LXFlyer wrote: » As I have posted many times, in order to effectively operate the inner stopping DART service operating every 10 minutes, the outer semi-fast DART, and an hourly Enterprise, an overtaking facility is needed between north of Clontarf Road and just before Raheny Station. That will allow for an outer DART or Enterprise to overtake a stopping DART at line speed. Otherwise the outer DART/Enterprise will continue to crawl at pedestrian speeds to Clongriffin. Loops at Clongriffin In both directions further assist in the ability to overtake. The whole line does not need three/four tracks. Just between north of Clontarf Road and Raheny.
Pete_Cavan wrote: » There are many houses less than 30m from the existing tracks. That is not a lot of space to operate large plant. You probably need 3m buffer from the operating tracks. You will need 10m for two tracks, plus another few metres for embankment/retaining wall. At the stations, 8m or more is taken up with platforms, ramps etc. which are need to remain. It may be possible that some properties would be left with up to 10m of a garden but for many, they would have little or nothing left. I doubt they'd be allowed to CPO a full garden and leave the house which is seriously devalued, they would probably be made but the whole lot. Even if possible to leave the houses, you have a long linear work site along the tracks with the only access at the bridges crossing the tracks which is not practical. The excavators/trucks cant operate on the embankment, they need to be on level ground which is the gardens. Most of the gardens seem to be less than 15m long, you would need all of that. You then need to dig out the embankment while keeping back from the operational tracks, remove all the material from the site and build replacement embankment/retaining walls in such a way to avoiding subsidence to the houses. The trucks once loaded probably can't continue straight on as that is where the excavation is, they would need to turn or reverse out. It really isn't practical from any point of view.
MJohnston wrote: » So the 'why' essentially boils down to not being able to close the line while working on the widening? I'm just saying that it seems perfectly practical to add a single extra track without having to CPO much more than a few metres of some back gardens IF you accept that the line will have to close for some period.
Pete_Cavan wrote: » Where's your sources? Unless you have a link to support, that means nothing. Even if it was said by someone in Irish Rail, it needs context, I mean is the 4 tracks an additional track on either side or two additional on the same side?
Brian CivilEng wrote: » Very quickly ran the exercise south of Raheny as far as east wall road. Again a 25m corridor, so final layout not including for construction. It is very tight, I see at least 20 house that are clipped, multiple houses that would have zero back gardens. And as stated this is just in 2D, a lot of this area is in cut or fill. Not saying it's impossible, but it would be a "courageous decision".
Sam Russell wrote: » This may sound dumb, but can they not use railway trucks to remove the spoil? Would working at weekends not allow the rail line work during the week? Would they need the third line all the way from Connolly to Howth Junction?
lucernarian wrote: » There would not be 25 metres needed for a third track, and a lot of space is available to one side (clontarf golf course as an obvious example).
Pete_Cavan wrote: » I assume his 25m corridor includes the existing trackbed.
bk wrote: » Not if it looks to make little difference in the numbers of people using the service. Afterall it isn't like people sitting in Malahide and who want to go to Stephens Green are going to say, nah, I won't use this service because it is 5 minutes slower versus some theoretical service that hasn't been built. They'll still take it because it is still much faster ...
bk wrote: » Wow, the reports in the ANNEX are a goldmine of their thinking about how all this will fit together, the cost and performance difference between Dart+ versus full Dart Underground and it also gives us the cheaper DART Underground options they were considering!!DART+ versus DU So first off, the report shows that this DART+ plan carries almost the same number of passengers (just 0.10% less) as full DART Underground, while being about 2 billion cheaper! So obviously this DART+ plan comes out with a significantly better cost to benefit ratio (not that DU's was bad either). Other benefits include that it can be rolled out much faster then DU, thus gaining those benefits quicker and supporting the development of West Dublin faster. And the fact that it can be phased, making it overall less risky. Of course it also doesn't preclude DU happening in future and most of the cost of this DART+ would be needed for DU anyway. It all strikes me as quiet a no brainer to proceed in this manner.Alternative Dart Underground plans They also looked at 3 other "cheaper" DU plans. - Follow the original DU alignment, but with an underground turnback station under Hueston Station. Basically this means people would have to transfer between DARTs at Hueston station coming from the west of the city. - Follow the original DU alignment, but with an underground turnback station under Pearse station, underground line does not cross the Liffey. This would mean people coming in from the West and wanting to go North of the Liffy would need to transfer at Pearse Station. - A tunnel just between East Wall and Pearse Station. Again would require folks to transfer. These 3 options all saved about 400 million (and more for the third one, I