Dublin - MetroLink South West [feasibility study proposed]

Brightlights66

https://www.boards.ie/discussion/comment/123069480#Comment_123069480

I absolutely will share those density figures, though it may take a couple of days - I'm switching computers at the moment. The figures came, I think, from census.ie, and detail the results from, unsurprisingly, the most recent census, and earlier ones.

I agree with OisinCooke above: the Green Line south of the canal is perfect for replacement by a metro, and I hope it will eventually be. At the moment, though, the priority needs to be making sure that all or most residents of the city have a rapid way into the centre.

At present, I see this as a metro between Swords and Tallaght, and I favour a route via Drumcondra. With a bit of decent planning, it's not difficult to envisage a spur to Walkinstown Cross, with all the public transport connections that that would provide. Reolacement of the Green Line by a metro would come later.

loco_scolo

https://www.boards.ie/discussion/comment/123069480#Comment_123069480

I find the first link below extremely useful. It's fed from CSO data (second link), most recent from 2022 census. The CSO link also has interactive maps but not sure it explicitly gives density.

https://www.citypopulation.de/en/ireland/dublin/

https://visual.cso.ie/?body=entity/ima/cop/2022&boundary=C04167V04938&guid=2ae19629-1d06-13a3-e055-000000000001

Consonata

https://www.boards.ie/discussion/comment/123067513#Comment_123067513

The speeds of the line are pretty significant as it was to involve higher capacity high floor metro trains running autonomous and closer together than is possible with driver trains. This trebles the capacity of an already congested line for a fraction of the cost of building a new one.

That Metrolink should be tied in with the Green Line is self evident. If a Metrolink South West is to be built, it should be an entirely separate project which should stand on its own.

The Green Line will need to be upgraded in future, that is a fact given how much development already has occurred on the line

tom1ie

https://www.boards.ie/discussion/comment/123070833#Comment_123070833

Yes the GL should be upgraded but we already know that will close the GL for at least a year, with some reports saying longer.

In the mean time let’s try and get a detailed route selected for MSW and get it to RO at the same time as planning a GL uprate that gets that uprate done in as short a timeframe as possible.

Once metrolink is operational, MSW gets RO, and past JR stage, plus the GL uprate is underway, let’s look at what we do with GL luas that will be truncated by metrolink tying into Luas GL south of charlemont.

Once this route has been selected and by that stage MSW is operational, let’s get a detailed route selection for metro west, and get the luas GL truncated route extension built.

Dublin would be in a fairly decent spot at that stage.

Brightlights66

https://www.boards.ie/discussion/comment/123070667#Comment_123070667

Thanks loco_scolo. I thought I had the most recent figures in my system, but I can't seem to find them.Your link will be helpful.

Relevant figures (from 2016) on the current Green Line show densities of 5,565 people per sq.km for Rathmines East (broadly where the Green LUAS currently goes) and 3,350 per sq.km for Dundrum, which includes Sandyford. Just to give an idea.

Correspondingly, relevant figures for a putative south-west metro include Rathmines West (through which a south-west metro might go, and includes Harold's Cross) are 7,523 per sq.km - almost 2,000 per sq.km more than Rathmines East! - Terenure (4,262 per sq.km), Rathfarnham (4,239 per sq.km), and Firhouse (including Knocklyon, 3,754 per sq.km). Tallaght (3,285 people per sq.km) would be the ultimate goal.

I don't see any figures from the census as to why Dublin would be upgrading stuff, while large chunks of the city need just to have a proper service. 90 minutes from Firhouse to the city centre should be deemed unacceptable in the modern world.

Consonata

https://www.boards.ie/discussion/comment/123070618#Comment_123070618

Sending the existing tunnel west to facilitate transit into town makes no sense if the end plan is to upgrade the Green Line. If you're doing it, it'll have to terminate as a Metro at Charlemont with no real future plans of extending it anywhere else short of digging a tunnel portal in the centre of town.

