains. For them, where there’s not so much getting on and off per journey, double decker carriages make more sense.