DART underground - options

gjim

https://www.boards.ie/discussion/comment/122484833#Comment_122484833

Your idea isn't actually novel. The proposal that came out of the 1975 DRRTS study included (heavy rail) branches to Blanchardstown and to Tallaght and while I believe the intended path to Blanchardstown is still almost legible on google maps (as a green strip between the backs of houses), the Tallaght one isn't at all given the amount of development since. These branches actually made some sort of sense back then as the alignments passed through green fields so they were seen as an "easy win" to add appeal to CIE's proposal. This is decades before the M50 for example. The current Naas road/Bluebell area was still mostly rural (development around here had only begun in the 1960s)

But with all the development and new roads in the last 50 years, there is absolutely nothing "easy" or particularly "winning" about these alignments today and there's no chance they could pass any sort of CBA - the amount of CPOing and disruption just makes the idea infeasible.

Note the proposals did not include the very tight bends which you have in your sketch because they would not be possible for our wide-gauge trains - a minimum of about 500m radius for curves would be required to avoid speed restrictions.

Finally, the tunnel to Inchicore is not going to happen - it's completely redundant once Hueston is 4-tracked as part of DART+SW. Any future DART tunnel will start in the Hueston yards.

loco_scolo

https://www.boards.ie/discussion/comment/122485968#Comment_122485968

Yeah that's totally fair on the Tallaght branch. The curves required now are completely unrealistic and Metro would be the only solution.

I'm not sure I agree on the tunnel in the Heuston yards though - Irish Rail launched a masterplan for the area in 2021. Is there still space for a tunnel Portal? I think their masterplan is extremely short sighted. If they want to make all Intercity trains at least hourly and also send Sligo/Wexford trains into Heuston, then they might need more platforms. It would also be useful to have a Luas extension to Heuston West.

Heuston-Masterplan-final.pdf

https://www.irishtimes.com/news/ireland/irish-news/heuston-masterplan-area-to-be-largely-car-free-with-more-than-1-000-residential-units-1.4730050

Pete_Cavan

https://www.boards.ie/discussion/comment/122478303#Comment_122478303

It's not about being accurate to the metre but what you drew misses the point which engineers have already identified as a potential GCD station location. No point in drawing lines on a map to suit yourself and ignoring information already available.

Both the CCD and PWC building have two basement levels. Planning drawings show the PWC building has a basement level of -3.5 and then slab and foundations below that. The tunnel would still have to be very deep if passing under them. If the tunnel goes west of them, you end up with a tight S curve (particularly as GCD would be further east of where you drew your line).

A new potential tunnel portal location further east has already been identified and given difficulties in finding a new depot site, taking part of the Inchicore works site is now less desirable. An above ground rail line would have a major impact on a substantial number of dwellings in Inchicore and other places along any potential route. Given the number of existing roads, it would have to be elevated It is something which would be quickly killed along with anything else associated with it.

loco_scolo

https://www.boards.ie/discussion/comment/122486443#Comment_122486443

The general idea here is to drop the X configuration (Northern Line into tunnel) and consider the U configuration (Royal Canal Line into tunnel). Given the difficulty connecting the elevated Northern Line (+8m), the U configuration has merit, which others have also acknowledged.

Ultimately it's a small alignment change with the tunnel moving 60m slightly west. Exact alignments south of Docklands would not be materially impacted by this change.

I don't know if the apartment blocks or PWC buildings can support a tunnel underneath - the tunnel needs to be 20m under the Liffey so there might be enough clearance. It might be acceptable to knock the PWC buildings, but certainly not the apartment blocks, so I acknowledge this is a major concern.

Pete_Cavan

https://www.boards.ie/discussion/comment/122487023#Comment_122487023

I understand the reasoning behind the U arrangement, I just don't think it stacks up. Several route options via SSG and GCD have already been considered and generally didn't look very attractive;

Ultimately the best performing route overall is via Tara and I think that is where the tunnel will have to go. There are issues associated with the Tara Street location but it significantly shortens the tunnel and you save the cost of a mined city centre station. If that's the route, the question then is how/where to tie-in.

blanch152

https://www.boards.ie/discussion/comment/122485968#Comment_122485968

The intended line to Blanchardstown is still there, however, not enough space for it to turn to join the mainline rail.

The reservation was preserved for Metro West, and is still there.

KrisW1001

@blanch152 do you have a modern map showing this intended alignment? I can see two possibles: one along Porterstown Rd-Diswellstown Rd (Yellow) and the other, through Sheepmoor (green), but the height differences here would make it very difficult to link them directly into the Sligo line: an interchange station would be needed.

blanch152

https://www.boards.ie/discussion/comment/122504918#Comment_122504918

The green alignment on your map was reserved for the alternate bridge over the railway and canal to the Coolmine level crossing. This alignment has been preserved even though the bridge ultimately did not form part of the DART West proposals.

