Could an anchor system help stop trains in an emergency?

[RichSwitch]

Moderator note: Split from

Incident at Talerddig, Wales - 21/10/2024

Two trains have collided at Talerddig, Wales. Both trains are reported to be Class 158s running in 2 car sets. (Source, Realtime trains) At this time this is a developing situation and not all details are out in the open. The trains involved are believed to be: 1S71 Machynlleth to Shrewsbury...

www.railforums.co.uk

I have plenty of questions about incidents such as this, and how to consider them holistically.

I don’t know much about the signalling in operation here, but I’d caution against any system/process that results in the driver looking down at a display more often than they are looking out of a window.

My main focus would be on studying wheel slide, the development of novel systems to prevent it, and the development of ‘last ditch’ systems that could be deployed in an emergency.

My initial thought is whether some sort of anchor-drag that drops from the underneath of the train might slow it enough in an emergency. OK, it might damage the sleepers, but surely a damaged sleeper or fifty is better than a broken train.

That’s for the engineers to think about. I’m just a HF person.

Importantly, my thoughts are with those involved and person who sadly lost their life afterwards.

 

[Fragezeichnen]

My main focus would be on studying wheel slide, the development of novel systems to prevent it, and the development of ‘last ditch’ systems that could be deployed in an emergency.

My initial thought is whether some sort of anchor-drag that drops from the underneath of the train might slow it enough in an emergency. OK, it might damage the sleepers, but surely a damaged sleeper or fifty is better than a broken train.

Most multiple units and coaches in mainland Europe are fitted with magnetic track brakes which hang between the wheels and use magnetic force to clamp tightly directly the track in an emergency when regular wheel braking is not sufficient.
I've never got a clear answer as to why they aren't fitted in the UK - some sort of regulation, or just "not invented here"?

 

[Snapper37]

Most multiple units and coaches in mainland Europe are fitted with magnetic track brakes which hang between the wheels and use magnetic force to clamp tightly directly the track in an emergency when regular wheel braking is not sufficient.
I've never got a clear answer as to why they aren't fitted in the UK - some sort of regulation, or just "not invented here"?

I believe they were invented here. Westinghouse London patented it.

 

[Western 52]

Most multiple units and coaches in mainland Europe are fitted with magnetic track brakes which hang between the wheels and use magnetic force to clamp tightly directly the track in an emergency when regular wheel braking is not sufficient.
I've never got a clear answer as to why they aren't fitted in the UK - some sort of regulation, or just "not invented here"?

I think some trams have this?

 

[norbitonflyer]

My initial thought is whether some sort of anchor-drag that drops from the underneath of the train might slow it enough in an emergency. OK, it might damage the sleepers, but surely a damaged sleeper or fifty is better than a broken train.

Could make matters worse if the damage to the track derials the train

 

[Killingworth]

Could make matters worse if the damage to the track derials the train

And even if it does stop the train it destroys the track for several days before repair!

 

[AndrewE]

I think some trams have this?

I think it depends on having lots of current available from OLE... you wouldn't carry a battery round just for this job, and you can't really design a brake system which puts a diesel engine into overdrive just because an emergency brake application has been made - and that's assuming it has a big generator fitted in the absence of electric transmission!

 

[Tramfan]

I think some trams have this?

The Tyne & Wear Metro units certainly have emergency track brakes, which do get used sometimes during autumn where particularly poor rail adhesion is encountered.

 

[bahnause]

I think it depends on having lots of current available from OLE... you wouldn't carry a battery round just for this job, and you can't really design a brake system which puts a diesel engine into overdrive just because an emergency brake application has been made - and that's assuming it has a big generator fitted in the absence of electric transmission!

The vehicle battery does the job.

 

[Bletchleyite]

Most multiple units and coaches in mainland Europe are fitted with magnetic track brakes which hang between the wheels and use magnetic force to clamp tightly directly the track in an emergency when regular wheel braking is not sufficient.
I've never got a clear answer as to why they aren't fitted in the UK - some sort of regulation, or just "not invented here"?

They're normally sometimes eddy current brakes that don't actually contact the track but instead induce a magnetic force using electrical currents.

Trams usually have contact magnetic brakes. The downside of these is that they can cause track damage if activated unnecessarily, and could cause problems if engaged across pointwork.

 

[hexagon789]

They're normally eddy current brakes that don't actually contact the track but instead induce a magnetic force using electrical currents.

No, they are proper track brakes.

Only a limited number of high-speed trains such as the German ICE 3 and previously certain Japanese Shinkansen have/had Eddy Current brakes, not hauled coaches or ordinary multiple units.

