Axle Counters ( Railbuses )

[sheff'd victoria]

On Saturday 3rd January the late running 1520 Cleethorpes - Sheffield Midland via Brigg service was put on the 1750 Leeds semi fast service ( Normally a booked 158 ), when this train get to Leeds it then makes a service to Nottingham, at Sheffield Midland the unit was changed again for a 158 as it became clear that 142/143/144's are banned south of Chesterfield due to axle counters.

Can someone throw some more light on this issue and are there any other parts of the next work where pogo stick railbuses are ( Not cleared ) banned due to this axle counter situation ?

 

[northwichcat]

I'm not sure if 'banned' is the correct word. To be banned they need to have failed to obtain clearance like is the case on the Buxton line. Have Northern ever tried to get clearance for Pacers to Nottingham? If not they are 'not cleared' rather than 'banned.'

 

[MarkyT]

I would be very surprised if this was true. It is true that Recent Nottingham area resignalling uses axle counters widely instead of track circuits (except in Nottingam station platforms according to the sectional appendix), but pacers of various types work over axle counters in many other places, the Dawlish sea wall area down here in Devon amongst them.

Historically, track circuits were more of a problem. When they were first introduced, Pacers, or Skippers in the west country, were not trusted to operate old fashioned battery powered low voltage DC track circuits reliably. All track circuits of that type where the units were expected to run had to be modified to use a higher rail voltage. In Devon those old tracks circuits were all replaced later by more modern designs with Exeter resignalling, but there are bound to be a few remaining in mechanical box areas in Cornwall and elsewhere around the UK.

 

[edwin_m]

Stoke-on-Trent was the first large-scale use of axle counters and I believe Pacers operate there from time to time.

A 158 with a lower axleload, disc brakes and a very smooth ride would be much more likely to "disappear" from track circuits than a Pacer. All modern DMUs on the network are now fitted with track circuit actuators.

I can confirm track circuits in Nottingham station. I believe the reason is that some platforms have several track circuits, and fitting axle counters here would mean putting a detector head in the platform itself. They apparently sometimes get confused if a train stops with a wheel over them.

 

[The Planner]

Indeed as that caused problems for the Coventry resignalling a while back.

 

[HSTfan!!!]

Pacers work just fine in South Wales over axle counter areas?

 

[MarkyT]

A 158 with a lower axleload, disc brakes and a very smooth ride would be much more likely to "disappear" from track circuits than a Pacer. All modern DMUs on the network are now fitted with track circuit actuators.

And these can be supplemented by a trackside widget called a TCAID (Track Circuit Assistor Interference Detector) in places where track circuit operation is still a problem. At the run on end of the section, this device detects the frequencies emitted by a TCA and creates a supplementary controlled short across the rails, further reducing the total shunt resistance and intending to greatly increase likelihood of successful safe operation.

I found a rssb steering group remit for TCA/TCAID systems here:

http://www.rssb.co.uk/library/research-development-and-innovation/research-brief-T893.pdf

I would agree about a smooth riding 158 or similar, but I think perhaps the very small number of axles on a 2 car pacer would have been seen to pose be the greater risk - i.e only 4 axles would have to fail to shunt rather than all 8 on a bogie 2 car unit. A single 153 car on the other hand . . .

I can confirm track circuits in Nottingham station. I believe the reason is that some platforms have several track circuits, and fitting axle counters here would mean putting a detector head in the platform itself. They apparently sometimes get confused if a train stops with a wheel over them.

Right side failures* are still common where a wheel stops directly above the inductive sensors. For this reason I understand Thameslink have also elected to retain track circuits on their core section, where there are multiple split sections along the platforms too (to allow closely following headway in that case rather than for multiple short trains stopped along the same platform as at Nottingham).

* the section remains indicating occupied with no train present and the whole time consuming rigmarole of reset and restore has to be carried out, not what you want at a major station.

 

[edwin_m]

And these can be supplemented by a trackside widget called a TCAID (Track Circuit Assistor Interference Detector) in places where track circuit operation is still a problem. At the run on end of the section, this device detects the frequencies emitted by a TCA and creates a supplementary controlled short across the rails, further reducing the total shunt resistance and intending to greatly increase likelihood of successful safe operation.

I found a rssb steering group remit for TCA/TCAID systems here:

http://www.rssb.co.uk/library/research-development-and-innovation/research-brief-T893.pdf

I would agree about a smooth riding 158 or similar, but I think perhaps the very small number of axles on a 2 car pacer would have been seen to pose be the greater risk - i.e only 4 axles would have to fail to shunt rather than all 8 on a bogie 2 car unit. A single 153 car on the other hand . . .