The yellow alignment is the Metro West alignment. It follows the previous alignment for the DART extension to Blanchardstown, but there is now insufficient space to link into the DART line, not only because of height. The Metro West proposal included an interchange station at Porterstown, more or less beside the Dr. Troy Bridge.

OisinCooke

Just robbed this from the DART+ thread but I thought it was topical given the talk of extensions to Blanchardstown, Tallaght, and even the airport. The inclusion of a central station in Temple Bar is particularly intriguing!

spillit67

https://www.boards.ie/discussion/comment/122491591#Comment_122491591

I’ve said it a few times that my favourite there is S1 R02. It stretches Dublin out on the southside to its true level of activity at the canal and will provide a lot more general utility.

Consonata

https://www.boards.ie/discussion/comment/122509248#Comment_122509248

The speed on it would be kneecapped by the sharp turns required, going all the way south for Charlemont would be too much.

riddlinrussell

Hadn't seen this, but according to the roadmap outlined here, Iarnrod Éireann themselves envisage intercity services running through the tunnel by 2050, not just Darts.

spillit67

https://www.boards.ie/discussion/comment/122528755#Comment_122528755

Why? That serves one of the economic hubs of the city and is of significant utility for more Dubliners.

Consonata

https://www.boards.ie/discussion/comment/122535302#Comment_122535302

Because doing such a doing 2 sharp turns like the above would hamper the new line with massive speed restrictions that would negate any benefit. Underground lines should be designed to be as straight as possible. Its why Metrolink was designed the way it was

bk

https://www.boards.ie/discussion/comment/122533800#Comment_122533800

Which is a terrible idea, which just continues the stupidity of trying to mix DART, DMU commuters, intercity and even freight on one set of tracks, completely the opposite of international best practice.

Imagine someone suggested running intercity trains through London Underground tunnels!

This really worries me that it shows IR have no idea what they actually want to do here and have all the wrong priorities.

Consonata

https://www.boards.ie/discussion/comment/122538863#Comment_122538863

If the plan was truly putting intercities underground along with Dart services, then they should be speaking in terms of a 4 track tunnel, not a two track one. Would be phenomenally expensive but would be the only serious DU plan.

In which case it should be tabled against Metrolink 2/3 in terms of CBA. Dart underground whilst important, is likely going to be cheaper than a single bore line under many of Dublins main transport corridors with no current decent access.

spillit67

https://www.boards.ie/discussion/comment/122535934#Comment_122535934

Except the report does not highlight this as an issue.

“Negates” any benefit. Really?

OisinCooke

Always wondered why a route like this following the Grand Canal and up onto the (at this stage, four-tracked) Northern Line, and delivering services to Dublin Airport wouldn’t work for DU… obviously more tunnelling but in less dense areas above ground where cut and cover may be more feasible

Yes it avoids Heuston, but I’ve always thought that it doesn’t really need to stop at Heuston does it…? Most intercity trains stop at Newbridge and/or Kildare but instead, these should be left as Portlaoise commuter stations (may even DART as far as Newbridge at least) and have all intercity trains stop instead at Hazelhatch and Celbridge where passengers for the airport and the north and south of the city can change to either a PPT DART or a DU service

Not the best be all and end all plan and yes it does leave the city centre a bit barren still, but this can be covered by an east-west Lucan - Docklands metro or by high density trams…? Anyone see any glaring problems I’ve missed…?

KrisW1001

https://www.boards.ie/discussion/comment/122555930#Comment_122555930

It’s very long, but is worse than the original proposal, I fear. By being so far out from the centre, it avoids serving the main trip generators in the south inner city - the only commercial/office district it serves is Baggot Street, but against that, it ignores the local and national government centres (Merrion Sqaure along to Wood Quay) as well as the city’s commercial centre immediately south of that. There’s really nothing of note west of Harolds Cross that would justify diverting the line so far West: you’ve even managed to avoid the new Children’s Hospital - its southern entrance will be at the current Rialto Luas stop.

I know it’s only as far from the Liffey as the current northern arc, but that’s too far from the centre as it is.

gjim

Yeah, not a fan of sending the tunnel so far south. If you're going to spend billions on building a heavy rail tunnel under a city, then build the tunnel under the part of the city with the greatest demand/trip generation, particularly for what would likely be the highest capacity rail alignment in the city.

Diverting the DART tunnel along a longer path to provide "more coverage" is not the most efficient way to provide more access to rail based public transport, particularly to places like Harold's Cross. Build the direct tunnel - at half the length and cost - and use the 3 billion you've spared to provide a bunch of new radial Luas lines to serve the likes of Harold's Cross and other inner suburbs. Or put the 3 billion into the pot for a Tallaght/Harold's Cross/Coolock/Howth Junction metro.

loco_scolo

https://www.boards.ie/discussion/comment/122555930#Comment_122555930

I really like this general idea - basically an orbital route that crosses every Bus Connects Corridor, Luas lines, Metro at Charlemont, Dart at either end. Such a high capacity, high speed orbital wouldn't necessarily have to go through high density areas, given the enormous interchange/connection opportunities it would create. It could also connect into areas such as the army barracks in Rathmines, which could be developed as high density in future.

