Pros and cons of different electrification schemes (e.g. 3rd rail / OHLE / battery power)

[Roast Veg]

I suppose you'd have to conduct trials.

Perhaps by getting two similar mocked up track sections, putting volunteers in coveralls, covering the conductive parts of the rail in paint and then asking people to cross over and over.
Then determine if the rail desgin reduces the amount of paint transfer.

I don't think you've accounted for arcing at all...

 

[edwin_m]

I don't think you've accounted for arcing at all...

Arcing basically doesn't happen at 750V.

 

[Mordac]

I thinks it’s reasonable to suggest that the ORR have developed their view following years of case law following the EaW regulations, and the rail industry not being minded to help much.

Instead of going through this rigmarole, wouldn't it be easier for Network Rail and the TOCs to lobby the Secretary of State to amend the relevant regulations to put it beyond all doubt that they were not intended to ban third rail?

 

[kieron]

But I don't think that this factor is sufficient to explain the disparity alone. If a network half the size has eight times the risk, then aren't we talking about CRE imposing something like 16 times more risk per mile than OLE...?

No it doesn't. From the description of that table you quoted (I haven't been able to find a source for the table itself), it just compares how many people were killed or injured on each part of the network.

If you made the same sort of calculation, you may well find that OHLE network in Essex is more dangerous than that in the rest of Great Britain. If this was the case, it wouldn't mean that extending the electrified network within Essex would be especially dangerous.

Third rail electrification does create risks which are different to the ones overhead electrification has. For your number to mean anything, the difference in risk to life would all have to be caused by the way the lines have been electrified. This remains to be proved.

 

[Dr Hoo]

And yet third rail electrification projects continued after the Electricity at Work regulations were promulgated and noone questioned it.
This is a later view, held by the ORR, that is not directly supported by legislation or case law.

It is not correct to say that "no-one questioned it". I can confirm that within BR there was concern that third rail was clearly outside the spirit and intent of the general Electricity at Work legislation and it was already under general Health & Safety at Work obligations to reduce risks "so far as is reasonably practicable". With the spread of dual voltage EMUs - most topically on Thameslink - and the electrification of various 'marginal' lines with relatively infrequent services (such as Braintree and Largs) on 25kV it was getting progressively harder to argue that there was no reasonably practicable alternative.

In practice very few projects 'continued'. Most of the later Southern schemes such as Hastings, East Grinstead, Weymouth and the 'Solent' lines around Fareham had already been completed or were well under way. The various bits and pieces associated with the Channel Tunnel had effectively been committed since the Treaty of Canterbury in 1986. Hooton was already electric on Merseyside with only the short extensions to Chester and Ellesmere Port to finish off.

And, as has been pointed out above, there have been plenty of other changes to legal frameworks, permissionning and standards regimes and so forth since 1989 as well.

'Case law' has moved on from a state where the tragic death of a child trespasser at a location where rail staff had made a hole on the fence for a shortcut (that I had to deal with in the 1980s) was basically shrugged off as 'one of those things' to an entirely reasonable 'ton of bricks', multi-million pound fines approach for recent railway electrocutions (regardless of system).

 

[HSTEd]

I don't think you've accounted for arcing at all...

The legal definition of low voltage is a voltage where arcing can be discounted.

This is considered to reach up to around ~1000Vdc.
Essentially if you don't touch it, you should be fine.

This is why electrical clearances for tram overhead wiring are essentially zero - clearances being for mechanical purposes.

EDIT:

One interesting question would be what time of day the tresspass fatalities occur.

Are they people on the track during the service hours or are they people on the track at 4am trying to steal cable.
Because obviously if we have a proper integration of electrical control rooms and the signal systems, we could just turn off the third rail on any track that does not have trains on it.

Or just turn down the voltage to ~120V, so it cant give a fatal shock but still gives a "you should not touch this" cue.

EDIT #2:

The other alternative is to convert to adopt a four-rail system, which can be made so that any individual rail is touch-safe.
Possibly with a referenced-to-earth 120Vac sine-wave imposed to remind people not to touch it.

 

[Bald Rick]

Instead of going through this rigmarole, wouldn't it be easier for Network Rail and the TOCs to lobby the Secretary of State to amend the relevant regulations to put it beyond all doubt that they were not intended to ban third rail?

No, because they are not for the Secretary of State to change.

 

[Mordac]

No, because they are not for the Secretary of State to change.

