[Irish Times - 29 Dec. 2009] Dart line to be split

Hungerford

Cookie_Monster wrote: »

I may well be wrong but I imagine its a lot more than 12 years that line & bridge has been there :P

Sorry - I forgot about the zero. It should of course be 120 years - the line opened in 1891.

strassenwolf

Olivia Kelly of the Irish Times wrote:

Presenting the proposed lines to a recent meeting of Dublin city councillors, Dart underground project manager Peter Muldoon said the severing of the current Dart line would not affect journey times.

“If you are going from one side of the city to the other, you will have to change trains; just like every other major city. We hope to have one train every five or six minutes, so the time from leaving your house to arriving at work will not be adversely affected,” he added.

This is not very encouraging. IE now "hope" to have a train every five or six minutes - i.e. ten-twelve trains per hour (presumably in each direction).

This is quite some way off the capacity of the tunnel.

According to previous statements by IE, the tunnel will have a capacity of 20 trains per hour in each direction, but it seems they are now only "hoping" to use the tunnel to around half of the capacity which they think it has.

And, of course, ten to twelve trains per hour is in or around a third of the capacity which the tunnel could have, going on the capacities of similar tunnels in other cities, including the main cross-city tunnel in Munich (which carries a steady 30 trains per hour in each direction).

It would be nice to see any plan from IE as to how they ever propose to use the tunnel to anything like its capacity. Otherwise the 20 trains per hour fantasy will remain an attempt to pull the wool over people's eyes as to what will actually happen with this tunnel.

At the projected cost of 3 billion euro for the tunnel project and related works, there needs to be precision about what is being proposed and what is going to happen in reality.

Barname

KC61 wrote: »

At the moment every train that operates to Maynooth uses a slot that could be used for a Northern line train from the loop line bridge. Every train from Maynooth blocks both Northern line directions.

At the moment every train that operates to the North uses a slot that could be used for a Maynooth train. Every train from the North blocks Maynooth trains

:P

paulm17781

Barname wrote: »

At the moment every train that operates to the North uses a slot that could be used for a Maynooth train. Every train from the North blocks Maynooth trains

:P

And that's what this plan will fix.

bush Baby

Don't forget about the 12% budget cut proposed in the budget?

http://www.insideireland.ie/index.cfm/section/news/ext/publictransport001/category/1111

That project will never happen - sadly

GerardKeating

strassenwolf wrote: »

This is not very encouraging. IE now "hope" to have a train every five or six minutes - i.e. ten-twelve trains per hour (presumably in each direction).

This is quite some way off the capacity of the tunnel.

If the tunnel is running at or near full capacity in the first few years of operation, then they have seriously under spec'ed it. The Loop-Line bridge is 120 years old, i would expect the Inter-Connector to last at least as long and be able to meet the demands of the 22nd century.

It should not be used at or near full capacity for many years if they get it right...

mysterious

Instead of writing about what they are planning.

Why they don't get on building what they planned to begin with.


I'm sick of this balony.

strassenwolf

GerardKeating wrote: »

If the tunnel is running at or near full capacity in the first few years of operation, then they have seriously under spec'ed it. The Loop-Line bridge is 120 years old, i would expect the Inter-Connector to last at least as long and be able to meet the demands of the 22nd century.

It should not be used at or near full capacity for many years if they get it right...

I think you might look at how some other cities of a similar size to Dublin approached it. Munich and, particularly, Frankfurt, would be cities which used their tunnels to capacity from pretty much day one.

In those cities, once the connecting tunnel was built, they were then able to rapidly expand overground services which could use the tunnel, without affecting throughput through the tunnel.

A quick look at the development of the rail transport systems of those cities would show you that it need not be a mistake to use the highest capacity, most expensive sections of the network to their peak capacity from day one.

There just needs to be a clear road map as to how this is to be done effectively.

strassenwolf

Let me give you an illustration of what I mean.

[Hypothetical situation]

Day one: interconnector opens, with 20 trains per direction per hour (tpdph). 5 of these trains travel between Malahide/Howth and Hazelhatch, 3 travel between Malahide/Howth and Heuston, and the remaining 12 travel just between Heuston and Docklands. (the latter would probably, initially at least, be 2-4 carriage trains, but they would enable people to know that they can go to the station and only have to wait a maximum of three minutes to get onto a train going right across the city, quickly).

8 of them provide something similar to what is currently provided between Malahide/Howth and the city. 5 of them provide hitherto unimaginable services between Hazelhatch and the city.

And all 20 trains enable very rapid travel between the east and the west of the city.

Year 2: the long-awaited line to/from Clondalkin opens: still 20 trains tpdph. 5 of these trains travel between Malahide/Howth and Hazelhatch, 3 travel between Malahide/Howth and Clondalkin, 3 travel between Docklands and Clondalkin and the remaining 9 travel just between Heuston and Docklands.

And all 20 trains enable very rapid travel between the east and the west of the city.

Year 4: the much-desired extension of the Clondalkin branch opens, enabling a 20 minute connection between Tallaght and the city: still 20 trains tpdph through the tunnel. 5 of these trains travel between Malahide/Howth and Hazelhatch, 3 travel between Malahide/Howth and Tallaght, 3 travel between Docklands and Tallaght and the remaining 9 travel just between Heuston and Docklands.

