DART underground - options

citizen6

If DU goes ahead, would TII be involved? Or just Irish Rail?

TII would have built up a lot of experience on Metrolink.

L1011

https://www.boards.ie/discussion/comment/123643304#Comment_123643304

Just Irish Rail. TII have no involvement in heavy rail, unless they are disrupting it (e.g. Glasnevin Station)

murphaph

Legislation should be passed to change that. Ireland is far too small to have two outfits being responsible for delivering underground railway infrastructure. It's niche stuff. TII should deliver DU. IE staff should move over to TII where it makes sense.

L1011

https://www.boards.ie/discussion/comment/123643367#Comment_123643367

A single rail infra provider would make sense, but they should not also be the roads authority.

Split TII back to the NRA and RPA; merge in the Infrastructure Operator component of Irish Rail in to the RPA. Leave the Railway Undertaking side of Irish Rail in CIE.

KrisW1001

https://www.boards.ie/discussion/comment/123643276#Comment_123643276

It wasn’t a “really poor” benefit. The Benefit-to-cost ratio for DART+ with the tunnel 2.34x. For DART+ without the tunnel it was 2.55x. (source: 20210910-DART-Programme-Preliminary-Business-Case_Final.pdf, p55-56; “Option 2” is DART+ and DU, “Option 6” is what is being built).

That’s not a huge difference in benefit. For each euro spent, the tunnel pretty much gave the same benefit as the rest of the DART+ upgrade. The big problem was that the tunnel cost so much - almost twice what the rest of the programme did. That's why it was dropped.

@gjim - Yes, DART has a bit of an image problem: it was built at pretty grim time in Ireland, when we could barely afford it, and it shows in the stations. Shiny new trains will help the image of the service a lot, as well as reliability and punctuality. However, there needs to be a station renovation project too: Tara St in particular will need capacity improvements as it will soon be taking passengers from the Western DART+ line: I hope that will prompt an architectural facelift to make it less grim. As far back as 2004, IÉ commissioned a new design for the station as part of a commercial development plan for the site (Tara Street Station Redevelopment - Adamson and AAI ) - another casualty of the Celtic Tiger bust. Still, that’s pretty much what’s needed now.

The proposed designs for Cork and Cabra are clean, friendly and open, so it’s clear that that IÉ know what needs to be done.

roadmaster

https://www.boards.ie/discussion/comment/123643373#Comment_123643373

They cant do that is it would make far to much sense

CatInABox

https://www.boards.ie/discussion/comment/123643703#Comment_123643703

I think Consonata might have been referring instead to the somewhat recent NTA discussion around it, where they said that the largest benefit from the old Dart Underground project would be from the newly electrified lines, rather than the Underground portion of the project. If I remember correctly, it came out when they were announcing the Dart+ projects, and canning the tunnel section.

Now, I think that what they came out with was a load of auld balls, and also the right thing to say. For the past decade, the NTA has had an admirable focus on keeping politicians attention solely on projects that they want progressed. You can see this with the Metrolink project, as soon as the sewer made the southern section unviable, they jettisoned it, with a report that was incredibly optimistic about capacity projects on the Green Line to take up the slack. Same with this Dart Underground Tunnel, focus on the easy part of the project and get that done first.

Both of these will make the case for follow on projects extremely easy, for example, as soon as Dart+ is completed (and perhaps even sooner), they'll have a report that says something along the lines of @"actually, now that we can see the passenger numbers on the Dart+ lines, we can see that there'll be a significant benefit from a Dart Interconnector, with benefit not just for Dart trains, but also intercity trains too!".

KrisW1001

https://www.boards.ie/discussion/comment/123643773#Comment_123643773

I suspect "auld balls". The document I linked summarised the reason why the tunnel was excluded from DART+. No proper analysis of DU has been done since that one.

Working back from the figures in that report, building the tunnel alone still had a Benefit-Cost Ratio of a little over 2x. That was a lower BCR than the electrification and SW four tracking, but still something that was with doing. The big barrier is the "cost" part: adding the tunnel to the rest of DART+ would have made the whole project very expensive, and politically hard to sell.

