DART+ (DART Expansion)

Nobody is against these big plans, but we must also be realistic about what is financially and politically possible within the near term. It will be politically and financially impossible to go straight from completing DART+ to commencing DART Underground, and not only because that could mean trying to have construction of both DU and MetroLink progressing at the same time. There is a large electorate outside of Dublin, and their trains are old and slow… if they have them at all.

There is now, finally, money available for rail investment, and it is being used in the areas where it will have the greatest impact. DART+ is the result of a long process of determining what “the greatest impact” means, and the tunnel did not make the cut.

I don’t disagree that DART Underground is essential for the long term in Dublin, and I’ve always been a big proponent of the plan, but against that, we have to accept that the latest cost estimate for it is around €10 billion. That’s a lot of money, and without DART+ bedded in, there’s no compelling evidence that it will deliver the necessary increases in ridership and, most importantly, private car diversion. Meanwhile, for that money, you could electrify Cork-Dublin-Belfast, and double-track a lot of the way to Galway and Waterford: all projects for which it is easier to project a return, and easier to predict the cost. While those inter-city routes won’t have as big an impact on CO2 emissions as DART, those services still need modernising, and that should be the next step, both from an engineering and a political standpoint.

@riddlinrussell’s earlier comment on this covers my own view of how to sequence this:

It [the tunnel] would be the next real 'gate' on further expansion of Dublins commuter rail, if you got the D+ team working out on the broader national schemes of rail improvement for a few years to continue the development ball you could build up steam for Dart+ Tunnel and hopefully keep some of the relationships and connections from Metrolink for further developing tunnel expertise etc.

The time to build the DART+ Tunnel is after MetroLink, because then the costs and challenges of building a railway underneath Dublin will be clearly known, which means there will be far less uncertainty about the real cost. By then, the ridership increases from DART+ will also make it easier to make the business case for the tunnel. Right now, you’re trying to get “uncertain number of billions” on a promise of “uncertain increase in ridership”.

It’s also not true to say that IÉ are trying to create the 1980’s Overground. If you look at the works and proposed works, there is a clear plan to fully segregate DART services onto their own ways: an essential prerequisite for automation. This segregation and eventual DART automation is independent of there being a tunnel, and can be achieved on a line-by-line basis already. Southwest would be the first candidate, as it will have its own dedicated way, but if Western IC services were brought into Heuston, that line would also be possible to automate in future. North would require Four North, plus the proposed direct Clongriffin-Drogheda link to be in place for inter-city: then the old Drogheda line could be given fully to automated trains.

When is construction due to start?

We've been so deprived of any infrastructure progress across the board for the last 10+ years I think people just want to see shovels in the ground.

Ironically successive governments have created a rod now for their own back because in the next 2 years so many projects will move to "shovel ready" that there must be a lot of doubt as to the capacity of the construction industry to deliver so many projects around the country which, in theory, would be under construction simultaneously.

Ah crap. A pox on the indo’s jittery fingers. “335 car” is “3 5-car” not “33 5-car”

Suggesting that FourNorth could even be considered before DART-U suggests you still don't see what the problem is. We could have 8 tracks stretching from north of Connolly all the way to Drogheda and we'd still be stuck with the DART+ limit of 12 DARTs per hour into the city from the North. Because of the Connolly bottleneck.

You are correct about the limitations of the FourNorth without DU. DART frequency will be limited due to the capacity south of Connolly. However you are completely ignoring the limitations of DU without FourNorth. DU by itself will add no additional capacity to the Northern line, meaning that if DU is built for FourNorth, service through the tunnel would be limited to the same 9 DARTs per hour as the Northern line.

The main benifit of the D+ Tunnel will always be its ability to allow the DART network to operate as two high frequency metro lines, potentially reaching or exceeding 20tph. However for it to operate at those frequencies DARTs need to be primarily operate on their own dedicated track. Otherwise they will conflict too much with regional and IC services to operate much higher than the 12tph frequency D+ is delivering. Removing those conflicts includes projects like FourNorth, the Maynooth-Adamstown Link, and potentially even the M1 Clongriffin-Drogheda alignment.

