DART underground - options

After reading the posts from someone who's done a decent job of pointing out how Dart+ will comprehensively impact the only railway order approved for an underground heavy rail corridor in this country, I'm surprised at the selective nitpicking that forms some of the replies. The conclusion I'm drawing is that DU is dying or dead and yet we need something that functions like what countless other cities have built. Projects that inspired DU in the first place.

So what's left on the table? I'm not really sure what's possible if DU isn't going to happen. So many sites and areas are off the table that it makes building heavy rail in useful/dense areas a challenge of almost biblical proportions. Is there a feasible way to have a tunnel extend from the vicinity of Spencer Dock to the Clontarf golf course while also maintaining northern commuter functionality? While avoiding rampant CPOs like quad-tracking of the northern line would conventionally involve. IMO it remains the best alternative if DU is no longer feasible, but it might inevitably become the even bigger victim of megaproject-itis, as high-speed transport northwards, a heavy rail link to the airport and extra capacity towards Louth all become relevant.

Varadkar cancelling DU for what now looks like spare change behind the back of a couch , was real genius...

Let's just spend billions on welfare increases every year and nothing on rail... I hope tge eu fine us billions for breaching emission limits , that's probably the only hope of them doing anything about rail development here...

In what is reminiscent of the AECOM North Dublin Transport Study and its fanciful if not fictional modelling and comparisons, I am really struggling to see how the 90% equivalency is reached - Dart+ as a project within Transport 42 doesn't envisage stations at Christchurch and St. Stephen's Green, and the effects of far faster journey times that come from having a tunnel to two potent trip generators (plus the interchange potential at other stations). It seems strange that the consultations released to this point seem to portray remodelling at Connolly and Docklands, or the Heuston West station/GSWR electrification as an "either-or" to the original DU concept.

I try to imagine the rail patronage in a city like Leipzig before its Citytunnel was built, and I just can't imagine alternatives that would achieve anything close to 90% of the peak capacity and trips that tunnel facilitates.

Perhaps some real-world examples of cities achieving great transit successes without cross-city rail would help inform the discourse here better. I can think of cities like Manchester in the UK and I wouldn't hold it up as a beacon of success or a place where significant modal shift occurred.

PPT solves the problem of tying the northern and southwestern lines, but it doesn't enable any more stations - although I sometimes think adding a new DART station here serving Dublin Zoo would be a big ridership generator: the tunnel runs about 200 metres from the Zoo entrance.

The biggest benefit of DU was the addition of two stations to the DART system in the southern core of the city that weren't served by any other mode. The South West quarter of Dublin city is densely populated, but badly served by rail, and the future metro plans don't seem to offer any hope for a change for that. I am aware that tunnelling would be prohibitively expensive, but any brownfield option for a line from Heuston heading south would be worth looking at.

As I said, PPT solves the problem of linking the two major stations in Dublin, and I am not in any way saying it shouldn't be done. But it does nothing for a part of Dublin that has no rail access. Most of Dublin's railways run North of the Liffey, and most of the city's economy is South.

For me, Stephen's Green wasn't the big positive in DU - I actually think it would have been a weakness, as the station design they presented wasn't nearly big enough to be a "Dublin Central", but within a year it would de facto become just that, and would quickly become heavily congested. The thing that I felt really added something to the city's transport was the station at Christ Church, as this is a part of the city that's difficult to get to by public transport, despite being very central.

So: PPT yes, but additionally a route serving south and south-west inner city Dublin should be on the plans somewhere, and not one that requires passengers to cross all the way over to the east first... This doesn't even have to be a tunnel, but I suspect it would need to be at some point, and that would probably kill the project.

I'm trying think through this logically, as I understand the points being put forward here and agree that DART Underground wouldn't make sense if its sole benefit over DART+ is to connect Christchurch. So I'm asking myself is it still necessary if we get everything else?

East West connections through the city are currently Luas or bus based. Post DART+ there will also be the option to go around the city centre to access destinations to the west when coming from the East and vice versa. Post Metrolink there will also be a new spine that travels through the centre of Dublin in a North South direction, closer to popular destinations and connecting with the DART network.

Thinking of some trip pairs.

1. Coming from Belfast, going to Cork.

With DART Underground you'd arrive from the Enterprise in Connolly, walk to Docklands and get a DART to Heuston, and get the Cork train.

With planned projects you'd arrive from the Enterprise in Connolly, get the PPT dart to Heuston West, walk from there to Heuston and get the train to Cork.

Neither is perfect but advantage planned infra in my opinion.

2. Coming from Kildare, going to Landsdowne Rd.

With DART Underground you'd take the commuter train to Heuston, take the Underground to Pearse and switch to a DART for Landsdowne.

With planned infra, you'd still take the commuter train to Heuston and get Luas to Connolly before switching. Alternatively you can switch to a PPT train in Hazelhatch and change to a DART in Connolly.

DART Underground would be better but not significantly.

3. Coming from Blackrock going to Stephen's Green

With DART Underground you'd take the Dart to Pearse then switch to the Underground.

With planned infra you'd take the DART to Tara and switch to Metrolink to backtrack to Stephen's Green.

Much of a muchness there.

OK, not sure what my point is. I'm sure there are plenty of trip pairs that are not served by planned infra but it does seem that a lot of the business case for DART Underground will be removed if all of DART+ and Metrolink go ahead.

TLDR: I believe DART Underground would make travel around the city easier, but not enough to justify the cost if DART+ and Metrolink are built in full

Another option would potentially be:

Intercity to Connolly, DART through the PPT and stay on the DART until an interchange station further out (i.e. hazelhatch).