I was involved in a small way in TCA and TCAID when I worked for BR Research. They were trying to make it more reliable even then, part of the problem being the need to minimise consumption so it would work through the autumn months on one battery. The would then be removed, stored and serviced the following summer ready for another season in service. While a TCA will overcome a certain amount of contamination it won't deal with continuous leaf film but a TCAID can detect the TCA current induced into the rail even when the wheels are fully insulated from it. I think they're fitted every hundred metres or so, not just at the ends of the track circuit.

The track circuit issue was "out there somewhere" with the 150s but didn't become really serious until the 158s came along - for a time they were only allowed out if paired with an older unit and some units were half a 158 with half a 156. The decision was then made to fit TCA to all Sprinters and Pacers but I think 158s were prioritised.

Incidentally automatic sanding systems were fitted most units from about 2000 onwards but were not allowed on four-axle units (153s and Pacers) until quite recently because of concern about dispensing too much sand and becoming invisible to track circuits. These trains, being short and often on lightly-used routes, were probably the most susceptible of any to poor adhesion.

 

[MarkyT]

I think they're fitted every hundred metres or so, not just at the ends of the track circuit.

That makes sense to maintain occupancy throughout a section especially for leaf fall areas which can be many hundreds of metres long through cuttings.

The track circuit issue was "out there somewhere" with the 150s but didn't become really serious until the 158s came along - for a time they were only allowed out if paired with an older unit and some units were half a 158 with half a 156. The decision was then made to fit TCA to all Sprinters and Pacers but I think 158s were prioritised.

Shows how good the 158 and derivative designs were with regard to bogie, suspension and wheel profile design with consequent smooth ride characteristics. I've always liked them from my first ride.

It's noticable where they run to the exclusion of other designs that the wheel treads tend to track a very fine consistent path along the railhead, the rest of which, if not ground away by wheels of other trains remains heavily rusted. Therein lies a particular risk as if the contact point moves from its regular position for any reason, the wheels can easily be running on rust, which, if dry, can be a good insulator. An example of this is Exeter - Salisbury, normally only worked by 159s. Recent resignalling employed axle counters throughout however so there shouldn't be any problems in this reapect any more.

Incidentally automatic sanding systems were fitted most units from about 2000 onwards but were not allowed on four-axle units (153s and Pacers) until quite recently because of concern about dispensing too much sand and becoming invisible to track circuits.

Thanks for that info I was not aware of until now. Makes a lot of sense, but how is the risk controlled now? conductive sand?

As I said in another thread, track circuits are a nightmare and axle counters are a much better modern solution to train detection, but they still are susceptible to that awkward miscount problem when a wheel stops right above a sensor. It's always a right side failure (falsely occupied), but that's still a real problem, as operations are limited thence until the section can be reset safely. Nottingham seems a sensible compromise: Axle counters for the majority on plain line and through junctions; track circuits just through the long station platforms where split sections are provided to assist permissive movements and sharing.

 

[edwin_m]

As I said in another thread, track circuits are a nightmare and axle counters are a much better modern solution to train detection, but they still are susceptible to that awkward miscount problem when a wheel stops right above a sensor. It's always a right side failure (falsely occupied), but that's still a real problem, as operations are limited thence until the section can be reset safely. Nottingham seems a sensible compromise: Axle counters for the majority on plain line and through junctions; track circuits just through the long station platforms where split sections are provided to assist permissive movements and sharing.

Agreed. Also the platform track circuits are fairly short, which makes them less prone to failures than longer ones.

 

[northwichcat]

Stoke-on-Trent was the first large-scale use of axle counters and I believe Pacers operate there from time to time.

Pacers aren't cleared to Stoke for 2 reasons:
1. Manchester-Stoke services are timetabled for 90mph EMU running and a 75mph DMU can't fill in without delaying a later Virgin or XC service, so Stoke (and Hadfield) services have priority for 323s if there's a shortage.
2. There's a platform clearance issue with Pacers at one or more of the stations between Macclesfield and Stoke.

 

[The Planner]

Incorrect, Class 142, 143 and 144 are cleared between Cheadle Hulme and Stoke station. Just because they don't fit in a timetable is not a reason for not being cleared!