I suspect that as additional capacity is added elsewhere (particularly the extra tracks on Northern line) the tunnel will become more valuable as the only way to fully exploit that extra capacity.

spark23

If the DU tunnel was built;

Would there ever be a situation with 4Northplus electricfication on say cork-dub or galway-dub of intercity trains using the tunnel through the city and onto the possible future airport station? Or would the hourly services from these cities adversely affect the dart service?

Consonata

https://www.boards.ie/discussion/comment/123695171#Comment_123695171

Unless DU was also 4 tracked, it would kneecap frequencies horribly for darts passing through it

spark23

https://www.boards.ie/discussion/comment/123695185#Comment_123695185

Was there ever a plan to have Belfast-Dublin direct services? imagine and hourly EMU each way through tunnel maybe wouldnt be too bad.

GerardKeating

https://www.boards.ie/discussion/comment/123695185#Comment_123695185

https://www.boards.ie/discussion/comment/123695284#Comment_123695284

An unpopular opinion, but qaud track DU and feed it into a quad tracked "metro/DART" line to the airport and onwards towards Rush.+

spark23

https://www.boards.ie/discussion/comment/123695321#Comment_123695321

Maybe add to that a Galway-Athlone-MUllingar-Dublin-Dublin Airport 200km link thru said tunnel to increase connectivity, other routes could feed into above cities/towns!

GerardKeating

https://www.boards.ie/discussion/comment/123695347#Comment_123695347

No, that should be a monorail

KrisW1001

DU was proposed as a twin-bore tunnel. A four track link would not be 2x the cost of a two-track one. I don’t think that should be done, though.

I’m not sure how current Inter City services would ever justify needing two dedicated underground tracks. If you wanted a (Galway/Cork/Limeric)-Heuston-Connolly-Belfast service, the Phoenix Park tunnel could be used for that purpose once DU is in service. It requires the train to back out of Heuston (and also Connolly), but the attraction of a no-change service might make it viable to run maybe two or three times a day.

The reason these services don’t exist today has nothing to do with needing to get across Dublin: that link has been in place for over a century. The problem is the difference in line signalling between IÉ and NIR that means only the a small number of trainsets (the Enterprise plus some adapted 22000 trains) are allowed to run across the border. The adoption of ETCS on both sides of the border removes that obstacle, and will allow ETCS-equipped trains from anywhere in the Republic to travel to Belfast if there’s commercial demand for such a service.

AngryLips

What if the really radical replacement for DU is going to be a 4-track solution that incorporates the new alignment of the northern line to separate IC services to Belfast from Commuter services and including an interchange at Dublin Airport?

riddlinrussell

The biggest bit of work for a multi city IC service would probably be a North facing curve from the Drumcondra branch. If you had that then you could run through trains direct via the PPT, with your "Dublin" stop being Glasnevin for metro or Dart?

Simplifies movements dramatically.

spark23

https://www.boards.ie/discussion/comment/123697882#Comment_123697882

Would it need to be 4 track, i can't see Darts even at peak maxing out the tunnel capacity.

AngryLips

https://www.boards.ie/discussion/comment/123698548#Comment_123698548

I mean the underground interconnector being intended for dart AND intercity services… a solution that can as easily facilitate Belfast-Cork as it does Drogheda-Hazelhatch.

thosewhoknow

The Enterprise did run to Cork at one point, but it was cancelled due to low ridership. I know things have changed since the ‘50s, but I can’t think of many people who’d need to go directly from Belfast to somewhere in Munster.

AngryLips

https://www.boards.ie/discussion/comment/123698605#Comment_123698605

If Dublin Airport were on the line, I imagine it would be much larger volumes than the 1950s

PlatformNine

Thoughts aside on an IC rail tunnel through dublin, building this as a part of DU/D+ Tunnel wouldn't make much sense.

The problem with sharing the same two tracks is that at the cost of DU, it will really only make sense as a way to allow DART service to operate at super high frequencies between the Kildare and Northern lines. This means full grade seperation of DART and regional/IC services is needed, so projects like four-tracking the northern line will likely be a prerequisite of DU. Mixing DARTs and IC services would kill any possible frequency increases post-D+. This is the difference between ~12tph post-D+, and upwards of 20tph as systems like the RER can operate at.

