Signalling Questions

[futureA]

So I understand many of basic concepts behind signaling such as blocks ect but what I want to know is how is a trains route managed throughout it's journey? How do signallers identify trains and how do they know where to send them? Also how was this done in the age before electronics? And do trains sometimes get sent to incorrect destinations?

Sorry if this is a duplicate post.

 

[edwin_m]

So I understand many of basic concepts behind signaling such as blocks ect but what I want to know is how is a trains route managed throughout it's journey? How do signallers identify trains and how do they know where to send them? Also how was this done in the age before electronics? And do trains sometimes get sent to incorrect destinations?

Sorry if this is a duplicate post.

I'll try to tackle the modern situation first.

Since about the 1960s every train has carried a "headcode" or "train description" comprising a number, letter, number, number. The first digit denotes the type of train and the letter gives some idea of the destination or route. There aren't enough codes to give each train a unique one but the assignment tries to ensure that there is no duplication in a particular control area.

The panel signal boxes built from the 60s onwards were fitted with "train describer" systems. There is a display near each signal, either on the main panel or a separate screen, that shows the headcode of the train (if there is one) approaching that signal. When the train passes the signal the system notes the occupation of the next track and "steps" the description to the next signal (according to which route is set, if there is more than one). There are facilities to edit discriptions manually but when a train enters or leaves the area of control the description is automatically transmitted between signalling centres. Signallers can also view maps of wider areas showing train desriptions and positions, and this is also the means by which train running information is fed to passenger information systems.

From around 1990 most new signalling centres used VDU displays instead of panels, but included the same train desciber functionality. Some of the larger centres have Automatic Route Setting, which can set routes for most trains depending on their position, the position of other trains, and the timetable. In others, including all the panel boxes, signallers have to know the route the train takes from the train description and the working timetable, and set it up manually.

In traditional signalling none of this exists (although a traditional box acting as a "fringe box" to a signalling centre will have a terminal to enter data into the train describer). The signalman asks the next signalman to confirm the line is clear by means of a code on the box to box bell, and different codes are used according to the type of train. For boxes on the approach to major junctions there would often be different bell codes for each route. The signalmen at these boxes would determine the route of an approaching train by means including listening out for the driver sounding a particular whistle sequence, or in some regions and eras reading the description that was displayed on the front of the locomotive. In very complex and busy areas electromechanical train describers were used to indicate the route of the train approaching a particular signal box.

 

[Cherry_Picker]

Some of the stuff is available online.

http://www.opentraintimes.com/maps/signalling/me_1

This display isn't a million miles from what they see on the screens at Marylebone IECC

 

[Millisle]

I don't know if trains still get sent to the wrong destination, but they used to. In the early '60s my brother and sister were sent off on the Rosyth Dockyard line instead of North Queensferry. The driver reversed, presumably without contacting the signalman who meantime corrected the route with the train foul and it was derailed.
Perhaps thirty five years ago I was on a train to Inverness from Edinburgh, before the Ladybank Hilton reroute, and it pulled up at Carmuirs East. I looked out the droplight as one did (happy days!) and the signal was pulled off for Carmuirs West, viz Glasgow, rather than correctly Larbert Junction, viz Stirling. The driver stopped at the incorrect signal and sounded the horn until the correct route was given.

 

[tsr]

I don't know if trains still get sent to the wrong destination, but they used to. In the early '60s my brother and sister were sent off on the Rosyth Dockyard line instead of North Queensferry. The driver reversed, presumably without contacting the signalman who meantime corrected the route with the train foul and it was derailed.
Perhaps thirty five years ago I was on a train to Inverness from Edinburgh, before the Ladybank Hilton reroute, and it pulled up at Carmuirs East. I looked out the droplight as one did (happy days!) and the signal was pulled off for Carmuirs West, viz Glasgow, rather than correctly Larbert Junction, viz Stirling. The driver stopped at the incorrect signal and sounded the horn until the correct route was given.

A train can still be given a "wrong-route", yes. The driver must make efforts to spot the wrong route and stop at the signal before the route diverges if it is possible to do so. Additionally, guards/conductors will be briefed during route learning as to which routes they may use and what signal indications are correct at each station from which they dispatch trains.

