The first of 26 new longer Luas trams is up and running on the Green Line.
The new tram is 11.1m longer (at 54.7m) than older models and will increase capacity by 30%, from 319 passengers to 408.
The remaining 25 new trams are expected to be in operation within the next 14 months.
It's hoped this programme of investment will go some way to ease the pressure on the Luas Green Line, which is in particularly high demand.
Tom Manning from Transport Infrastructure Ireland said there will not be the same roll out on the Red Line.
"We're not planning on introducing any longer trams because there are constraint issues on the Red Line. It wouldn't be appropriate to have the longer trams.
"We will increase the number of trams over time [to match] demand."