Elizabeth Line - total loss of signalling 26/11

[starlight73]

Could someone please explain the difference between ETCS and CBTC and how both systems work? Thanks

I’m not an expert at all… I believe the difference is:

ETCS is a standard system - different manufacturers make their own ETCS equipment. But in theory, it should behave in a similar way to other ETCS systems and it should be able to work with other ETCS equipment from different manufacturers.

CBTC is a generic term that means Communications Based Train Control. It means that there’s some kind of computerised system that drives and signals trains, and it sends signals over specialised radio or Wi-Fi signals (note that some forms of ETCS do use radio signals and ETCS can also drive trains)

There are different varieties of CBTC from different manufacturers. For example, Siemens CBTC (Elizabeth line) and Thalys CBTC (Circle, District, Ham & City, Metropolitan lines). However, these are all proprietary systems and cannot communicate with each-other.

So a very inaccurate analogy could be: ETCS is a common standard, a bit like email (you can send an email from Gmail to Outlook to Yahoo mail, and it will basically look and do the same thing, with small differences). And CBTC is a bit like a specific messaging platform that can only communicate with itself (Facebook messenger, Telegram, etc.). Of course, there’s a ton of differences between email and train signalling

now to hear about everything that’s inaccurate in this post,,, in a separate thread maybe - sorry this should probably move into a separate thread mods!!

 

[Horizon22]

Trouble was their onboard signalling system, from Alstom if I remember correctly, wasn't compatible with the Siemens product. Nobody had a contract to interface the two systems and neither company really wanted to share their intellectual property rights. Net result was a long delay and a massive amount of money to write bespoke safety critical software in order to interface the two systems.

I wonder if the recent problems revolve around this bespoke software?

Nothing to do with that. There were no 345 trains in system when the Siemens CBTC signalling crashed (twice) overnight. Things like interlocking and visibility of the track for signallers were lost.

 

[kevin_roche]

Could someone please explain the difference between ETCS and CBTC and how both systems work? Thanks

ETCS is the European Train Control System. It is used on the Line to Heathrow in a mode called Level 2 where it has fixed signalling blocks and lineside signals are not needed. Trains are given movement authority to the end of a block. It uses an in-cab display to tell the driver when to stop and how far and how fast to drive to the next stop. The onboard systems communicate with a central signalling centre via the radio system which is based on GSM mobile phone technology.

The Trainguard CBTC system used in the Crossrail Core is a moving block signalling system where each train gets movement authorities up to the back of the train in front (with a small safety margin) and uses the same ETCS display to tell the driver what to do but can also operate with Automatic Train Control where the train is driven by the onboard computer. It operates as a subsystem of ETCS where a module can be plugged in to run the Trainguard CBTC software. It communicates with the central signalling centre via a wi-fi like system which can handle higher traffic rates so movement authority is updated more often and the number of trains per hour can be much higher.

Both of the above use Eurobalises in the four foot to pass position information to train so that it knows where it is.

The ETCS system on the Elizabeth Line Trains also has a plug-in module for handling the more common TPWS signalling used on the GWML and GEML and most other UK network rail lines.
The main difference between the switchovers between signalling at each side is that on the GWML the switchover on the GWML is done while moving while the one on the GEML is done while stationary at the platform at Stratford.

I hope that helps.

 

[Winthorpe]

Nothing to do with that. There were no 345 trains in system when the Siemens CBTC signalling crashed (twice) overnight. Things like interlocking and visibility of the track for signallers were lost.

Yes. In software the interface between systems is thought of as a ‘contract’. It is not necessary to know how the other party does it, just that if one party wants to use the interface/contract the other responds as expected.

If either party to the contract doesn’t do what it is supposed to do it breaks down.

I’m guessing this is what’s happened.

 

[Horizon22]

Yes. In software the interface between systems is thought of as a ‘contract’. It is not necessary to know how the other party does it, just that if one party wants to use the interface/contract the other responds as expected.

If either party to the contract doesn’t do what it is supposed to do it breaks down.

I’m guessing this is what’s happened.

It's all very technical - Siemens engineers from Germany were apparently drafted in such was the extensive and complex - and to some extent novel - nature of the fault.

 

[hwl]

Siemens has just won the signalling contract for HS2 - with ETCS.

Different part of Siemens signalling business though...

 

[Winthorpe]

It's all very technical - Siemens engineers from Germany were apparently drafted in such was the extensive and complex - and to some extent novel - nature of the fault.

I’m not surprised. It must be mind boggling complex software.

As a developer you rely on the software out of your direct control to do what it is supposed to do.

If it doesn’t, you rely on the others to fix it.

 

[Joliver]

ETCS is the European Train Control System. It is used on the Line to Heathrow in a mode called Level 2 where it has fixed signalling blocks and lineside signals are not needed. Trains are given movement authority to the end of a block. It uses an in-cab display to tell the driver when to stop and how far and how fast to drive to the next stop. The onboard systems communicate with a central signalling centre via the radio system which is based on GSM mobile phone technology.