I apologise if I'm referring to the wrong piece of legislation, but as far as I can tell these regulations have made under Health and Safety at Work etc. Act 1974, which provides that while the Health and Safety Executive and various other quangos propose, the secretary of state is the one who has the final authority on what gets made into regulation, subject to parliamentary approval. At any rate, even if it requires primary legislation, all it would take it a one page bill to amend the Health and Safety at Work Act.

 

[aleggatta]

I suppose you'd have to conduct trials.

Perhaps by getting two similar mocked up track sections, putting volunteers in coveralls, covering the conductive parts of the rail in paint and then asking people to cross over and over.
Then determine if the rail desgin reduces the amount of paint transfer.

You would also have to assess the maintenance requirements of this type of insulator also. I've attached a photo(not mine) from a better angle, you can't see the distance between the running rail and the insulator, but assuming the inside edge has the same angle as the outside edge, the accumulation of dirt on this type/shape of insulator might result in an arc risk, that x years down the line results in multiple miles of con rail catching fire if this had a large scale deployment on an operational railway. Personally I think there might be scope for development of a fibreglass/resin wrapped con rail, top face exposed, with printed warning labels and notches every meter on the under side for a short circuiting bar to be applied in the event of emergency. Complex pointwork might be tricky and require custom fabrication, but a wrapped con rail would have the added benefit of reducing the chance of a short between running and con rail like we have seen many tin cans do!

 

[HSTEd]

You would also have to assess the maintenance requirements of this type of insulator also. I've attached a photo(not mine) from a better angle, you can't see the distance between the running rail and the insulator, but assuming the inside edge has the same angle as the outside edge, the accumulation of dirt on this type/shape of insulator might result in an arc risk, that x years down the line results in multiple miles of con rail catching fire if this had a large scale deployment on an operational railway. Personally I think there might be scope for development of a fibreglass/resin wrapped con rail, top face exposed, with printed warning labels and notches every meter on the under side for a short circuiting bar to be applied in the event of emergency. Complex pointwork might be tricky and require custom fabrication, but a wrapped con rail would have the added benefit of reducing the chance of a short between running and con rail like we have seen many tin cans do!

I'm not sure I can think of an obvious technical reason for the insulation to have to taper like that.
So I think it might just be an attempt to reduce the potential for people to catch boots on the ege of the rail, trip and drop across the top of the conductor rail/running rails - with obviously not particularly nice consequences.

Ofcourse, on new construction there is no reason the aluminium/steel portion of the conductor rail even has to be a rectangle section......

 

[Grumpy]

This is why electrical clearances for tram overhead wiring are essentially zero - clearances being for mechanical purposes.

So for short lines without freight, with trains not needing to reach any great speeds, why don't we consider putting up tram style overhead wiring on NR tracks, and use 750v dc?
Avoids the costs of achieving clearances for 25kv overhead and avoids the safety risks of third rail

 

[A0wen]

As someone who once worked around the 3rd rail, and has the scars to show for it, I marvel at how often people defend it in comparison to OLE.
Pat

It's always the way - the armchair experts who have little or no experience of the risks can't see why it's a problem.

I always liked the response the late Roy Mason, a former miner, gave when challenged over his view of a policy which would result in pit closures: "Neither you (Tam Dalyell) nor Dick Crossman have had to work down a pit as I did for 15 years. I was carried out three times on a stretcher. The price of coal is the price of pneumoconiosis and chronic bronchitis and too often the price of life itself.''

Same goes for those advocates around here of 3rd rail who don't have to work with it.

 

[Joseph_Locke]

Arcing basically doesn't happen at 750V.

So what are 750VDC trains doing to make all those flashes and that burning smell?

EDIT - BTW I think you all mean the Electricity at Work Regulations regulation 7

 

[HSTEd]

So what are 750VDC trains doing to make all those flashes and that burning smell?

Drawing an arc by breaking an extant circuit is very different from striking one across an air gap.

Unless you suggest that people near a third rail have thousands of amps flowing through them and its the cessation of that current that kills them!

It's always the way - the armchair experts who have little or no experience of the risks can't see why it's a problem.

I always liked the response the late Roy Mason, a former miner, gave when challenged over his view of a policy which would result in pit closures: "Neither you (Tam Dalyell) nor Dick Crossman have had to work down a pit as I did for 15 years. I was carried out three times on a stretcher. The price of coal is the price of pneumoconiosis and chronic bronchitis and too often the price of life itself.''

Same goes for those advocates around here of 3rd rail who don't have to work with it.

Because I understand given the catastrophic failure of the 25kV programme to deliver acceptable economic performance, its third rail or no electrification.
And given the climate imperative, that probably means line closures.

