Michael Bell wrote:
It is a fairly obvious feature of railways south of the river that
many run at roof level.
I once got into correspondence with somebody who said "It is the
long-term objective to put these routes underground".

I felt like asking "Are you on the same planet as me? The cost
would be astronomical, and for what benefit?", but I let it drop.


Well yes and no, they run at a relatively flat uniform level it's the
land around it that determines whether the line is level with roofs. SO
most railways I can think of alternate between being on embankments and
in cuttings

Surely his idea s flawed by the fact that it would be difficult enough
to put a 'roof level' railway underground, let alone lowereing a railway
line in a cutting by the same amount