The Trainguard CBTC system used in the Crossrail Core is a moving block signalling system where each train gets movement authorities up to the back of the train in front (with a small safety margin) and uses the same ETCS display to tell the driver what to do but can also operate with Automatic Train Control where the train is driven by the onboard computer. It operates as a subsystem of ETCS where a module can be plugged in to run the Trainguard CBTC software. It communicates with the central signalling centre via a wi-fi like system which can handle higher traffic rates so movement authority is updated more often and the number of trains per hour can be much higher.

Both of the above use Eurobalises in the four foot to pass position information to train so that it knows where it is.

The ETCS system on the Elizabeth Line Trains also has a plug-in module for handling the more common TPWS signalling used on the GWML and GEML and most other UK network rail lines.
The main difference between the switchovers between signalling at each side is that on the GWML the switchover on the GWML is done while moving while the one on the GEML is done while stationary at the platform at Stratford.

I hope that helps.

The transition on the GEML is also done whilst on the move. Heading Westbound it's when you're more or less Country End of Stratford. Heading Eastbound, it's departing Country end of the platform.

 

[modernrail]

I retired over seven years ago now so haven't had any dealings with Crossrail in all that time.

Back then there were ongoings discussions revolving around the fact that Crossrail Limited had bought Siemens CBTC fixed equipment but that Boris had insisted that TFL purchase the trains and bought Bombardier trains because they would be British made in Derby.

Trouble was their onboard signalling system, from Alstom if I remember correctly, wasn't compatible with the Siemens product. Nobody had a contract to interface the two systems and neither company really wanted to share their intellectual property rights. Net result was a long delay and a massive amount of money to write bespoke safety critical software in order to interface the two systems.

I wonder if the recent problems revolve around this bespoke software?

Should this not have been foreseen when ordering the signalling. If you don’t know what it might have to interface with, make sure the signalling contract makes it clear an interface will need to happen within the contract value?

 

[Winthorpe]

Should this not have been foreseen when ordering the signalling. If you don’t know what it might have to interface with, make sure the signalling contract makes it clear an interface will need to happen within the contract value?

The contract shouldn’t change.

If it changes, the calling code should deliberately call the new contact.

 

[Tio Terry]

Should this not have been foreseen when ordering the signalling. If you don’t know what it might have to interface with, make sure the signalling contract makes it clear an interface will need to happen within the contract value?

I think it was a case of politics interfering with Engineering.

Crossrail limited made it quite clear to Boris and TFL that the sensible procurement option would be trains compatible with the Siemens CBTC signalling system. At the time the decision was made to use CBTC it was being installed in, I think Hong Kong, so would be a tested and proven system before being used on Crossrail.

But Boris was on a crusade to wave the flag and buy British. Hence the mismatch.

 

[Bald Rick]

I wonder if TfL regret not buying ETCS, an industry standard signalling system?

I was going to stay, why on earth did they not just fit ETCS in the first place? Surely then at some point the whole line would have the same signalling system.

Test trains will run in the COS shortly.


ETCS plus ATO allows 24tph in the thameslink core. I was told that ETCS wasn’t chosen for Crossrail as CBTC worked with Platform Doors while ETCS didn’t have that capability yet.

The decision on the Crossrail signalling system was taken at a time when ETCS did not have an ATO product, nor couldd interface with screen doors, nor could it tackle auto reverse, which was a requirement. ETCS still does not have the latter two, and only gained the ATO product properly very recently.

Of course we hindsight we now know that ATO over ETCS would have been fine, but at the time it was too much of an additional risk.

Yes and no. ATO over ETCS used in the TL core is actually a Siemens bespoke product, and has limited capacity, hence why it runs only for about 8km. I have heard it is not extendable on Thameslink for that reason (unfortunately) but would be delighted to be proved wrong. However if this is the case, then there would not have been capacity for the same system to be used for Crossrail which is more than 3 times longer.

 

[boiledbeans2]

Any chance of Mayor Khan changing the name of this line to the Liz Truss line to avoid our late lamented monarch from being mired in this?

"The Elizabeth line is part suspended due to a damaged truss"

 

[MadMac]

"The Elizabeth line is part suspended due to a damaged truss"

Oo Er Missus…..

 

[Harpo]

Re: ETCS lack of ‘Auto Reverse’. When the Lotschberg base tunnel opened with ETCS in 2007 its passenger trains were able to be driven in reverse from the leading cab in an emergency. Was TfL seeking an even higher and yet more complex/expensive level of contingency?

 

[MCR247]

Re: ETCS lack of ‘Auto Reverse’. When the Lotschberg base tunnel opened with ETCS in 2007 its passenger trains were able to be driven in reverse from the leading cab in an emergency. Was TfL seeking an even higher and yet more complex/expensive level of contingency?

But auto-reverse isn’t driving the train in reverse - it is the train driving itself in reverse.