At the end of the day, third rail is only responsible for a tiny handful of FWI per year.
If doubling the number of FWI caused in third rail related electrocution incidents cut road fatalities by 0.5% by making practical high intensity services that cut road traffic - that would still be an equal trade!

 

[Dunfanaghy Rd]

It's always the way - the armchair experts who have little or no experience of the risks can't see why it's a problem.

I always liked the response the late Roy Mason, a former miner, gave when challenged over his view of a policy which would result in pit closures: "Neither you (Tam Dalyell) nor Dick Crossman have had to work down a pit as I did for 15 years. I was carried out three times on a stretcher. The price of coal is the price of pneumoconiosis and chronic bronchitis and too often the price of life itself.''

Same goes for those advocates around here of 3rd rail who don't have to work with it.

Thanks for that.
Pat

 

[Horizon22]

One interesting question would be what time of day the tresspass fatalities occur.

Are they people on the track during the service hours or are they people on the track at 4am trying to steal cable.
Because obviously if we have a proper integration of electrical control rooms and the signal systems, we could just turn off the third rail on any track that does not have trains on it.

Or just turn down the voltage to ~120V, so it cant give a fatal shock but still gives a "you should not touch this" cue.

There are very few in the middle of the night when trains aren't running. Additionally they're often going for cabinets that aren't necessarily adjacent to the trackside.

It's always the way - the armchair experts who have little or no experience of the risks can't see why it's a problem.

I always liked the response the late Roy Mason, a former miner, gave when challenged over his view of a policy which would result in pit closures: "Neither you (Tam Dalyell) nor Dick Crossman have had to work down a pit as I did for 15 years. I was carried out three times on a stretcher. The price of coal is the price of pneumoconiosis and chronic bronchitis and too often the price of life itself.''

Same goes for those advocates around here of 3rd rail who don't have to work with it.

With no offence, safety with regards to the 3rd rail has certainly increased over the past 15 years. The biggest fear for many at the moment is uncontrolled train evacuations (Lewisham etc.).

 

[O L Leigh]

No it doesn't. From the description of that table you quoted (I haven't been able to find a source for the table itself), it just compares how many people were killed or injured on each part of the network.

If you made the same sort of calculation, you may well find that OHLE network in Essex is more dangerous than that in the rest of Great Britain. If this was the case, it wouldn't mean that extending the electrified network within Essex would be especially dangerous.

Third rail electrification does create risks which are different to the ones overhead electrification has. For your number to mean anything, the difference in risk to life would all have to be caused by the way the lines have been electrified. This remains to be proved.

I too have been unable to find the table itself. I presume that it is either a printed document or an internal one for industry bodies only.

But without seeing the table itself it's hard to discount it. The ORR states that it shows an eightfold increase in risk as measured by fatalities and weighted injuries for CRE routes compared to OLE routes and cites it's source. This being the case, what else do you suppose makes the difference between the different routes?

Because obviously if we have a proper integration of electrical control rooms and the signal systems, we could just turn off the third rail on any track that does not have trains on it.

That sounds like a horribly complex and expensive solution.

Because I understand given the catastrophic failure of the 25kV programme to deliver acceptable economic performance, its third rail or no electrification.

At the end of the day, third rail is only responsible for a tiny handful of FWI per year.

Those sound like startling facts. Can you cite any sources?

If doubling the number of FWI caused in third rail related electrocution incidents cut road fatalities by 0.5% by making practical high intensity services that cut road traffic - that would still be an equal trade!

That is not an approach that the railways (nor any other industry) is permitted to take by law.

 

[HSTEd]

That sounds like a horribly complex and expensive solution.

Well there is no particular reason that, in a modern system, the electrical control room's staff cannot be colocated with the signalling staff.
Indeed I would prefer if we onyl had one combined control centre.

Those sound like startling facts. Can you cite any sources?

Find attached an FOI document I got detailing FWI incurred for different electrical systems on the railway (and it was a pain to get!)
It is slightly out of date but its the most modern data I've seen on the subject.

It apparently ran, in the years of the dataset, to 8 FWI per annum for the conductor rail network.
Well over ten percent was passengers at stations - I assume by falling onto the track?

The number of road fatalities is a matter of public record.

That is not an approach that the railways (nor any other industry) is permitted to take by law.

As a climate researcher, I am often called upon to look at things on the "system" level.
The current legal framework is not necessarily entirely fixed and unchanging.

The HSE could utilise its established authority under the EaW regulations to consider the "greater good" caused by such a situation and issue an exemption from compliance with the regulations.
Or the responsibile minister could make replacement regulations that were more explicit in this.

