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[Thread] There's some interesting changes along the northern section of #Metrolink between Stephen's Green and Swords. Let's briefly look at them and the large decisions that have been made. 
Big change is that the tunnel will now be single-bore and not twin-bore like before. This means one tunnel with the two trains side by side. This can be cheaper and provides more flexibility. It also means the tunnel boring site can be moved from Na Fianna lands to land near M50
Other big decision is that the metros will be fully automated with platform screen doors, similar to the Copenhagen metro. #Metrolink is modelled on the Copenhagen Metro 3 line in many places.
At the Estuary stop will be a Park and Ride with 3,000 spaces. The metro will also build a new bridge over the Broadmeadow river instead of using the Lissenhall Bridge, which is a national monument. That leaves the existing Lissenhall bridge for pedestrians and cyclists.
The depot has been moved from Estuary to between the airport and M50. The report says this is more flexible. It also makes better use of space. This land south of the airport is within the Inner Airport Safety Zone, so it's unsuitable for housing development, unlike Estuary lands
Moving the depot frees up land around the Estuary stop, which is designated as the Metro Economic Corridor by @Fingalcoco. This area will support huge housing development in the near future. More details here: dublinontrack.ie/news/metrolink…
The metro line will not run down the middle of the Swords bypass on an elevated track. This seems to be in response to residents concerns about overlooking. I suspect it's also cheaper/easier to build. The track will be in a cutting (a trench) or short tunnels under roads.
The tunnel boring site for the airport tunnel will be south of the airport, so it's closer to the M50. This will reduce construction traffic. There's a new ventilation tunnel and evacuation tunnel in this area. The tunnel is now single bore so this changes evacuation procedures.
You need an evacuation option roughly every 1km. The stations are roughly 1km apart so that works most of the time. At Albert College Park there is an evacuation shaft. Essentially stairs up to ground because the section from Griffith Park to Collins Avenue is greater than 1km.
At the airport you can't just put in a set of evacuation stairs or passengers would pop up on the runway. So they need ventilation and evacuation tunnels to bring people out of the airport ground first then up to ground level.
The metro will cross over the M50 on a bridge because metro is above ground north of M50. It looks like this bridge will be metro only. The @Fingalcoco development plan has Objective MT15 about using this bridge to improve pedestrian and cycle permeability as part of Metro North
There is a new tunnel boring site at Northwood/Ballymum Road. This replaces the previous tunnel boring site at Na Fianna. This site is close to the M50 and good roads, which will make construction easier.
The Ballymun station has been moved from under the road to under the old shopping centre. This will reduce traffic impacts on Ballymum Road.
The Griffith Park station will be located under the Home Farm Road football pitch instead of at Na Fianna. There will be no tunnel boring site here, just a station box. I suspect construction period has dropped from 6 years to 2 years and is limited to just one pitch.
At the Glasnevin station (Cross Guns Bridge) they are continuing with the Irish Rail/Metro station interchange though with less private property impacted. They also are now reconfiguring part of the Irish Rail lines in order to provide more flexibility. DART Expansion related?
The O'Connell Street station has been moved from under the road to under the old Charleton cinema, which is being redeveloped. This will reduce impact on Luas Cross City and bus services on O'Connell Street, which is good news.
The Tara Street MetroLink station, connected to the DART station is not moving. This means knocking College Gate apartments and the leisure centre. I've attached the full response from TII/NTA on this decision. The alternate report will be interesting when published.
The Stephens Green station is being moved slightly in order to maintain traffic flow on nearby street during construction. However, this will have an impact on the edge of the park. Though nothing like the original Metro North.
Those are the big changes on the northern section of #metrolink. If you have any questions ask and I'll try to answer them. In another twitter thread I looked at the potential impact of abandoning the Luas Green Line upgrade for those interested.
