DART+ (DART Expansion)

DART+ fleet will have fully automated on the move transitions from OHLE to battery and back again

On the move is straightforward, done probably thousands of times a day across Europe

What you need is a level piece of track where the train can coast through during the transition where it won’t get stopped

I wasn’t suggesting this; I was probably arguing against it. And really, the only place where they possibly could have 25 kV alongside 500 V would be on the 4-track approach to Heuston, where DART and IC trains are segregated anyway, but as I said this creates an operational problem where none needs to exist.

Connolly has too many shared stretches for mixing.

I suspect we'll have a “pale” of 1500 V in Dublin, with the rest of the island at 25 kV. An odd arrangement, but nothing unsual internationally, and it has saved hundreds of millions on DART+.

It is exactly the reason. The report with that conclusion is attached to an earlier post here by @A1ACo. Here's the link again:

https://www.dartplus.ie/getattachment/1b0a4eed-b96f-4752-bdff-a747d08a772b/Annex-5-1-DART-Expansion-Rail-Electrification-Assessment.pdf

The authors repeated an analysis first done in 2011 but using new population and usage projections and updated plans for the network future. They investigated and costed three general scenarios for expanding the DART system: A. extend the 1500 V network; B. keep the existing 1500 V and build the new part at 25 kV, use dual-system rolling stock (there were two versions of this approach considered); C. switch to 25 kV, replacing the existing 1500 V DC with 25 kV AC, and use AC-only rolling stock.

Of those three general approaches, the 1500 V DC option won out on cost and risk grounds. This was the same result as 2011.

Of the other options, a mixed-voltage systems were rejected because it increased the cost of implementation, increased operational risks, made the rolling-stock more expensive and prevented existing rolling-stock from ever using the extended sections of the DART network. The all-AC option was considered a good technical approach, but it would have been highly disruptive and it nearly doubled the cost of the DART+ project due to the need to re-electrify and existing electric railway, replace DC substations with (fewer, but higher-power) AC ones, and replace all of the non-life-expired 1500 V DC rolling stock (now made obsolete) with new AC stock.

The orders for DART+ rolling-stock were based on the findings of this report, and it also informed the request-for-tenders for new Enterprise stock: 1500 V DC operation would not have been needed if DART was switching to 25 kV AC.

The choice of AC versus DC also affected the design of the network itself: DC needs more substations to be built than AC, and each substation needs to be designed and be included in the Railway Order application.

Does anyone have a higher quantity version of this paths per hour diagram. And is it still feasible if PP are granted and built in full.

In light of the disaster of the recent timetable changes, is this just pie in the sky aspirational stuff here?

Wouldn't there be sufficient demand for 2-3 trains per hour to travel from Malahide to Maynooth via Spencer dock.

Trains drive into Spencer Dock, and then the driver switches to the rear cab and it becomes the front end for the trip to Maynooth.

As someone who lives on the Maynooth line, even 2 direct northerly trains per hour would be amazing.

Rail experts, is this technically feasible under the Dart Plus plan?

Ah thats really interesting. I like that they plan on sending some Maynooth services to Bray, though I am surprised if they are doing that, they aren't sending at least one HH past GCD.

I hope 4 tph to Greystones includes one going to Wicklow town., I think 4 tph of just Greystones services would mean 7 minute paths through Bray head? Which even with all the upgrades we might see around Bray head, I feel like 7 minute paths is insane unless they plan on some adding more upgrades then what was mentioned in the last study.

I think its interesting that they plan on having ALL Drogheda DARTs running to Bray, but it makes sense if they can use regen braking to charge the batteries as much as possible before having them go to Drogheda. Also I do find the Drogheda-Laytown service funny, I understand why its there and hopefully it will show there is capacity for 6 tph of just DART services.