 

[Bald Rick]

But auto-reverse isn’t driving the train in reverse - it is the train driving itself in reverse.

without a driver!

 

[Harpo]

without a driver!

Aha! (Sound of pennies dropping). The turnbacks at the west end?

 

[Horizon22]

Aha! (Sound of pennies dropping). The turnbacks at the west end?

Yes. The driver initiates autoreverse at Paddington Platform B and the train goes into Westbourne Park and back into Paddington Platform A.

Auto reverse can also be set up elsewhere in fully tunnelled sections in emergency / degraded situations if needed but is more complex to set up.

 

[hwl]

I think it was a case of politics interfering with Engineering.

Crossrail limited made it quite clear to Boris and TFL that the sensible procurement option would be trains compatible with the Siemens CBTC signalling system. At the time the decision was made to use CBTC it was being installed in, I think Hong Kong, so would be a tested and proven system before being used on Crossrail.

But Boris was on a crusade to wave the flag and buy British. Hence the mismatch.

Siemens didn't bid for the Crossrail rolling stock contract. The Thameslink and Crossrail contracts were too large for any manufacturer to do both. Siemens won't the Thameslink contract and withdrew any interest in the later Crossrail rolling stock.

The signalling system Siemens bid with was very new and also very new to Siemens as they had just purchased Matra's signalling business, the MT in TrainGuardMT stands for Matra Technology. Siemens UK had zero experience with it at that point.

At that point in time it was only being rolling out on simple Paris Metro line where it was the only signalling system (equivalent to Victoria line complexity but at lower TPH).

The Crossrail and similar contract in Hong Kong (also had delays and issues) effectively paid for the development of more advanced functionality in TrainGuardMT. (Simliar for the Thales systems with Jubilee/Northern/SSR effectively paying for new functionality development that could then be sold else where)

In both the Crossrail and HK cases the CBTC system had to interface with other signalling systems, a first for it.

The ETCS rules are clear in that the ETCS EVC is always the master signalling system and other signalling systems and devices interface with it. Trainguard MT had never had to work with ETCS before or use the same balises as ETCS via the ETCS system. This appears to have been an understanding gap at Crossrail.

Siemsen decided they were going to bid with TrainguardMT before they purchased Invensys and if the purchase had been slightly earlier or procurement slightly later would probably have gone with something based on Invensys's TDG (e.g Victoria Line) instead.

 

[kevin_roche]

A Standard for ATO over ETCS is currently under development. Prototypes have been tested by Network rail on the test track near Harpenden. My guess is that it is still a couple of years away. I have recently seen comments that Auto Reverse with ATO on ETCS will be discussed after that.

 

[Sly Old Fox]

The decision on the Crossrail signalling system was taken at a time when ETCS did not have an ATO product, nor couldd interface with screen doors, nor could it tackle auto reverse, which was a requirement. ETCS still does not have the latter two, and only gained the ATO product properly very recently.

Ok good yeah coz this is much better.

 

[Acton1991]

Any idea what’s going on this morning? Multiple delays and now some cancellations in the west - citing an ‘operational incident’. Although TfL still saying a good service

 

[John Webb]

A Standard for ATO over ETCS is currently under development. Prototypes have been tested by Network rail on the test track near Harpenden. My guess is that it is still a couple of years away. I have recently seen comments that Auto Reverse with ATO on ETCS will be discussed after that.

As a resident of St Albans I'm curious to know where the test track at Harpenden is? (and apologies for a deviation away from the main topic of this thread.)

 

[swt_passenger]

As a resident of St Albans I'm curious to know where the test track at Harpenden is? (and apologies for a deviation away from the main topic of this thread.)

Hitchin?

 

[Stampy]

Hitchin?

Top part of the Hertford Loop, isn't it??

 

[class397tpe]

Any idea what’s going on this morning? Multiple delays and now some cancellations in the west - citing an ‘operational incident’. Although TfL still saying a good service

TfL mentions a signalling issue at Ealing Broadway - seems like it’s been fixed now but some trains picked up pretty hefty delays.

Looks like some eastbound trains were diverted onto the fast lines and some stopped at Ealing Broadway platform 2.

 

[swt_passenger]

Top part of the Hertford Loop, isn't it??

Yes. NR publicity refers to it as being ‘at Hitchin’ for some reason, perhaps that’s where the test control centre is.

 

[Bald Rick]

A Standard for ATO over ETCS is currently under development. Prototypes have been tested by Network rail on the test track near Harpenden.

As a resident of St Albans I'm curious to know where the test track at Harpenden is? (and apologies for a deviation away from the main topic of this thread.)

Hitchin?

Yes. NR publicity refers to it as being ‘at Hitchin’ for some reason, perhaps that’s where the test control centre is.

It’s between Watton at Stone and Hertford. The office base is at Hitchin.

 

[liam456]

It’s between Watton at Stone and Hertford. The office base is at Hitchin.

The same location and project that used the modified ETCS Class 313's on the Down line a few years ago?