The Taoiseach has officially opened the LUAS red line from Tallaght to Dublin city centre.
Speaking at a launch event in Tallaght, Mr Ahern described it as an historic day and said the system was a vital component in the Government's transport strategy.
South Dublin Chamber of Commerce welcomed the launch, saying LUAS would make a big difference to the business community of Tallaght and South Dublin County, where there are 1,800 businesses and seven industrial estates along with 14 business parks.
'LUAS will be a catalyst for a new era of economic growth for Tallaght and South Dublin County, it is a 21st century mode of transport for Ireland's fastest growing 21st century town,' said CEO Peter Byrne.
