Irish Rail says the Dart line should be extended to commuter towns using hybrid trains.
The trains would run on overhead electric wires or diesel engines.
It would allow the Dart service to go as far as Maynooth, Co Kildare and Drogheda, Co Louth.
Iarnrod Éireann Spokesman Barry Kenny says capital investment is needed for the plan to go ahead.
"We need to start investing in new trains, but obviously we've got electrification coming down the line," he said.
"So while we wait for electrification to proceed, in order to build the capacity of our train fleet, we are looking at hybrid trains, that can operate on both diesel and electric power, so we get that early benefit with the growth in passenger numbers that we're seeing, and the growth in demand, and then that we're ready and we don’t have a redundant fleet when the electrification takes place."