DART underground - options

PPT is a very low capacity link with speed restrictions. It was considered to be the "not good enough" option back when both DART Underground and Metro North were being planned. DART via PPT means using Heuston West, which looks like being a surprisingly inconvenient connection for mainline passengers arriving into Heuston, despite the relatively short point-to-point distance.

DART+ can function via PPT, but DU was to address the city-rail connection to the south side of the city. DU plus PPT would provide a full loop of the city allowing much greater interconnection between Metro services (<15 km from city centre) and DART (<40 km from centre).

I think DU needs to be kept in the plans, but I don't think it should be a priority. A second Metro line and and adding more loops, links and spurs to Luas to create new tram services would be of more benefit to the city. Particularly, if Luas could be diversified into a network of routings inside the city core, you could stop most bus routes needing to enter this part of the city at all, which would give huge improvements in bus punctuality.

@bk

There really isn’t anywhere near enough demand to justify all the above cost! Specially when people will be able to get to the airport by Metrolink anyway. Extend Metrolink to the Northern line and passengers from Belfast can use that.

It depends on how you gauge demand. Right now everyone wants to live in the greater Dublin Area because that's where all the jobs are and there is no effective way to travel more than 40km away into the City centre in less than 30 mins. (Enterprise comes close, but it doesn't run often enough). In fact given the traffic restrictions and the fact that Dublin is the 2nd worst congested city in the world, people have no option but to pay mad money for a place in Dublin.

Services to Heuston are decent, but Heuston is to far away from the City Centre, (about 2.5KM) and even further away from the business area of the city (3.5km)

I live on the DART line, I specifically got a place there because I want to be able to get into Dublin city in less than 30 mins.

If I could have that option (In Dublin City Centre in 30 mins) living in a place like Naas, Enfield, Trim or Navan for example, I'd move there, bigger house, cheaper, Big front and back garden, less traffic. etc

You're correct, however Ireland is at risk of becoming a City State, in fact it's at risk of becoming a South Dublin City state.

HSR to satellite cities, works well at dispersing overcrowded population centres, which Dublin is. The bureaucracy and lack of planning up til now means that having a densely populated city isn't workable because the supporting infra is lacking. Our position on the planet also means High Rise apartments are not possible in the way they are in other cities as the bottom floor would never get sun light.

That being said HSR eventually becomes a victim of its own success. (Enough people move and eventually the jobs move too, then no one really uses HSR to the extent it was once used). I actually think this would help the nation A LOT. Like at the moment, everything has to be in Dublin, there is no 2nd city (Sorry Cork).

There's nothing wrong with wanting to have a bigger house with a front and back garden in a country with a population density as low as Irelands. Apartment living in Ireland is the worst, I've done it, never again. It will never change. It's completely unsuitable in Ireland, especially if you have kids.

Edit: when I say big house I mean a semi d with 4 bedrooms. Enough to comfortably raise 3 kids.

People constantly say Ireland isn’t planned or is too Dublin centric in its thinking are hilarious. In many ways this is exactly how we planned it, with rural ideals pushing against the tides of urbanism for several decades. This leaves Dublin as the only option, although this is exaggerated. Cork is a wealthy city with lots of excellent jobs, it just so happens that as a county it endured a famine more than most and also had Belfast on the same island. There are neat formulas often attributed to city sizes within countries but in Ireland in particular, they don’t really apply.

Anyway, we have more than enough semi detached houses in the city for the people who want them. It is the lack of apartments that is the issue and it lack of high quality public transit which is the topic at hand.

I am not sure what you are talking about in terms of CBD. College Green is the effective centre of Dublin and that is 2.5km. The business areas are split fairly evenly from around College Green to the Docklands.

There are hundreds of thousands of people in the canals right now who are being provided with sub optimal transit within the city.

There is absolutely no reason why Heuston cannot be the edge of the core of the city, indeed Christchurch once was the centre of the city. If we give people the ability to transit from a Pearse Street to a Heuston, watch what happens with infill development and densification (if we allow it). Already there is an awful lot happening, and for the most part what we are offering in a bus service, bikes and walking to get around.

We absolutely have to change the culture, otherwise we will continue to destroy the planet.

All one-off housing should be banned.

It's absolutely no way to run a country though. Any sensible government would say, look we have a housing crisis and we're operating a modern economy on 19th century infrastructure so the normal planning process, when it comes to infra and high density housing is suspended for 10 years so we can catch up to the developed world, close all nimby legal avenues and just build. Metrolink was announced 6 years ago and not a spade in the ground, farce.

The Dublin Port Tunnel has already got a pretty unavoidable claim on the immediate subsurface volume below Fairview Park. Emerging at Clontarf Golf Club might be possible.

