ERTMS rollout on ECML and GWML

kevin_roche · 13 Jul 2019

This recent article about ATO on the Rail Engineer website has some interesting points and is well worth reading.

It highlights the capacity issue of the current GSM-R system with regards to running 24tph on Thameslink with short fixed blocks. Thameslink does not have moving blocks.

To achieve an optimum journey experience with timetable adherence, optimum performance, maximum capacity and good safety will require other technical systems to be added in. Traffic Management is vital since accurate train regulation is required, particularly if an ATO railway has multiple junctions and routes. On Thameslink, where the TMS has yet to be completed, a 30-second update of timetable to each train is proving insufficient and real time updating is now regarded as necessary. This, in turn, demands a very high data exchange rate to every train, something that is beyond the capacity of the present GSM-R system. Thus, a replacement 4G or 5G radio link may take on more urgency with Wi-Fi enhancements likely to be included as well.

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gsnedders · 13 Jul 2019

I thought Crossrail was fixed block signalling too, just very short blocks?

MarkyT · 13 Jul 2019

gsnedders said:
I thought Crossrail was fixed block signalling too, just very short blocks?

I don't know about Crossrail, but on Thameslink there are signal sections that are subdivided into smaller ETCS blocks, each employing fixed train detection by track circuits and delineated by ETCS block markers, in some cases as close as 70m apart. Non fitted or faulty ETCS trains can proceed through on normal signalling with AWS and TPWS, but clealy may not close up on a preceding train to the extent a ETCS-functional train could. As far as I understand it this is operationally also what is desired with the new hybrid system, but using virtual fixed blocks for the intermediate ETCS block sections that still have marker boards but no additional train detection equipment. Eventual removal of the signals could occur in the future if there's no longer any need for them, but actually that wouldn't save very much if they're modern lightweight low maintenance integrated examples, although you may be able to remove some physical fixed train detection equipment.

coppercapped · 13 Jul 2019

MarkyT said:
Correct. There are signal sections that are subdivided into smaller ETCS blocks, each employing fixed train detection by track circuits and delineated by ETCS block markers. Non fitted or faulty ETCS trains can proceed through on normal signalling with AWS and TPWS, but clealy may not close up on a preceding train to the extent a ETCS-functional train could. As far as I understand it this is operationally also what is desired with the new hybrid system, but using virtual fixed blocks for the intermediate ETCS block sections that still have marker boards but no additional train detection equipment. Eventual removal of the signals could occur in the future if there's no longer any need for them, but actually that wouldn't save very much if they're modern lightweight low maintenance integrated examples, although you may be able to remove some physical fixed train detection equipment.

Crossrail ETCS? Certainly in the Heathrow tunnels. But in the core it is CBTC - or am I missing something?

MarkyT · 13 Jul 2019

coppercapped said:
Crossrail ETCS? Certainly in the Heathrow tunnels. But in the core it is CBTC - or am I missing something?

Oops sorry my mistake - I was thinking of Thameslink. As to Crossrail, I'm not sure but the system can be supplied in a number of configurations according to the supplier's literature.

Bald Rick · 13 Jul 2019

gsnedders said:
I thought Crossrail was fixed block signalling too, just very short blocks?

All moving block signalling is, in essence, ‘fixed’ block but with short blocks. The block length is determined by the cycle time of the RBC-train messaging, and the speed of the train.

For example, if the speed of the train is 100km/h, and the cycle time is 1 second then the block length is 27.78m. Of course, as the train slows down the block length reduces.

ComUtoR · 13 Jul 2019

Bald Rick said:
For example, if the speed of the train is 100km/h, and the cycle time is 1 second then the block length is 27.78m. Of course, as the train slows down the block length reduces.

How does that link with 'Braking Distance' ?

If the speed was 100 km/h and the braking distance is 55.56m. Would you then have a 'moving block' of 2 blocks (2x 27.78m) ? or a single block of 55.56m ?

edwin_m · 13 Jul 2019

ComUtoR said:
How does that link with 'Braking Distance' ?

