T.S. Cordiner typed:
I am trying to understand what the real issue is and, other
than the flat fare which I accept is a big difference, how NYC
manages to operate a subway safely without the gateline staff.

And the real issue keeps getting explained to you! NYC manages to
operate without gateline staff because, as in Paris, the exit gates
don't require a ticket. This is not the case in London, where in order
to combat fraud in connection with a fairly complex fare structure, the
exit gates require a ticket to open them. This means that situations
can arise where passengers' health and safety could be endangered if
they were unable to exit from a station, or unable to do so sufficiently
quickly in an emergency. Is it clear to you now?
--
Richard J.
(to e-mail me, swap uk and yon in address)