ETCS signalling from signaller's perspective

[Egg Centric]

Suspect answer to this is "it depends" - but anyway - in conventional UK signalling of whatever means (and correct me if I'm wrong) you basically set routes to set points which are 95% of the time other signals, but sometimes e.g. buffers, a goods yard, a stop sign, whatever. But a specific physical location designed for routing to, anyway.

If I understand (higher level) ETCS correctly, from the train's perspective a route could be set to any arbitrary point via any arbitrary points (in this usage of points I mean points as in crossovers etc, while I mean points as in dots with the rest of it). EG 500m past station XYZ or whatever. So long as there was sufficient overlap etc

Is this sort of hypothetical freedom something that the signaller actually has access to in reality? So for example if there were trouble on a line send them to the furthest station they could reach, then a reverse direction a couple of stops then go back via a random crossover that was installed for another move that was never intended for this?

Or is there far less freedom and the advantage just coming from moving block more or less?

I've struggled a bit to explain what I mean - please ask if it's not clear.

 

[JN114]

ETCS isn’t a moving block system - at least it hasn’t been implemented as such outside of a couple of test setups on the continent - and to my knowledge it still isn’t planned for anywhere using the moving block standards.

Full supervision movement authorities are issued from signal to signal; or equivalent (block marker, buffer stop, etc); and so to the signaller are exactly like normal entrance/exit routesetting.

For permissive working or similar an on-sight movement authority is issued by the radio block centre, but from the signaller’s end it is just like setting any other permissive route.

The advantage from ETCS, even if it is still fixed block, is that you can put the block markers anywhere you wish, at any spacing. Lights on sticks signals are spaced based on linespeed.

 

[Annetts key]

Lights on sticks signals are spaced based on linespeed.

For MAS (multiple aspect signalling) track circuit block, also based on intended line capacity and the total cost of the provided signalling system. Hence why the line speed may be limited by the provided signalling rather than the other way round.

For the railway, the main advantage is ETCS costs less if block marker boards are used (no line side colour light signals being provided).

 

[Fragezeichnen]

ETCS is just a train control safety system which receives information about what a train is allowed to do and monitors how fast it travels, like TPWS, or AWS, or TVM430, or any other; just a lot more complicated. It brings no extra capabilities by itself, it will always depend on the interlocking it is connected to, which could be anything from a purposed designed computer system to a retrofitted electromechanical interlocking.

A prerequisite for moving block(i.e. a movement authority to an "arbitrary point") is that trains have to continually monitor the position of their rear end in a safety-compliant way, which is particularly complex in the case of goods trains; without that you can't safely set a route to anywhere except a axle counter/track circuit boundary. No-one has yet implemented or even attempted to implement a system of this kind in a main line application.

If moving block were to be implemented I would imagine it would be used only to enable closer train separation on sections of plain line and would be handled fully automatically by the interlocking. The consequences of allowing supervised moves to arbitrary locations in junctions and stations would be a vast increase in interlocking complexity and potential confusion for the operating staff.

 

[GraphitProjekt]

ETCS is just a train control safety system. It brings no extra capabilities by itself, it will always depend on the interlocking it is connected to

The advantage from ETCS, even if it is still fixed block, is that you can put the block markers anywhere you wish, at any spacing. Lights on sticks signals are spaced based on linespeed.

So can you or can you not put block markers where you wish.
And in general, is the main point for ETCS just to have a cross national standard for cab signalling? Because I've definitely heard a lot about "digital railway will enable higher capacity from the pre-existing ECML"

 

[Annetts key]

So can you or can you not put block markers where you wish.
And in general, is the main point for ETCS just to have a cross national standard for cab signalling? Because I've definitely heard a lot about "digital railway will enable higher capacity from the pre-existing ECML"

You can put conventional colour light signals where you wish if you want to. But in practice, the available amount of money limits things. And sometimes physically it's difficult (in tunnels for example).

As I said earlier, the main advantage of ETCS is that if you don't have lineside signals, block marker signs are much cheaper.

Of course, ETCS also has the safety features of ATP (Automatic Train Protection) which is a very good thing to have. And in cab signalling should remove problems with drivers missing signals or misinterpreting them.

IMHO (and I used to work in signal engineering) the phase "digital railway" is and always was just marketing hype. BR introduced digital signalling as in computer controlled interlocking (SSI - Solid State Interlocking) and computer displays and trackballs (IECC - Integrated Electronic Control Centre) in the "signal box" long before Railtrack or Network Rail was a glint in a politicians eye.

And besides which, relay based interlocking is digital technology anyway. A normal DC "line" relay has two normal states, it's either energised with the "front" contacts made or it's de-energised with the "front" contacts not made.

What they really meant was that all new signalling would be using computer based interlocking and the modern versions / equivalents of IECC. And that there would be a small number of large control centres controlling entire routes or regions. But that plan soon got burned by lack of money and poor planning.

Hence we still have sizeable amounts of semaphore signalling and manual mechanical signal boxes on some secondary routes even today.

The claim for higher capacity was because some time ago in the past, they hoped that ETCS moving block would be soon practical. But this hasn’t happened.

ETCS controlled by a conventional interlocking, which in turn still uses track circuits and / or axle counters doesn’t of itself add any significant extra capacity. You can get some extra capacity by having shorter block sections (and hence more of them) and by having less restrictions approaching junctions (no longer need to use signals showing restricted aspects to slow a train for the lower speed route at a junction).

 

[HSTEd]

A prerequisite for moving block(i.e. a movement authority to an "arbitrary point") is that trains have to continually monitor the position of their rear end in a safety-compliant way, which is particularly complex in the case of goods trains; without that you can't safely set a route to anywhere except a axle counter/track circuit boundary. No-one has yet implemented or even attempted to implement a system of this kind in a main line application.

There is a semi high speed railway operational in India with LEvel 3 Hybrid, with on board train completeness checking.

The technology for safety grade train completeness in freight trains exists and has been in some service for years (Electronically Controlled Pneumatic braking). The major problem holding back deployment is that the savings would accrue to different people to the costs of installation. Freight operators would have to pay to save the infrastructure operator money.

 

[kevin_roche]

The claim for higher capacity was because some time ago in the past, they hoped that ETCS moving block would be soon practical. But this hasn’t happened.

With ETCS Level 2 it is also possible to have signals at green instead of yellow prior to red signal. The train can slow down later in the middle of a block rather than at the start. This means that sometimes a new movement authority for the next block can be issued when the red ahead turns green and train never has to slow down.

 

[Harpo]

ETCS has many advantages including lower installation costs compared to lights on sticks and it takes away signalling’s impact on line speeds.

ETCS can mimic moving block as it does in the Thameslink core with lots of short detection sections which don’t impact on line speeds in the way that closing-up signals do.

 

[Taunton]

A prerequisite for moving block(i.e. a movement authority to an "arbitrary point") is that trains have to continually monitor the position of their rear end in a safety-compliant way, which is particularly complex in the case of goods trains; without that you can't safely set a route to anywhere except a axle counter/track circuit boundary. No-one has yet implemented or even attempted to implement a system of this kind in a main line application.

USA has for quite some time had Smart End Of Train Device on freight trains, which communicates electronically from the last vehicle to the locomotive. Actually quite clever - the batteries are charged by a small turbine which taps brake line pressure.

End-of-train device - Wikipedia

en.wikipedia.org