Few Questions about IE Signilling System

RonanM123

A few weeks ago I noticed that between Cherryville Junction and Waterford (except Kilkenny Station) that before the signal that controls the points at stations there is always a signal thats two oragne lights, This compares to the Cork line from what I can tell there is only a signal with one orange light then the signal for the points. Why is it different and what is the point of two as I can't see why its revelent.

One final thing is why can't trains not stopping in a station on the line not maintain the normal speed like on the Cork line. I know better track etc but I don't see why a train has to drop from 80 soon to be 100 to 40 to go over a set of points on the line compared to being allowed operate at 1000mph out of Heuston. Take Ballyhale services can run through at 60-80 mph (varied as up is slower than down services) when not crossing with a train but can't through a station like Athy or Muine Bheag at 80. The double signal I refer to above is always orange even though the train isn't stopping again it would be green on the Cork line.

Is it just a case of IE not bothering to allow (wouldn't suprise me) it or is there some safety issue as I can't see any safety problems in doing so except for Thomastwon when IE could of positioned the line better when the platform works were done a few years ago but decied it would be alright.

Victor

RonanM123 wrote: »

compared to being allowed operate at 1000mph out of Heuston.

Sir, I must protest, the G-forces are killing me.

RonanM123 wrote: »

One final thing is why can't trains not stopping in a station on the line not maintain the normal speed like on the Cork line. I know better track etc but I don't see why a train has to drop from 80 soon to be 100 to 40 to go over a set of points on the line compared to being allowed operate at 1000mph out of Heuston. Take Ballyhale services can run through at 60-80 mph (varied as up is slower than down services) when not crossing with a train but can't through a station like Athy or Muine Bheag at 80. The double signal I refer to above is always orange even though the train isn't stopping again it would be green on the Cork line.

A few factors:
* The Dublin-Cork line is two tracked or more for the entire distance. Other than sometimes Heuston-Inchicore, Limerick Junction, possibly Mallow and Cork Station the train stays on the same track the whole way. With the single-track on the Cherryville-Waterford line, the train needs to negotiate the points at each passing loop, branch, siding, etc. While sometimes, it negotiates the points straight through, often they will be changing track at one end of loop/branch or other.
* The signalling controlling the points was originally installed for the relevant track speed, such that if the driver saw a red signal that he would have enough distance to stop before the points / level crossing, etc. However, you don't want a situation where the train is waiting needlessly. So sometimes the speed through a section (at stations in this case) can't be changed until the signalling is changed.
* The relevant points may be in relatively poor physical condition - this lead to a derailing at Limerick Junction at one point and no doubt in countless out situations. Reducing the speed reduces the further wear on the points until they can be replaced.

RonanM123

While sometimes, it negotiates the points straight through, often they will be changing track at one end of loop/branch or other.

Not that you will know but why would they of built the line like that. Would it not make sense to keep one track running through the stations and not changing sides at either end. It would probably allow faster speed through the stations and not as you say change tracks at either end.
Having checked a video on U Tube it looks that they change sides at either end of most stations on the line. Odd setup IMO.

* The relevant points may be in relatively poor physical condition - this lead to a derailing at Limerick Junction at one point and no doubt in countless out situations. Reducing the speed reduces the further wear on the points until they can be replaced.

Don't think thats the case but overall what sort of time frame would IE get out of doing that before they have to replace them.

Victor

RonanM123 wrote: »

Don't think thats the case but overall what sort of time frame would IE get out of doing that before they have to replace them.

As speed and mass increase, wear and tear increase disproportionately.

Twice the speed means four times the energy and quite possibly four times or more wear and tear. Importantly, there may be a point below which a certain vehicle weight creates no discernible wear. Conversely, going above that point may dramatically increase wear and tear. So half the speed through the points might mean the points lasting four times as long.

For bridges, a ten-fold increase in axle weight will increase damage in the order of one-hundred fold.

However, this is something I haven't studied in any detail, so I may not have it quite right.

kc56

RonanM123 wrote: »

A few weeks ago I noticed that between Cherryville Junction and Waterford (except Kilkenny Station) that before the signal that controls the points at stations there is always a signal thats two oragne lights, This compares to the Cork line from what I can tell there is only a signal with one orange light then the signal for the points. Why is it different and what is the point of two as I can't see why its revelent.

Not only on single lines. Take Kildare station:

On approach to Kildare station from either direction are double yellows. These are used as pre-warning of a route change with signal yellow and then red. Also, there are short blocks either side of Kildare which makes signalling more flexible.

Approaching Kildare from Dublin, the double yellow is used if the points are being set to bring the train to platform 2 - local train terminating. IE never clear a train through a turn-out until it has entered the points; this is a safety procedure in that the driver is always given a caution signal to enforce a speed reduction before the points. Technically it's called approach release.

Approaching from Cork direction the double yellow is used in the same way if a train is turning into the platform 2 loop.

I think the double yellow does the same for single line ops when the train will take the diverging route and a lower speed is needed. Don't know why they can't travel at speed if staying on the main line.

The 4 track section has double yellow options at every signal.

Hungerford

kc56 wrote: »

Don't know why they can't travel at speed if staying on the main line.

I presume that the crossover isn't capable of handling maximum speed?

Victor

Oh, there was a recent incident in the UK where a driver took a set of points at 60mph - where the points were designed for 15mph - and derailed.

Is there an argument that anywhere that there are diverging points that a lower than maximum speed should be used?

cbl593h

Victor wrote: »

Oh, there was a recent incident in the UK where a driver took a set of points at 60mph - where the points were designed for 15mph - and derailed.

Is there an argument that anywhere that there are diverging points that a lower than maximum speed should be used?

Driver error/ incompetence....... http://www.raib.gov.uk/cms_resources.cfm?file=/121121_R242012_Bletchley_Junction.pdf

Jamie2k9

not crossing with a train but can't through a station like Athy or Muine Bheag at 80.

Platform 2 only at Muine Bheag (07.10 service uses) has being cleared for 60mph from today was 40. Other stations have also being cleared for higher speeds to.