Metrolink south of Charlemont

The latter option is how I suspect it might go. I think a route down St. Raphaela’s Road is certainly useful but I do see the line likely using either of Brewery Road or the Leopardstown Road, before joining the existing viaduct via a ramp.

Now this could be compete overkill (and I could be underestimating this) but I don’t see a new ramp to join the viaduct being all that expensive, probably equal to the length and cost of the overbridge being built at Broombridge to cross the Western Mainline as part of Luas Finglas, which is a relatively small enough portion of Luas Finglas’ €600m budget.

(Worth noting that adding a rail spur to/from a viaduct isn’t anything new either and was done recently in Manchester as part of the Red Line’s extension from Pomona to the Trafford Centre).

A delta junction could also be made to allow trams coming up the existing ramp from the depot to be able to turn northbound or southbound but this would be cost dependant I suppose.

The metro would then run past the site of the existing Sandyford stop to whichever of the roads the N11 Luas line uses - either by cut and cover beneath the road or on a viaduct over it and the old rail trail walking path if it has to traverse Brewery Road to get to the Leopardstown Road. A grade-separated stop could be retained here for S8 bus connections if stop spacing allows.

Again, I don’t see this being too complicated as if St. Raphaela’s Road has to be grade separated anyway, simply continue whatever grade separation - either a viaduct or a cut and cover tunnel - out over/under the Luas depot, road and park to an interchange stop with the N11 line.

This also allows the depot to operate relatively unimpaired, with trams running down the existing ramp from Central Park to either a turnback reverse at the site of the current Sandyford surface level Luas stop to access the depot, or a very sharp curve, which would cut into the siding length of the depot. Though this could be offset by expansion at Broombridge or a new depot on the line to Bray but at least Sandyford is still viable this way.

Yes this will of course be expensive and there is always a chance that they simply end the metro at the existing Sandyford stop and require a walking connection (minimum 5 minutes to Brewery Road and at least 10 to Leopardstown Road) but that would be overall quite a poor solution and I think this kind of an interchange would be far more beneficial.

Is there a reason why a pumped sewer or diverted sewer solution wasnt considered to allow for the planned tie in? Also odd that they never seemed to consider starting the dive into tunnel north of the canal which could be achieved with some cpo and re arranging access at Peter's place.

They’ll find room for the N11 one at Sandyford regardless. What’s more interesting to me is what they do in the city. Charlemont tie in is mooted but where does another line fit along the canal or at Adelaide Road turning onto Leeson Street bridge? I don’t really get why they don’t just go the full way down Leeson Street to St Stephen’s Green East (short walk to MetroLink) and maybe along SSG South for a short run to the Green Line again and potentially Lucan Luas. Indeed the most recent Luas 2050 vision had both the Lucan and N11 Luas getting to around Charlemont which seems ambitious.

Bray would be better, but there's no point in just going to Bray Daly, because most of Bray is nowhere near the existing station and half the catchment area is in the Irish Sea, so we'd need to see ML penetrate the housing estates to bring any extra amenity in going to Bray. If we just barely got into Bray and interchanged at Daly, we may as well just interchange at Woodbrook. It would be cheaper and much easier and deliver the same amount of interchange.

I don't see an obvious path for ML to penetrate the housing estates without tunneling and I'm thinking that's less likely than "simply" going to Woodbrook and offering interchange there.

And someday we might even stick Donnybrook-Broadstone underground and get a really high quality, highly segregated Finglas-Bray pre-metro for "small money". It's 4.85km as the crow flies from the end of the dual carriageway at Donnybrook garage to Broadstone garage. I suppose with some temporary relocation of some of the bus fleet rhose locations would make decent places to launch a TBM from. A straight line passes right under St. Stephen's Green, offering interchange with ML there.

Yeah ok I can see that argument but if Rosslare trains do terminate at Daly, that's only because DART will be operating at turn up and go metro like frequencies and a passenger could change twice. I often change twice going to work in Berlin.

Alternatively, Woodbrook could be given a pair of turnback platforms and a third track could be laid from Daly to Woodbrook for Rosslare trains to use. I am sure it would be much easier and cheaper to add a third track along the existing heavy rail alignment than trying to thread two ML tracks through to Daly and somehow finding apace for a ML station there.