 

[Bletchleyite]

No, they are proper track brakes.

Only a limited number of high-speed trains such as the German ICE 3 and previously certain Japanese Shinkansen have/had Eddy Current brakes, not hauled coaches or ordinary multiple units.

Thanks.

There's an interesting thread on them here:

Why don't trains in Great Britain use eddy current brakes?

As I understand it, eddy current brakes have been routinely fitted to trains running in Germany since the 1990s. This technology uses an electromagnet to induce an electric field in the rails, the resistance of which produces braking force. Unlike the emergency electromagnet 'track brakes'...

www.railforums.co.uk

 

[tram21]

I think some trams have this?

Yes, all trams in the UK certainly have this, partially as an 'emergency brake' to stop quicker due to being near traffic etc., and also to help when wheels slide which they often do on tram systems which often have steep gradients and frequent stop/ starts which makes them more prone to wheel slips

 

[Lemmy282]

The Tyne & Wear Metro units certainly have emergency track brakes, which do get used sometimes during autumn where particularly poor rail adhesion is encountered.

All modern UK trams have some form of track brake, either magnetic or just pure force, along with sanding equipment. It is nothing new, as far back as the early 1900's trams were so equipped.

 

[edwin_m]

Yes, all trams in the UK certainly have this, partially as an 'emergency brake' to stop quicker due to being near traffic etc., and also to help when wheels slide which they often do on tram systems which often have steep gradients and frequent stop/ starts which makes them more prone to wheel slips

The track brake on trams is usually referred to as the Hazard Brake, and because of the abrupt deceleration it is considered hazardous to any passenger who is standing up and not holding on. It should not be used if driving normally, only if something unexpected happens such as another road user swerving into the path of the tram.

I'd say trams are very sure-footed compared with trains. They have more motored axles, and normally use electric braking which can be controlled more finely than air brakes. I was involved when some colleagues were testing the Bombardier trams in Croydon in 1998. They fitted dispensers for soapy water dispensing that would reliably slip a train but it was almost impossible to make the tram slip, even after the sanders were disabled.

 

[43096]

My main focus would be on studying wheel slide, the development of novel systems to prevent it, and the development of ‘last ditch’ systems that could be deployed in an emergency.

The main focus should be on dealing with the source problem. In other words, cutting the trees down.

 

[spellbound330]

As far as I’m aware they can’t cut the trees down, because trees act as a natural flood defence by absorbing water from the ground. They also help keep the ground stable, so removing trees could inadvertently lead to more problems such as landslides.

 

[Harpo]

What are the impacts on signalling systems of powerful magnetic forces on or around the railhead?

It’s something that might suit a small standalone single-tech, undetected network but might not suit a spawling network with diverse piecemeal-engineered tech.

 

[507020]

My main focus would be on studying wheel slide, the development of novel systems to prevent it, and the development of ‘last ditch’ systems that could be deployed in an emergency.

My initial thought is whether some sort of anchor-drag that drops from the underneath of the train might slow it enough in an emergency. OK, it might damage the sleepers, but surely a damaged sleeper or fifty is better than a broken train.

That’s for the engineers to think about. I’m just a HF person.

This seems like an immediately good idea. It wouldn’t work on slab track, but given the design of sleepers, especially the stronger concrete ones, it should be possible to drop something quickly between them that catches them and stops the train at the next sleeper, preventing it colliding with either another train or an animal/tree/car or any other obstruction that may cause death or injury otherwise, if wheel-based braking is ineffective.

And even if it does stop the train it destroys the track for several days before repair!

Surely this is totally irrelevant. A derailment also destroys the track. A collision of this kind closes the line for a very long time while the emergency services, RAIB, coroner etc carry out their investigations.

If any piece of equipment is able to prevent a collision between 2 trains, or a train and another object that prevents human injury or death, even at the expense of sacrificing a short section of track, the resulting renewals would consume vastly less resources than the alternative.

Although damaged rolling stock can be removed, access to some locations with a crane may be too difficult, requiring it to be cut up on site. Even if it can be moved by rail, the repairs will take more than days, if it isn’t written off and with the precarious state of nearly every DMU fleet, may make it impossible to run a full service on other lines.

I think it depends on having lots of current available from OLE... you wouldn't carry a battery round just for this job, and you can't really design a brake system which puts a diesel engine into overdrive just because an emergency brake application has been made - and that's assuming it has a big generator fitted in the absence of electric transmission!

This would explain why these systems can be used on most trains in Europe, which are electric, but not most trains here. I’ve been on an M5000 that made an emergency brake application, meaning the magnetic track brake was used, because otherwise it would have hit a pedestrian.