And all 20 trains enable very rapid travel between the east and the west of the city.

Year 6: the eagerly anticipated line to/from Lucan (or along the West Dublin route originally proposed for the crazy metrowest) opens: still 20 trains tpdph. 5 of these trains travel between Malahide/Howth and Hazelhatch, 3 travel between Malahide/Howth and Tallaght, 3 travel between Docklands and Tallaght, 4 travel between Docklands and Lucan (or areas which were to be "served" by the crazy metrowest proposal) and the remaining 5 travel just between Heuston and Docklands.

And all 20 trains enable very rapid travel between the east and the west of the city.

No diminution of service has occurred to any area in the above plan. All of those trains make a serious contribution to linking the east and the west of the city, and an increasing number are gradually able to provide rapid connections into the city, out of the city, and across the city.

[/hypothetical situation]

All of this should be possible except that, while IE have spoken about 20 tpdph, they really don't intend more than about 10 max. And they've got the station layout plans at Docklands to prove it.

Hungerford

strassenwolf wrote: »

Let me give you an illustration of what I mean.

Erm... I don't think you fully grasp the value of train paths. Your suggestion only works if IE can increase train lengths to an infinite amount to meet increasing demand. Unless you are suggesting that demand will remain constant over the period involved.

But trains have maximum potential lengths, meaning that at some point, to increase capacity, you need to use more paths.

The only way you can do this is to have surplus paths that you can use and I would sincerely hope that IE would have lots of spare paths through the interconnector to meet future traffic growth.

All the problems with capacity on the Loop Line at the moment stem from a lack of available paths at peak times.

strassenwolf

Hungerford, I'm erm...having some difficulty understanding your post.

Would you care to point out specifically where I am incorrect.

strassenwolf

Actually, Hungerford, there's no need to reply.

I get it now. Cities like Frankfurt and Munich screwed up, right, running 24 trains and 30 trains per hour (in each direction) through their tunnels, serving considerably over 100 destinations in each case.

IE though, with their proposed 10/20 trains per direction per hour, whichever figure one is supposed to believe, have got it right.

Right?

noelfirl

There's no capacity for 20 tph from Hazelhatch to Howth/Malahide/Drogheda (short of tri/quadding the Northern Line, or taking all non-DARTs off it). All well and good that there would be capacity for 20tph from Hazelhatch/Heuston to Docklands and vice versa, but there's probably not going to be anywhere near enough demand for that sort of service for a decade at least.
Personally IMO, starting out with 10-12tph (a vast improvement over current 4-6tph) will be sufficient, and usage of the capacity can be bumped up over time if demand needs it, and other infrastructure is improved to allow it.

dowlingm

As a daily user of a system which tries to push >24tpdph (< 2m30s headway) on a fully segregated line (Toronto subway), I can tell you it's trickier than it looks. Dwell times and passenger flows at interchange stations such as Heuston, SSG and Pearse are going to have to be seriously examined right up to safety maximum passenger loads. The problems that humans introduce seem to trump most improvements in signalling and so on.

The design of the Toronto Bloor-Yonge interchange station is now being found seriously deficient for modern loads and because of the structures above it cannot be changed. For instance, all of the passengers coming from the lower line emerge at one end of the platform and are not distributed evenly along the 6-car train when it arrives. This leads to delays because of crushloading - people lean against the doors and the safety mechanisms prevent the train from moving off. This is exacerbated by delays on one line or the other which causes a surge load as soon as this delay is cleared. There are also issues with stair and escalator capacity.

They are now trying to deal with this by putting 10+ personnel (started with 30) on the platform during morning rush to direct people and to stop more people trying to get on once the carriage is full.

The critical issue is to find out what the number of passengers is that will make the tunnel pay its way not just financially but operationally. However, there will come a point where you're becoming over-reliant on that line - that's when investment in smart cards pays off because DTA (should) look at boardings data and design "interconnector relief lines" and other point-to-point services which DON'T go through An Lar, and do so based on demand and not crayons on maps which make sense for marginal seats on councils and in the Dail.

SeanW

Ok, the weak link in the Malahide/Howth-Hazelhatch line will not be the Interconnector, but the Northern DART line, which will still be only twin-track despite hosting Enterprise, Northern Commuter and whatever DARTs come through the Interconnector. The Interconnector itself AFAIK, doesn't have an inherent upper limit of trains (it could always be resignalled with shorter blocks, if needed) that it can carry, but other trackage on the route would cause any bottleneck.

Oh and I doubt that (for example) Munich's 2.5 minute headways are by original design: the Stammstrecke (sp?) main underground tunnel that is the rough equivalent of our Interconnector was built in the 1970s to transport 250,000 passengers per day, it's now carrying 750,000, or so I read.

murphaph

SeanW wrote: »

Oh and I doubt that (for example) Munich's 2.5 minute headways are by original design.

That is correct Sean. The Stammstrecke was extensively resignalled about 4 years ago, causing large scale disruption (full weekend closures and many evening closures) to the S Bahn in and around Munich. I reckon if the Interconnector is signalled for 20 tphpd from the off it will suffice forever as Dublin will likely never have as many lines feeding into it as Munich has feeding into their's, simply owing to the fact that Dublin is a coastal city and Munich isn't.