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DART underground - options

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    #152
    DoctorPan
    Registered Users Posts: 132 ✭✭DoctorPan


    The Down Loop is the Platform 10 road. What impacts the speed is the flooding along the Royal Canal section, some bridges and the tunnel itself. They had to slew the tracks closer together in it to allow clearance for higher containers to travel through it so there's now a non standard track centres that there's the possible hazard of two trains hitting each other at speed, hence the low speed to reduce the variance in dynamic envelope. Same with a few bridges on the route, they're restricted clearances so lower speed to prevent strikes.



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    #153
    gjim
    Registered Users Posts: 1,122 ✭✭✭gjim


    The main point of DU is to allow city centre through-running. For the sake of 5 or 6km of heavy rail tunnel, you enable fast, high-frequency and reliable services that can use nearly 150km of "legacy" heavy rail alignments. DU is a heavy rail "utility multiplier" for the entire network. Rail line capacity and frequency is constrained by the slowest/most limited bottleneck and stopping a train at a terminus, drivers doing a cab switch and heading out in the other direction is simply a huge bottleneck.

    Look at what Crossrail has allowed in London - DART-style trains every 2.5 minutes per direction in the centre at peak time. Anything approaching this kind of frequency/capacity is simply physically impossible anywhere near a terminus. The idea with all interconnector/crossrail/durchmesserlinie type projects is that trains terminate far from the centre allowing speed and frequency in the critical section with the most demand - the centre.

    The PPT does not solve this problem - it just moves the terminus to another city centre location. So of course trains can fly along until they get to Heuston West and then slow to a crawl in the area where it there is the most demand and where capacity (which is a function of speed) is most valuable. Nor would a Luas to Lucan (another peeve of mine - why the fixation with using trams as a mode to serve the outer suburbs?) or buses or even a new metro line be an alternative. It's not about whether passengers have alternatives to get to location A or B, it's about operational efficiency of the entire DART network.

    Clearly, there would be no case for building DU if the existing S, N, SW and W heavy rail alignments didn't exist. You'd build something like an East-West version of metro-link. But they do exist and they could be exploited to support metro like levels of service over a wide area, but only if trains can run through the city centre and not if they have to stop there.

    This is why Crossrail was built, instead of a new tube line. Or why Zurich chose to link up their heavy rail lines with a tunnel (now two) instead of building metro lines. This is why S-Bahn tunnels have been built all over Europe - particularly in Germany - in the last few decades or why (heavy rail) RER expansion is now the priority in Paris over new metro lines.



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    #154
    Murph85
    Registered Users Posts: 1,068 ✭✭✭Murph85


    No doubt the report recommends whatever outcome whoever commissioned it wanted...



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    #155
    bk
    Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 22,540 Mod ✭✭✭✭bk


    "For the sake of 5 or 6km of heavy rail tunnel, you enable fast, high-frequency and reliable services that can use nearly 150km of "legacy" heavy rail alignments"

    You say this like that 5 to 6km tunnel won't cost at least €6 Billion!

    Of course DU is a lovely idea, but it looks like it has a pretty poor Cost Benefit Analysis and DART+ and PPT likely can handle 90% of the needs.

    Crossrail of course is cool, but Dublin isn't London, nowhere near as big. I'm not saying DU will never happen, but I suspect PPT will match our needs for decades to come and when it looks like it is reaching capacity, we can look at DU again.



  • Options
    #156
    gjim
    Registered Users Posts: 1,122 ✭✭✭gjim


    Even €6B, if it allowed providing metro levels of service (sub 5 minute headways) over a 150km network is a bargain. Whatever the figure is, ML is going to cost more than DU for 19km. And nobody here is whining about the cost of ML.

    "Dublin isn't London" - of course it isn't - that's why I listed a bunch of cities - some smaller than Dublin, some the same size and some much bigger. All of which had 19th century legacy rail infrastructure (with city terminuses) and all built tunnels to allow through running and now heavy rail does the heavy lifting for moving commuters in and out of their cities.