The modern way for drivers to deal with this will usually be to advise the signaller by phone if the route is suspected of being set incorrectly. Generally some form of in-cab radio (eg. GSMR) will be used, or signal post telephones (SPTs) if not. Obviously if the train has actually entered the incorrect route then there may also be further action taken to correct this. On some lines this may be to proceed until the next point at which the train can join the correct route; on others the train may not be cleared for certain routes, so at some point once the risks are assessed and options taken into account, the service would need to return to the point at which it is cleared to operate.

Setting a wrong route can happen for a number of reasons and is usually down to failings/oversight/problems at some level of Network Rail equipment or personnel (on the National Rail network), but if the driver or guard/conductor was able to react to the route being set incorrectly but mistakenly did not, this will be investigated as the "wrong route being given and taken" (or similar) and blame may also be apportioned to them.

 

[QueensCurve]

I don't know if trains still get sent to the wrong destination, but they used to. In the early '60s my brother and sister were sent off on the Rosyth Dockyard line instead of North Queensferry. The driver reversed, presumably without contacting the signalman who meantime corrected the route with the train foul and it was derailed.
Perhaps thirty five years ago I was on a train to Inverness from Edinburgh, before the Ladybank Hilton reroute, and it pulled up at Carmuirs East. I looked out the droplight as one did (happy days!) and the signal was pulled off for Carmuirs West, viz Glasgow, rather than correctly Larbert Junction, viz Stirling. The driver stopped at the incorrect signal and sounded the horn until the correct route was given.

I have personally observed 3 instances of trains being routed wrongly.

First was at Dundee just after commissioning of the new signalling in 1985. An Aberdeen - Glasgow train was running through the downside platform (common then to allow a parallel dep to Edinburgh). The platform staff did the train ready to start bit and wondered why the signal at the end of the platform was not pulled off. I had observed the up direction signal from the down through line pulled off with the "feather". Eventually the platform staff observed this and got on the phone to the signalling centre who dropped back and set the correct route.

Second was a Reading around 1990 give or take a year or two. On a sunday Trains to Bristol Temptation were diverted via Westbury. I boarded one such and the signal pulled off for the Down fast (Main in GW-speak). Since the driver departed I thought the diversion had been terminated early. Having gone onto the Down Fast the train stopped and had to set back.

Third was at Crewe in November 2003. I was changing there on a journey from Bath to Penrith there. Two trains were due to stop on the "up side" one for Manchester, one for Glasgow. The first appeared on Platform 1 so I assumed it was the Manchester. It was however announced as the Glasgow. I queried this with the platform staff who said it was for Glasgow. I queried it again on the train and more reassuringly was told it was the Glasgow. This was just after introduction of the "super" Voyagers so no droplight to check the signal. We departed on the Manchester route and again had to set back departing about 23 mins late in the end.

In both the last two instances on-train announcements attributed the error to a "signalman's mistake". I think the bigger mistake is made by the driver who should know the road and who departed despite the signal clearly indicating that the wrong route was set.

Oh for the return of the the droplight That alas has gone for ever.

 

[edwin_m]

Some years ago I was on a Nottingham train that was sent down the Derby route at Trent South. The speeds on the two routes were both about 60mph so no approach control or flashing aspects were provided, and the first indication to the driver of the wrong route would be on seeing the junction signal. Not surprisingly the train was only stopped at the next signal beyond, and after some delay it set back cautiously to the junction to resume the correct route.

This was one of the few trains that ran from London to Leeds via Nottingham instead of via Derby as most of them did (and still do). I suspect the reason for the error was it having a headcode indicating a Leeds destination, and the signaller forgetting this one didn't take the usual route.

 

[Tio Terry]

Modern systems use Automatic Route Setting Equipment (ARS), the E is usually left off for obvious reasons. This uses the train code that is input by the signaller before the train starts it's journey. The system knows where the train is going and how it is meant to be routed, it will automatically set the route and signal the train without any further signaller input. It only makes a mistake if it's programmed wrongly in the first instance.

The future Traffic Management System (TMS) has even more intelligence. If you tell it a certain piece of infrastructure is not available - say a points failure - it will automatically start to re-route services to avoid the problem and to calculate the effect on services so that delays can be anticipated. This is all to reduce Signaller workload and improve efficiency. It's been in use in Japan on their commuter routes for some time.

 

[driver_m]

I have personally observed 3 instances of trains being routed wrongly.

First was at Dundee just after commissioning of the new signalling in 1985. An Aberdeen - Glasgow train was running through the downside platform (common then to allow a parallel dep to Edinburgh). The platform staff did the train ready to start bit and wondered why the signal at the end of the platform was not pulled off. I had observed the up direction signal from the down through line pulled off with the "feather". Eventually the platform staff observed this and got on the phone to the signalling centre who dropped back and set the correct route.

