Signalling - is there an international standard?

[whole diary]

[Mookiemoo]

Got delayed on way home tonight because of an aspect failure just before didcot........... random conversation with a north american friend of mine and I said it probably would not mean anything to him but XYZ.

Had used trains in NE corridor for years.

I made the assertion that I don't think there is an international standard for signalling......... I cant see how there can be since we have so many different types of signalling in the UK^▸ (United Kingdom)!

I stand to be proven wrong by the panel....

[Electric train]

There is ETRMS - European Rail Traffic Management System this has different levels, NR^» (Network Rail - home page) are trialling one of the levels on the Cambrian coast Crossrail will have an ETRMS signaling system.

[grahame]

There is ETRMS - European Rail Traffic Management System this has different levels, NR^» (Network Rail - home page) are trialling one of the levels on the Cambrian coast Crossrail will have an ETRMS signaling system.

I was learning last night that ETRMS will allow up to 30% additional traffic on a line, and that it's likely that it will be used on the GW^▸ (Great Western) main line (electric section) as that's resignalled for electrification.

I have a scenario where a certain section of line - 2 tracks, 7 miles long from a station where every train calls - has a projected 92% occupancy with 6 HSTs^▸ (High Speed Train) and 1 regional diesel train per hour (15x type), and without ETRMS.  At that 7 mile out point, there's a fast junction and lower occupancy beyond. A bunch of questions for the experts if I may ...
a) If I were to replace the HSTs with IEPs^▸ (Intercity Express Program / Project.) in my projection, should I expect a reduction in that 92% - any guesses how much?
b) If I considered ETRMS too, would that also give a reduction? By 30%?  By 30% of 92%?  By 30% of 85% (if that's what the switch to IEP gives)? Rather less?
c) With IEP and ETRMS, would I then have the capacity for extra (electric) trains - something like a 321?

[Phil]

Sorry, but someone had to say it.

Yes, there is an International Standard for Signalling

[eightf48544]

ERTMS^▸ (European Rail Traffic Management System.) maybe a European Standard but I don't know of an international one.

Even with ERTMS just look at the problems SNCB and NS have had implementing it on the Brussels, Antwerp, Amsterdamn high speed line. This was due to the two states implementing different versions of the software  which made it very difficult for the trains to switch over at the border.

As for capacity gains it all depends on how it is implemented. If you take TV430 French system used on  the LGV^▸ (Large Goods Vehicle) and HS1^▸ (High Speed line 1 - St Pancras to Channel Tunnel) and  which is I believe ERTMS level 1 compliant. using aprroximately 1 mile long blocks on open line and there has to be around 7 clear blocks between trains for both to travel at full speed. AT 186 mph you do a mile in around 20 seconds that so that around 2 min 33 seconds between trains or a theorectical 35 tph per line. However that is a theorectical capacity and only apply on lines many hundreds of miles long without any intermediate station stops or speed restrictions. Even then you might have a problem despatching 25 trains an hour from a terminal  station.

On the East Coasrt I once read (I believe Roger Ford Modern railways) that currently you can have two trains around Retford both doing 125 mph around 2.5 miles apart both running on green. So  around 1.25 minutes apart. But 60 mph slower so quicker braking.

1.5 minutes is certainly the rough time it takes for the autos from Maidenhead to Twyford to change from Red to Green after being passed at by an HST^▸ (High Speed Train) at 125.

So to answer Grahame's question capacity under any signalling system is a complicated mix of line speed maximum and minimum and the lengths at each speed, acceleration/braking  characteristics of the trains intermediate stations and number of trains stopping at each, number of junctions with conflicting moves plus the length of the signal sections. Plus even if you increase the capacity of your section of track you are still limited by the  capacity of the other sections of track over which the majority of the trains travel.

True moving block without defined sections is i believe still some time away. Even Docklands which is the nearest we get has around a minimum of 20 metre sections close to stations. But then it's a slow speed line.

If you are reffering to Swindon Wotton Bassett, which I make just over 5 miles, a flying /burrowing junction at Wotton Basset would considerably increase capacity. As would an extra platform at Swindon to allow the  slower 321 to be passed by the IEP^▸ (Intercity Express Program / Project.) plus giving a cross platform interchange. I've got a short section of video taken at Mannheim showing this in action. ICE arriving on one side with an IC^▸ (Inter City) arriving in parallel on the other.

[paul7575]

I made the assertion that I don't think there is an international standard for signalling......... I cant see how there can be since we have so many different types of signalling in the UK^▸ (United Kingdom)!

I stand to be proven wrong by the panel....

It may look like there are many different systems, but there are really only two systems in widespread use in GB^▸ (Great Britain).  Lines are either worked using 'absolute block' (AB) regulations, or 'track circuit block' (TCB^▸ (Track Circuit Block)) regulations - everything else is a matter of detail.  Areas signalled under AB principles are those where one train at a time is basically passed from signal box to signal box.  Signals are often semaphore, but colour light equivalents may also be used, particularly where the distance from the controlling box is too far for manual operation.   In areas signalled on TCB principles, there will usually be either two, three or four aspect colour light signals, but they are just a means of reducing headways (ie allowing more trains to run closer together) - they are still all fundamentally the same system.  Some recent resignalling has introduced axle counters rather than conventional track circuits for train detection, but they are still considered to be lines under TCB regs.   