    It's not obvious what a terrible effect having to stop in a terminus has on the capacity and frequency of a line. Say if you have a safety and operation constrains that demand a 5 minute headway, then with through-running, you can accommodate 12 trains an hour per direction on twin tracks.

    Terminus station turn-around takes at least 4 minutes (the fastest I've ever experienced) - so maintain the 5 minute gap between running trains the approaching trains have to be 9 minutes behind. This reduces the capacity of your twin tracks to just over 6 trains an hour per direction. And the quality of service drops with a 9 minute frequency instead of a 5 minute one.

    Getting rid of the terminus almost doubles the capacity of the line approaching the terminus. This is the simple calculation they've done in endless cities around Europe which justified building tunnels to link up heavy rail alignments. This is before considering the benefits in terms of any new stations or connecting up places in the city that had previously been separated.



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    #157
    bk
    Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 22,540 Mod ✭✭✭✭bk


    “Even €6B, if it allowed providing metro levels of service (sub 5 minute headways) over a 150km network is a bargain. Whatever the figure is, ML is going to cost more than DU for 19km. And nobody here is whining about the cost of ML”

    Metrolink has a very strong CBA, DU seems to have a very weak CBA with DART+ and the PPT, it is as simple a that.

    Metrolink will likely carry more passengers per day, then the entire Intercity rail network combined.

    To be honest, nothing you have wrote is particularly convincing to me, that we need DU in the next few decades. I won’t say it will never happen, I hope it will eventually, it would of course be nice to have. But it simply doesn’t look to deliver enough for now when we have more important projects to do.



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    #158
    Ronald Binge Redux
    Registered Users Posts: 239 ✭✭Ronald Binge Redux


    https://www.boards.ie/discussion/comment/121067064#Comment_121067064

    We can't get the PPT running on weekends, let alone at Metro frequencies. The will to 'do' mass transit properly at Official Ireland level isn't there. If it was, we wouldn't have such logjams and hurdles to nearly every project that doesn't involve tarmac and shifting lines on maps.



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    #159
    gjim
    Registered Users Posts: 1,122 ✭✭✭gjim


    If what I've written can't convince you, then there isn't much more I can add.

    But I'm not even sure that further arguments would help since I don't think that you're particularly open to be convinced. But maybe I am being unfair? Is there some line of argument that would convince you? From what I recall of your previous comments on the topic, you were anti-DU before this discussion and your responses here tend to avoid addressing my points.

    As it is, DART will never be able to provide S-Bahn or metro levels of service if lines terminate in the centre. To me this is a massive wasted opportunity. Particularly as there are so many examples of cities around Europe which have embraced the opportunity to exploit existing heavy rail alignments, resulting in massive positive impact on public transport and quality of life.

    I don't understand why people convince themselves that Dublin is uniquely different that we've nothing to learn from all these other cities which are recognised as having decent PT and have - in the past - addressed similar issues as Dublin faces now.



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    #160
    Ronald Binge Redux
    Registered Users Posts: 239 ✭✭Ronald Binge Redux


    Official Ireland has been reinventing the wheel for so long that there is a significant chunk of the economy devoted to constant redesign of projects that are always ten years away from being implemented.



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    #161
    bk
    Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 22,540 Mod ✭✭✭✭bk


    "But I'm not even sure that further arguments would help since I don't think that you're particularly open to be convinced. But maybe I am being unfair?"

    I'm absoutely open to being convinced. I was a big fan of DU for years, but I'm not really sure where it stands today, which is why I'm asking these questions.

    I love your vision of high speed, high frequency metro like service serving the city.

    But to be honest, I'm not sure Dublin has that level of demand. Again above you talk about Berlin and S-Bahn and sub 5 minutes heavy rail frequency. But again, like Crossrail and RER, Berlin is a much more massive city and Metro area with requirements far in excess of Dublin.

