Luas passengers face massive disruption if construction proposals for the new Metrolink are given the green light.
Options being considered by planners could see passengers having to get off the Luas, get on to a bus and then back on to the Luas after several stops.
Initial estimates are that there could be around six months of disruption while the construction is completed to merge the Metrolink line with the Luas Green line.
However, there are concerns that this could take much longer.
Disruption would be caused between Charlemont, by the Grand Canal, and Sandyford, near the end of the Green line on the south of the city.
Transport sources said a number of options are on the table for planning stakeholders.
It is understood the National Transport Authority (NTA) is hoping to cause as little disruption as possible, and has indicated a six-month deadline for work to take place in order to put pressure on construction companies to get it done quickly.
One of the two main options being discussed is to remove services completely between the two stops, which accounts for a large part of the Green line.
Planners may decide to use buses entirely between the two stops or "staggered tie-ins" that will leave different stops out of action over different periods.
This option would see construction taking place in different sections of the Luas line and could leave a smaller number of stops under construction at the one time.
However, in practice, this would see passengers on the busy service get off the Luas at a particular stop and bypass the stations or stops undergoing work.
The bus will then revert back to the Luas at a stop that is not under construction and passengers will continue their journey by tram.
A spokesman for Transport Infrastructure Ireland (TII) said it is still in the early plann- ing stages and that the public consultation process is continuing.
He added that nothing has been finalised in relation to the process of integrating both lines.
Along with completing construction works on the new line, the NTA and TII must be given the go-ahead to put the line into operation.
"Our approval process takes place in parallel with design and construction," said a spokesman for the Commission for Railway Regulation.
"We have no application for approval at this time."