The first train journey on the new Midleton to Cork line took place this afternoon.
The opening of the new commuter route, which is a €75m investment, is part of the Government's Transport 21 programme.
Trains will operate every 30 minutes at peak time and journey times between Midleton and Kent Station in Cork city will be 24 minutes.
The line was officially opened by Minister for Transport Noel Dempsey. To mark the occasion, travel on the new service will be free to the public today.
An initial service will operate up to Bank Holiday Monday 3 August, before the full commuter service begins on Tuesday 4 August.
All trains will serve the new stations of Midleton and Carrigtwohill, as well as Glounthaune, Little Island and Kent Station.
Each train will be a two-carriage commuter train, with capacity for 320 passengers, including seating for 129 passengers.
Platforms have also been built to accommodate future expansion to four-carriage trains.
Minister Dempsey said: 'The reopening of the Cork to Midleton rail link is fantastic news for all those living and working in the region.
'I have no doubt that Midleton, and the Cork region in general, will benefit enormously from these new services in the years to come.'
Full details of and timetables for the new service are available on Iarnród Éireann's website.
