City Thameslink OHLE

[swt_passenger]

I expect the action described in my post above (#14) will take place as planned?

 

[Edvid]

I'd forgotten about the Network Change documentation. If these two PDFs are anything to by...

http://www.networkrail.co.uk/browse...ion of rolling stock north of blackfriars.pdf
http://www.networkrail.co.uk/browse...005 completion of overhead line extension.pdf

...northbound changeovers should be happening at City Thameslink now, though I'm sure the last time I travelled north from Farringdon (19 May) the DC->AC changeover happened there and not at City.

 

[swt_passenger]

Thanks for digging those links out Edvid, the requirement for further NCNs to bring the OHLE into use is clearly mentioned in the original NCN about the temporary earthing I linked to earlier.

Interesting that they've introduced another pretty explicit reason to explain why the changeover will normally be at City T/L. When the 24 tph peak service is running trains will be too close together to do it at Farringdon. Previously I'd only found the reasoning mentioned before about tipping out defective trains at City T/L in various online info, this stuff about following trains blocking the route over the crossover seems to be new (as far as public info is concerned).

It implies changeover at City T/L is required - not an optional extra...

 

[Class377/5]

Thanks for digging those links out Edvid, the requirement for further NCNs to bring the OHLE into use is clearly mentioned in the original NCN about the temporary earthing I linked to earlier.

Interesting that they've introduced another pretty explicit reason to explain why the changeover will normally be at City T/L. When the 24 tph peak service is running trains will be too close together to do it at Farringdon. Previously I'd only found the reasoning mentioned before about tipping out defective trains at City T/L in various online info, this stuff about following trains blocking the route over the crossover seems to be new (as far as public info is concerned).

It implies changeover at City T/L is required - not an optional extra...

The main reason for the changeover is if a unit fails on DC and can't getvAC is at City you can dump it in Smithfield. Or turn around in platform south out being trapped. Come 24tph and if a unit failed at Farringdon the train behind would already be blocking the crossover at City. Result, two cancelled trains instead if one.

The changeover at City will be required soon enough (haven't seen a date for implementing this yet).

However a 12 car can fit in Smithfield sidings, it seems it will foul the track circuit meaning it blocks the mainline. So reversing at City is the only soluation for a failed changeover. Not that even reversing a train will take 15mins mimimium by the book so will destroy the peak one way. (10mibs walking time to walk 12 cars).

One thing I don't understand is banning 377/1, /3 & /4 and 375 but not the 376's?

 

[swt_passenger]

The main reason for the changeover is if a unit fails on DC and can't getvAC is at City you can dump it in Smithfield. Or turn around in platform south out being trapped. Come 24tph and if a unit failed at Farringdon the train behind would already be blocking the crossover at City. Result, two cancelled trains instead if one.

The changeover at City will be required soon enough (haven't seen a date for implementing this yet).

Previously though, a number of people had taken the view that changeover at City wasn't going to be the normal routine. Eg westcoaster in post #10, and yourself in the last response of post #16

So all the evidence is now in place to confirm what I've been posting for 18 months or so, based on the descriptions in the Thameslink rolling stock specs, and in Network Rail's NCN.

 

[westcoaster]

Further to the post above a 12 car train can not fit in smithfields as it would foul the core by about 3 coach lengths, still afaik the change over will be at farringdon.

 

[swt_passenger]

So you are saying that a Network Change Notice published last month, and linked to earlier should be disregarded?

I'd be interested to know your reasoning...

 

[transmanche]

Can I just clarify a couple of things, because I'm getting a bit confused. is this what is planned?

For southbound trains, the AC>DC changeover will normally take place at Farringdon. If the changeover fails, the train will continue to City Thameslink on AC, where it will go out of service and reverse into Smithfield siding.

For northbound trains, the DC>AC changeover will normally take place at City Thameslink. If the changeover fails, the train will be taken out of service and and diverted into Smithfield siding.

Is that correct?

 

[westcoaster]

No if a southbound traind can't change current it will go to city, and come back north via a crossover in snowhill tunnel, you can't access smithfields from the southbound platform at city.

 

[swt_passenger]

A northbound 12 car train would probably [1] be detrained at City T/L, and then reversed from the platform, or (according to some earlier DfT Thameslink info) run through to Farringdon empty and reverse from there.

