12 Trains Per Hour ?

EvilDoctorK

Does anyone know where Irish Rail's often quoted 12 trains per hour limit on the Loop Line between Connolly and Pearse Stations in Dublin comes from ?

12 Trains per Hour = One train every 5 minutes

Why is this spacing necessary ?
Is this similar practice in other European Countries ?

I an sure that on other Urban Heavy Rail systems with simple double track layouts between and through stations in other European countries that 4 or even 3 minute intervals are possible. (I'm thinkin S-Bahn lines in German cities ... Dutch city services too)

Is it perhaps because if there more than 1 train every 5 minutes we wouldnt all be able to go in slow single file past the ticket "checker" at the barrier :eek: ?

If we could operate trains on the line with 4 minute intervals i.s.o 5 minutes this would give an instant 25% peak capacity increase. Why can't we do this ?

Tarabuses

Probably due to the inadequacies of the signalling system. The "sections" on the loop line seem to be very long.

John R

Intervals are not governed by time but sections of track, a train cannot enter a section no matter how long it is until the previous one has left. Currently a train in Tara St. cannot depart until the preceeding one has left Pearse. 12 trains per hour is not a rule, it is the result of operating conditions. If there were only electric trains this could be increased as the diesel trains have lower acceleration.

BrianD

I thought there was also a signaling issue here? The upgrade has been delayed apparently.

EvilDoctorK

JohnR

Yes fair enough - but still surely there does not need to be a 5 minute gap because the train can't depart Tara St. before the train ahead departs Pearse .. transit time from Tara to Pearse must be not much over 1 minute ..probably less ... loading time at the station should be no more than 2 minutes (surely all the trains that don't have automatic door closing are now gone!)

Acceleration on the Arrow Diesels is pretty good isn't it ? .. the issue would only be with the (not very many) locomotive hauled trains.

As far as I know there are 3 track blocks on the Loop line .. Pearse-Tara , Tara-~Talbot St bridge , Talbot St. Bridge-Connolly ? So this should mean that a train can be departing connolly southbound while the train ahead is still on the platform at Tara waiting for the train ahead of it to clear the platform at pearse

However the current timetabling with a 5 minute gap seems to almost assume that the trains can only leave connolly southbound when the train ahead is in pearse (which is what a 5 minute gap would imply)

L5

Well once the northern dart upgrade is finished, in about 10 months time, it will be increased to 16 movements per hour.

Borzoi

L5 wrote:

Well once the northern dart upgrade is finished, in about 10 months time, it will be increased to 16 movements per hour.

Really, that little of an improvement, for the apparent amount of work and disruption. It just seems very small

L5

Well all of the darts will then be 8 carriages long, with lengthened platforms, improved signalling etc, so it will be a bit improvement in capacity

drane2

Don't forget that the Loop Line includes Northern Commuter routes, Western Commuter Routes, services from Sligo, Belfast etc.. So add it all together and there probably is one train movement every five minutes.

The Real B-man

enjoy no trains the weekend for the next year northsiders it was a pain coming from greystones on the bus to go shopping the last year yay its back

EvilDoctorK

Drane2 - That's really 1/2 the problem I think

Because all these services are running down the same constrained line this is why you get problems... to offer a reasonable peak hour frequency on any one route is hard if you have limits like this (seemingly somewhat artificial) 12 trains per hour

The 12 trains per hour limit is accross all trains - DART, Arrow, Rosslare Express, Freight trains they insist on moving at busy period etc.

KC61

L5,

I hate to disappoint you, but the current DART upgrade involves platform lengthening, catenary overhaul, increased power supply and some minor tweaking at Platform 7 in Connolly.

The resignalling of the Loop Line to allow 16 trains per hour between Connolly and Grand Canal Dock and also the redesign of Grand Canal Dock to bring all three platforms into operational use is DART Upgrade Phase 2, for which funding is not yet fully secured! It would be another year-long project at the very least.