I doubt going under the DPT would be an option due to potential damage/settlement. I also don't think it would be possible to get from the elevated Clontarf Road Station down far enough under the DPT, the gradient would be too steep.

You could potentially cross above the DPT but the tunnel with the tunnel portal north of the Tolka. I don't know if there'd be enough space to pass above the DPT but then get down below the Tolka. The Tolka is not very deep so might work.

I can't see how the extra costs of tunnelling further north than Clontraf Road would be justified. Clontarf Road also has the potential for at least 4 platforms which isn't possible at stations north of it.

I do see the logic in the tunnel connecting to the above ground network at Clontarf Road. It has operational benefits (both during and post tunnelling) and should be much easier to construct.

The tunnel portal would have to be immediately north of the bridge of Alfie Byrne Road over the Tolka. Not sure why people are talking about EastPoint or looping round anywhere, there's an obvious route there. It would give ~250m of space to work with to accommodate the necessary change in levels. The problem is there are two limiting factors, the DPT and the Tolka. The question is, how deep could the cutting be about the DPT and is that deep enough to then get under the Tolka in the 100m available?

Questions about the vertical alignment aside, Clontarf Road would make sense from the horizontal alignment pov. With the original DU plan, after passing through the new Docklands station going east, the tracks had to swing back slightly west to meet the existing alignment to the Northern Line which again goes east. That S curve in the horizontal alignment, combined with the vertical level change (from under the Liffey to the elevated Northern Line, both fixed levels) made everything very difficult.

If the tunnel goes to Clontarf Road instead, you eliminate that S curve and instead have a more natural alignment. The station box at Docklands (yes there'd still be a station there) wouldn't have to align north/south, it could be rotated slightly (the northern end slightly east, southern end slightly west). This would then help with the alignment south of the Liffey and potentially open up other route options.

Th original DU station at SSG is off the table now (Metrolink will build a standalone station, not like the combined station planned under MN). Also, the owners of a part of the proposed DU station box won a court case allowing them to develop the lands. Alternative station locations can be looked at for a new tunnel plan with a potential different alignment. Ideally, a DART tunnel station would be built at Tara Street which would link two DART lines and Metrolink and become the defacto Dublin Central station. The difficulty with this is the large sewer line but the benefits of such a plan would likely outweigh the additional costs (you save on the cost of an underground station and shorten the tunnel).

I see now that predictive text gave "about the DPT" instead of "above" which I intended. It would have to be a cutting from around the Clasac building to just before the Tolka and then go underground. Maybe dropping 2.5m below ground level as it crosses the DPT and a further 5m by reaching the Tolka, something like that. That’s just by way of an example, not saying that is definitely possible.

Are you referring to the DART+ Route Options & Feasibility by Jacobs? I only see R21 Heuston – North King Street (King’s Inns Park) – Parnell – Croke Park – Fairview which is rejected early due to poor travel demand, which is hardly surprising given it misses most of the city centre and has poor interconnection opportunities. That high level route is the only reference to Fairview in the report.

The report recommends basically the original DU route, mostly because it says SSG and Pearse stations will be as previous design without further assessment. We know that a SSG station taking a chunk of SSG park (far more required than for Metrolink) is going to face major objections which could kill it. The Pearse proposal is a mined station with cut and cover shafts on sites which have been partially developed recently. Basically the Pearse station as proposed can't be built any more.

By the time Metrolink and DART+ are completed, that report will be more than 10 years old. The city centre will also continue to see development which will affect any potential options. Basically, everything will need to be looked at again but in the context of what sites are available at the time.

The DPT emerges 150m from where I suggested the tracks might be able to go. The tunnel is continuously getting deeper is obviously sufficiently deep under ABR and it's build up. Further back by the rail tracks it is deeper again. The entire section from Fairview Park to where the road emerges was cut and cover, it wasn't done with TBM.

Like I said, its a question of geometry; whether its possible to get to the above ground point to deep enough to pass under the Tolka without interfering with the DPT. You or I don't have the answer to that. There might be sufficient depth available where it crosses the tunnel.

The route options in that report cross the Metrolink tunnel at depth in the city centre with multiple buildings with basements in the vicinity, crossing the DPT close to surface level isn't that big of an issue. That report recommends a route with at least one station location which can't be built now (a very important station as it is the connection to the existing DART line). Other options will have to be looked at.

As I said, the report mentions one route to Fairview and in the matrix it is one of the better performing routes on the Environment and Cost criteria. It is however the worst performing on Travel Demand, which isn't surprising when you consider the proposed route and central stations. There is no indication that they ruled out Fairview due to the DPT.