In message , at 23:33:00 on Mon, 3 Apr 2017,
Anna Noyd-Dryver remarked:

If a train is stranded without a functional driver then the situation
can serious especially if the signalling is such that the signaller
doesn't know exactly where the train is. I dread to think what might
happen if this is somewhere without mobile coverage.

It's a balance between what might go wrong once a year, and the cost of
all those guards.

Taking the recent concrete example of introduction of DOO, I'm pretty sure
the agreements on Southern (for now at least) involve a member of staff
being on every train (with limited exceptions), and I'm pretty sure they
were re-employed on their new contracts with no loss of pay. Obviously both
of these things may change in the future, but at present, where does your
huge cash saving come from?

The ongoing training programme, training of new guards, and as you
suggest the employment of new on-train staff at a different grade,
despite not "demoting" the grandfathered-in existing guards.
--
Roland Perry