Train GraphicClick on the map to explore geographics
 
I need help
FAQ
Emergency
About .
Travel & transport from BBC stories as at 08:55 28 Mar 2024
* Easter travel warning as millions set to hit roads
- Man suffers life-threatening injuries after train stabbing
Read about the forum [here].
Register [here] - it's free.
What do I gain from registering? [here]
 02/06/24 - Summer Timetable starts
17/08/24 - Bus to Imber
27/09/25 - 200 years of passenger trains

On this day
28th Mar (1988)
Formal end to carrying coffins by BR (link)

Train RunningCancelled
06:57 Swansea to London Paddington
07:28 London Paddington to Bristol Temple Meads
07:43 Swansea to London Paddington
08:18 London Paddington to Cardiff Central
08:30 London Paddington to Weston-Super-Mare
09:00 Bristol Temple Meads to London Paddington
09:12 London Paddington to Cardiff Central
09:29 Weston-Super-Mare to London Paddington
09:30 London Paddington to Bristol Temple Meads
10:15 London Paddington to Cardiff Central
10:30 London Paddington to Weston-Super-Mare
10:41 Cardiff Central to London Paddington
11:00 Bristol Temple Meads to London Paddington
11:16 London Paddington to Cardiff Central
11:23 Weston-Super-Mare to London Paddington
11:30 London Paddington to Bristol Temple Meads
11:50 Cardiff Central to London Paddington
12:15 London Paddington to Cardiff Central
12:30 London Paddington to Weston-Super-Mare
Short Run
05:40 Bristol Temple Meads to Penzance
06:38 Weymouth to Gloucester
06:48 Cheltenham Spa to London Paddington
06:54 Taunton to London Paddington
07:12 London Paddington to Cardiff Central
08:25 Okehampton to Exeter Central
08:34 Exeter Central to Okehampton
08:38 London Paddington to Westbury
09:50 Cardiff Central to London Paddington
10:50 Penzance to Cardiff Central
Delayed
05:03 Penzance to London Paddington
05:23 London Paddington to Swansea
05:33 Plymouth to London Paddington
05:55 Plymouth to London Paddington
06:00 London Paddington to Penzance
06:50 Westbury to Weymouth
08:03 London Paddington to Penzance
08:30 Liskeard to Looe
09:04 London Paddington to Plymouth
An additional train service has been planned to operate as shown 09:13 Bristol Temple Meads to Gloucester
09:37 London Paddington to Paignton
10:04 London Paddington to Penzance
10:23 London Paddington to Oxford
10:35 London Paddington to Exeter St Davids
PollsOpen and recent polls
Closed 2024-03-25 Easter Escape - to where?
Abbreviation pageAcronymns and abbreviations
Stn ComparatorStation Comparator
Rail newsNews Now - live rail news feed
Site Style 1 2 3 4
Next departures • Bristol Temple MeadsBath SpaChippenhamSwindonDidcot ParkwayReadingLondon PaddingtonMelksham
Exeter St DavidsTauntonWestburyTrowbridgeBristol ParkwayCardiff CentralOxfordCheltenham SpaBirmingham New Street
March 28, 2024, 08:56:44 *
Welcome, Guest. Please login or register.

Login with username, password and session length
Forgotten your username or password? - get a reminder
Most recently liked subjects
[146] West Wiltshire Bus Changes April 2024
[117] would you like your own LIVE train station departure board?
[80] Return of the BRUTE?
[63] Infrastructure problems in Thames Valley causing disruption el...
[49] Reversing Beeching - bring heritage and freight lines into the...
[27] CrossCountry upgrade will see 25% more rail seats
 
News: the Great Western Coffee Shop ... keeping you up to date with travel around the South West
 
   Home   Help Search Calendar Login Register  
Pages: [1]
  Print  
Author Topic: Track circuits explained  (Read 1809 times)
grahame
Administrator
Hero Member
*****
Posts: 40687



View Profile WWW Email
« on: April 25, 2019, 21:20:39 »

Track circuits explained ... by Network Rail

Quote
What are track circuits? How do they keep the railway safe? And why do they sometimes delay journeys?

A track circuit forms part of the broader signalling system, which comprises many parts to enable trains to move safely around the network.