Metro South West if done should be an entirely separate project, separate tunnel, instead of attempting to shoe horn it into Metrolink at the cost of GL Up

tom1ie

https://www.boards.ie/discussion/comment/123073262#Comment_123073262

The DSW and Metro GL could share the tunnel?
You’d still have the tunnel north of charlemont having a metro using it every 90s but every second one would be form sandyford and the other from tallaght.

Consonata

https://www.boards.ie/discussion/comment/123073299#Comment_123073299

Sharing the tunnel would kneecap the frequencies south of the same tunnel. You could only run trains about half as frequent from anywhere south of Charlemont which would be very bad forward planning.

OisinCooke

https://www.boards.ie/discussion/comment/123073299#Comment_123073299

This is not an outright terrible idea and with the maximum frequency possible of 90s definitely be a just about acceptable consolation if excrement hits the proverbial fan so to speak, but should in no way be anything we should aim for.

A southwest line should be entirely separate and brand new (same spec of course and maybe a physical crossover somewhere just for depot access etc.) and should aim to cross ML at least once, and link up with DART and all existing and most future Luas lines before continuing out the far side of the city to somewhere similarly unserved to the southwest. Anything other than this would be a vast injustice to the city and to the southwest part of the line

salmocab

https://www.boards.ie/discussion/comment/123073299#Comment_123073299

The maths on that are complicated by the 2 sections not being the same length. I would involve trains holding at the end of one section to avoid 2/3 in a row from the same direction which would choke the other direction. It’s not as easy as it seems to split the far end on a very busy schedule.

blanch152

https://www.boards.ie/discussion/comment/123070618#Comment_123070618

Why would you send a route from Tallaght to Swords through Drumcondra, duplicating the Metrolink? That doesn't make any sense. Clongriffin as a destination makes sense for ML2. It should start at Tallaght, interchange at Hueston and Glasnevin, before heading east and terminating at Clongriffin.

Idbatterim

Hang on... you'd be talking about making maximum use of metrolink one infrastructure.... I'm all for the better solution, if politicians here would actually fund it... but if they won't. Then work with reality and what you have...

What about metrolink two serving one rathmines. Rathgar. Rathfarnham knocklyon, ballycullen, firhouse. Tallaght.... maybe link it up with the existing crap that is the red line luas in Tallaght..

Consonata

https://www.boards.ie/discussion/comment/123075948#Comment_123075948

Because it's worse value for money than just sending the tunnel north east. Forcing Tallaght metro's and Sandyford metro's in the one tunnel halves the frequency of both and makes the benefits of both harder to justify.

Idbatterim

Yeah that would be an issue at peak times .. how long before the line is at capacity ? Its ten years away, watch it be at or near capacity on opening, that is what i expect...

I'll tell you all that matters here when it comes to justification the price tag, those fools in office, dont think the way you do...

Every other proper European capital this size, has several metro lines, that is what we need here. The planned one, one serving south west. We need high capacity east to west line too...

Then greenline to metro from sandyford stop, to bray, deviating from current alignment at sandyford.

Metrowest too.... they are the schemes needed without any question...

Consonata

https://www.boards.ie/discussion/comment/123077360#Comment_123077360

These are 100 year old investments designed to pay off over similar time frames, similar to the London Underground.

Would be mad to build an underground which would hit capacity in 30/40 years because we're trying max out the capacityby shoving two lines into it.

It's similar to how the business case for Dart Underground falls to pieces when you try and get Darts and Intercity services using one two track tunnel. Wrecks the frequency and potential capacity of both and makes a very expensive tunnel relatively low yield and arguably builds in obsolete much earlier than it should.

Larbre34

The Swords Metrolink should not break ground without a design approved to continue it southwest from Charlemont, bisecting the territory between Luas Red and Green; to Rathmines, Rathgar, Terenure, Templeogue, Knocklyon, Firhouse and onward to a Terminal link with the Luas Red Line, either by bringing it to the Luas, or the Luas to meet it.