Additionally one of the major considerations for FourNorth is not just it's benifit to the DART network, but how much it will improve IC and regional services. A major component of D+ is the Spencer Dock station which will help relieve pressure from Connolly's terminating platforms and after completion of FourNorth may leave room for additional services, such as a half-hourly peak Enterprise service and/or an additional Dundalk service.

Compared to the cost and complexity of DART tunnel, yes most other things are low hanging fruit.

There is a lot of 'tinkering' that will at least slightly improve Connolly as stated above with the added advantage that it will improve the whole network outside Dublin

A huge value add of D+ is full quad tracking of the South West line. Not only because it takes intercity trains off the DART route entirely but because it takes DART/high frequency services off the intercity routes.

Just having those separated means that most of the intercity routes in Ireland suddenly have conflict free transit out of Dublin, so more frequent and faster services can happen.

Build the kildare interlink and boom, Sligo gets added to the list of conflict free services (while improving DART capacity again and further benefiting Connolly)

Outside the capital area you then have a series of "relatively" cheap and easy interventions (LJ-Limerick dualling, LJ reconfiguration, speed improvements and passing loops on lines like LJ to Waterford and the Sligo line, Dualling Portarlington to Athlone and Kildare to Waterford) that can all be done for a fraction of the cost of the Tunnel, making them:

a) more palatable to the politicians

b) good, decent sized projects for the team to continue developing their skill sets

c) improve the service quality of the national network, increasing both ridership and more critically goodwill towards rail in Ireland

I want to ask a question about the DART+ Fleet.

Has there been any Government funding allocated from Budget 2025 to IÉ to sign contracts with Alstom to pay for the 100 carriage order to replace the original 8100 class LHB DART fleet? If not; it might be inevitable to say at this point that we have to wait until Budget 2026 in October to get any new funding to get the new fleet ordered from Alstom.

Is it possible to build DART Underground without ripping out the new Spencer Dock station do you think?

Given money wasn't an issue, you would simply continue underground from Spencer Dock all the way to the airport, and then either direct to Drogheda or rejoin at Rush and Lusk.

The GNR(I) had some planning back a long time ago about 4 tracks, it a pity more care wasn't taken at Kilbarrack when it was redeveloped to allow space

Would it be better to tunnel from west of Heuston to Clongriffin via Docklands? Or is there another way to tie in with Connolly?

You wouldn't need FourNorth as Belfast trains would only share the line in from Clongriffin with a more limited Howth Service.

Yeah the old DART-U proposal had some irritating flaws. It was a companion for MetroNorth - another flawed plan which ML improved on massively. So no doubt it will be subject to significant redesign/improvement if dusted off.

I agree with PeteC - the site of the northern portal was a never a good one. Digging from here would have required cutting off all existing dockland rail traffic. And worse you're stuck to using that junction just south of the East Wall Rd to split DARTs from IC traffic. Which would mean north bound DARTs emerging from the tunnel having to cross south bound IC and non-DART traffic at grade - a capacity and speed killer and a huge miss in terms of improving flow in and out of Connolly.

A redesigned DU tunnel will emerge further north I'm sure - either Fairview park or around Clontarf Golf club. At these locations you can dig without affecting any existing rail services and you can design the portal so that north bound DART traffic emerges to the west of the existing tracks while south bound leaves the existing tracks to the east - thus providing grade separation so trains going in opposite directions would never have to face each other.

At the other end, the good news is that DART+ will deliver 4 tracks right into Heuston so no need to dig as far as Inchicore - you could start digging just where the PPT branch starts so the overall tunnel length would be about the same. And your Hueston DART station would be a simple cut n' cover job where the car park is and not the hugely complex mined station under the old plans.

I'm also sure that the lessons learned from the MN redesign will be taken on board - far simpler stations than were planned before, possibly go single bore, etc.

Terminating Rosslare services at Pearse means they'll need to bring back terminus platforms. I always thought it was a waste having a station as large as Pearse have only 2 platforms anyways.

On an unrelated note, would it be possible for the DU tunnel to be a steep incline out of the planned Spencer Dock station, similar to what they have on Elizabeth Line stations in London? Or would that be impossible?