Second was a Reading around 1990 give or take a year or two. On a sunday Trains to Bristol Temptation were diverted via Westbury. I boarded one such and the signal pulled off for the Down fast (Main in GW-speak). Since the driver departed I thought the diversion had been terminated early. Having gone onto the Down Fast the train stopped and had to set back.

Third was at Crewe in November 2003. I was changing there on a journey from Bath to Penrith there. Two trains were due to stop on the "up side" one for Manchester, one for Glasgow. The first appeared on Platform 1 so I assumed it was the Manchester. It was however announced as the Glasgow. I queried this with the platform staff who said it was for Glasgow. I queried it again on the train and more reassuringly was told it was the Glasgow. This was just after introduction of the "super" Voyagers so no droplight to check the signal. We departed on the Manchester route and again had to set back departing about 23 mins late in the end.

In both the last two instances on-train announcements attributed the error to a "signalman's mistake". I think the bigger mistake is made by the driver who should know the road and who departed despite the signal clearly indicating that the wrong route was set.

Oh for the return of the the droplight That alas has gone for ever.

You are also showing a lack of knowledge on that last wrong route. If you had route knowledge of platform 1 at Crewe. You would know that you depart on a signal with no route indicator. The signal AFTER has the route indicator on it and at that point it is probably too late to stop in time.

 

[hounddog]

You are also showing a lack of knowledge on that last wrong route. If you had route knowledge of platform 1 at Crewe. You would know that you depart on a signal with no route indicator. The signal AFTER has the route indicator on it and at that point it is probably too late to stop in time.

That's a point that has often puzzled me. Why is the route indicator not placed at a point far enough before the junction that the train can stop before it gets there?

 

[LowLevel]

Some years ago I was on a Nottingham train that was sent down the Derby route at Trent South. The speeds on the two routes were both about 60mph so no approach control or flashing aspects were provided, and the first indication to the driver of the wrong route would be on seeing the junction signal. Not surprisingly the train was only stopped at the next signal beyond, and after some delay it set back cautiously to the junction to resume the correct route.

This was one of the few trains that ran from London to Leeds via Nottingham instead of via Derby as most of them did (and still do). I suspect the reason for the error was it having a headcode indicating a Leeds destination, and the signaller forgetting this one didn't take the usual route.

That's an age old problem at that location. Leeds via Nottingham services run with 1Dxx or 1Bxx headcodes rather than 1Fxx or 1Cxx to try and mitigate against it.

 

[cool110]

That's a point that has often puzzled me. Why is the route indicator not placed at a point far enough before the junction that the train can stop before it gets there?

There are preliminary route indicators that go between signals but they're not that common as most junctions are dealt with by approach release and flashing aspects.

 

[hounddog]

There are preliminary route indicators that go between signals but they're not that common as most junctions are dealt with by approach release and flashing aspects.

I've no idea whether that answers my question. Do approach release and flashing aspects give a driver enough time to stop if the route is set wrong? If not why isn't there a system that does?

 

[MarkyT]

I've no idea whether that answers my question. Do approach release and flashing aspects give a driver enough time to stop if the route is set wrong? If not why isn't there a system that does?

You can't rely on there being sufficient time for all train types in either case. At some fast junction sites, preliminary route indicators (PRI) have been used before the splitting distant or flashing yellow approaches to ensure drivers know sufficiently far in advance that they CAN stop before the junction. These have been provided on very busy lines where mis-routing could result in a train of a non-permitted type being sent along a particular line or where backing up and routing correctly again would be particularly disruptive. An examples is Heathrow airport junction on the GWML, where only the Heathrow Express and Connect electric units are permitted on the branch, and they would quickly run out of juice if incorrectly routed to Slough. Shortlands in south London near Bromley is another, where freights are banned via Herne Hill and must run via Catford. Before HS1, the junction used by Eurostar from the SE main line towards the tunnel was also provided with PRIs, which are probably still there but no train routinely takes the tunnel route anymore (freights turn off further back into Dollands Moor yard).

 

[driver_m]

That's a point that has often puzzled me. Why is the route indicator not placed at a point far enough before the junction that the train can stop before it gets there?

