Neil Williams wrote:
...which would instead cause similar crowds in stations or just
outside.

It wouldn't work, which is probably why it hasn't been done.

Why can't we air condition the stations at least? These can be just as
unbearable, and it can't be TOO difficult to do. Expensive, yes, but a
decent system could clean and filter the air too.

I know the deep level stations have the problem of heat extraction, but
if you can sort out the stations then it must help overall passenger
comfort. Else have part of a train that collects the extracted heat,
which is then vented at a station?

Jonathan