    I'm just not sure Dublin actually needs that level of service at the moment. I mean the South West line currently just has a train roughly every 30 minutes!

    DART+ will be a massive increase in capacity compared to what the West of Dublin currently enjoys. DART+ feels more suitable to a city the size of Dublin. In some ways we are lucky to have 4 heavy rail lines feeding into the city and we should of course make the most of them.

    My heart loves your idea, but my realist head struggles with it!

    Honestly, I hope I'm wrong, I hope DART+ opens to be a massive success, massive usage that means we have to go straight into planning DU.

    As an aside, the big question that this all brings up for me is why didn't we do DART+ 20 years ago! It seems like a really good plan to affordably add massive capacity into the city. Shouldn't we have done DART+ 20 years ago, the people of West Dublin could be commuting into Dublin on frequent DARTs for 20 years now and we could be planning/building DU now to enhance it.



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    #162
    Pete_Cavan
    Registered Users Posts: 6,762 ✭✭✭Pete_Cavan


    I think that a few years after DART+ has been completed (which is many years away yet), the Business Case for a tunnel will be extremely strong. There is huge unmet demand for massive transport which DART+ will tap into and that demand will only grow, particularly with the improved journey times and new destinations opened up by Metrolink and BusConnects.

    DU was always doomed to fail because it tried to do too much all at once. With the existing lines upgraded and the rolling stock available, the case for the tunnel to link everything up becomes very strong.

    DART+ took a pragmatic approach and I'd say the case for the tunnel was intentionally downplayed. This made the €1bn investment in DART+ more palatable and they could claim to be maximising investment already made in the PPT. The same pragmatic approach was taken with not extending Metrolink along the Luas Green line, the Businnss Case for something that was going to kill the project was conveniently not strong enough. After DART+ has been completed, the way to maximise that investment is to allow through running.

    We will also be limited in increasing intercity services if DARTs are taking up terminating capacity, there is no point in many of the investments proposed in the AIRR if there is nowhere for these trains to go in Dublin.

    Post edited by Pete_Cavan on


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    #163
    MICKEYG
    Registered Users Posts: 757 ✭✭✭MICKEYG


    https://www.boards.ie/discussion/comment/121067667#Comment_121067667

    I agree no need for Dart U now as other projects have better business cases but given our history we could plan for it now so it is ready when all these qualified and experienced project teams are done with the current projects and need something to work on.

    Having a steady supply of big infrastructure projects "shovel ready" will help retain skills and ensure we don't ever fall as far behind as we are now



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    #164
    CatInABox
    Moderators, Computer Games Moderators, Recreation & Hobbies Moderators Posts: 10,263 Mod ✭✭✭✭CatInABox


    I've been wavering between thinking that DU will never happen, to thinking that it'll happen at some point, in the future, when it's chronically needed. I've finally decided that I don't care any more, I just want what's planned now to get under construction.

    One of the questions that I'm still thinking about though, is what a new DU project will look like, after the experience of planning and building Metrolink. I very much doubt that the NTA/TII will go for mined out stations, they moved heaven and earth to make every station on the Metrolink project a cut and cover station, so I think that's the way it'll go for these now. I could see a significantly pared back project, with only one or two stations, one at Dame St, down the Christ Church end, so that they can cut and cover the station in the road there, and then an interchange station, which might, just might be a mined out station at Tara St.



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    #165
    KrisW1001
    Registered Users Posts: 1,463 ✭✭✭KrisW1001


    "But Dublin isn't as big as Berlin" doesn't really stand up as an argument. It's not like the Berlin S-Bahn was built in the last 5 years.. When Munich built its S-Bahn trunk tunnel, the city was of similar size to Dublin today. Copenhagen's S-Tog connector was built when that city was considerably smaller than Dublin is now.

    Another cross-city heavy-rail link could be very useful to improve DART service frequency, or provide Dublin with a true central station, or both.