If you specifically mean platform 1 at Crewe then I'be honestly no idea why there are two signals. I'd have thought one at the platform north end would be sufficient but there'll be some sighting or interlocking reason why. If you mean in general though you'd lose far too much capacity by having huge overlaps after signals. The only time I've known a problem with wrong routing on the routes I sign was Colwich before the Primary Route Indicators got put in. They were able to show green aspects in either direction for a short time and wrong routing did occur.

 

[Lockwood]

The panel signal boxes built from the 60s onwards were fitted with "train describer" systems. There is a display near each signal, either on the main panel or a separate screen, that shows the headcode of the train (if there is one) approaching that signal. When the train passes the signal the system notes the occupation of the next track and "steps" the description to the next signal (according to which route is set, if there is more than one). There are facilities to edit discriptions manually but when a train enters or leaves the area of control the description is automatically transmitted between signalling centres. Signallers can also view maps of wider areas showing train desriptions and positions, and this is also the means by which train running information is fed to passenger information systems.

How did the signalling centre know that 1P12 was 1P12? Was it fed from a timetable?
I can't imagine that a 4CIG would have had a transponder broadcasting a headcode and that being picked up by something trackside.

Working on the assumption that it is using naïve information from the timetable...
If a train was going along and something activated a track circuit a few sections up (say you have circuits A,B,C,D,E... the train is going from A to Z, is currently in C and something activates E or F), so it is a section you would reasonably expect this train to occupy on its route. Would the panel show C and E as both occupied by the same headcode? Would it assume that the train jumped from C to E missing D, and that C is no occupied by the next service due?

 

[driver_m]

I've no idea whether that answers my question. Do approach release and flashing aspects give a driver enough time to stop if the route is set wrong? If not why isn't there a system that does?

To answer that question, typically it should. Approach control means you're being brought down to a red, so you should be in a position to stop anyway. It's always drummed into us to not assume that the signal will come off.

Flashing aspects, this is your route knowledge coming into play. If I get flashing yellows South of Tamworth on the down fast. I know I'm going on the slow lines. If I have to stop at Tamworth or Lichfield I must get these signals. Greens are no good in that situation. However, if I'm not stopping there, it just means I'm probably going lose a few minutes as it doesn't affect my stopping pattern. Hope this helps.
--- old post above --- --- new post below ---

How did the signalling centre know that 1P12 was 1P12? Was it fed from a timetable?
I can't imagine that a 4CIG would have had a transponder broadcasting a headcode and that being picked up by something trackside.

Working on the assumption that it is using naïve information from the timetable...
If a train was going along and something activated a track circuit a few sections up (say you have circuits A,B,C,D,E... the train is going from A to Z, is currently in C and something activates E or F), so it is a section you would reasonably expect this train to occupy on its route. Would the panel show C and E as both occupied by the same headcode? Would it assume that the train jumped from C to E missing D, and that C is no occupied by the next service due?

It will have been put in at the originating signalbox. It would then pass via train describers. It would have been entered manually for example at the old Euston box then passed on accordingly to Wembley, Watford etc etc.

 

[matchmaker]

I was on a Glasgow - Stirling service, years ago. As we were passing through Castlecary I noticed that the signal was showing green, rather than flashing double yellow. On went the brakes and the driver brought the train to a halt at the next signal - also showing green. The driver got down and there followed what appeared to be a fairly animated conversation on the signal post telephone with the signaller at Greenhill, who had obviously routed us towards Edinburgh, rather than the approach controlled Stirling turnoff!

 

[rebmcr]

How did the signalling centre know that 1P12 was 1P12? Was it fed from a timetable?
I can't imagine that a 4CIG would have had a transponder broadcasting a headcode and that being picked up by something trackside.

The signalling berth at the originating terminal platform is programmed when the unit enters service, and then the track occupancy carrries it forward through the signalling panels. If it's lost en-route for whatever reason, it can be manually re-entered into an intermediate berth (with the aid of the WTT).

 

[edwin_m]

How did the signalling centre know that 1P12 was 1P12? Was it fed from a timetable?
I can't imagine that a 4CIG would have had a transponder broadcasting a headcode and that being picked up by something trackside.

Working on the assumption that it is using naïve information from the timetable...
If a train was going along and something activated a track circuit a few sections up (say you have circuits A,B,C,D,E... the train is going from A to Z, is currently in C and something activates E or F), so it is a section you would reasonably expect this train to occupy on its route. Would the panel show C and E as both occupied by the same headcode? Would it assume that the train jumped from C to E missing D, and that C is no occupied by the next service due?

