DART+ (DART Expansion)

there's already been a veeery extensive discussion of the conflicts between Docklands Nua and the dart tunnel, really no need to restart it. Dart Underground is effectively cancelled, it's no more than a notional possible future project for after we're all long dead.

Don't worry. They'll just get the contractor back to dig it up and add a new stop.

A DART tunnel may be a "notional future project", but I do expect the ABP inspectors to push IÉ on why the submitted station design effectively prevents any future cross-river rail tunnel without either a massive disruption or orphaning of the new Spencer Dock station.

DU as originally proposed may be dead, but it's not realistic to assume that there will never, ever be any DART extension within Dublin City Centre. Extension within the city core will need a tunnel, and this is one of the very few places in the city centre where such a tunnel could emerge.

Haha after our success in North Strand, we can make it happen!! They started digging up that section of new cycleway/parking last week in North Strand, just FYI.

At this point I would prefer a Lucan to Ringsend metro instead of DART U.

Also need a Tallaght to Coolock metro to have a complete network.

Everyone agrees that the original proposal from the 2000s is not implementable - but that's not surprising at all since the genesis of that plan stretches back to when the entire area was undeveloped so plans could liberally use a huge surface area.

Everything else, including claims that it "prevents any future cross-river rail tunnel", is just a bunch of non-engineers arguing about what might or might not be technically possible while making bold claims about inclines and clearances, etc.

For the next round of plans after T42/DART+, there will be a share for DART/heavy-rail and I can't see any more pressing issue for DART than relieving central bottleneck and there's no way to do so, and to offer more city centre through running services than build a DART tunnel largely following the alignment of the the old plan.

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Does anyone understand why building the bridge at Forbes Street would be twice as expensive? The DU tunnel would be fully underground at that stage, so I don't understand the issue.

Frustrating as it is, I'd agree with ABP that the Forbes Street location is a better location in the long run.

I know that too well, as I commute past it every day!

What was planed for the two branches, was a five minute frequency on each branch, and 2/3 minute frequency on the "common" section, which was basically the city centre.

It doesn't quite work like that. You can't just divide straight line capacity between two branches. Spurs are a capacity killer because they require merging and crossing oncoming trains which necessitates greater time spacing for safety reasons. Building spurs off Metrolink will just undermine what they are trying to achieve. A DART tunnel will have to happen some day, it is the best way to reduce the conflict of the merger north of Connolly.

It's true that in traditional block signalling systems, merges are very expensive, but in an automated railway using modern signalling, the time penalty for merging is very low.

This is also true without a branch/merge.

I think merges can work well if they are done not to fan out a line but to allow crossovers, and increase the number of possible end to end routes. An example of this is the Munich U-Bahn that, with only a few additional links, allows the creation of multiple services on what is basically a three-line central network.