  • Options
    #166
    AngryLips
    Registered Users Posts: 2,681 ✭✭✭AngryLips


    https://www.boards.ie/discussion/comment/121067064#Comment_121067064

    Sorry what is there to support DU having a 'weak CBA'? The fact is that the CBA for DU is positive. The only reason the modeling for DU does not envision it being required in the lifetime of the current transport strategy for the city is because the NTA changed the long term demand assumptions to account for changed travel patterns as a result of the pandemic ...but those assumptions are already beginning to look totally dated.



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    #167
    bk
    Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 22,540 Mod ✭✭✭✭bk


    ""But Dublin isn't as big as Berlin" doesn't really stand up as an argument. It's not like the Berlin S-Bahn was built in the last 5 years.. When Munich built its S-Bahn trunk tunnel, the city was of similar size to Dublin today. Copenhagen's S-Tog connector was built when that city was considerably smaller than Dublin is now."

    Berlins population in 1925 was 4 million people! It is over 6 million today. Completely different scale.

    "I've been wavering between thinking that DU will never happen, to thinking that it'll happen at some point, in the future, when it's chronically needed. I've finally decided that I don't care any more, I just want what's planned now to get under construction."

    You are reading my mind here, I feel exactly the same way. We need to get Metrolink and DART+ started, we can look at the DU again in 2040.

    "One of the questions that I'm still thinking about though, is what a new DU project will look like, after the experience of planning and building Metrolink. I very much doubt that the NTA/TII will go for mined out stations, they moved heaven and earth to make every station on the Metrolink project a cut and cover station, so I think that's the way it'll go for these now. I could see a significantly pared back project, with only one or two stations, one at Dame St, down the Christ Church end, so that they can cut and cover the station in the road there, and then an interchange station, which might, just might be a mined out station at Tara St."

    Again, I've been thinking exactly the same. Redesign DU as a more Metroish type service. Shorter 90 meter 4/5 carriage DARTs, but running at higher frequency, thus small simpler cheaper cut and cover stations.

    But then the AIR Report seems to go the completely opposite way, suggesting running intercity trains into the tunnel! Which would mean massive expensive mined out stations.

    Honestly I don't get this idea, I don't see the benefits (of intercity) given the massive costs that would be involved. It kind of makes me what is gonig on in Irish Rail, what is the thinking.

    Anyway, probably doesn't matter, looks like DU is off the table for at least another decade.



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    #168
    KrisW1001
    Registered Users Posts: 1,463 ✭✭✭KrisW1001


    Odd... you seem to have stopped reading before I used Munich as my example. Let's try again: That city's population was about 1.1 million in 1965 when the east-west S-Bahn tunnel was signed off. That's very much comparable to Dublin today. At the same time, Munich also commenced the building of a three-tunnel metro under the city. Copenhagen remains the same size as Dublin, and is probably the closest model for Dublin in Europe, as it has the same kind of geographic limits. And still, it has a heavy-rail commuter system that runs through the city, and a Metro.

    Neither of those systems carry inter-city trains, by the way. They are used solely for higher capacity commuter rail - DART services, effectively. Unless IE basically rebuilds it, low running-speeds make Phoenix Park Tunnel capacity constrained from the get-go, and fairly soon (<10 years) we'll end up having to look at a better solution anyway.

    An inter-city link between the lines radiating from Dublin is also needed, but it doesn't have to be in the city, it doesn't have to be underground, so it is not necessarily DART Underground.

    If there were such an inter-city tunnel, it probably should be a wholly underground tunnel with no intermediate stops - any intermediate station would become "Dublin Central" simply by existing, and there just isn't the amount of space needed to properly create a station of the necessary capacity. The original plan for DU was to give Connolly and the Loop Line over to commuter rail entirely, and bring inter-city services through the higher-capacity Docklands station - it wasn't a bad idea, but it does seem that later developments at the site will now prevent that.