When everything works normally the description is stepped along automatically as the train moves.

An unexpected track circuit occupation probably wouldn't cause a legitimate train description to go to the wrong place, but it might cause a "non-described alarm" and a dummy description where there was no train. A genuine description will usually over-write any non-legitimate descriptions.

If a train has to pass over a track circuit showing as occupied with no train present, then the description may be left behind and need to be re-inserted manually at the next signal.

 

[urpert]

Shortlands in south London near Bromley is another, where freights are banned via Herne Hill and must run via Catford. Before HS1, the junction used by Eurostar from the SE main line towards the tunnel was also provided with PRIs, which are probably still there but no train routinely takes the tunnel route anymore (freights turn off further back into Dollands Moor yard).

Thanks for this. I'd been wondering for years what made Shortlands Jn special enough to merit a PRI.

 

[DerekC]

How did the signalling centre know that 1P12 was 1P12? Was it fed from a timetable?
I can't imagine that a 4CIG would have had a transponder broadcasting a headcode and that being picked up by something trackside.?

The headcode is now entered by the driver into the GSM-R terminal at login together with the signal berth the train is standing at (or in some cases a special GSM-R location code). This is transferred by GSM-R to the signalling centre and arms the train describer, which then tracks the train as it moves along, as described by others.

 

[Tomnick]

The headcode is now entered by the driver into the GSM-R terminal at login together with the signal berth the train is standing at (or in some cases a special GSM-R location code). This is transferred by GSM-R to the signalling centre and arms the train describer, which then tracks the train as it moves along, as described by others.

I'm not aware of any way in which GSM-R registration has any effect upon the train describer. Indeed, registration usually fails if the headcode hasn't already been interposed into the relevant berth!

 

[driver_m]

I'm not aware of any way in which GSM-R registration has any effect upon the train describer. Indeed, registration usually fails if the headcode hasn't already been interposed into the relevant berth!

I was just thinking that myself. Trying to register your GSM at the wrong location code (such as a different numbered signal or platform that the code corresponds to) will result in a fail to register.

 

[Sunset route]

The headcode is now entered by the driver into the GSM-R terminal at login together with the signal berth the train is standing at (or in some cases a special GSM-R location code). This is transferred by GSM-R to the signalling centre and arms the train describer, which then tracks the train as it moves along, as described by others.

No it's the other way round when a driver inputs his train ID it goes looking at our train describer and when the two agree the GSM-R sets up, I've lost count of the amount of times where a driver has called me with a failed set up because I've either had the wrong ID in the TD berth or haven't got round to putting the new outward bound ID in.

 

[LowLevel]

I'm glad I wasn't the only one who found it a bit odd - when I worked on a station and had access to CCF or P2 we quite frequently had to nudge the panel to correct the head codes as it buggered up the departure boards as well - the head codes/TDs on stabled trains were there long before any driver turned up and set up the cab.

 

[MarkyT]

I'm glad I wasn't the only one who found it a bit odd - when I worked on a station and had access to CCF or P2 we quite frequently had to nudge the panel to correct the head codes as it buggered up the departure boards as well - the head codes/TDs on stabled trains were there long before any driver turned up and set up the cab.

There is data in the national timetable database for when a particular terminating train is supposed to form the next outgoing service from the same platform under a different headcode. In some cases this information is visible online through Realtime Trains. Automatic route setting (ARS) uses that data routinely to change the headcodes automatically. Some more modern train describers also do this at boxes where there's no ARS. The process can be upset fairly easily however if sets stray from their planned diagrams due to late running or failure and when other spare sets are substituted for the departure from a different platform. I think the ARS and TD systems are intelligent enough to not try and implement a planned automatic substitution where the new headcode has already been used (i.e set up manually elsewhere by the signaller) but I believe there remain some scenarios where the incorrect information can still be interposed automatically under such very short notice real time changes.

 

[zuriblue]

What about when you have a box interfacing between a Signalling Centre/ IECC and Absolute Block? Above it says that the box will have a terminal to input the headcode, what if the signaler needs to send another code (worst case Obstruction Danger)? Would this be a hot key on the terminal or does the IECC still have Block Bells?

 

[Tomnick]

There'll usually be an emergency alarm, with its own dedicated control, or an emergency block bell in a fringe box.

 

[carriageline]

Our workstations have a button for the emergency alarm on the screen, which interfaces with a alarm NX button on panel in the associated box.