Metrolink south of Charlemont

The image posted above by not1but4 clearly states "Tunnel sealing wall and access to TBM gallery" and "End of the tunnel and sealing of the TBM". The plan is clearly to leave it there.

InInterestingly, right beside the sealing wall there is access to a "Ventilation/Evacuation tunnel". I assume that this is to facilitate a future extension in case the next station is too far away for standard escape distance? Not sure why else you'd have it for an operationally unused section of tunnel.

Are sure about trains being stored in the tunnel overnight and cleaning happening in the tunnel? I thought all this would be at the depot. Running back empty isn't a big deal as it isn't far, there are no drivers and the control centre will likely be manned anyway. Having cleaning staff operate there would probably be more hassle than it is worth.

If/when Metrolink gets it's RO approved, a new RO application to extend the line wouldn't throw it into legal uncertainty. The original RO would still stand and works can be completed in accordance with it, even if another RO is rejected.

What would see as an acceptable Luas diversion? The N11 is the obvious route but how do you get to it on the northern end? Any route is going to be vigorously objected to and almost certainly not going to happen. And the people served by the Luas stations between the two diversion points (potentially every station between SSG and Sandyford?) aren't going to be happy about losing the service. It doesn't appease them as they lose their service for the entire time taken for the Green Line upgrade to Metrolink, regardless of the diversion. The tie-in works don't actually become any easier either, Luas services can't run during the works either way.

Ultimately the Luas diversion doesn't actually solve anything, it just brings a whole new pile of issues and objectors into play. Like I said before, immediately north of Dunville Ave is the only possible place I see for an offline tunnel portal. You can get over 200m alongside the existing Luas line to create the portal without impacting Luas services. It is also only 400m from the currently planned TBM end point, so not much further to go with it. The actual tie in would require a closure but that would likely only be a few months. That length of closure is probably required regardless, to adjust stations, change power supply (which I believe is required if Metrofying the Green Line), etc.

Any extension would have to be tunnelled from the suburbs in. There isn’t anywhere to insert a TBM remove the spoil and insert all the materials needed anywhere along the end of the tunnel at charlemont. Also there would be no appetite for the extra trucks in the area.
the TBM will be effectively stripped and buried and will never see the light of day once it goes into the ground.

Also in addition to what bk said above, you're missing a big reason for the upgrade. The Green Line from Charlemont to Sandyford uses an old heavy rail alignment meaning it has fewer level crossings, pedestrian crossings, and is often separately graded. All that meaning it is capable of a much higher frequency than what a tram system, even one as high frequency as ours, has the capacity for. It would be a waste to have an alignment capable of such high capacity, and to limit it to just a tram/metro-lite as it exists as now.

If anything I think they should look for ways to continue the metro alignment to Carrickmines and onto Brides Glen, as it could also have the capacity, however it can't be done with the existing alignment between Sandyford and Carrickmines. Than also if they extend the line to Bray, it could be done as a metro rather than a tram.

Assuming the current RO is approved (and survives any subsequent legal challenges), that is what will be built. The purpose of this thread is to discuss what could happen after that (the presumption being that Metrolink is built as per the current RO). I have no idea why you are talking about the "potential for a new plan causing legal problems", problems for something which has successfully passed through the system and has been built? The starting point south of Charlemont will be the end of the tunnel as per the RO, the next section might face legal challenges of it's own but that is an entirely separate issue.

Where does it state "a Ranelagh in line tie in was chosen"? The official line is that Metrolink doesn't necessarily extend along the Green Line and that future Green Line capacity issues will be dealt with by turning trams back at Charlemont. There is no tie-in currently. I'm sure that once Metrolink is well under construction, it will be realised that turning trams back is a crap solution for the Green Line and that sometimes else needs to be done (hence the existence of this thread).

A Luas diversion doesn't remove political fallout or disruption. If all stations between Beechwood and Stillorgan are closed for over a year, you can be sure there will be major objections. Do you think the owners/tenants/staff/customers of Dundrum TC are just going to accept that? Nobody from north of Charlemont or south of Sandyford uses any of the Green stops between Beechwood and Stillorgan? It's the reason Metrolink has been curtailed

The diversion idea only solves a small part of the problem but by doing so creates a huge alternative problem. Trying to run Luas from the city centre to UCD will be peak NIMBYism, unlike anything we have seen yet. It could spend 10 years in consultation/planning/courts and still be rejected. That is not a solution for anything. Would be better off putting that effort and resources into the Metrolink extension. If the Luas diversion idea gets floated, it effectively kills the Metrolink extension because anyone who feels put out by the extension will say "you have to divert the Luas first", knowing full well that buys them at least a decade of peace.

This goes back to discussion about where the tie-in should be. For exactly the reason you mention the most recent report/consultation reccomending the tie-in between Beechwood and Cowper will hopefully be tossed aside for another option. I think they will need to pick some solution that would have minimal on-line works before the final connection. Some of the options mentioned implied a closure of only a few months, which while still not ideal, is much better than a few years.

I think a large reason for the 3-4 year number was because the Beechwood tie-in needs a large amount of work that disrupts the green line. Including the construction of a new underground metro station that for the entire construction needs the closure of the green line. An option that doesn't have a new station along the green line alignment, and one with minimal work on the existing tracks would massively reduce closure time. In paticular if its still possible with the current RO, I am a fan of the at-grade Ranelagh option.

Additional lines and the metro upgraded are both needed, they are two solution for two different problems. Dublin needs more luas and metro lines, I will always agree with that. Would new lines likely help the green line? yes, but it isn't a proper solution to the capacity issues the green line has. And in that same way, increasing capacity on the green line wont help other parts of the city with no access to a DART or luas.

I honestly don't see 30tph on the Green Line as realistic. Dunville Ave isn't going to be closed and I can't see Charlemont being able to handle so many trams. I suspect that this is a bit like the recent IÉ timetable change; "we tried to do more with the existing infrastructure but it just doesn't work, now let us develop the necessary infrastructure".