The first of Northern Ireland Railway's new fleet of trains has made its first journey from Portadown to Bangor.
The new trains will not be fully operational until later next year
The three-carriage train is the first of 23 to be purchased from Spanish firm CAF in an order worth £80m.
Two more trains are scheduled to enter passenger service by the end of the month and another train is expected to be added every fortnight after that.
Translink chief executive Keith Moffat said the trains would help tackle overcrowding and reliability.
The new trains were manufactured by CAF at Zaragoza in northern Spain.
Journey times are set to be cut with the new 90mph trains, which have faster start-up and braking mechanisms.
The silver and blue carriages are air-conditioned, carpeted and fitted with aircraft-style seating for up to 200 passengers per train.
They have CCTV, audio announcements, wheelchair access and toilets for the disabled.
All trains are expected to be in passenger service by the end of 2005.
Mr Moffat said: "Reliability is the number one priority. That is the biggest first objective, to get a more reliable service.
"But you can't expect too much until we have got the whole fleet in. We are not going to try and accelerate the timetable until we have got the whole fleet working.
"And that will be done progressively through next year."
He said the new trains would give more capacity.
"Once we have got all the trains we can develop a new timetable which will include higher frequencies, so there will be more service, more seats," he said.
"Obviously if we attract more people we will get more crowding but that is a nice problem which would then justify more trains."
"The aim is to expand the use of the train service."
Translink chairman, Dr Joan Smyth said: "This is an historic day for Northern Ireland, and marks the beginning of a very exciting period for rail travel."