It isn’t even sacrificing the railhead, because the damage is relatively minor compared to dragging something into the road surface for a tram or between sleepers.

Sacrificial braking techniques which destroy the infrastructure to preserve life and even rolling stock which doesn’t have to be repaired if it hasn’t been in a collision, are definitely an area of research.

Have we seen those circular saw brake cartridges, which will destroy the blade to stop it if it detects it has come into contact with skin? The idea is just that but scaled up.

 

[bahnause]

This seems like an immediately good idea. It wouldn’t work on slab track, but given the design of sleepers, especially the stronger concrete ones, it should be possible to drop something quickly between them that catches them and stops the train at the next sleeper, preventing it colliding with either another train or an animal/tree/car or any other obstruction that may cause death or injury otherwise, if wheel-based braking is ineffective.

Surely this is totally irrelevant. A derailment also destroys the track. A collision of this kind closes the line for a very long time while the emergency services, RAIB, coroner etc carry out their investigations.

If any piece of equipment is able to prevent a collision between 2 trains, or a train and another object that prevents human injury or death, even at the expense of sacrificing a short section of track, the resulting renewals would consume vastly less resources than the alternative

It is only irrelevant if the system is used exclusively to avoid an otherwise certain collision. However, it is also likely to be triggered in other cases, whether due to a technical fault or a misjudgement on the part of the operator. Even the magnetic rail brake should only be used in emergencies, due to the high level of wear and tear.

 

[MarkyT]

What are the impacts on signalling systems of powerful magnetic forces on or around the railhead?

It’s something that might suit a small standalone single-tech, undetected network but might not suit a spawling network with diverse piecemeal-engineered tech.

Eddy current brakes on some ICE trains caused problems with inductive axle counter wheel sensors initially I recall, but they solved that by some means. Axle counters are very common in Germany, having been the default train detection system for many decades. The friction type rail brakes by contrast are not designed to create a large changing field around the rails to induce eddy currents so shouldn't have the same problem and their wide historic use in Germany, with all it's axle counters, suggests that is the case.

 

[bahnause]

Eddy current brakes on some ICE trains caused problems with inductive axle counter wheel sensors initially I recall, but they solved that by some means. Axle counters are very common in Germany, having been the default train detection system for many decades.

A lot of the equipment had to be replaced, not only parts of the signalling and safety systems, but as well parts of metallic pieces like covers of points. The track has to be able to disperse the heat generated by the eddy current brakes (slab track). Use of the eddy current brake as a service brake is therefore only allowed on the newer HSL and as an emergency brake on some other lines (sometimes with speed restrictions). On many lines, the use is not allowed at all.

 

[Snow1964]

There is a grant to a company called Rivelin in todays DfT announcement regarding understanding low friction on rail

Friction measurements from our new on-board (vehicle-based) system will allow safe and efficient rail inspection, to improve safety, reduce delays, and prevent wheel/rail damage. This will identify low friction "hotspots" and assess whether current management methods (such as the £64 million/year spent on rail cleaning) are effective. The on-board system reduces the requirement for in-person inspection and the numerical data will be used for more informed decisions on friction management.

Company : Rivelin Rail

Transport Research Innovation Grant (TRIG): funding winners

Projects receiving Transport Research Innovation Grant funding since 2014.

www.gov.uk

 

[Annetts key]

What are the impacts on signalling systems of powerful magnetic forces on or around the railhead?

It’s something that might suit a small standalone single-tech, undetected network but might not suit a spawling network with diverse piecemeal-engineered tech.

Yes, extensive research and testing would be needed before any stock fitted with such a system would be allowed on Network Rail lines. The cost means that it's only really an option for brand new trains.

In terms of signalling equipment that would have to be proven not to be affected we have each and every version/type of track circuit, axle counter, AWS, TPWS, ATP, balises, point operating equipment (some types use magnetic sensors to detect the position of the switch rails), treadles, HABD etc.

As for the original question about an anchor-drag system. As well as damage to the sleepers, the possible damage to the rails and rail fixings also has to be considered. Also, not all track is conventional sleepers, over some bridges and in some other areas, the rails are on longitudinal timbers that have either wood or steel spacers/bars to hold the track to gauge.

Plus level crossings and point work or diamond crossings.

And then there's the potential damage to the signalling equipment that is mounted in the middle of the track (four foot).

So although it sounds simple, there is a lot that someone has to investigate before we even get to the thinking about how to fit to a train. And what work would be needed to existing stock.

