This design was sent in by one of our readers. It is indeed a useful idea and could be implemented at several locations. An additional advantage is the reduction in air friction to the passage of the train.
If sufficient numbers of these shafts were to be installed then alternative shafts could be designated as hot and cold to prevent 'pendulum effect'.
Apologies to the originator of the post, we lost his details. Please contact the site so that we can give credit for this submission -
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