| The Wikipedia page has detail on this:
https://en.wikipedia.org/wiki/Dartmoor_line Essentially the line went through the closure procedure and was completely closed to passengers back in the 1970s, however it remained open for stone trains from a quarry on the line. The quarry bought the line and ran their own trains. They occasionally allowed occasional passenger services. Various groups tried to run the route as a heritage railway between 1997 and 2019. The local county council subsidised a few experimental timetabled services on Sundays to see if there was a demand. This is very expensive for the council and they probably couldn't afford a 5 or 7 day a week service. Plus Sundays are a less busy timetable in general so some spare trains may be available that is not available the rest of the week.
(Saving the need to obtain additional trains for the extra work) Also I seem to recall, but can't source the statement, that the quarry owners may have set a limit on when and how many passenger trains could run over their line. Ie possibly Sundays ok, Weekdays not. It probably made them next to nothing, while incurring extra expense because passenger lines have higher requirements than freight lines. The more that run the higher the cost. Finally a government programme to reopen railways supported the full reopening that happened a few days ago. This involved buying the line and repairing the track. |