Trams will begin running on the new Luas Cross City Line in June as engineers begin testing in advance of full passenger services.
A gauge run will take place in the summer which will last for up to 12 hours and allow experts to examine performance on each stretch of the 5.9km line.
A spokeswoman said that full passenger services would begin in the first half of December, more than four years after construction works began.
"In mid-June, there will be a gauge run", she said. "We will run a tram from St Stephen's Green at walking pace, with people from Transdev (the operator), the contractors, gardaí and Dublin City Council running diagnostics. It will take between 12 and 14 hours.
"We have to check every single inch of the route from the perspective of the driver, checking signalling, and how the tram physically moves through the city. Another tram may also run in the opposite direction."
Luas Cross City will cost €368m, and works began in June 2013. It will add 10 million passenger trips per year, and reduce private car trips by one million.
It is an extension of the Luas Green Line, and runs between St Stephen's Green and Broombridge, where it will interchange with Irish Rail services. The journey will take 21 minutes. Those intending to switch to the Red Line, serving the Point Depot and Tallaght, will change at O'Connell Street.
Some 13 stops will be installed, eight in the city centre. All track has been laid in the city, and the depot at Broombridge will be completed by May.