Accordingly, when the Irish Government published a new national spatial strategy in 2018, the revised plans dropped the DART Underground scheme in favour of these existing lines.

In 1975, CIÉ commissioned the "Dublin Rapid Rail Transportation Study" (DRRTS),[19] which recommended a four-phase plan including a prototypical Dart Underground: The DRRTS, if completed as envisaged in 1975, would have resulted in a cross shaped pair of tunnels in the city centre meeting at a central station in Temple Bar.

[19] The next plan, proposed in 2001 as an "Interconnector", was included in the Platform For Change strategy report issued by the now defunct Dublin Transportation Office (DTO).

In August 2014, then Minister for Transport Paschal Donohoe TD was told that both the Dart Underground and Metro North projects would have had to rely on private funding if they were to be built.

In 2010, the estimated projected cost for DART Underground was €4 billion, more than half of which was expected to be provided by a public private partnership arrangement.

Donohoe was told he had to decide on whether to proceed with DART Underground by 24 September 2015, by which time the Railway Order and planning approval would expire.

[4] By April 2018, the Irish Independent reported that the DART underground plans had been "dropped [..] completely in favour of four new stations at ground level".

[10] In April 2021, the project was reportedly "being resurrected"[6] but in November 2021 the NTA stated that the DART Underground / Interconnector would not proceed until after 2042, although they would "preserve and protect an alignment to allow its future delivery".

[4][18] As of 2021[update], Jacobs Engineering were reportedly charged with devising route options for the line, with no direction to "adhere to the previously alignment" or "location of new stations required [if any]".