Track Circuits (rural, mainline, metro)

[Dynamo]

Originally Posted by Foghut

We've been told on our NR briefing days that in future there will be a move away from track circuits towards axle counters on high speed lines, due to the signal sections being so long.

I've had personal experience of unreliable track circuits. Coming happily out of a cutting at 90 mph after travelling for over twenty miles on greens, the next signal which controlled a junction was red. There was no way I could stop in time, so that was a category B SPAD on my licence for evermore.

I lost count of the number of cat B Spads I've had. I even had one last week when a signal went to red against me as I was approaching it because of a power surge at the signalbox controlling it. Its the cat A ones you gotta worry about.

I remember when the old chestnut of leaves on the line first made an appearance in the newspapers. I'm pretty sure it was something to do with the Pacer trains that had just been introduced. When I first learned the 143's, they had some sort of a track circuit booster fitted to them because the engineers figured they'd have trouble activating track circuits because the vehicles were so light and only had four wheels per unit. Unfortunately the booster system proved to be unreliable and units were disappearing from the signallers panels because of the leaves which is the reason why there were so many problems.

You are correct about the fact that axle counting is the way that Network Rail wants to move foreward. As far as I am aware, the only section of track that actually uses this system so far is between Toton and Clay Cross Junction near Chesterfield. This system is used in conjunction with a new radio system thats being introduced called IVRS (Interim Voice Radio System) which will replace the currently out of date NRN system and also be used instead of Track Circuit clips which will now become obsolete with the axle counters being used.

I am one of the few drivers on the network who has been issued with my own personal IVRS unit because I sign that particular section of track that the system is in place on. Being issued with my own personal unit is only a temporary thing because all trains will eventually have the units fitted as standard. Some have already been fitted to some Class 66's.

Here's a small report about the new masts being put up and how some people aren't very happy about them.

http://www.mastsanity.org/index.php?...=100&Itemid=44

[Foghut]

Originally Posted by Shed Cat

But give the inevitable trend in all walks of like to huge centralised automated computer control I begine to imagine the Rail Network becoming like a giant model railway - with DCC control maybe rather than Block sections signalled from the trackside.

I appreciate that this is said with an element of fun, but this is a subject that I've given quite a bit of thought to over the years, so I'll jump in and have a rant. Remote control of trains certainly works on 'closed' systems like LUL and DLR, but these are pretty simplistic arrangements and were conceived as shiny new installations. The mainline railway on the other hand still hasn't received enough money/attention just to keep it turning over in reasonable order.

Firstly of course there's unbelievable investment required for the automation itself, but much more significantly is the fact that our railway has been operating under "make do and mend" since 1945. Railstaff wrestle on a daily basis with a system which is permanently knackered. Being on the spot enables signallers/drivers/station staff/etc to step in and prevent the house of cards collapsing. Layman understandably view the railway as a large trainset, whereas it's actually unbelievably complex when lift you the lid and look at what goes on.

I think you may be right about automation and remote control - it would make financial sense to do this, but it's gonna take a while. I've got 19 years service still to go and I doubt very much whether I'll be out of a drivers job before I go (at least I b****y well hope so ).

HTH,
Foggy

[Foghut]

Originally Posted by Dynamo

I lost count of the number of cat B Spads I've had. I even had one last week when a signal went to red against me as I was approaching it because of a power surge at the signalbox controlling it. Its the cat A ones you gotta worry about.

Yup, amen to that

I remember when the old chestnut of leaves on the line first made an appearance in the newspapers. I'm pretty sure it was something to do with the Pacer trains that had just been introduced. When I first learned the 143's, they had some sort of a track circuit booster fitted to them because the engineers figured they'd have trouble activating track circuits because the vehicles were so light and only had four wheels per unit. Unfortunately the booster system proved to be unreliable and units were disappearing from the signallers panels because of the leaves which is the reason why there were so many problems.

I've heard of this, the legendary leaf fall 'stealth trains'

I am one of the few drivers on the network who has been issued with my own personal IVRS unit because I sign that particular section of track that the system is in place on. Being issued with my own personal unit is only a temporary thing because all trains will eventually have the units fitted as standard. Some have already been fitted to some Class 66's.

I've seen the IVRS units when I rode in the cab of a mate, but I didn't twig what the technology was behind them. The link mentions GSM-R masts. Does this mean that the IVRS you are using is GSM-R technology, or is it just that the people who wrote the link are having a good old rant at everything ?

Cheers,
Foggy.

[Dynamo]

I'm no expert but yeah it does seem that they are using GSM-R technology. I can think of quite a few places where the masts are going up. There's one on the up side of the main line at York Yard North is (where the junction for Clifton Loop was) for instance, and another at Thirsk. I can make a note of them when I see them if you like.