 

[northwichcat]

Incorrect, Class 142, 143 and 144 are cleared between Cheadle Hulme and Stoke station. Just because they don't fit in a timetable is not a reason for not being cleared!

I meant they aren't cleared to run Manchester-Stoke services because they are too slow and can't stop at one or more stations due to a clearance issue. I was responding to a comment where edwin_m implied Northern use 142s on Stoke services, yet apart from an early morning Macclesfield-Manchester service they never operate on that line.

ATW were refused permission to operate 158s on Bidston-Wrexham and Conwy Valley services because they need longer dwell times at stations than 150s but that doesn't mean a 158 can't run on those lines but it does mean ATW can't run timetabled services on those lines using 158s.

 

[edwin_m]

The comment arose from a question on technical compatibility of Pacers with the signalling, which could be a safety issue. The fact they are used, however occasionally, confirms they are officially "cleared" for the route and no such safety problem exists.

 

[northwichcat]

The fact they are used, however occasionally, confirms they are officially "cleared" for the route and no such safety problem exists.

Can you tell me exactly when you've seen a 142 in Stoke in passenger service? I've just asked a Piccadilly conductor who confirmed my thoughts that 142s are never used to Glossop/Stoke. Also that if a 323 on a Glossop/Stoke diagram fails and there isn't a spare one, a replacement 142/150 is put on to an Alderley Edge/Airport service in place of a 323 to free up a 323 for Glossop/Stoke. He should know considering he signs the route!

 

[carriageline]

I meant they aren't cleared to run Manchester-Stoke services because they are too slow and can't stop at one or more stations due to a clearance issue. I was responding to a comment where edwin_m implied Northern use 142s on Stoke services, yet apart from an early morning Macclesfield-Manchester service they never operate on that line.

ATW were refused permission to operate 158s on Bidston-Wrexham and Conwy Valley services because they need longer dwell times at stations than 150s but that doesn't mean a 158 can't run on those lines but it does mean ATW can't run timetabled services on those lines using 158s.

I don't think you understand. They are CLEARED for the route, but that doesn't mean they will operate on it.

 

[northwichcat]

I don't think you understand. They are CLEARED for the route, but that doesn't mean they will operate on it.

edwin_m says he thinks they are occasionally used on the route.

I believe Pacers operate there from time to time.

The fact they are used, however occasionally

I think he's either seen a Pacer between Macclesfield and Cheadle Hulme and wrongly assumed it's a service to/from Stoke or seen a Pacer at or near Stoke at some point (possibly when they were moved to and from FGW) and assumed it's arrived there on a Manchester-Stoke passenger service.

I'm also still doubtful if they are in fact cleared for the service even if time constraints weren't an issue as I've heard there's at least one station between Macclesfield and Stoke Pacers can't stop at due to a clearance issue. The Northern conductor I just asked about the route said he didn't know whether that was or wasn't the case.

 

[The Planner]

I'm also still doubtful if they are in fact cleared for the service even if time constraints aren't an issue as I've heard there's at least one station between Macclesfield and Stoke Pacers can't stop at due to a clearance issue. The Northern conductor I just asked about the route said he didn't know whether that was or wasn't the case.

Sectional appendix shows them route cleared as I said earlier with no notes on platform restrictions, therefore if someone wanted to run one to Stoke from Manchester they can.

 

[carriageline]

Sectional appendix shows them route cleared as I said earlier with no notes on platform restrictions, therefore if someone wanted to run one to Stoke from Manchester they can.

I got a feeling he thinks cleared means they run, or will run on service on that route!

 

[northwichcat]

I got a feeling he thinks cleared means they run, or will run on service on that route!

I responded to your earlier post and you obviously can't be arsed to read it or any of the posts edwin_m posted.
--- old post above --- --- new post below ---

Sectional appendix shows them route cleared as I said earlier with no notes on platform restrictions, therefore if someone wanted to run one to Stoke from Manchester they can.

OK so if there were clearance issues then they were rectified.

The problem with a 142 actually getting to Stoke would still be no 75mph path except possibly for an ECS.

 

[edwin_m]

I don't have any knowledge of whether they operate to Stoke, thought I read it on here somewhere but I may be wrong. However if The Planner confirms they are cleared that's good enough for me, as the question relates to whether they can operate rather than whether they do.

 

[MarkyT]

Agreed. Also the platform track circuits are fairly short, which makes them less prone to failures than longer ones.

Good point. Shorter tracks are easier to keep in adustment through all weather conditions, and a major station is likely to be well drained and free of leaf contamination.