Track Circuits (rural, mainline, metro)

[RailProject]

Hi all,
I'm new here! I am a University student studying electronic and electrical engineering. I am currently doing a project titled: Monitoring systems for Rail Networks. The task is to find a new innovative way of track signaling and locating trains.

I am having trouble finding out some specific information regarding current methods revolving around track circuits.

I would like to find out the number of track circuits employed around the UK and IF possible where these are located (i.e. rural, mainline, metro)

If anyone has any of these stats I would greatly appreciate this.

Thanks a lot!

[Shed Cat]

Welcome Railproject.

What sources have you already tried?

[RailProject]

I've tried quite a lot of websites, many of them not too good.

I did however find the following site to be good, having a lot of useful statistics I can use:
http://www.railway-technical.com/index.shtml

Most of my research has been through the internet. I have emailed Network Rail asking for any statistics they can share about trach circuits/signaling methods.

Can you suggest any useful sites?

Thanks!

[Shed Cat]

Give up on the internet except to look for companies who might take pity on a poor student and help out.
Which are the signalling equipment supply and installing companies? e.g. Westinghouse, Plessy, GEC (must be more modern ones)

Which are the key Journals in S&T ?

This lot might help............http://www.irse.org/

The Institution of Mechanical Engineers has always been very helpful to me...even though I'm not a Member.

Speaking as a fool who has done two Research Degrees in my time.......eventually there is no alternative to getting out of the armchair and going to meet people, and librarians are generally embarissingly helpful and have spent hours helping me out. (except for the Library Dragon at the NRM )

[Yorky]

I would imagine that the number would be astronomical. Then you will have to split it into ones under the wires as opposed to the more normal circuits, you may also like to check out those in wet tunnels?? The ones in Huddersfield tunnel on the right as you face it from the plaform had special dispensation to use a 4 ohm relay as opposed to the standerd which in those days was 8 ohm. This was because the ballast was always saturated and leakage occured across the sleepers etc.

[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. But it was a relief at the time just to know that this was a system fault and that there wasn't a train making a conflicting move towards me as I'd feared.

An investigation into the signal 'going back' on me gave the reason as damp ballast in the signal section in advance.

I've often wondered about whether it would be possible to use digital signals to indicate the prescence of a train in section instead of having to tweak analogue circuits all the time.

[Shed Cat]

The "obvious" way forward is to use GPS to locate every train in Britain to 1 metre accuracy in a giant computer, and do away with all trackside signals and circuiting. (You would need a transmitter at front and rear of the train so that if the tail end broke away it would be identified)

But would I have the confidence to hurtle at 125mph through busy junctions relying on a bunch of electrons in a supercomputer in Watford being right 100% of the time?

[Foghut]

The trouble is that GPS was designed for use out in the open; like in the middle of the sea or in a desert. It constantly under-performs on the railway because of steel infrastructure, tunnels, and built up areas. The satellite antenna needs to see a large part of the sky in order to perform well, and this frequently doesn't happen on a train.

If you look at the 377 fleet, which use GPS in the Selective Door Opening process, they are constantly having problems. When a train arrives at a station where the on-board GPS doesn't have a satisfactory fix it will inhibit the door release. The train then sits there for an eternity while the the driver has to manually override the system and put up a manual release. It's farcical to have a safety system that needs to be bypassed.

I believe that one day we'll be extensively using a system like ERTMS with trackside beacons and in-cab signalling, but the investment will be so large that I wouldn't hold my breath.

ERTMS website...http://www.ertms.com/2007v2/what.html

[RailProject]

Thanks for the info guys.

THe project brief our group has been given revolves around using the rails as a transmission line to send a signal down the line. When the signal hits the S/C (Train) it will reflect back to the source.

The idea is that we can then detect exactly where a train is within a section through monitoring the time taken for the reflected signal to be seen.

With this system we could also find out the speed of the trains and calculate time to enter next section etc....

[Shed Cat]

Originally Posted by Foghut

The trouble is that GPS was designed for use out in the open; like in the middle of the sea or in a desert. It constantly under-performs on the railway because of steel infrastructure, tunnels, and built up areas. The satellite antenna needs to see a large part of the sky in order to perform well, and this frequently doesn't happen on a train.

A good description, and I agree that GPS isnt anywhere up to the failsafe reliability needed on a railway. 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.

Whether that is the right way forward is another debate, of course.