If the speed was 100 km/h and the braking distance is 55.56m. Would you then have a 'moving block' of 2 blocks (2x 27.78m) ? or a single block of 55.56m ?

I would think the two must be separate. The movement authority will be given for a specific distance and the train can then manage itself to stop within that distance if it doesn't receive an extension of authority in the meantime. Because the "blocks" shrink as the train slows down on the approach to the end of the movement authority, it could in theory approach very closely to a train in front. In practice however there would be a safety margin to allow for inaccuracies in distance measurement etc, and I assume some sort of manual override if the trains are to be coupled.

Bald Rick · 13 Jul 2019

ComUtoR said:
How does that link with 'Braking Distance' ?

If the speed was 100 km/h and the braking distance is 55.56m. Would you then have a 'moving block' of 2 blocks (2x 27.78m) ? or a single block of 55.56m ?

edwin_m said:
I would think the two must be separate. The movement authority will be given for a specific distance and the train can then manage itself to stop within that distance if it doesn't receive an extension of authority in the meantime. Because the "blocks" shrink as the train slows down on the approach to the end of the movement authority, it could in theory approach very closely to a train in front. In practice however there would be a safety margin to allow for inaccuracies in distance measurement etc, and I assume some sort of manual override if the trains are to be coupled.

Yes they are separate principles. One is block length, and the other is the calculated braking distance. The train knows its braking distance at all times (plus safety margin), and separately knows how much distance there is clear in front of it (as it knows the length of each block).

ComUtoR · 13 Jul 2019

So the train is going at 'caution*' ?

The train has a movement authority of 10 blocks (or to point x). It knows the braking distance so it can calculate how fast it can go to be able to stop within the movement authority ? If so, that now makes perfect sense...

*inside joke

gsnedders · 14 Jul 2019

Bald Rick said:
All moving block signalling is, in essence, ‘fixed’ block but with short blocks. The block length is determined by the cycle time of the RBC-train messaging, and the speed of the train.

For example, if the speed of the train is 100km/h, and the cycle time is 1 second then the block length is 27.78m. Of course, as the train slows down the block length reduces.

Right, okay, that makes sense given the messaging. I guess I've always viewed moving block signalling as simply absolute block with an asymptotically short block, though obviously messaging necessitates delays on top of that theoretical behaviour.

ComUtoR said:
So the train is going at 'caution*' ?

The train has a movement authority of 10 blocks (or to point x). It knows the braking distance so it can calculate how fast it can go to be able to stop within the movement authority ? If so, that now makes perfect sense...

*inside joke

This is fundamentally my understanding of how both ETCS and most CBTC systems work, yes.

kevin_roche · 14 Jul 2019

On Crossrail Central Core, Abbey wood to Paddington, Siemens Trainguard CBTC is being used. It has moving blocks with train reporting position every 0.4 secs.

In normal operation the block will extend to the back of the previous train or the stopping place at the next station whichever is closest.

More information the Trainguard Brochure (pdf).

kevin_roche · 16 Jul 2019

Today in New Civil Engineer

Jacobs identified the principal risks to opening on time were delays in train software development, which it said had slipped further, and safety authorisation. The report also concludes that there are issues with the ETCS (European train control system) wayside system that Network Rail must resolve to avoid impact upon driver training.

Consequently, the report adds that an opening date can only be “given with some certainty” after driver training has started.

https://www.newcivilengineer.com/latest/high-risk-crossrail-opening-will-delayed-16-07-2019/

kevin_roche · 1 Aug 2019

I noticed this in the Crossrail PRep Project Status Report124–Period1 on page 31. Downloadable from the Crossrail Reports page on the TfL web site.

NR ETCS Programme. NR’s ETCS project team remainsfocussed upon completing ETCS Stage B at Easter 2020, subject to planning and contractor resources.

ETCS Stages A an B cover GWML Paddington to Airport Junction. I believe Stage B is the Paddington end.

This appears to indicate that the ETCS installation between Paddington and Airport Junction is still planned (or was in April 2019).

ERTMS rollout on ECML and GWML

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