parliamentary train

noun1

1. •
   (UK) Originally a requirement in the Railway Regulation Act 1844 for railways to run at least one train a day each way, at a cost to passengers of no more than one penny a mile, on every railway line in the country. Presently the term is used for passenger trains that serve a line or station only once a day or week to avoid the cost of applying for closure.

   • He [Gladstone] also required the operators to run 'Parliamentary Trains' - one each day calling at every station at a fare of not more than a penny per mile for Third Class. — 2012