HOWEVER, that being said, it would be a huge mistake not to connect directly with Heuston Station. If/when Sligo and Wexford trains are diverted to Heuston, every single intercity in Ireland except Belfast will operate out of Heuston. It has to be included in any proposal.

OisinCooke

Understood completely and all very valid counterpoints made. Just a bit of a thought that crossed my mind earlier so I thought I’d share for this exact reason. Thanks for the feedback folks :)

I do still think however that there’s sense in stopping intercity trains at Hazelhatch or one of those stations for example for DART interchange rather than Newbridge and Kildare. Eventually extending the DART to Sallins and eventually Newbridge and maybe Kildare will pick up the slack there too

loco_scolo

https://www.boards.ie/discussion/comment/122556806#Comment_122556806

Oh I couldn't agree more with this. Others here have suggested changing to the Dublin commuter network should be done at Portlaoise with IC trains continuing directly to Heuston. However Portlaoise is 82km from Heuston. Kildare is 'closer' but still 48km out, while HH is just 16km.

Better still, IMHO, would be Clondalkin Fonthill as this would also connect with Metro West (recently relabeled Orbital West). The connections this would enable are huge - train from Cork, Orbital to Blanch/Tallaght, bus/Luas to final destination.

The difficulty is that an interchange station would require 8x platforms, realistically, to function properly. They should plan for this now to protect the space required.

AngryLips

https://www.boards.ie/discussion/comment/122538863#Comment_122538863

But why would it be a stupid idea to send IC services through dart tunnel? There's going what, three stations in DU(?), all of which will be city centre stations. Most likely IC services will serve all those stations meaning that there's no need for through-running of intermediate stations/slowing down of IC services by other stopping services. It's the same way many longer distance trains serve all city centre stops through to CGD on the loop line instead of terminating at Connolly.

KrisW1001

https://www.boards.ie/discussion/comment/122557171#Comment_122557171

Inter city trains have longer dwell-times at platforms than DARTs, they have to, because there are more passengers carrying luggage on inter city services. That messes with the frequency of DART services.

The bigger issue is station capacity: what would happen, do you think, if every national train stopped in St Stephen’s Green. Where would people from outside of the capital choose to get off or on? In effect, St Stephen’s Green becomes a terminus station for most inter-city passengers, and there is simply no room for this to happen.

Every “S-Bahn” link (which is what DU is) has excluded mainline services for this exact reason: there simply isn’t space to build an inter-city terminal station right under the heart of the city centre.

bk

Mixing different types of services is a terrible idea. It makes the system more complicated and reduces reliability, speed, frequency.

Frankly it is considered very bad practice internationally.

Luas works so well because it keeps things simple. Simple design, simple systems, but because of that it is highly reliable and frequent.

You would be laughed out of the room if you suggested putting intercity trains in a London Underground tunnel. The new Elizabeth Line doesn't even do that, no intercity trains, instead it uses hybrid urban-suburban trains like the new DART's. In fact a single class only, the Class 345, nothing else! It is that simplicity that will allow the Elizabeth Line to operate 24 trains per hour per direction.

In Berlin they actually have up to 6 tracks, one pair for S-Bahn (DART), one for long distance commuter and one for intercity!

We already see the problems we end up with mixing services on the Coastal South line and they are trying to fix that on the other lines now with quad tracking. I've no idea why anyone would think it is a good idea to repeat that mistake again with a multi billion euro tunnel!

OisinCooke

https://www.boards.ie/discussion/comment/122557048#Comment_122557048

Yeah I agree with you that Portlaoise is a bad option, it locks out trains from Waterford, Galway and Westport from changing to Commuter and as you say is way too far out. Clondalkin would indeed be an excellent idea with Metro Orbital, I hadn’t thought of that! The station also have plenty of space on its southern side (the fast lines) for at least 2 extra tracks which in fairness I think would be enough… Newbridge functions perfectly well seeing the majority of IC’s stop with only 2 platforms on the main so 4 ‘fast’ platforms so to speak, would be a fantastic addition

Pete_Cavan

Heuston will remain the main intercity train terminus for a very long time, likely for ever. Outer stations don't have the capacity for enough platforms, train servicing, overnight stabling, etc. They also don't have the space to create that. Heuston has it all already.

If you were to run intercity services through a tunnel under the city, you'd have nowhere to terminate them. They'd have dead running out the other side, unnecessarily using capacity in both directions.

There is no benefit to terminating trains elsewhere, just a huge list of problems it would create.