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    #169
    Chris_5339762
    Registered Users Posts: 5,858 ✭✭✭Chris_5339762


    Munichs Stammstrecke tunnel was so successful that they are now spending a small fortune building a second one next to it.



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    #170
    KrisW1001
    Registered Users Posts: 1,463 ✭✭✭KrisW1001


    Yes - it's a high capacity link, but every single S-Bahn service has to traverse it, and the intermediate stops are, in hindsight, too close together, especially the four central ones (Hauptbahnhof, Karlsplatz, Mairienplatz, Isartor) which are only 700 metres apart on average - you can often walk between any two neighbouring stations along here in the same time it would take to go down, wait for a train and come back up again.



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    #171
    AngryLips
    Registered Users Posts: 2,681 ✭✭✭AngryLips


    https://www.boards.ie/discussion/comment/121072462#Comment_121072462

    Dublin Airport would be a perfect terminus for all intercity trains into Dublin, IMO.



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    #172
    bk
    Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 22,540 Mod ✭✭✭✭bk


    https://www.boards.ie/discussion/comment/121073216#Comment_121073216

    No it is absolutely terrible idea. Would cost a fortune to do with almost no demand.



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    #173
    bk
    Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 22,540 Mod ✭✭✭✭bk


    “Let's try again: That city's population was about 1.1 million in 1965 when the east-west S-Bahn tunnel was signed off. “

    Sure, let’s try it again, Munichs Metro population is 6 million!

    When the population of The Greater Dublin Area reaches 6 million, I’ll happily agree to the DU tunnel!

    Seriously, Berlin/Munich are at a whole different scale to us and London/Paris are another level above them.

    Amsterdam and Copenhagen are better examples for us.

    Amsterdam Central Station is an incredible station, but I note all the rail lines that serve the station are above ground, no underground. Yes of course separately there are the Metro lines, but they seem to be able to do great heavy rail without expensive tunnels.

    Copenhagen is probably closer to us with the S-Tog basically being DART. Their central station has a tunnel, but correct me if I’m wrong but it looks to be just a 1.6km long, pretty simple cut and cover tunnel, with just one underground station. Looks sort of like the Cork tunnel. Of course Copenhagen has their excellent Metro too, which we seem to be replicating with Metrolink.

    Neither Amsterdam or Copenhagen seem to have much or any underground heavy rail tunnels.

    BTW Interesting aside, it seems that Copenhagen is planning to fully automate their S-Tog. Could fully automated DARTs be possible in the future?



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    #174
    Brian CivilEng
    Registered Users Posts: 1,017 ✭✭✭Brian CivilEng


    Would Oslo be a good comparison? Similar population to Dublin, maybe geographically it's shape makes it better suited to public transport, but two major railway tunnels though the city. The Oslo Tunnel, a 3km heavy rail tunnel bringing regional trains to the central station and serving Nationaltheatret with an underground station in what I'd consider the dead centre of Oslo. Then there's the T Bane common tunnel, a 7km tunnel that is used by all 6 lines of the metro.

    Oslo has a population of around 700,000 in the city proper maybe double that in the surrounding area.

    My heart knows that DART Underground would be a huge success, my head wants more numbers.



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    #175
    Strumms
    Registered Users Posts: 24,901 ✭✭✭✭Strumms


    We can’t get a single thing done to commence building the metro. So anything representing an underground Dart ? 20+ years…. Same as the metro…Before design, costing, planning, delay after delay, building….

    its an inefficient country, with scandalously bad leadership and with priorities askew…. Unlikely that will change.

    As citizens we won’t be listened to, so not to worry…. If / when it happens it happens …🥱



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    #176
    Brian CivilEng
    Registered Users Posts: 1,017 ✭✭✭Brian CivilEng


    There is nothing unique about Ireland. Our leaders are no more inept or competent than our peer countries. One thing I do think is different is that we seem to be so afraid to waste money on building something that we spend 10 times as long to get the design "perfect", but still find it doesn't work when we put a shovel in the ground.