[1] We discussed the relative merits of detraining a northbound failure at City or Farringdon earlier in this thread.

 

[thelem]

[1] We discussed the relative merits of detraining a northbound failure at City or Farringdon earlier in this thread.

Which basically boils down to there being more platform space at City. But what about giving passengers the choice, i.e. at City you would make an announcement saying "Due to a technical fault this train will now terminate at Farringdon. Any passengers for stations to Bedford should change here." (edit: This only applies to 12 coach trains, as these need to travel to Farringdon anyway to reverse where 8 coach trains can go to the sidings)

That way passengers travelling to Farringdon or changing for tube or crossrail wouldn't need to change trains for one stop, and Farringdon wouldn't need to cope with a whole train's worth of people being dumped onto the platform.

Only possible disadvantage I can see is it taking slightly longer to reverse at Farringdon because you've got passengers to worry about, but I don't think that should add much time at all.

 

[transmanche]

Only possible disadvantage I can see is it taking slightly longer to reverse at Farringdon because you've got passengers to worry about, but I don't think that should add much time at all.

The Network Rail documents linked to earlier suggest that's not possible, becasue "If a train fails to change to AC at Farringdon, this would result in it being trapped in Farringdon platform 4 unable to return south as the following train is foul of the AC/DC crossover."

 

[swt_passenger]

The Network Rail documents linked to earlier suggest that's not possible, becasue "If a train fails to change to AC at Farringdon, this would result in it being trapped in Farringdon platform 4 unable to return south as the following train is foul of the AC/DC crossover."

Not quite the same scenario - once the train had failed at City T/L, if you needed for operational reasons to reverse from Farringdon the signallers would be able to get involved, and hold the following train clear of the crossover.

That assumes that when the train fails to changeover at City T/L the driver will inform the signallers at the time, rather than keeping quiet and surprising everyone at Farringdon...

 

[transmanche]

Not quite the same scenario - once the train had failed at City T/L, if you needed for operational reasons to reverse from Farringdon the signallers would be able to get involved, and hold the following train clear of the crossover.

Not at all. Holding northbound trains whilst the failed train continues to Farringdon and reverses is going to be far more disruptive to the 24tph service than simply sending the failed train straight into the siding from City Thameslink.

 

[swt_passenger]

Not at all. Holding northbound trains whilst the failed train continues to Farringdon and reverses is going to be far more disruptive to the 24tph service than simply sending the failed train straight into the siding from City Thameslink.

Except when it is a 12 car train. There seems to be some debate as to whether or not a 12 car train will fit...

This is from the train infrastructure interface specification:

2.4.3.1 Proposed Arrangements
All service trains are expected to stop at both City Thameslink and Farringdon stations in both
directions. Hence the proposed arrangements are that during normal operation southbound trains will
change over from AC to DC during the stop at Farringdon, while northbound trains will change over
from DC to AC during the stop at City Thameslink.

If a southbound train is unable to take traction on DC but can continue on AC the train will work
forward to City Thameslink where passengers will be de-trained. The train will then reverse and return
north as empty stock on AC (or pick up a timetable working from Farringdon).

If a northbound train is unable to take traction on AC but can continue on DC passengers will be
detrained at City Thameslink. The train will then be worked forward to Smithfield Sidings (subject to
an 8-car limit) or to Farringdon to reverse via the crossover and return south as empty stock on DC
(or pick up a timetable working from City Thameslink).

http://webarchive.nationalarchives..../thameslinkrollingstock/itt/specification.pdf

 

[thelem]

Not at all. Holding northbound trains whilst the failed train continues to Farringdon and reverses is going to be far more disruptive to the 24tph service than simply sending the failed train straight into the siding from City Thameslink.

Sorry, I should have clarified that my suggestion only applies to 12 carriage trains that need to travel to Farringdon anyway.

 

[transmanche]

Except when it is a 12 car train. There seems to be some debate as to whether or not a 12 car train will fit...

Although that doesn't actually change the fact of what I wrote.

The documents that Edvid linked above state that Class 376 trains are permitted north of Blackfriars; a) only to access Smithfield sidings and b) subject to a maximum of 10 cars. So obviously two units (10 cars) must fit, but not three units (15 cars).

No limit is mentioned for Class 319, 377/2 or 377/5 units; which may imply that 12-cars are permitted.

