DART Underground

DART Underground (Irish: DART Faoi Thalamh), also known as the Interconnector or DART+ Tunnel, is a proposed mainline-rail tunnel in Dublin, Ireland. First proposed in 1972, as of 2021 it was not funded or scheduled. While the Greater Dublin Transport Strategy 2016-2035 (published in 2016) included the DART Underground as a proposed National Transport Authority project, the tunnel was not included in the National Development Plan published in 2018 or DART+ expansion plans published in August 2020.

The original plans, which proposed an expansion of the electrified Dublin Area Rapid Transit (DART) network, projected the development of a tunnel between Heuston Station and Pearse Station. It had been planned to leave an existing line, via the Phoenix Park Tunnel, idle in the event of the scheme being built. This line however was subsequently reopened, connecting Heuston station with Dublin's Docklands - a cross-city connection which the DART Underground scheme was supposed to achieve. 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. Having previously secured planning consent, the project was initially deferred until after 2016, and by 2015, it had been announced that the project would be redrafted to a lower cost design. In October 2016, a "scaled down" plan was published with a potential commencement date "in 2020". As of September 2017 however, it was suggested that the developments would be deferred until after 2030, with the National Transport Authority undertaking a review of the project and its route; this review projected to complete sometime between 2018 and 2027. While the planned alignment was to be preserved, it was announced in November 2021 that DART Underground would not proceed in the period 2022–2042.