Victor

EvilDoctorK wrote:

Is it perhaps because if there more than 1 train every 5 minutes we wouldnt all be able to go in slow single file past the ticket "checker" at the barrier

I'm tempted to ban you, just for being stupid and trolling.

On top of the signalling upgrade proposed by Irish Rail, but not sanctioned by hte governement, there is of course the slight matter of 5 level crossing to negotiate in Sandymount that puts restrictions on train frequencies.

EvilDoctorK

No trolling at all ... asking a serious question.. just being flippant about the ticket "checking" .. (though that is something that needs a few questions asked about it elsewhere I'd say)

I'm still left wondering as to where this 12 trains per hour limit on the loop line comes from ... good point about the level crossings .. I hadn't thought of that ... it's certainly relevant to the southside frequency limitations

However I still don't understand why they have to have 5 minutes between trains running between Pearse and Connolly. The level crossings for sure will cause issues with max frequency south of Pearse/Grand Canal Dock.

I just think it's a question worth asking ... do other European Railway systems have similar intervals between trains on similar track configurations ? What can be done to get around this limitation ?

maxheadroom

EvilDoctorK wrote:

I'm still left wondering as to where this 12 trains per hour limit on the loop line comes from ... good point about the level crossings .. I hadn't thought of that ... it's certainly relevant to the southside frequency limitations

Its to do with the acceleration / decellaration speeds of the various types of trains used (Darts have better numbers than the intercity trains for instance) and the need to keep the trains a safe distance apart. Also to do with loading times at Connoly, Tara St, and Pearse.

antoinolachtnai

Victor wrote:

On top of the signalling upgrade proposed by Irish Rail, but not sanctioned by hte governement, there is of course the slight matter of 5 level crossing to negotiate in Sandymount that puts restrictions on train frequencies.

You could shorten the gate-down time on these crossings without any great loss of safety if the appropriate technology were in place. A number of the level crossings are beside stations where a large proportion of the trains come to a complete standstill anyway.

I accept that there would be a big problem at Merrion, where the volume of traffic is just too great.

KC61

The reason that only 12 trains per hour can cross the loop line boils down to the signal spacing. The current signalling can allow for perhaps 14 trains at an absolute push, but the acceptable regular spacing is 12. The gap between the signals should be much tighter than it is at present.

A train currently cannot leave Connolly until the train ahead of it has cleared the Tara Street signal section. Given a two minute transit time between Connolly and Tara Street, two minute peak hour dwell time at Tara Street, and say 30 seconds acceleration time for the first train to clear the section, that is where the 12 trains per hour comes from!

A total revamp is needed of the city centre signalling and this is what IE have planned, together with a redesign of Grand Canal Dock that will see northbound services using the currently unused platform and the current northbound platform being used for turnaround services ex-Drogheda and Maynooth. This latter move will greatly improve reliability as terminating services will no longer have to cross the northbound line after their arrival at Pearse before heading north again as at present.

EvilDoctorK

Thanks for the reply trainuser .. what you say certainly makes sense but I had thought that there was more than one signal block between Tara and Connolly heading southbound.

Reading the other interconnector thread I guess if IE get the go ahead to build the interconnector capacity on the Loop line won't be an issue ... they probably won't need to upgrade the signalling as according to their schema they only plan a peak time frequency of 8 trains per hour on this section "DART Line 1". If the signalling upgrade would cause considerable disruption (and presumably cost a fair bit) and wasn't to be completed until 2007? then it would hardly be worthwhile doing it if the interconnector were to come on stream soon after that ?

Victor

EvilDoctorK wrote:

If the signalling upgrade would cause considerable disruption (and presumably cost a fair bit) and wasn't to be completed until 2007? then it would hardly be worthwhile doing it if the interconnector were to come on stream soon after that ?

I don't think it would cause a huge amount of disruption as it could be installed with the existing system in place. I think it was budgeted in the low tens of millions (I suspect this was for more than just Grand Canal Dock - Clontarf Road).