If someone has access to Sectional Appendix table D for SO280, that might provide the definitive answer.

 

[LE Greys]

Why the heck didn't they dismantle the OHLE and go 3rd rail to St Pancras, where there is a lot more room and the possibility of turning back services from the south without having to change over?

 

[jon0844]

Or take the wires further south. Like to Brighton...!

 

[Gareth]

How common are problems on Thameslink in regards to AC/DC switchover? Dual voltage operation is often mooted as a possible way to expand Merseyrail but it sounds like it can be a lot of bother.

 

[jon0844]

I always thought the problem was more down to the time taken to switch, than it actually failing.

When there are problems, is it down to a 319 failing or a 377? I'd bet it's usually the latter, even though the former are far, far older.

313s seem to rarely fail at Drayton Park, although I've actually been on one that did - and I presume there are wires that continue in the tunnel a fair bit - as we went forward, then reversed to come back on the northbound platform and go back to Finsbury Park, where we were chucked off to get a train to King's Cross. It did take a while, but that was mostly down the driver having to walk through all 6-cars (not sure if he used the end doors to transfer trains, or stepped out and back on via the track).

 

[transmanche]

313s seem to rarely fail at Drayton Park, although I've actually been on one that did

In my commuting experience, I was lucky not to ever experience an AC>DC changeover failure . Loads of tripcock test failures at Finsbury Park though - which at least allowed for diversion into Kings Cross.

And to respond to Gareth's point. AC>DC changeover takes place all the time on the WLL & NLL too - without bother. But when planning for 24tph through the core, they have to plan for the 'what-if' scenario.

Just like having the tripcock tester at Finsbury Park rather than at Drayton Park; making it easy to divert trains into Kings Cross, instead of leaving passengers 'stranded' at Drayton Park and disrupting the service.

 

[Class377/5]

Previously though, a number of people had taken the view that changeover at City wasn't going to be the normal routine. Eg westcoaster in post #10, and yourself in the last response of post #16

So all the evidence is now in place to confirm what I've been posting for 18 months or so, based on the descriptions in the Thameslink rolling stock specs, and in Network Rail's NCN.

I've spoke to the TLP team over this recently which filled me in. And yes I believe your correct. But not sure when changeover comes in, may be this year.

General rule is failed changeover northbound terminates at City. Also add that due to the crossover south of City, any failed changeover unit can head south without issue.

Southbound, unit terminates at Farringdon or City, then uses crossover north of the station to get back right road.

Further to the post above a 12 car train can not fit in smithfields as it would foul the core by about 3 coach lengths, still afaik the change over will be at farringdon.

According to the TLP team it fits but its to do with the track circuits being fouled. Fact a 10 car fits mean it can't be as much as you think.

Although that doesn't actually change the fact of what I wrote.

The documents that Edvid linked above state that Class 376 trains are permitted north of Blackfriars; a) only to access Smithfield sidings and b) subject to a maximum of 10 cars. So obviously two units (10 cars) must fit, but not three units (15 cars).

No limit is mentioned for Class 319, 377/2 or 377/5 units; which may imply that 12-cars are permitted.

If someone has access to Sectional Appendix table D for SO280, that might provide the definitive answer.

I do have access to said document, will dig it out later when I'm in but not sure its up to date.

Will point out that a 12 car 377/5 has been in Smithfield during a possession, know so as I was on duty at the time but couldn't check how it fitted.

Or take the wires further south. Like to Brighton...!

Original plan was wires to Tulse Hill!

 

[Firestarter]

I've spoke to the TLP team over this recently which filled me in. And yes I believe your correct. But not sure when changeover comes in, may be this year.

General rule is failed changeover northbound terminates at City. Also add that due to the crossover south of City, any failed changeover unit can head south without issue.

Southbound, unit terminates at Farringdon or City, then uses crossover north of the station to get back right road.



According to the TLP team it fits but its to do with the track circuits being fouled. Fact a 10 car fits mean it can't be as much as you think.



I do have access to said document, will dig it out later when I'm in but not sure its up to date.

Will point out that a 12 car 377/5 has been in Smithfield during a possession, know so as I was on duty at the time but couldn't check how it fitted.



Original plan was wires to Tulse Hill!

What happened?

 

[Class377/5]

What happened?

I don't know that. Tulse Hill is rather random place to end the wires tho.

 

[swt_passenger]

What happened?