The Donnybrook - Broadstone tunnel that @murphaph mentions is a a very good idea, especially with the two bus garages as tunnel starting points. Diving a more versatile tram line would be far easier to do in a confined space too so the entire portal could theoretically be confined to TII-owned property. It’d a great potential goal for a premetro/straßenbahn type line for TII to explore further.

An added side bonus would be freeing up the existing city centre section of the Green Line for use as the spine of maybe a Balgriffin - Harolds X/Terenure route too which again could all interchange around Stephen’s Green.

This would all compliment ML Charlemont - Sandyford very very well.

In terms of a Bray extension though I do see that being Luas only, I can’t see metro getting into Bray without need for serious amounts of tunnelling which is very expensive and possibly not worth it. The Rosslare argument is also moot as @bk mentions. Even a metro link to Woodbrook is tenuous at best, and would again likely need some sort of tunnelled section.

I think metro doesn’t need to go further than Sandyford/Leopardstown Racecourse if the Luas line to Bray is built to a sufficiently high standard - a seamless interchange with the metro, good grade separation and liberal stop spacing (between Cherrywood and Bray anyway - maybe no more than 3/4 stops) then it will still provide major time savings when switching to Metro.

In a parallel universe somewhere the Broadstone and Harcourt termini stations never closed and we are now building a Harcourt-Broadstone DART interconnector to compliment the Heuston-Connolly one we already built.

Harcourt Street line was always pet peeve of my late father, stopped him voting FF at the time :-) he used to bring me as child to the top of the Milltown Viaduct to look at the walls both sides that where put up after it closed to stop people climbing on the bridge and say "they should have never closed this".

Anyway we would have been in different position now if they had of even preserved the line to Bray but it goes back to successive Governments having no interest in rail and kicking the can down the road.

The green line from Cowper to Sandyford was built to metro spec, the use of ballasted track and the loading gauge is slightly greater

Clearance might be a issue at the original arch over bridge south of Dundrum but otherwise its just a platform and signalling reconfiguration job. Power supply would need attention but thats not intrusive

The challenge at Sandyford is you would have to climb up to over several roads (the line is already in a fairly steep climb from Dundrum so need to ensure this is within limits), but you then hit serious problems as the extension to Cherrywood was made on the basis that it will never metro.

It gets worse at Cherrywood as its a very tight S curve to get to the Brides Glen viaduct to get to Bray as the planners favoured development over the alignment.

Metro will get you to Brides Glen via the original alignment but bridging over a number of roads, that kills going to Bray in the future. Metro is driverless so needs an enclosed system so street running is out.

Alternative is metro on original alignment to Carrickmines only, in both cases you need to you need to find a solution to retain Carrickmines to Sandyford and continue that to the city via a new on street alignment i.e. find a way to the N11 to UCD which Brewery Road would be ideal for but its not facing the right way vs the line coming in from Central Park

You could probably use the existing Luas ramp by CPOing the 4 houses beside number 25 Woodford and just going along the southern edge of the existing depot building. ML could drop down under Brewery Road if it's ever extended.

I’d have thought keeping a depot at both ends would make good sense for logistics. Early and late trains not having to position before and after hours.

I think the fact the system is driverless kind of eliminates the need to consider this as the trains can be started remotely from stabling sidings anywhere really. In Berlin trains are parked off peak in sidings underground as well as at the surface depots. I wonder will there be any provision for underground stabling with ML or is this something reserved for cut and cover type systems? I would expect that stabling for several trains will definitely be provided at the Sandyford end in any case, even if the maintenance depot is no longer required there. I imagine the stub of Harcourt line south of Brewery Road might be used from the get-go, including dropping the line down under Brewery Road to allow N11 Luas to cross ML there. The N11 Luas would definitely need an alternative depot in the area though if the existing depot is handed over to ML. There appears to be land available in Carickmines.

no sidings planned. Think the tunnel extends past charlemont stop 300 mts so room to stable a few overnight, I think if it’s extended to sandyford then that is gone and I’d assume they would want store some overnight at the far end (admittedly this is very much an assumption but to me it makes sense rather than running empty in the morning and evening which at the very least reduces the maintenance window).