Details of a planned DART extension to Maynooth will include the closure of six level crossings, according to the National Transport Authority.
The NTA says it will treble capacity on the Maynooth/M3 Parkway lines.
DART+ West is the first phase of a programme that will eventually see the electrification of other lines bringing the service to Celbridge and Drogheda.
Minister for Transport Eamon Ryan said: "The first phase, DART+ West will have a hugely positive impact, not just at its terminal points in Maynooth and Dunboyne, but in areas like Glasnevin, Broombridge, Pelletstown, Ashtown, Castleknock, Coolmine, Clonsilla, and Leixlip, all of which will now be on an integrated, electrified, fast and reliable, rail network.
"If we are serious about reducing greenhouse gas emissions – and I know I am – this is precisely the kind of project that should be happening."
The expansion to Maynooth/M3 Parkway will involve the electrification of 40km of track and increase capacity from seven services an hour to 15 which increase passenger numbers from 4,500 to 13,750.
The increased frequency will mean the closure of six level crossings.
Although the NTA has promised to provide alternative arrangements including bridges, local residents are concerned about the impact.
Residents in Coolmine feel they will be cut off from schools, churches and shops.
There are also concerns about how the disabled and elderly can cross high pedestrian bridges.
The NTA say it is beginning public consultations with a planning application to be made next year with a completion date for 2024.
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The deputy chief executive of the NTA has said it was not possible to extend the DART to Maynooth without changing road networks and building bridges to replace existing level crossings.
Speaking on RTÉ's News at One, Hugh Creegan said the extension of the DART network to Maynooth would take between two to three years to construct after planning is obtained, with plans to apply for permission to An Bord Pleanála next summer.
He said "good proposals" have been put forward to replace the six level crossings with three road bridges and three pedestrian bridges.
Mr Creegan said currently the level crossings close very frequently in busy peak times - sometimes for 40 out of 60 minutes - and as train frequencies increase they will need to shut more frequently, which is unsustainable.
He said that these new roads and bridges will allow people to continue their journeys and will not hinder access to anyone's home.
The final cost will not be known until the final design is finished, Mr Creegan said, adding that there is €2 billion earmarked for it in the National Development Plan.