In message , at 16:48:32 on Fri, 29 Mar
2019, Ian Clifton remarked:

I’m struggling to make the conditions of the puzzle really concrete.

I'm tempted to say "don't you just love it when civilians try to be
policy wonks".

But the question as posed was almost tightly enough drawn nevertheless.

My own reservations were only about whether doubling back (thus
requiring perhaps specialised ticketing) was allowed as part of the
challenge, as well as enforced overnight - or even longer - layovers.

For example, Denton to Reddish South, which until recently took a week
with two double-backs, if we stick to the "on the same line" rule.
--
Roland Perry