Stormont has splashed out £1.5m on a railway track that has not been used since 2003.
The Knockmore line is a 20-mile stretch between Lisburn and Antrim that passes Belfast International Airport.
Despite not being in service for 13 years and with no plans to reopen it, almost £1.5m has been spent on the line since 2012.
Some £67,200 was spent on repairing damage after a section of railway embankment collapsed, but the bulk of the money - £1.3m - was spent on essential safety works.
The figures were revealed in response to an Assembly question asked by East Londonderry MLA John Dallat (SDLP).
He blasted a "lack of long-term vision" with regard to trains.
In response to the question, Regional Development Minister Michelle McIlveen said the line was maintained sufficiently to allow it to be used for the occasional diversion of passenger services, for engineering runs and for training purposes.
Mr Dallat said keeping the line closed was a missed opportunity to create a direct service from Londonderry to Dublin.
"The Knockmore line is critical to re-engaging Derry with Dublin. At the moment you have to go to Belfast and change trains, and get another one to Dublin," he said.
"The experts I have talked to believe you could have a three-and-a-half hour journey from Derry to Dublin if the Knockmore line was back in operation."
He also pointed out that reopening the line could see a train service to the International Airport. "But it seems that we have almost gone deliberately out of our way to ensure our trains and planes are not linked," said Mr Dallat.
"For example the Derry to Belfast line literally passes through the City of Derry Airport. In Coleraine, the railway is just at the back of the new hospital, and [it is at] Belfast City Airport. I see people every day having to make that walk along the road up to the bridge to the Sydenham halt. Aldergrove is also missed out. Some time we are going to have to seriously organise the railways around people."
A DRD spokesman said: "Belfast International Airport is served by a designated Airport 300 Service, departing Europa Bus Centre. The service operates from Monday to Friday with a frequency of 15-20 minutes at peak times and every 30 minutes at peak times on Saturdays and Sundays."