Belfast-Dublin Enterprise train service needs £239m
The Belfast-Dublin train service needs £239m spent on it to cut journey times and improve its timetable.
A plan by Translink and Iarnród Éireann, who jointly run the Enterprise, suggests it would take five years to make the changes.
New trains costing £44m would enable hourly departures from each city.
A further £195m would allow track improvements to be made, reducing journey times by 15 minutes to under two hours.
Enacting the plan will require funding commitments on each side of the border.
About one million passengers use the Enterprise annually.
Speed restrictions on "lengthy sections" of track add 15 minutes to the travel time between Dublin and Belfast.
Eight daily departures each direction "compares poorly" with many other paired European cities, which have five times the frequency.
Investment for a significant overhaul
The plan states the "minimum service standard" should be an hourly service in each direction.
Longer term improvements, including cutting journey times to 90 minutes, would cost an estimated £630m and involve electric trains and lines.
"The next steps are to secure funding to take this project forward," said Frank Allen, Chairman of Iarnród Éireann.
Chairman of Translink Frank Hewitt added: "Developing the Enterprise service will be essential to further strengthening economic links and is key to building competitiveness and increasing close communication links between our two capital cities."