The problem with a four-tracked DU is just that it wouldn't suit an IC interconnector very well. DU is likely to take a more indirect and slower route to best serve the commuter rail service pattern the DARTs have. An IC interconnecter alignment on the other hand would be better suited to either a direct route to the Northern line or the airport. An IC interconnecter would probably only have 1 station in the city at Heuston and possibly a second outside of the city at the Airport. Particularly if the new IC fleet is a comparable length to the current Enterprise or MkIV fleet, as they would need very long platforms for an underground station, so adding a second station in CC could be very difficult and very expensive.

AngryLips

https://www.boards.ie/discussion/comment/123698657#Comment_123698657

An IC interconnector would want to hit all the same city centre trip generators as DU. I don't think any slight detour of an underground route is going to add much travel time for intercity-type journeys.

KrisW1001

Stopping at the intermediate DU stations would not be an option, because as soon as you do that, St Stephen’s Green will become the de facto Dublin Central railway station, and there is simply not enough room there for that to be accommodated. Because of the lower frequency, people arrive earlier for IC trains: that means more people along the platforms, many carrying luggage, all of which needs a lot more space on the platforms.

The other major problem for mixing the trains, even when both are EMUs is that IC trains have to stay at stations much longer than DART trains: typically 1-2 minutes, versus 30 seconds for DART. Passengers carrying luggage is the main reason for this, so there’s no technological solution available.

gjim

I don’t think a discussion about providing through-running intercity service belongs in a discussion about DART-U - there are absolutely no synergies between the two. The goal of DART-U follows that of hundreds of through running projects all over the world - support metro-level frequencies and capacity using legacy heavy rail infrastructure - by building relatively short tunnel sections under the central core of cities.

Tbh I’ve no idea what spending billions to offer through-running for intercity services is supposed to achieve - especially as Dublin is the biggest city on the island and thus the biggest by far (nearly by 10x) intercity rail destination so the demand for through running will be minuscule.

While I could list 10 or 20 hugely successful DU type projects around Europe off the top of my head, could someone who thinks spending billions on an intercity through-running path makes any sort of sense, point out such projects elsewhere?

gjim

This means full grade seperation of DART and regional/IC services is needed, so projects like four-tracking the northern line will likely be a prerequisite of DU. Mixing DARTs and IC services would kill any possible frequency increases post-D+. This is the difference between ~12tph post-D+, and upwards of 20tph as systems like the RER can operate at.

The D+N limit to 12 tph is not due to different services sharing tracks - it’s due to a lack of terminal and through-running capacity and conflicts all over the system - particularly around Connolly.

That the loop line can manage over 20 tph with a mixture of DARTs and intercities proves this. Obviously it’s not ideal to mix services but it’s not the bottleneck for D+N.

If 4N magically appeared in the morning DART+N would still be limited to 12 tph. With DU without 4N, 20 DARTs/h would be possible. So DU is a prerequisite for 4N, not the other way around.

KrisW1001

Agreed. As a good rule of thumb for line capacity, Munich's S-Bahn tunnel carries 29 trains per hour on each track at peak times, using driver-operated trains and a signalling system from the 1990s. That's one every 2 minutes, with a spare slot to recover punctuality in the event of delays.

This is the sort of capacity that DART Underground would enable. Longer term it would allow for automation of the DART, as it is a key step on the way to complete segregation of inter-city and high-frequency (DART) services. (4 North and building a new IC spur from Clongriffin to Navan are the other necessary steps)

AngryLips

https://www.boards.ie/discussion/comment/123698970#Comment_123698970

How are you so sure Stephen's Green doesn't have the capacity when it hasn't even been designed, yet alone built?

KrisW1001

https://www.boards.ie/discussion/comment/123699964#Comment_123699964

Because I know the size of St Stephen's green, and the size of Heuston station.

plodder

https://www.boards.ie/discussion/comment/123699348#Comment_123699348

Worth mentioning that fairly elaborate station design in the Munich S-Bahn, is what enables those short dwell times, by having simultaneous entering and leaving the trains on opposite platforms, in the key central interchanges.