ERTMS^▸ (European Rail Traffic Management System.) is in a minority of one on the mainline, so I'd just ignore it for now.

Paul

[grahame]

As for capacity gains it all depends on how it is implemented ...

That is a fantastically thorough answer which confirms a lot of the metrics, but gives me some specific and useful timings as food for thought.  Yes indeed - it relates to acceleration characteristics too (which we don't yet have for IEP^▸ (Intercity Express Program / Project.)), it gets reduced by crossover / conflicting movements, and (yes) you have to have systems for feeding trains on and off the line section at the rate it can take.

[Rhydgaled]

So, the ERTMS^▸ (European Rail Traffic Management System.) installation on Great Western is still scheduled to be done around 2017 - 2020 then? I thought the delays experienced on the Cambrian might have knocked that date back a few years! Anyway, electrification and ERTMS fittment, perhaps Brunel's masterpiece will become the first "classic line" to permenently break the 125mph barrier and get to 140mph (BR^▸ (British Rail(ways)) did it for a while on the ECML^▸ (East Coast Main Line) didn't they, how long was it before they decided they needed cab signalling?)

Anyway, would the capacity improvments of ERTMS, including 140mph running, be enough to allow extra INTERCITY services to be added to serve Didcot and Swindon? That would mean 1tph from each of the current half hourly services to Bristol TM^‡(resolve) and Wales could ommit these places, perhaps that's where the claimed 20 min saving for Cardiff trains will come from.

[eightf48544]

Anyway, electrification and ERTMS^▸ (European Rail Traffic Management System.) fittment, perhaps Brunel's masterpiece will become the first "classic line" to permenently break the 125mph barrier and get to 140mph (BR^▸ (British Rail(ways)) did it for a while on the ECML^▸ (East Coast Main Line) didn't they, how long was it before they decided they needed cab signalling?)

BR did try 225 running on the ECML it was branded as InterCity 225 for a while. It was done by adding a flashing green to indicate next signal green. You can only effectively run at 225 on the flashing green because the next signal after a green might be double yellow, which would require a very heavy brake application to stop at the next but one signal, whereas on seeing a green the driver need only slow down to 125 to keep within a comfortable braking curve.

However even with the flasing green 225 running  is probably too fast for a single manned driver with no real non overidable train slow/stop mechanism. TPWS^▸ (Train Protection and Warning System) is only really effective up to 75mph and AWS^▸ (Automatic Warning System) can be cancelled.

Hence if ERTMS is installed with electrification then hopefully 225kph on the GWML^▸ (Great Western Main Line) will be the norm.

[eightf48544]

Paul has given a very through expalnation of AB and TCB^▸ (Track Circuit Block) inoperation in GB^▸ (Great Britain).

On thing he forgot to mention is that ours is a directional system the signal the driver receives is dependant on the route set.

Most continental (German origin) and some US systems are so called speed signalling where the driver is shown how fast to go not where he is going.

The latest German system Ks is very logical.

You get an aspect which shows you what the next signal is showing a proceed aspect or stop. In addition if required you get an indication (Upward facing triangle above signal) With a white figure giving the speed you must travel in the immediate points zone. In addition if you are required to drive at a different speed after the next signal this speed is shown in yellow in a downward facing triangle under the signal. However you normally don't know where you going you just hope the signalman has set the route correctly.

Although i did notice in February that in at least one place there was a direction angle in white screen on the signalpost. So maybe they've had problems with incorrectly set routes.

ERTMS^▸ (European Rail Traffic Management System.) is really a speed system the speed info being fed into the cab directly and not via lineside siganls. Plus an automatic safetyover-ride which makes an emergency stop if  the driver does not slow down at the appropriate rate to be at the appropriate speed when required.

[Rhydgaled]

Anyway, electrification and ERTMS^▸ (European Rail Traffic Management System.) fittment, perhaps Brunel's masterpiece will become the first "classic line" to permenently break the 125mph barrier and get to 140mph (BR^▸ (British Rail(ways)) did it for a while on the ECML^▸ (East Coast Main Line) didn't they, how long was it before they decided they needed cab signalling?)

BR did try 225 running on the ECML it was branded as InterCity 225 for a while. It was done by adding a flashing green to indicate next signal green. You can only effectively run at 225 on the flashing green because the next signal after a green might be double yellow, which would require a very heavy brake application to stop at the next but one signal, whereas on seeing a green the driver need only slow down to 125 to keep within a comfortable braking curve.

However even with the flasing green 225 running  is probably too fast for a single manned driver with no real non overidable train slow/stop mechanism. TPWS^▸ (Train Protection and Warning System) is only really effective up to 75mph and AWS^▸ (Automatic Warning System) can be cancelled.

Yeah, that's what I was refering to. Anyone know how long it lasted?

[paul7575]

It was never used in service AFAIK^▸ (as far as I know), as it was considered unsafe.  Problem is that the required sighting time/distance is clearly prorata to the speed, but then has to be at least doubled for a flashing aspect.  As you probably realise, an unlit signal is treated as red.  So a driver has to be able to see enough of the on/off cycle to realise it is the intentional flashing and not a normal green that's just failed, IYSWIM.

Paul