There will never be a cheaper way to build it not a quicker timeline to deliver it.

The government know this infrastructure does not need a study, or a business case. It is a self-evident investment for the future and the improvement and renewal of the City.

And so the TII must be given the order to go and get whatever surveying and design is necessary, from experienced professionals across the globe to make it happen.

Podge_irl

https://www.boards.ie/discussion/comment/123077643#Comment_123077643

The government know this infrastructure does not need a study, or a business case

LoL. Obviously this is absurd on every possible level.

The Swords Metrolink should break ground the absolute second it is able to. If they can push for a SW routing while its in the ground fine, but it shouldn't delay things one minute.

salmocab

https://www.boards.ie/discussion/comment/123077643#Comment_123077643

Cheaper and quicker?

It might be cheaper for the extension but would increase the costs of what’s planned, it would delay the opening of the planned bit in all likelihood. They should certainly be planning what happens after but the last thing Dublin needs is an attempt to change anything planned at this stage.

tom1ie

https://www.boards.ie/discussion/comment/123077083#Comment_123077083

It massively increases connectivity all over the city though.
I agree DSW should be in a separate tunnel that connects at certain station with metrolink- however if there is a chance we could get the tunnel extended to tallaght easier and quicker than getting planning on a full new tunnel- then we should look to extend metrolink to tallaght as a phase 2 once the TBM is in the ground.

Also it should be a totally separate TBM starting in tallaght heading towards metrolinks TBM.

Idbatterim

Totally agree, money is no longer an issue, these figures, are loose change with the money being flung at every bloody area they choose to waste it on...

Larbre34

I'm not talking about changing anything.

I think the most reasonable assessment at this point, doesn't see significant civil works on site for the existing project until mid-2026, or lets face it, early 2027.

I'm saying thats time enough for a well enough resourced effort to have a detailed design solution for a SW line published and early consultations begun.

You continue with the Swords line without breaking stride, but with a four year programme, you get the SW line approved early in that time and make contractual preparations to move assets on immediately to that continuation of the line, without any break in actual work.

You open Swords as per contract, and you deliver SW perhaps 18 months to two years later.

If the political will is there, and the bureaucratic and legal barriers are obviated by legislation.

bk

https://www.boards.ie/discussion/comment/123077865#Comment_123077865

No, as was explained only a few posts ago, you can't open the Swords to Charlemont section if you want to continue on SW like that. The tunnel has to be used to carry out the earth excavated material, etc. So you would delay opening the Swords to Charlemont section by 4 years as you continue SW.

It is a terrible idea with no benefit and frankly a real threat of project creep and thus the project getting delayed indefinitely and never built.

murphaph

Personally I don't accept that it would be impossible to send the TBM onwards towards the south west and I remain convinced that it would the most cost effective option. I know that it would pass under many areas that have sub-optimal density at present but with infrastructure comes density.

Other countries would see opportunity where we see only problems. Charlemont is on a barely used canal. There is nothing stopping the tunnel spoil being extracted out via conveyor belt (as it is inside the tunnel) directly loading it onto barges (each with significantly higher capacity than the largest truck) and floated down to the docks and out into Dublin bay for dumping wherever they currently dump the dredged material from the port. No environmental damage. No need for any trucks at all. The locks could be upgraded and automated. It's only a short stretch and it would be a drop in the ocean in the grand scheme of things.

I can cite several metro extensions that were built from the live side out without preventing the operation of services. Munich's U1 terminus used to be Rotkreuzplatz. The line was gradually extended out to it's current terminus, opening stations as they went along. There are ways to extract the material even if you don't have the luxury of a canal and the open sea just a few kms away. Berlin's U5 was extended from Alexanderplatz (in two stages) to the Bundestag. These were both bored tunnel projects.

tom1ie

https://www.boards.ie/discussion/comment/123078019#Comment_123078019

Just start the metrolink TBM but instead of burying it, take it out of the ground somewhere in bushy park which is only 3.5kms south of where the TBM is due to be buried.