Ah sorry, should have said why they are doing it. It is meant to be a trial service to prove Drogheda has capacity for 6 DARTs per hour. If all goes well it could mean 6 DARTs to/from Drogheda rather than 5, though if I had to guess it would probably replace one of the Malahide or Clongriffin services. I don't know if it will be possible to run that frequency before OHLE are installed, it depends on the charging capacity at Drogheda, either way it is good for them to test 6tph before throwing at it and hoping it works.

I assumed 3/4 means the 4th train would be run back-to-back with a Greystones service. My point was more that I hope they aren't hoping to attempt 4 paths per hour per direction, and use 3 as the backup plan. The diagram was made 2 years after the upgrade report which I believe still only allowed for 3 paths per hour per direction reliably. However I just assume the 4th train, ran back-to-back with a Greystones service, would be the hourly Wicklow town service. It doesn't show the Wicklow service on the diagram, but I think it's the only time to feasibly schedule it without otherwise extending one of the 3 Greystones services.

However I did notice that diargram shows Rosslare services ending at Greystones, which I believe with the upgrade could technically make 4 paths per hour per direction possible. However I think ending Rosslare services in Greystones isn't a good solution, and even then I still don't think 4 paths per direction is practically possible. There just isn't enough room for error.

Practically? no it doesn't make enough of a difference and 6 paths per hour and 3 per direction is the way to go. However in terms of number, the gap between the two back-to-back trains is still a few minutes(shortest I found was 4 minutes), and above 6 paths per hour a few minutes is a massive difference. With the improvements from the report the single track section is supposed to take 5 minutes, which technically makes a 7 minute path possible if each path is a single train. But if a second train tries to use the same path then it would need at minimum a 10 minute path. Removing the back-to-back service technically makes it possible to get 7 minute paths and 4tph per direction possible.

All that said, 7 minute paths for a 5 minute travel time is not practical. It's such a small difference that 4tph per direction is possible in the same way the August 26th timetables were possible. Its technically possible with the changes, but practically it only takes a small delay before everything falls apart. Thankfully after that disaster I doubt they will try something that insane again.

Greystones/Wicklow wasn't in the plan at all, it was tacked on by politicians later

In the UK they mainly have catenary-diesel and catenary-3rd rail changeovers to worry about, and the catenary is always 25kv AC at 50hz (excluding the Tyne and Wear Metro around Newcastle Upon Tyne). These types of changeovers can easily be done in stations: have the train raise or lower its pantograph while stopped at the station. A change between different voltages on catenary wire is always going to involve a short "dead" section between the two, although I think there are some border stations on the European mainland where the voltage delivered to catenary can be switched, so that "local" trains from either side of the border can go into the station.

If hypothetically the entire line from Dublin to Belfast were to be electrified with a mixture of voltages/currents, IMO the most likely outcome would be dead section on some flat stretch of line just North of Drogheda with 1500VDC below that and 25kv AC at 50hz North of that.

It is very practical to do it this way, in North America for example the Amtrak services on the North East Corridor between Washington DC and Boston change voltage and frequency many times during the journey (all between different voltage/frequency of AC on catenary) while local services like New York's Metro North Railroad New Haven Line changes from 3rd rail DC to overhead wire AC at Pelham - and trains run through that changeover at speed.

Any such DART services would have to be operated by dual-voltage EMUs, or by battery EMUs, as the core DART stock would be unable to run on the 25 kV railway. This isn't really a downside, as at for a Drogheda-Dublin all stops service, the regular DART trains would not be suitable, and it could be served using inter city EMUs.

DART+ Coastal South

Connolly to Greystones

Emerging preferred option being developed

Public consultation commences early 2025

Also contains confirmation that the public consultation for Dart+ Costal South (or what remains of it) being pushed back yet again.

I was just thinking about the amount of development that is planned for the Dart + South West corridor over the coming year. Between Adamstown, Clonburris, the City's Edge stuff, the Railworks at Inchicore and the LDA stuff at Heuston (which I'm a bit dubious about), there'll probably be about 100k more people living along the corridor within the next 20 years.

Interesting to think about, and good to see us making use of our transport infrastructure to facilitate development in the right places.