The shutdown of the southside DART line at weekends for the next nine months will put a massive strain on Dublin traffic as people are forced to take buses and cars into the city, according to the AA.
The announcement that the line between Grand Canal Dock and Greystones will be closed on Saturdays and Sundays until next May or June - apart from two Saturdays before Christmas - has alarmed city centre businesses. The closures begin this weekend.
Iarnród Éireann estimates that between 34,000 and 39,000 DART passengers will be displaced by the loss of the southside weekend service. It will be replaced by additional Dublin Bus services.
"It puts massive pressure on the infrastructure of the city, both with private cars and the Dublin Bus service," according to AA spokesman Mr Conor Faughnan.
The weekend closures are to make way for the first phase of a €176 million track and station upgrading to increase DART capacity by 30 per cent. The upgrading work will take place on every weeknight and every weekend from late Friday until early Monday morning.
Similar work will be carried out later on the DART line in the city centre and on the northside. It is expected to begin next summer, with a completion date of early 2005.
Up to 40,000 people could be displaced by the absence of the southside trains each weekend, Mr Faughnan said. "Those people either choose not to go to Dublin, which is a loss to city businesses, or they have to go a different way.
"A challenge now presents itself to Dublin Bus to offer greatly-enhanced service."
Dublin Bus is doubling the buses that operate on southside routes, including the 7, 45, 46A, 59 and 84.
Many commuters who will be affected by the DART line closures only found out yesterday morning.
"It's disgraceful that they would put out a notice on a Tuesday morning that the whole thing is going to be suspended four days later," said Progressive Democrats TD Ms Fiona O'Malley.
Ms Róisín Shortall TD, the Labour Party spokeswoman for transport, said Iarnród Éireann should have better informed their customers.
"Like a lot of people I was aware that there was upgrading to be done, and goodness knows it's long overdue, but I don't think anybody realised the extent of the disruption that would be caused to services."
Mr Barry Kenny, a spokesman for Iarnród Éireann, said the rail service announced upcoming closures in March, and has said it repeatedly since.
He said the project was moved along quickly because of the urgent need for improvements.
"It is going to cause disruption in the short-term, but it's about building badly needed capacity into the DART system.
"There are thousands more people using the system and service, and we need to start now because the demand is going to keep growing."
The closures coinciding with the run-up to the Christmas shopping season also caused some concern. In response to the criticism, Mr Kenny said: "The project takes 18 months. It will be running up to Christmas at some stage."
Mr Cian Connaughton, of Dublin Chamber of Commerce, said Christmas was worth €3 billion in sales last year for city businesses, and that the chamber was supportive of the improvements, but was concerned that there would be alternative transport for people who would normally use the DART to go shopping.
The DART will run on the two weekends just before Christmas.
This phase of the project includes lengthening the platforms to facilitate eight-carriage trains instead of the current six-carriage trains, and enlarging stations to accommodate more passengers.