A track circuit itself is an electrical system that detects the absence of a train on a section of track. This information then helps the signalling system know if it’s safe for another train to proceed.

etc

Good article (I think) providing just the sort of FAQ (Frequently Asked Questions) data we should be carrying on the Coffee Shop
Logged

Coffee Shop Admin, Acting Chair of Melksham Rail User Group, Option 24/7 Melksham Rep
bobm
Administrator
Hero Member
*****
Posts: 9809



View Profile
« Reply #1 on: April 25, 2019, 21:34:09 »

I wonder how much of the railway operates with track circuits and how much now uses axle counters?
Logged
johnneyw
Transport Scholar
Hero Member
******
Posts: 2257


From station to station, back to Bristol city....


View Profile
« Reply #2 on: April 25, 2019, 21:35:56 »

Track circuits explained ... by Network Rail

Quote
What are track circuits? How do they keep the railway safe? And why do they sometimes delay journeys?

A track circuit forms part of the broader signalling system, which comprises many parts to enable trains to move safely around the network.

A track circuit itself is an electrical system that detects the absence of a train on a section of track. This information then helps the signalling system know if it’s safe for another train to proceed.

etc


Good article (I think) providing just the sort of FAQ (Frequently Asked Questions) data we should be carrying on the Coffee Shop

Agreed and helps inform me of the very basics of a complex but personally, interesting subject.
Logged
MVR S&T
Transport Scholar
Hero Member
******
Posts: 438


View Profile
« Reply #3 on: April 25, 2019, 21:50:32 »

Further reading on track circuits at:

http://www.irse.org/minorrailways/publicdocuments/TC01%20v1-0%20DC%20Track%20Circuits.pdf

Page six has the basic circuit.

And they scale down to 7.25 inch too:

http://www.moorsvalleyrailway.co.uk/pages/signalling
Logged
rower40
Transport Scholar
Sr. Member
******
Posts: 292

Turning signalling into a video game since 1988.


View Profile
« Reply #4 on: April 26, 2019, 12:24:26 »

I wonder how much of the railway operates with track circuits and how much now uses axle counters?
For the bits of the GW (Great Western) controlled from TVSC» (Thames Valley Signalling Centre - about) at Didcot:
Paddington to Airport Junction, and Airport Junction to Heathrow: Track Circuits
Airport Junction to ... everywhere else: Axle Counters.
Except the B&H (Berks and Hants - railway line from Reading to Taunton via Westbury) (Berks and Hants) from Hungerford to Westbury (the non-electrified bit) still uses Track Circuits.
And a few track circuits still exist on fringes to other signalling centres, and depots/yards etc.

Logged
Bmblbzzz
Transport Scholar
Hero Member
******
Posts: 4256


View Profile
« Reply #5 on: April 27, 2019, 19:24:05 »

I spy Filton Bank!
Logged

Waiting at Pilning for the midnight sleeper to Prague.
paul7575
Transport Scholar
Hero Member
******
Posts: 5316


View Profile
« Reply #6 on: April 27, 2019, 20:48:16 »

If I understand it correctly though, as far as the overall signalling system is concerned the Axle Counter train detection is logically used in the same way as Track Circuit train detection?

The sections of railway with Axle Counters are still operated under track circuit block regulations, so they don’t in themselves make a massive operating change?

Paul
Logged
rower40
Transport Scholar
Sr. Member
******
Posts: 292

Turning signalling into a video game since 1988.


View Profile
« Reply #7 on: April 30, 2019, 16:54:35 »

If I understand it correctly though, as far as the overall signalling system is concerned the Axle Counter train detection is logically used in the same way as Track Circuit train detection?

The sections of railway with Axle Counters are still operated under track circuit block regulations, so they don’t in themselves make a massive operating change?

Paul
Exactly so ... right up to the moment that a count of axles goes wrong, and the counter has to be reset.  Then there's a whole host of procedures to be followed, which have changed and evolved over the years.  Many of which have to be implemented in the interlocking logic and the control system.  As a technician-initiated reset is no longer allowed, the signaller has to reset the counter, then allow a "sweep train" through the section to prove that it's now clear.  The Sweep train is authorised past the entry signal at danger.