It has been said that the costs would have been vastly increased because firstly they'd have to AC immunise all the signalling on the lines that cross under Thameslink en route to Charing Cross.

Then you'd have had to decide whether to AC electrify all four lines through Elephant and Castle, all four platforms at Blackfrairs, whether to do the curve towards London Bridge etc etc...

My suspicion is that they decided to choose a simple (ish) two track section once all the additional costs became clear...

 

[jopsuk]

Or take the wires further south. Like to Brighton...!

I bet there's been plenty of people involved in Thameslink down the years who've wished they could do that! Most of the combined Thameslink/South Central franchise EMU fleet will be dual voltage capable too- only the 455s are pure DC*- which would make an AC Brighton mainline with DC branches much more workable.

Would upset a lot of people of course!

*the 456s are off to the South West division...

 

[hwl]

I don't know that. Tulse Hill is rather random place to end the wires tho.

Not random at all

a) The TL routes diverge at Tulse Hill.
b) The wires could have been run from City TL to Tulse Hill without any overhead clearance issues (i.e. no expensive civils), however south of Tulse Hill before the next stations there are very low bridges on either TL route (Sutton or Croydon fast via Crystal Palace) then plenty of low bridges and tunnels beyond the next stations too make it very expensive.

I suspect OHLE will move a little further south at a later stage to increase reliability and reduce disruption in the core probably to just south of London Bridge + Elephant and Castle, but leaving a large overlap with 3rd rail. i.e. north bound through train fails to swap to AC at LBG/E&C is diverted to the terminating platforms at Blackfriars...

 

[Class377/5]

It has been said that the costs would have been vastly increased because firstly they'd have to AC immunise all the signalling on the lines that cross under Thameslink en route to Charing Cross.

Then you'd have had to decide whether to AC electrify all four lines through Elephant and Castle, all four platforms at Blackfrairs, whether to do the curve towards London Bridge etc etc...

My suspicion is that they decided to choose a simple (ish) two track section once all the additional costs became clear...

Think they choose City as the clearance heading up the ramp to Blackfriars gets extremely tight.

Not random at all

a) The TL routes diverge at Tulse Hill.
b) The wires could have been run from City TL to Tulse Hill without any overhead clearance issues (i.e. no expensive civils), however south of Tulse Hill before the next stations there are very low bridges on either TL route (Sutton or Croydon fast via Crystal Palace) then plenty of low bridges and tunnels beyond the next stations too make it very expensive.

I suspect OHLE will move a little further south at a later stage to increase reliability and reduce disruption in the core probably to just south of London Bridge + Elephant and Castle, but leaving a large overlap with 3rd rail. i.e. north bound through train fails to swap to AC at LBG/E&C is diverted to the terminating platforms at Blackfriars...

The TL route diverge clear at Blackfriars with only a handful of peak services diverging at Tulse Hill. But guess putting up the wires while rebuilding London Bridge would make some sense when all TL trains would go that route. However as 12 cars would have to changeover at an 8 car station, doesn't seem as useful.

Point of multiple junctions south of Blackfriars means what would they have wired in the end? Loughborough Junction is a classic example of what I mean.

As for long term, there is no route from London Bridge to Blackfrairs. After getting a diagram of today's interim layout and briefed on the final layout come 2018, the bays will still not be connected to London Bridge unless a new design is made. And it's an easy change to make.

 

[westcoaster]

I've spoke to the TLP team over this recently which filled me in. And yes I believe your correct. But not sure when changeover comes in, may be this year.

General rule is failed changeover northbound terminates at City. Also add that due to the crossover south of City, any failed changeover unit can head south without issue.

Southbound, unit terminates at Farringdon or City, then uses crossover north of the station to get back right road.



According to the TLP team it fits but its to do with the track circuits being fouled. Fact a 10 car fits mean it can't be as much as you think.



I do have access to said document, will dig it out later when I'm in but not sure its up to date.

Will point out that a 12 car 377/5 has been in Smithfield during a possession, know so as I was on duty at the time but couldn't check how it fitted.



Original plan was wires to Tulse Hill!

I'm sorry but a 12 car train will not fit in smithfields without fouling the main line, the max coaches in there Is 8 car lenght, or any length less than 8. I know this as I've been in there many times, you have about 5-10 meters between an 8 car and the exit signal.