Start a brand new TBM in tallaght and send it to meet the metrolink TBM in the bushy park area.

murphaph

https://www.boards.ie/discussion/comment/123078054#Comment_123078054

That works too. If the TBM is moving as fast as some here prophesise ("thousands of trucks") then just running it out to Bushy Park in a few weeks is not a problem. We've waited decades. We can wait a few more weeks. If it takes months/years rather than weeks then that indicates the amount of spoil per day would be far less than some imagine. A few truck loads but for heaven's sake, that sort of spoil is being removed from the city in other building projects all the time. Basements are constructed where spoil once was. The material that replaces that spoil (concrete) is trucked in to the city in vast quantities too. The notion that the TBM cannot possibly proceed beyond Charlemont without completely torpedoing Metrolink is a little bit absurd to me.

Zebra3

So there’s the proposed feasibility study that could well fail.

That will mean more delay as another feasibility study will have to be done for what should be a second ML from Tallaght to NE suburbs?

Idbatterim

Nothing should he done that would jeopardise the chance that we may get the metrolink that is currently in planning...

Also even if you were to use the same tunnel, could you not start it from tallaght etc and work your way in ?

tom1ie

https://www.boards.ie/discussion/comment/123078168#Comment_123078168

That feasibility study is done as part of DSW.

1. metrolink TBM starts tunneling
2. At the same time the feasibility study is carried out into DSW
3. RO is granted for DSW and JR timeframe completed.
4. Metrolink TBM gets to its proposed burial site.
5. Around the same time as 4 the DSW TBM starts in tallaght
6. Metrolink TBM continues tunneling from charlemont to bushy park under the RO granted in step 3.
7. When metrolink TBM exits at bushy park the rails and electrical etc for the tunnel section can start.

Consonata

I don't know how many times this needs to be deconstructed again and again. There are so many reasons stitching on the South West section onto Metrolink is a bad idea.

1. It likely would delay the whole project by several years as the TBM would have to continue excavating spoil through the existing portal to avoid being hideously expensive. It's why that any proposed GL tie in, opts for digging a cut and cover trench to where the TBM terminates rather than re activating it.
2. If you then agree that the GL upgrade is the best bang for the buck metro upgrade we can do in this country, then attempting to force the two branches to use the same tunnel halves the frequency of both.

Lets assume that the Metro is working at maximum capacity at launch (it isn't it is roughly working at about half that but leave that to one side) introducing a spur line introduces significant logistical issues to actually achieve the 90second headways per direction as they all have to merge at Charlemont and continue northwards.

Now let's also assume that demand from the South West is equivalent to demand from the existing GL (dubious but for the sake of argument), then we would likely split the possible passenger capacity in half. (The benefit of embarking on such a project becomes radically less attractive if you do anything else)

Metrolink at a theoretical max capacity is approx **20,000** passengers-per-hour-per-direction (pphpd)

Currently the AM rush hour for the Green Line Luas is **6,400** pphpd.

Now if you give half of the capacity to the Green Line, assuming for the sake of argument that running two spur lines into one tunnel does not reduce the max total capacity of just running one single tunnel, then that only gives **10,000** to the Green Line segment, a pretty miserable 35% increase in potential capacity, vs. 135% increase which is the actual potential of that line on its own.

This is ignoring that building a spur out south west, will basically need to go all the way to nearly Tallaght to get any sort of population density to warrant such a line, at great cost, cost to only yield half of the actual potential capacity.

_______

TL:DR: Making the South West stitch onto the existing Luas is bad that it will delay the main Metrolink Project, bad that it can nearly sink the whole project, and bad as it reduces the potential capacity gains from upgrading the Green Line from 135% to 35%.

If you want a South West Metro tunnel it should be a simple, single tunnel, existing as its own project, easy to run, to get the best value for money out of running that TBM.

Idbatterim

OK, so one blatant issue with 60m long platforms, is how much they hinder capacity through the tunnel...