Only potential issue with this is that everything would need to be running smoothly as depending on timings there could be a missed connection!

The idea that the PPT is any kind of replacement for a cross city tunnel is incredibly misguided. For a efficient system, we need trains running through the city and out the other side. Terminating so many trains in the city centre is far from ideal but in the absence of a tunnel, it is what we have to do for now. The LLB can't indefinitely be the only city centre heavy rail Liffey crossing.

Not sure why people are still talking about the DART tunnel going via SSG and Pearse. SSG is almost certainly off the table as the DU plan was based on that station already being pretty much already built for the MN station. The Metrolink station at SSG wont have any provision for a heavy rail station and going to SSG adds a lot to the tunnel length. Part of the area for the intended Pearse DU station has been built on so its gone.

A new route will have to be looked at for the new tunnel. Tara Street is the ideal place for a combined DART/Metrolink interchange and effectively a "Dublin Central" station. I reckon the new tunnel plan will have to be based on shorter station boxes and that opens more possibilities.

Facilitating the tunnel portal at Spencer Dock is likely to be cheaper than tunnelling somewhere else.

The whole Cork - Belfast thing is a weird obsession here. The number of people making such a journey would be tiny, it is an irrelevance. It is so far down the list of considerations that it's not worth mentioning.

PPT route is snail-pace slow. Are there any plans to change that? If not, then people should stop praising it as an equally good substitute to the DU tunnel.

I think this is the conclusion I'm reaching, though I'm not convinced by the second scenario. A) because Dart Underground will not be possible with its original alignment so it's not a very useful comparison, b) the Dart+ SW and W plans go beyond what Dart Underground envisaged for the terminal stations in particular and c) ridership figures involving Kildare as a starting destination are not much more relevant than the Enterprise to Cork ridership projections.

What I'm still bothered by is the cost projections - we don't seem to believe that a tunnel can be built cost-effectively for heavy rail even though central Dublin has relatively suitable subsoil/bedrock for a TBM and the marginal cost per km should still be reasonable if densified locations (like Christchurch) are not considered. Case in point, the Bray Head situation that isn't really dealt with in any of the aspirational plans for the GDA's rail system even though a tunnel would be relatively simple, welcomed, and effective in increasing capacity towards the southeast

I don't assume the SSG station is off the table, it is a fact that the Metrolink RO contains a SSG station with no provision for a heavy rail station. Adding an east/west underground heavy rail station at SSG would require utilising a much larger chunk of the Green, look at the issues OPW have been raising about losing a small number of trees for Metrolink. Going to SSG would only make a tunnel longer and make the station box more difficult, it's almost certain a new tunnel plan wouldn't go there.

The original Pearse DU station box plan isn't possible now. A new plan at the same location may be possible but would require excavating the station box directly under said building. It would be far more difficult than later adapting Spencer Dock to a thru station which you insist wont happen. It is almost certain that station locations will be chosen that don't require building station boxes directly under recently built buildings. As I said, shorter stations opens more possibilities.

A new tunnel plan wouldn't just be for one station, no idea where you got that from. And Luas and Metrolink aren't/wont be city centre heavy rail Liffey crossings so no idea why you mention them. My point is that discussing things in the context of the old DU station locations is pointless. You seem to ignore most details in a post and just focus on a few high level points in isolation rather than considering a post in its entirety.

As I said, a tunnel will be needed to allow for future heavy rail capacity increases, PPT is only a stopgap. With the LLB maxed out, every train not using it will has to terminate at Heuston, Connolly or SD (and a small number at GCD). That includes all intercity, outer commuter and DART trains. If we ever want to increase rail services into and around Dublin beyond what's currently envisaged, we need more thru-running DARTs and use the city terminating capacity for longer distance services.

I'm avoiding off-peak comparisons as they are not reflective of potential or expected bottlenecks to maximum capacity. By doing that, I'm assuming that the end goal of a given project is commuter/capacity oriented, but I think that's a reasonable assumption.

The MGWR track (i.e. the Dart+ West) proposals looked into permanent way restrictions more than any of the other studies did. And intriguingly, no works were recommended - The bulk of expenditure beyond electrification and fleet purchase will be for level crossing closures. The PPT line (Heuston to Glasnevin Junction) has a ~2 km straight section with currently a 30mph speed limit, and a station that will be built roughly halfway along this. I also think it's very unlikely that Cabra would be built without a station in the vicinity of Inchicore, however that is equally the case with the approved railway order for Dart Underground.

So, if that is a valid basis for the journey time hypothesis, I could not see a way where addressing line speed could shave more than 2 minutes off the CO&PW to Pearse journey on the existing infrastructure. The Connolly - Glasnevin Junction stretch was explicitly studied in the Dart+ reports for potential speed increases but I'm not an expert in how or why the report's conclusions were made. Heuston to PW&CO takes 7 minutes in both directions without a stop, but Heuston to Pearse with DU would involve 2 other stops and a rather tight curve. The two stops in question would be expected to have a relatively high patronage, as would the proposed Glasnevin station on the PPT route.

And then there's the issue of signalling. The PPT route involves 2 at-grade junctions (I'm ignoring Heuston itself) with other DART lines on its journey to Pearse, while DU itself involves none. Signalling optimisations for heavy mainline trains can only achieve so much. Beyond that, the differences are less to do with engineering/permanent way choices and more to do with with operational factors.

As for the starting point, Pearse is the busiest train station in the country and seems like a more worthwhile commuter traffic comparison than Connolly does, along with the fact detailed investigations were made for the Heuston-Pearse route and also those details were used literally when the Dart+ investigations were subsequently carried out.