ERTMS Operation

A few years ago a departure from Aberyswyth almost hit a petrol tanker on a level crossing. If you can find the RAIB accident report, there was a fair amount of detail in it.

The position of the train is determined by the balise units at the track side, they are placed at fairly regular intervals and are calibrated so the ERTMS system knows there location (a real pain if a tamper takes one out apparently). Movement authoritys are transmitted to the train via radio (GSMR).

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The position of the train is determined by the balise units at the track side, they are placed at fairly regular intervals and are calibrated so the ERTMS system knows there location (a real pain if a tamper takes one out apparently). Movement authoritys are transmitted to the train via radio (GSMR).

So does that mean that there are no track circuits or axle counters on a Level 2 route? That must be tricky over pointwork.

ERTMS Level 1 (With Infill) - Still an overlay over an existing signalling system, so you still have lineside signals. The movement authority is either transmitted to the train through a continuous loop placed along the track (similar to how the underground works on one of the ATO lines), through extra balises placed (Without infill the balises are placed only at signals; think cheap!), or through radio (aka GSMR).

This allows the train to recieve a new movement authority sooner, and thus accelerate quicker if the new limit allows it to.

ERTMS Level 2 - Lineside signals are a thing of the past in theory; however block markers are placed in various physical locations to give a method of degraded working

If I've given your train an MA from MH1000 to MH1008, and the train is just passing MH1000, and I shorten the authority down so you only have it as far as MH1006 the train will automatically recalculate a safe braking curve, and will do nothing if it's within that braking curve.

As I understand it the spec doesn't require track circuits or axle counters for a level 2 route.

I'm still waiting for someone to show how this is more cost effective and/or more reliable than proven technology like coded track circuits. The people who thought wireless technology would be cheap and reliable are the children of those who said we'd all be wearing jetpacks.

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I'm still waiting for someone to show how this is more cost effective and/or more reliable than proven technology like coded track circuits. The people who thought wireless technology would be cheap and reliable are the children of those who said we'd all be wearing jetpacks.

While running into a real risk of replying to a flamebait, I have to remind you that while there are many successful ATPs based on other technologies (loops, balises, radio), I don't know of any ATP with speed supervision for mixed traffic mainline based on coded circuits. So "proven technology"? I'd say proven wrong.

" said:

ERTMS Level 1 (With Infill) - Still an overlay over an existing signalling system, so you still have lineside signals. The movement authority is either transmitted to the train through a continuous loop placed along the track (similar to how the underground works on one of the ATO lines), through extra balises placed (Without infill the balises are placed only at signals; think cheap!), or through radio (aka GSMR).

Citation needed. I don't think sending MA over radio is possible without Level 2.

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This allows the train to recieve a new movement authority sooner, and thus accelerate quicker if the new limit allows it to.

Not only that, it allows the train to run faster by advising the train of the new MA well in advance (that's how they use it in Slovakia).

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ERTMS Level 2 - Lineside signals are a thing of the past in theory; however block markers are placed in various physical locations to give a method of degraded working

Block markers are not a method of degraded working, they are the main signals governing traffic in full supervision! Passing a block marker without a MA, even if the engine allows you to, is PSAD!

Also, ETCS L2 doesn't preclude lineside signals. They may be there eg. for unfitted trains, maybe giving them more adverse signals.

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If I've given your train an MA from MH1000 to MH1008, and the train is just passing MH1000, and I shorten the authority down so you only have it as far as MH1006 the train will automatically recalculate a safe braking curve, and will do nothing if it's within that braking curve.

What you describe is an ACOA. While it is certainly possible, describing operation in terms of ACOAs and PSADs is severely misleading. Also, it might not be really successful, because the train may be in a radio hole.

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As I understand it the spec doesn't require track circuits or axle counters for a level 2 route.

Yes they do! There must be some automatic vacancy detection and interlocking for ETCS L2 to work. OTOH, ETCS L1 could be quite easily deployed on a line without track circuits, just with signallers observing tail-lamps.

The level 2 spec doesn't require physical signs to denote block markers as I understand it, but on the other hand it doesn't preclude it.

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" said:

I'm still waiting for someone to show how this is more cost effective and/or more reliable than proven technology like coded track circuits. The people who thought wireless technology would be cheap and reliable are the children of those who said we'd all be wearing jetpacks.

While running into a real risk of replying to a flamebait, I have to remind you that while there are many successful ATPs based on other technologies (loops, balises, radio), I don't know of any ATP with speed supervision for mixed traffic mainline based on coded circuits. So "proven technology"? I'd say proven wrong.

TVM-430 would be one, but I was specifically referring to the reliance of ETRMS and similar systems of wireless data links for continuous wayside to train communication.

Just to add to some of well explain responses.

Level 2 can also have overlay, in fact the initial design for the Great Western Main Line will have Level 2 with signaling to allow for mixed traffic operation.

taffy in post 83816 said:

Just to add to some of well explain responses.

Level 2 can also have overlay, in fact the initial design for the Great Western Main Line will have Level 2 with signaling to allow for mixed traffic operation.

How does that work? Would drivers of trains running under level 2 just ignore the fixed signals?

" said:

" said:

I'm still waiting for someone to show how this is more cost effective and/or more reliable than proven technology like coded track circuits. The people who thought wireless technology would be cheap and reliable are the children of those who said we'd all be wearing jetpacks.

While running into a real risk of replying to a flamebait, I have to remind you that while there are many successful ATPs based on other technologies (loops, balises, radio), I don't know of any ATP with speed supervision for mixed traffic mainline based on coded circuits. So "proven technology"? I'd say proven wrong.

TVM-430 would be one, but I was specifically referring to the reliance of ETRMS and similar systems of wireless data links for continuous wayside to train communication.

jamieP in post 106721 said:

taffy in post 83816 said:

Just to add to some of well explain responses.

Level 2 can also have overlay, in fact the initial design for the Great Western Main Line will have Level 2 with signaling to allow for mixed traffic operation.

How does that work? Would drivers of trains running under level 2 just ignore the fixed signals?

Talking generally (not ETCS) any fixed signals would show a favourable aspect to the driver, or show a specific aspect meaning "cab signalling effective". Unfitted/faulty trains would generally be the only train permitted between fixed colour light signals which drastically reduces the number of trains per hour depending on section length. IIRC the Thameslink core has fixed signals at typical UK spacing for the line speed, plus intermediate marker boards for fitted trains.

Am I right in saying there are no physical overlaps since the system just alters the braking curve of a train to ensure it will never fail the path of another train?