DART+ (DART Expansion)

OisinCooke · 03-07-2025 03:33AM

https://www.boards.ie/discussion/comment/123600221#Comment_123600221

Very well put, and l agree wholeheartedly, a DART+ Tunnel that linked the Western and Southwestern Lines would be a poor use of resources and would not provide nearly as much benefit as a link with the Northern Line.

@murphaph put it very well. It should be built to link the two quad tracked (ie. separated DART and Intercity) spines into the city to allow for effectively a metro style DART service frequency-wise and allow for potential automation in future.

I’m afraid however that putting the northern tunnel at Fairview Park very likely wouldn’t work due to the now required deeper depth of Spencer Dock station and both the Tolka River and Port Tunnel both being in the way of the line rising above ground. It would also have to get high enough to bridge the Clontarf Road in a very short distance. Trying to avoid all of these obstacles would result in a gradient that would be much too steep.

I think avoiding a Clontarf Road station entirely and emerging above ground at Clontarf Golf Club before Killester would work far more comfortably. The only issue is it would add around 2km extra of tunnel length, but as @gjim mentioned, four-tracking all the way to Heuston means that the tunnel portal could be brought east by about 1.5/2km from the previous location of Inchicore depot, so would make the tunnel extension in the north a lot less expensive.

This also means that quad-tracking of the Northern Line may not have to start all the way back at Connolly. As the vast majority of Northern Line trains will be going straight into the tunnel, there may not be enough DART traffic between Killester and Connolly - aside from the odd service to Bray/Grand Canal - but nowhere near the level of conflict that will be present without the tunnel - to warrant separate running lines, so this would make FourNorth cheaper too.

In relation to a Heuston cut-and-cover station under the car park, this could work very nicely actually, and be tied into the station with a new underpass at the western end of the Heuston platforms, something which Heuston station could definitely benefit from. An exit could also be built to Heuston West, and too linked to the underpass, making it feel a lot closer to Heuston that it otherwise would and further increasing the overall DART+ Tunnel station inter-connectivity.

gjim · 03-07-2025 07:14AM

@OisinCooke - you're probably right that the golf course would be better.

Either that or Clontarf Rd would be FAR superior to branching off south of East Wall Rd, which would put a huge dint in possible frequencies/capacity because of the "crossing at grade in opposite directions" consequences.

Another advantage is that as part of the portal works, you could expand Clontarf to 4 platforms or build a new station at the golf club (replacing Killester) with 4 platforms allowing IC passengers direct interchange to DART N-SW. This was another failing with the old plan - Belfast/IC passengers would have had 2 changes to access stations along the DART N-SW and vice versa. While this way allows an interchange at Clontarf for DART N-SW or stay until Connolly for DART S-W - basically one change access for IC passengers to the entire DART network. Incredible connectivity.

And with the grade separation offered by such an arrangement, you could immediately offer 18 DART/hour before starting on FourNorth - leaving enough room for 2 IC slots per hour. A DART every 3.5 minutes is easily "metro level" service.

There's no need to consider digging up DART+W Spencer Dock - this was forced by old choice of location for the northern portal. You have plenty of choices now to swing further East for a docklands DART N-SW station.

This also gets rid of two complex and expensive underground stations from the old plan replacing them with a simple cut n' cover at Heuston and a surface station at Clontarf (Rd or Golf club). You'd still have the complexity of mined stations at Stephen's Green and either Pearse or GCD but for the initial project I'd drop the underground Christchurch and Docklands stations. Since these would require mining, so there's little benefit to bundling them into the initial tunnel project - they could be part of a follow-up project given that a 4 station DART-U achieves the goal of freeing the system from the Connolly.

This effectively creates 2 new metro lines crossing the city, and would offer one-change access from any of of about 80 DART or ML stations to any other - creating a genuine network and with metro-style "turn up and go" frequencies throughout the system.

AngryLips · 03-07-2025 09:27AM

If a Dart-U tunnel was built north of Fairview then what rail service will serve Clontarf Road station or would that station be mothballed? If all Dart services on the northern line are routed via DU then the only passenger services passing through Clontarf Road would be IC services to Belfast and Dundalk trains.

KrisW1001 · 03-07-2025 11:07AM

Putting the portal anywhere near Heuston is a non-runner. The place @gjim mentions is a particuarly bad pinch point:

Trying to put a proper, grade-separated portal here would be hugely disruptive, and getting from ground level here to the depth needed for the Heuston deep DART station would need a fairly steep gradient of close to 3%.

Building it at Inchicore might add the cost of more tunnelling, but it wouldn’t have anything like the operational headaches during construction or commissioning, and would allow a more streamlined, faster approach into the Heuston deep station.

One nasty problem with trying to extend the tunnel beyond Fairview is that there is no way to do this without crossing the M50 tunnel. Worse is that you’re trying to cross that tunnel while trying to ascend to surface level. The M50 is not deep enough here for the railway to go over it.

DrivingSouth · 03-07-2025 11:43AM

If the tunnel was to ascend at clontarf golf club, then does it need to go near docklands / Spencer dock at all? A mined station at connolly, Tara St, South city somewhere and then heuston?

OisinCooke · 03-07-2025 11:57AM

https://www.boards.ie/discussion/comment/123601153#Comment_123601153

The angle of the curve necessary to get between Connolly and Pearse and Stephen’s Green would be too sharp I think. While a stop at Connolly would be nice and would really make this an all-rounder of an underground link, I don’t think it’s doable or all that necessary

DrivingSouth · 03-07-2025 12:35PM

https://www.boards.ie/discussion/comment/123601182#Comment_123601182

Sorry, I probably wasn't clear enough. What I'm suggesting is to not have Stephen's green, or pearse or docklands. Effectively go straight from heuston to tara and then north to connolly. With maybe another stop between heuston and Tara, e.g. Christchurch or Temple Bar.

Just an idea. Not saying I've thought of everything and this is definitely better than the old plan.

goingnowhere · 03-07-2025 12:41PM

The DART underground tunnel per the offical plans was to surface within Inchicore, and then remain subsurface to join the Dublin Cork mainline with via an underpass

Heuston was ruled out long ago, the NTCC building is built on top of the previous location for the portals

KrisW1001 · 03-07-2025 01:49PM

https://www.boards.ie/discussion/comment/123601286#Comment_123601286

A direct route like this was ruled out during the feasibility phase. It’s cheaper than the final proposal, but it dumps people at Connolly which is already crowded (your version adds Tara, which is extremely cramped too), and crucially it didn’t do anything to increase the catchment of DART.

The reasoning was that if you’re going to spend billions on a tunnel, it needs to providing something more than just making what we already have run a little better. The two stations at High Street/Christchurch and St Stephen’s Green are right in heart of Dublin’s commercial core and adding service to here would create huge passenger growth for DART. A station in Docklands, Dublin’s newest commercial district just increases those benefits to potential passengers

As I see it, the various planners have pretty much ruled out Connolly as part of a solution, and the long-term plan for DART is to have an X-shaped core network, made from Hazelhatch-Tunnel-Drogheda and Maynooth-Connolly-Bray with the two lines meeting at Pearse.

DART+ (DART Expansion)

Comments