Funding under the National Development Plan will allow preparatory steps - including compulsory purchase orders from next year - but no construction timeline is set.
DART+ South West is entirely dependent on the successful delivery of DART+ West, according to the Department of Transport.
In a letter to Kildare North TD Aidan Farrelly, Transport Minister Darragh O'Brien said DART+ West must deliver city-centre electrification, additional rail capacity and a new depot before DART services can extend to Hazelhatch and Celbridge.
Although DART+ South West received planning approval in November 2024, the Department makes clear it cannot function on its own.
Procurement and contracts are being driven through DART+ West, with South West intended to follow only once those works are delivered.
Funding under the National Development Plan will allow preparatory steps - including compulsory purchase orders from next year - but no construction timeline is set.
According to the letter, "DART+ West will deliver the critical electrification of the city centre rail network and the necessary city centre capacity upgrades. This is a prerequisite for future trains coming from Dart+ South West to enter the city centre network at Glasnevin Junction from the Phoenix Park Tunnel on an electrified and capacity upgraded rail system."
It further detailed how upgrades delivered under DART+ West such as re-signalling, and electrification, are "vital" for accommodating increased frequency and longer, electric trains envisaged for DART+ South West.
"The new station at Spencer Dock, introduced as part of DART+ West, is a key node for future service integration, supporting the operational flexibility required for DART+ South West, as several services will now terminate in the new station, helping to address capacity issues around Connolly Station," the letter stated.

Kfm Obituary Notices
Sharp Rise In M9 Collisions With Garda Call-Outs Up Year-On-Year
Councillor Seeks Clarity On How Often Nightclubs and Late Bars In Naas Are Inspected For Fire Risks
Unpaid Eight-Month Work And Training Placement For Adults With Disabilities Branded "Extremely Unfair"
Department Of Education Defends Kildare SNA Cuts Amid Claims Of Reduced Need At Some Schools
Naas Nurses Threaten Escalation As Staffing Row Deepens
Driving Tests Face Disruption As RSA Testers To Strike Next Week