Looking at the ORR station stats the following 'lines' are very quiet:
Ely to Norwich
Hello,
What train lines in the UK have the least annual ridership?
Looking at the ORR station stats the following 'lines' are very quiet:
Newcastle-Edinburgh (local services)
Grantham to Skegness is heavily seasonal however, it can get quite busy in the summer but is dead in the winter.
That's because they don't exisit (yet...hopefully)
You may mean the Newcastle - Chathill services, which I do believe are pretty quiet, especially north of Morpeth