Major changes to plans for the expansion of the Dart have dropped the underground element completely in favour of four new stations at ground level, the Irish Independent can reveal.

The cost of the revised proposals is half what was originally budgeted by the National Transport Authority - but, controversially, will benefit only the northside of Dublin city.

Documents seen by this newspaper show the NTA now wants to extend a Dart service from Heuston Station through the Phoenix Park Tunnel to new stops in Cabra, Glasnevin and finally the Docklands.

Aside from the fact it completely boycotts the southside, the route is likely to draw political comment as it will primarily serve the constituencies occupied by Taoiseach Leo Varadkar and Finance Minister Paschal Donohoe.

The long-delayed underground project had proposed stations in Inchicore, Heuston, Christchurch, St Stephen's Green, Pearse Street and the Docklands.

It is understood the estimated cost for the revised expansion is €1.95bn, compared with €4bn for the original plan to tunnel under the city.

According to the documents, the NTA believes it should "prioritise" investment in non-tunnel elements as "this will enable additional services to be put in place much earlier". The plan is to rely heavily on existing infrastructure rather than create new routes, meaning a large part of the cost will be new trains.

The expectation is that Irish Rail will buy hybrid trains that can run on electricity or diesel.

The Government's 'Project Ireland 2040' sets out plans for high-frequency electrified services to Drogheda on the Northern Line, Celbridge/ Hazelhatch on the Kildare line, Maynooth and M3 Parkway on the Maynooth/Sligo line, while continuing to provide Dart services on the south-eastern line as far south as Greystones.

But the NTA documents outline how it wants to push ahead with the Dart expansion, initially without electrification.

According to an indicative timeline, it will be four years before the new Demu hybrid fleet will be available.

Between 2022 and 2025, the new Dart vehicles will be deployed to provide services on the Drogheda line every five minutes, while the frequency on the Maynooth and the Celbridge lines will be every 10 minutes.

Electrification of the lines will be completed between 2023 and 2027.

Project Ireland 2040 includes maps showing the underground route, but doesn't include any funding for it.

The alternative now being drawn up would enable commuters - who would currently have to exit their Dart at Heuston - continue into the city.

The service will link up with the Metro line at a new station at Cross Guns Bridge, on Whitworth Road in Glasnevin.

From there, the Metro will travel north to the airport or south through the city centre, including St Stephen's Green.

Irish Independent