More complex yet if the axle counter section contains pointwork.  Because then the sweep train may have only proved that PART of the axle counter section is free from obstruction.

Logged
bobm
Administrator
Hero Member
*****
Posts: 9809



View Profile
« Reply #8 on: April 30, 2019, 19:59:11 »

What are the advantages with axle counters?  Are they easier to maintain than track circuits?
Logged
bradshaw
Transport Scholar
Hero Member
******
Posts: 1450



View Profile
« Reply #9 on: April 30, 2019, 20:49:53 »

Found this just now
https://www.arema.org/files/library/2010_Conference_Proceedings/Axle_Counters_vs_Track_Circuits-Safety_in_Track_Vacancy_Detection_and_Broken_Rail_Detection.pdf

As I see it the axle counter is a digital device whilst track circuits rely on a voltage drop which could vary for a number of reasons. One example was the introduction of Sprinter Cl 15x on the line between Castle Cary and Yeovil Pen Mill. While the old dmus operated the track circuits properly the 15x Sprinters would not always operate them leading to them disappearing from ‘view’. Additional electronics were needed to get a reliable operation.
Logged
SandTEngineer
Hero Member
*****
Posts: 3485


View Profile
« Reply #10 on: April 30, 2019, 21:24:19 »

Now, where are the S&T (Signalling and Telegraph) when you need them........oh....... Grin

The are many types of track circuits, varying from very simple DC (Direct Current) operated ones to very complex Coded Digital ones.  Each type has it plusses and minuses (too complex to explain here).  There is one thing to be clear on though, and that is they are not guaranteed to detect a broken rail.  This is often quoted as being their advantage over axle counters.  The rail bonding rules are very complex and generally these days there is a huge risk from ending up with parallel bonding, in particular in electrified areas.  Track Circuits also have a high maintenance requirement (rail bonding, rail chair insulations, insulated rail joints etc.).  Hence the move towards axle counters.
Logged
Reginald25
Transport Scholar
Hero Member
******
Posts: 301


View Profile
« Reply #11 on: May 01, 2019, 19:18:02 »

Now, where are the S&T (Signalling and Telegraph) when you need them........oh....... Grin

The are many types of track circuits, varying from very simple DC (Direct Current) operated ones to very complex Coded Digital ones.  Each type has it plusses and minuses (too complex to explain here).  There is one thing to be clear on though, and that is they are not guaranteed to detect a broken rail.  This is often quoted as being their advantage over axle counters.  The rail bonding rules are very complex and generally these days there is a huge risk from ending up with parallel bonding, in particular in electrified areas.  Track Circuits also have a high maintenance requirement (rail bonding, rail chair insulations, insulated rail joints etc.).  Hence the move towards axle counters.
I find the coded AC Track circuits fascinating, they work in a completely different way (I think!) to the DC relay based ones that are usually described in general information documents. They all seem to work so credit is due to the technicians.
Logged
Do you have something you would like to add to this thread, or would you like to raise a new question at the Coffee Shop? Please [register] (it is free) if you have not done so before, or login (at the top of this page) if you already have an account - we would love to read what you have to say!

You can find out more about how this forum works [here] - that will link you to a copy of the forum agreement that you can read before you join, and tell you very much more about how we operate. We are an independent forum, provided and run by customers of Great Western Railway, for customers of Great Western Railway and we welcome railway professionals as members too, in either a personal or official capacity. Views expressed in posts are not necessarily the views of the operators of the forum.

As well as posting messages onto existing threads, and starting new subjects, members can communicate with each other through personal messages if they wish. And once members have made a certain number of posts, they will automatically be admitted to the "frequent posters club", where subjects not-for-public-domain are discussed; anything from the occasional rant to meetups we may be having ...

 
Pages: [1]
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.2 | SMF © 2006-2007, Simple Machines LLC Valid XHTML 1.0! Valid CSS!
This forum is provided by customers of Great Western Railway (formerly First Great Western), and the views expressed are those of the individual posters concerned. Visit www.gwr.com for the official Great Western Railway website. Please contact the administrators of this site if you feel that the content provided by one of our posters contravenes our posting rules (email link to report). Forum hosted by Well House Consultants

Jump to top of pageJump to Forum Home Page