 

[MarkyT]

Yes, extensive research and testing would be needed before any stock fitted with such a system would be allowed on Network Rail lines. The cost means that it's only really an option for brand new trains.

In terms of signalling equipment that would have to be proven not to be affected we have each and every version/type of track circuit, axle counter, AWS, TPWS, ATP, balises, point operating equipment (some types use magnetic sensors to detect the position of the switch rails), treadles, HABD etc.

As for the original question about an anchor-drag system. As well as damage to the sleepers, the possible damage to the rails and rail fixings also has to be considered. Also, not all track is conventional sleepers, over some bridges and in some other areas, the rails are on longitudinal timbers that have either wood or steel spacers/bars to hold the track to gauge.

Plus level crossings and point work or diamond crossings.

And then there's the potential damage to the signalling equipment that is mounted in the middle of the track (four foot).

So although it sounds simple, there is a lot that someone has to investigate before we even get to the thinking about how to fit to a train. And what work would be needed to existing stock.

It's a bizarre notion dragging an unconstrained anchor device under or behind a train, bouncing around, smashing up track, cables, equipment including on the underside of the train itself, flailing wildly from side to side before briefly establishing a hold on a random something then immediately destroying it, flinging debris everywhere. Something that grips the firmly secured rails better is a more elegant solution. Eddy current brakes seem a nightmare electrically, but simple friction rail brakes for emergency use, with magnetic hold down are unlikely to affect signalling beyond possibly axle counter sensors on the track the train is on currently, and the most likely result is section occupied with a miscount due to the additional metal masses detected in the flange zone. That might even be considered a protective benefit as the section may remain occupied even if the train slips completely clear of its boundaries (including if derailed). An inherent 'slide interrupter'.

Edit - Notes:
1. A rail brake might be christened a 'rail anchor' if someone was looking for a snappy product name.
2. A marine anchor system used in an emergency derives almost all its stopping power from the length of chain dragging on the bed of the waterbody rather than the traditional anchor itself, with much unseen damage to the bed and its inhabitants.
3. Eddy current brakes work most efficiently at higher speed and their retardation drops to near zero as speed approaches zero, so they're not suitable for low speed emergency stops, and must be supplemented by other systems for a complete practical vehicle braking system.

 

[HSTEd]

Most multiple units and coaches in mainland Europe are fitted with magnetic track brakes which hang between the wheels and use magnetic force to clamp tightly directly the track in an emergency when regular wheel braking is not sufficient.
I've never got a clear answer as to why they aren't fitted in the UK - some sort of regulation, or just "not invented here"?

The RSSB did a study on the installation of magnetic track brakes on new train fleets in the UK (T1099), its downloadable with an account.
It decided there were probably no technical showstoppers but the business case wasn't amazing - although they noted that the model did not capture the benefits of preventing some large catastrophic accident in the future.

Installing them on all new trains was estimated to only cost £10m per year.
I think there is little reason not to proceed, especially with all the new trains that will be needed in the future.

 

[Russel]

The main focus should be on dealing with the source problem. In other words, cutting the trees down.

Agreed.

This thread is looking for a complex and expensive solution to a problem that can be solved with a chainsaw.

 

[RGM654]

Do we actually know whether the leaves that (apparently) caused this incident were from trees on the land within the railway's fenced area or from further away?

 

[HSTEd]

Agreed.

This thread is looking for a complex and expensive solution to a problem that can be solved with a chainsaw.

It can be solved with a chainsaw and a lot of expensive staff time.

A technical solution on the train itself could well end up being cheaper for this reason.
The £10m a year the RSSB is proposing to fit all new trains with track brakes won't pay for much at all in the way of vegetation clearance, but would more or less eliminate this problem in the long term.

Something like 20% of the entire rolling stock fleet is due for replacement in the next few years, at least. Expressed as a fraction of the trains most vulnerable to this (short formations in rural areas) it will be a rather large fraction.

 

[43096]

It can be solved with a chainsaw and a lot of expensive staff time.

A technical solution on the train itself could well end up being cheaper for this reason.
The £10m a year the RSSB is proposing to fit all new trains with track brakes won't pay for much at all in the way of vegetation clearance, but would more or less eliminate this problem in the long term.

Something like 20% of the entire rolling stock fleet is due for replacement in the next few years, at least. Expressed as a fraction of the trains most vulnerable to this (short formations in rural areas) it will be a rather large fraction.

Vegetation clearance needs to be done regardless: as well as the obvious risk from leaves, it needs to be cleared to avoid fouling the loading gauge, prevent signal sighting issues and avoiding risks to trackside staff. You cannot just get rid of the need for clearing it.