    I've watched other countries build something then tear it down and rebuild within a couple of decades when it was shown to not be working. We're still talking about it.



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    #177
    KrisW1001
    Registered Users Posts: 1,463 ✭✭✭KrisW1001



    https://www.boards.ie/discussion/comment/121073301#Comment_121073301

    Why are you persisting in bringing up today's figures when I'm talking about 60 years ago? Dublin today is at the same scale as Munich was in the 1960s. A core of 1.2 million, with a hinterland of close to the same again. If at that stage of its development, Munich could justify a major S-Bahn tunnel and a three-line underground, where is the argument that Dublin, now at a similar stage of development, cannot?

    I am not comparing Munich today with Dublin today - you and I both know that would be stupid, so I don't know why you keep doing this rather than engaging properly.

    Regarding automation, it's unlikely on DART as long as it shares any track with mainline services. Metro can, and should, be fully automated.



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    #178
    bk
    Moderators, Motoring & Transport Moderators, Technology & Internet Moderators Posts: 22,540 Mod ✭✭✭✭bk


    Oslo, yes, an amazing city. The thing about Norway is the incredible wealth the country has, for a relatively tiny population. We are currently doing well with tax intake from the multinational’s but nowhere near Norways level of wealth.

    “There is nothing unique about Ireland.”

    I do think there is one thing unique about Ireland compared to the other European countries. The level of infrastructural deficit in Ireland. We are easily 50 to 60 years behind other similar sized cities.

    Take Oslo, they have 5 Metro lines! We don’t even have one!!

    It isn’t that I don’t think that some day we should build a heavy rail tunnel, what I’m wondering is if the time is right? If DART+ gets 90% there, then should the first priority be to build like 3 or 4 Metro lines like Oslo, before coming back to the DU tunnel?

    Honestly I don’t know the answer, I’m just musing.

    I think once Metrolink/DART+/BusConnects start building, we really need to plan out what the next steps are once they are completed. What projects are next? What are the CBA’s of each project? The priorities of each project?

    I know people don’t like the constant reports, but I think we are actually seriously lacking a vision for what the next steps are in a post Metrolink/DART+/BusConnects world.

    I think we maybe facing long term structural issues with lack of staff/drivers, which may drive us towards bigger vehicles and more automation. BRT, more Luas lines, more Metro, maybe DART automation and yes this might even make a DU tunnel necessary sooner.



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    #179
    loco_scolo
    Registered Users Posts: 479 ✭✭loco_scolo


    https://www.boards.ie/discussion/comment/121073812#Comment_121073812

    But does Osla really have 5 Metro lines? From Satellite imagery it seems like one or two main, relatively short, tunneled sections with surface lines branching out into several suburbs.

    You could argue Dublin has Howth line, Malahide/Drogheda line, Bray, Maynooth, HH lines. Obviously we're not doing great but let's not compare unfairly...



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    #180
    Pete_Cavan
    Registered Users Posts: 6,762 ✭✭✭Pete_Cavan


    https://www.boards.ie/discussion/comment/121073301#Comment_121073301

    Neither Amsterdam or Copenhagen have much or any underground heavy rail tunnels because they have the necessary above ground infrastructure. Dublin needs a tunnel to replicate what they already had.



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    #181
    Brian CivilEng
    Registered Users Posts: 1,017 ✭✭✭Brian CivilEng


    https://www.boards.ie/discussion/comment/121073946#Comment_121073946

    Oslo has five Metro lines now, but they weren't built as such. They were upgraded piecemeal over many years from old railway and tram lines. The city centre tunnel being the largest piece of infrastructure. Bit by bit speed restrictions were removed, grade separation added, 3rd rail electrification rolled out. Just this week they opened up a new stretch of tunnel that speeds up lines 2 and 3 by 2mins.



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