forget how much) out of the roughly 4 billion full DU cost. However 400 million isn't that much in the greater scheme of things and they all ended up carrying less passengers and thus had worse benefit to cost ratios compared to both the full DU and the Dart+ plans and thus they were all rejected.Modified full DU plan They also looked at a slight modification of the full DU plan, which takes into account Metrolink. It saves about 200 million of the full DU plan and looks like so. It follows much the same route as original DU, with the same stations, except: - Stephens Green DU Station moved closer to the Metrolink station at Stephens Green, an obvious change. - The Western DU portal moved closer to Hueston Station and instead an above ground station at Kylemore road. It would require more quad tracking closer into Hueston. All seem like sensible changes for a future DU IMO.Other tibits - They are looking to lengthen station platforms to take 10 carriage DARTs - That would be too much capacity off peak, so they are looking to operate 4 carriage DARTs at 2/3'rds frequency off peak. - They are thinking of building another turn back at Dun Laoghaire to handle more DARTs coming across the Loop line Bridge. - The three lines, Kildare/PPT, Maynooth and Northern will all be able to terminate at either Connolly, Spencer Dock or across the loop line bridge, however the division looks something like this per hour at peak time: -- Kildare/PPT line, 16 total, 4 into Hueston, 12 into the PPT and on into Spencer Dock. -- Maynooth, 16 total, 6 Connoly, 3 Spencer Dock, 7 Loop line bridge -- Northern Line, 19 total, 5 Connoly, 3 Spencer Dock, 11 loop line bridge The report is here (warning big PDF):https://www.irishrail.ie/Admin/getmedia/d34065cd-6540-4be1-9cb3-bcea61273fdd/Annex-3-3-DART-Expansion-Programme-Options-Assessment.pdf All very interesting. Of course some of the above details may have changed since this report (2018) and could change yet as it goes through planning process. But a veery interesting insight into what has been going on.
bk wrote: » Absolutely, worth stressing again, this report is 2 years old. Very interesting report that shows the overall thinking, but I'm certain some of the details have and will change. BTW Another point about the report, they also looked into the quad tracking the Northern line, but they rejected it quickly based on the high cost versus relatively modest gains in passenger numbers.
cgcsb wrote: » The recently announced high speed rail study will likely superceed quad tracking the northern line by moving intercity service to a whole new line. In this scenario the existing Drogheda-Connolly line becomes DART only.
bk wrote: » Not if it looks to make little difference in the numbers of people using the service. Afterall it isn't like people sitting in Malahide and who want to go to Stephens Green are going to say, nah, I won't use this service because it is 5 minutes slower versus some theoretical service that hasn't been built. They'll still take it because it is still much faster then the alternatives. And 2 billion extra is a ton of extra money to have in your pocket. With that extra money you could do the more expensive Green Line Metro upgrade and say a second South-West Metro branch line. I mean that would get you far more extra people into the city, then just taking a few minutes off a DART journey. Because they are looking at the bigger picture. The goal isn't to get more people on heavy rail, the goal is to get more people using public transport in all it's forms. To increase public transports share of all transport into the city. There is no point in spending billions extra, just to cannibalise people off bus/tram/metro, if it then leaves those other services half empty. Specially as I mentioned above, those billions extra can be put to better use increasing public transport elsewhere, where the demand actually exists.
bk wrote: » To be clear, you are talking about spending 2 Billion extra just to reduce a journey time by a few minutes!
AngryLips wrote: » If they're really serious about a high speed line Belfast-Dublin-Cork then there's really no need to bring it into the city centre. Just bypass the whole city and build a station out at Dublin Airport, this would be a similar approach to what's done in Paris and other parts of France.
cgcsb wrote: » To be honest I don't like the service patterns. I'd prefer to have 3 lines interconnected with well defined terminii. Eg: - Docklands to Maynooth/M3 - Hazelhatch to GCD - Drogheda to Greystones - Howth to Howth junct I think this is much easier for commuters to get their head around and easy to represent on a colour codded map. The high frequencies of 16 to 19 trains per hour on each line make any destination convenient even with 2 changes, it's a turn up and go service.
eguiney wrote: » Except that each required change is still likely to add at least 5 mins to the journey. Given that they appear to be planning to do almost nothing at Connolly, the best operational solution would be to move closer to the Maynooth-Bray service planned under DU.
Sam Russell wrote: » I would have thought: - Bray to Maynooth - Greystones or Dun Laoghaire to Drogheda - Howth to Howth Junction - Hazelhatch to GCD or Docklands Frequency would be driven by demand. Four coach trains off peak.
Equium wrote: » A small point in the grand scheme of things, but I would hope and imagine that a higher standard of station design will be forthcoming. The Option B location in particular offers IE/IR a fantastic opportunity to make use of air rights above the tracks for commercial/residential development right in the heart of the Docklands.
