The number of trams on the Luas line from Tallaght to Connolly Station is to increase by 30 per cent.
The route has been operating at almost full capacity since it opened two months ago.
The Minister for Transport said the increase from six trams to eight trams per hour would allow the Luas to carry another 10,000 passengers. The trams will arrive at seven and a half minute intervals, instead of ten minute intervals, from next month.
"If the trams run more frequently, we can carry more people. This will get more people out of their cars and onto public transport," said Mr Cullen. The waiting times are set to reduce again in the new year when trams on the Tallaght line will run at five minute intervals.
The Tallaght and Sandyford lines are now carrying 40,000 passengers each day.
The €800 million system is expected to carry six million passengers by the end of the year.
However, the Railway Procurement Agency had to review warning signs on the routes following a series of collisions between trams and cars. It is currently planning to extend the Tallaghtline to the Dublin Docklands and the Sandyford line to Cherrywood.
Mr Cullen is also investigating the possibility of building a one kilometre stretch of track to line the two rail lines together.
PA