Or Parliament could be persuaded to make new legislation that made such a system analysis exception explicit.

 

[O L Leigh]

Well there is no particular reason that, in a modern system, the electrical control room's staff cannot be colocated with the signalling staff.
Indeed I would prefer if we onyl had one combined control centre.

It's not merely the location of the staff but the amount of switching that would be needed. Electrification sections can be quite large and may require to be kept live due to a train still quite some distance away from any given location. It also opens the door to some horrible reliability issues, such as what happens when the switches fail to make/break the circuit?

I'm also a little concerned about the message that this puts into public's mind. If they start getting used to the idea that the juice rail is generally dead/low voltage (or in other ways non-lethal) are we not likely to see people take more risks around it rather than less?

Find attached an FOI document I got detailing FWI incurred for different electrical systems on the railway (and it was a pain to get!)
It is slightly out of date but its the most modern data I've seen on the subject.

Ah!! You have the fabled Table 2.1!! Kudos, that man.

It apparently ran, in the years of the dataset, to 8 FWI per annum for the conductor rail network.
Well over ten percent was passengers at stations - I assume by falling onto the track?

The number of road fatalities is a matter of public record.

This table doesn't actually aid your case in showing either the failings of the 25kV AC OLE system nor the relative "safety" of the 750 V DC CRE system. I fear you may also be confusing the number of incidents with the measure of risk. In that table only one heading has an FWI of more than 1, and that is for adult trespassers receiving an electric shock from the CRE which scores an impressive 6.2097. More trespassers received electric shocks from the CRE than from the OLE, and it's the same for workforce electric shocks, workforce observing arcing and passengers at stations receiving electric shocks. And these are clearly not just any old accidents like falling off platforms or tripping on the stairs, but actual incidents involving the traction or non-traction electrical supply.

As a climate researcher, I am often called upon to look at things on the "system" level.
The current legal framework is not necessarily entirely fixed and unchanging.

The HSE could utilise its established authority under the EaW regulations to consider the "greater good" caused by such a situation and issue an exemption from compliance with the regulations.
Or the responsibile minister could make replacement regulations that were more explicit in this.

Or Parliament could be persuaded to make new legislation that made such a system analysis exception explicit.

Yes, but who signs it all off? Who is going to put their name to this and grant the exemptions from current standards? Or do they just insist that all new electrification schemes be completed to the safer 25kV AC OLE system? I'm not sure that, in the event of an accident involving a member of the public and the traction supply at a newly laid section of CRE, the public or the courts are necessarily going to be kind to that person.

 

[HSTEd]

I'm also a little concerned about the message that this puts into public's mind. If they start getting used to the idea that the juice rail is generally dead/low voltage (or in other ways non-lethal) are we not likely to see people take more risks around it rather than less?

This is quite a dangerous argument to make though. It can be used to argue against all manner of objectively safety improving changes.
Tresspassers are unlikely to know too much about the operation of the railway, and we have to trust the professionalism of railway staff not to go messing with it.

In the nuclear industry we put interlocks on systems but go to great lengths to prevent people treating systems in a cavalier fashion even though it should be fine 99.9% of the time.

And I've had a ~60Vdc shock, I have absolutely no desire to repeat that experience.
~120V won't kill anyone, but I very much doubt someone who recieves one will go looking for another any time soon.

Ah!! You have the fabled Table 2.1!! Kudos, that man.

It took months and asking whether I should take the case up with the ICO to get it, but I did.

This table doesn't actually aid your case in showing either the failings of the 25kV AC OLE system nor the relative "safety" of the 750 V DC CRE system. I fear you may also be confusing the number of incidents with the measure of risk.

The sum of all the FWI in the conductor rail column is ~8, as can be seen on the next page.

In that table only one heading has an FWI of more than 1, and that is for adult trespassers receiving an electric shock from the CRE which scores an impressive 6.2097. More trespassers received electric shocks from the CRE than from the OLE, and it's the same for workforce electric shocks, workforce observing arcing and passengers at stations receiving electric shocks.

As I tend to look at things from a position of societal utility, the number of incidents is less important to me than the consequences.
Turns out OLE is not so much safer in FWI terms than conductor rail for staff as it is overall- despite the lower unmber of incidents the FWI figure is much closer due to the much greater consequences of a 25kV shock.
FWI for a 25kV workforce shock is 0.17/incident, as compared ~0.1 for conductor rail. Which makes sense if you think about it.

We have people in this thread with scars from 3rd rail incidents.
Do we have any with scars from 25kV incidents?

And these are clearly not just any old accidents like falling off platforms or tripping on the stairs, but actual incidents involving the traction or non-traction electrical supply.