[Shed Cat]

Originally Posted by Foghut

I appreciate that this is said with an element of fun, but this is a subject that I've given quite a bit of thought to over the years, so I'll jump in and have a rant. Remote control of trains certainly works on 'closed' systems like LUL and DLR, but these are pretty simplistic arrangements and were conceived as shiny new installations. The mainline railway on the other hand still hasn't received enough money/attention just to keep it turning over in reasonable order.

Rant accepted ! My point is a bit more subtle. I am interested in failsafe and "robust" systems. Another word is "redundant", ie if any one part of a system fails, there are unused systems that will take over. The Internet is a example of a robust operating sytem.

Yet there are people and big multinational companies with commercial motives for centralising and controlling everything in the face of practical experience which says that what is being attempted is impossible e.g the NHS computer system.

So while Railproject is trying to solve the technical problem of bouncing signaling data up and down rails or catenary wires, the bigger question is whether this solution fits into a centralised or decentralised contol system.

[Foghut]

Originally Posted by Shed Cat

Rant accepted

Well thankyou

My point is a bit more subtle. I am interested in failsafe and "robust" systems. Another word is "redundant", ie if any one part of a system fails, there are unused systems that will take over.

OK, that's a very interesting view. With regard to redundancy I remember reading somewhere that in Japan their points have two sets of motors, so that if one motor stalls or fails it is clutched out, leaving the other one to continue. Diagnostic data is sent to the technicians for immediate attention.

[Yorky]

There was in the 50s talk of an experimental single tracking the service to Hull using a loop system for passing. This was to mainly operated by wireless control. I never heard any more than the rumours at York but the way it was described it sounded feasable for lightly trafficted lines.

[RailProject]

Thanks for the input from so many people, athough I would like to know what any of your thoughts are regarding the concept of our 'solution' (measuring time taken for signal to be reflected from train short-circuit)

As a group we are only about to start the design stage of this project.

Any thoughts as to what are going to be major issues regarding this method of detection?

[Foghut]

Originally Posted by RailProject

Thanks for the input from so many people, athough I would like to know what any of your thoughts are regarding the concept of our 'solution' (measuring time taken for signal to be reflected from train short-circuit)

No probelms with reliable track circuits - that can only be a good thing and I wish you well with the project.

But as future user (driver) of this system I'm afraid I feel fairly luddite about real time speed information. Given the current situation of delay attribution that already causes a Spanish Inquisition over who is to 'blame', I can only see shedloads of grief being caused a system that could be used to display running speeds.

The concept is fine, but the problem is what is done with the information. Every driver regulates his train differently according to his/her assessment of weather, adhesion conditions, braking force, etc. As is so common in British Industry, the data for delays is handled by clerks who wouldn't know the difference between a fishplate and a fish supper. They have the authority to make hell for people at the front end, and they consistently do. It can only put addtional pressure on signallers and drivers, and give rise to thousands more accountants.

(NB, this isn't paranoia about drivers having overspeed events, as trains have carried data recorders for years).

Any thoughts as to what are going to be major issues regarding this method of detection?

Well not surprisingly you've been very coy and not told us anything technical about what you will be doing. If I were to assume that you might be 'firing' very high frequency signals along the rails and measuring the 'echo' time, I would suggest that you might find alot of nasty harmonics generated by the traction packages and electric motors on the trains themselves (since even modern diesel locos use electric motors). However DSP is dead clever nowadays, so you can probably filter out the noise once you know what the nasties look like.

Hope this helps,
Foggy

[RailProject]

Originally Posted by Foghut

The concept is fine, but the problem is what is done with the information.

As a group we do not need to 'worry' too much as to what will be done with this information. The project is set up as though we have been given the task of increasing accuracy of current technology. We have also been given guidelines that suggest using the method I wrote about earlier (sending pulse....receiving reflection....)

We have decided as a group that we need to focus on a particular type of track, as they do vary quite a lot, in terms of electrification, characteristics etc.... From what I've read and looked up it seems that most mainline railway lines are powered by 25kV AC 50Hz. Am I correct in this?

As you pointed out, we would need to know the 'noise' generated by the traction systems/electric motors and also the noise generated by the electrification system. Once these are known we should theoretically be able to filter them out. I've been searching forthis info but I honestly have no idea where to start! There is just so much information around. Any pointers....

I have also been trying to find the characteristics (generally) of a railway line in terms of impedance and admittance (resistance, inductance, conductance and capacitance). With these figures we should be able to work out the 'best' frequency to send down the line.