No, I mean passengers tripping and falling off the platform and getting a shock from the third rail.

Yes, but who signs it all off? Who is going to put their name to this and grant the exemptions from current standards? Or do they just insist that all new electrification schemes be completed to the safer 25kV AC OLE system? I'm not sure that, in the event of an accident involving a member of the public and the traction supply at a newly laid section of CRE, the public or the courts are necessarily going to be kind to that person.

The cynical voice in my mind would suggest that since a vast majority of the risk will be to tresspassers, and passenger risks are probably comparatively easy to mitigate, it would be very difficult for any victim to generate significant sympathy in the press.
And given the low (absolute) value of the risk on any given route section, in all likelihood, large scale third rail expansions will be a fait accompli.

EDIT:

Interesting that whilst a 25kV shock incident is worse for the workforce than third rail, the reverse is true for tresspassers.
I suppose a workforce shock is likely to recieve immediate medical care because its far more likely that there are people around?

 

[O L Leigh]

This is quite a dangerous argument to make though. It can be used to argue against all manner of objectively safety improving changes.
Tresspassers are unlikely to know too much about the operation of the railway, and we have to trust the professionalism of railway staff not to go messing with it.

The problem is that assuming ignorance on the part of the public is dangerous too. There is more information out there (a lot of it on this forum) than perhaps you realise, and folk are prepared to take risks to experiment with the CRE themselves. I guarantee that it wouldn't be long before some wrongheaded person works out that the juice rail is sometimes non-lethal and then the whole enterprise becomes a 750V DC game of Russian Roulette.

And I've had a ~60Vdc shock, I have absolutely no desire to repeat that experience.
~120V won't kill anyone, but I very much doubt someone who recieves one will go looking for another any time soon.

I wouldn't like to guarantee that.

I've had a belt off the control circuits of an EMU (110v DC) and I can't say it would stop me pressing the AWS reset button again. My hand tingled for a while but nothing worse.

No, I mean passengers tripping and falling off the platform and getting a shock from the third rail.

Perhaps, but that is not explicitly stated so maybe we should rule out such speculation.

The cynical voice in my mind would suggest that since a vast majority of the risk will be to tresspassers, and passenger risks are probably comparatively easy to mitigate, it would be very difficult for any victim to generate significant sympathy in the press.

Experience shows otherwise. We've had crossings closed due to misuse, including one where there had been a double-fatality that the driver involved swears was down to nothing more than horseplay. All it needs is a moderately clued-up compo lawyer to go digging into the standards and asking why CRE was laid down when it doesn't meet all the safety standards and demanding to know who granted the exemption that allowed this lethal piece of equipment to be laid where little Johnny could skateboard along trip over it.

And given the low (absolute) value of the risk on any given route section, in all likelihood, large scale third rail expansions will be a fait accompli.

Nope. Not even close. When there is such a huge disparity in the calculation of risks and where the absolute numbers of incidents are higher across a smaller network, there has to be a very convincing argument for continuing with CRE. As the ORR states in it's policy document, it's going to expect to see something spectacular if it's going to permit new schemes to go ahead and overturn it's presumption against further CRE electrification.

This is why the RSSB is consulting. It's not looking to see where CRE can be laid, as it already identifies certain schemes (including those mentioned above), but if industry can come up with proposals for systems that will permit CRE to be laid in the first place by ensuring that it can meet all the regulatory and safety requirements that will be brought to bear on such a scheme. This is a very very long way from being anything even remotely like a fait accompli.

 

[A0wen]

With no offence, safety with regards to the 3rd rail has certainly increased over the past 15 years. The biggest fear for many at the moment is uncontrolled train evacuations (Lewisham etc.).

No offence taken.

But you can argue safety around railways in general has improved in the past 15 years - the mile upon mile of pallisade fencing which protects even relatively quiet lines now is a reflection if that. So too are the closure of both foot and vehicle level crossings.

Have 3rd rail areas seen additional safety beyond that? Don't know - I'm sure somebody will be able to answer that.

The fact remains having an exposed HV power supply at foot level is dangerous to anyone in close proximity to it - and that is both people who should be there and know the risks and those who shouldn't and don't.

 

[hwl]

Have 3rd rail areas seen additional safety beyond that? Don't know - I'm sure somebody will be able to answer that.

Yes, higher risk areas for track workers are better boarded (or having the bottom yellow strips), tools and other equipment improved (e.g. more 3rd rail compatible tampers etc so less hands on work in 3rd rail area), less day time work with juice on and more night time with juice off and isolation arrangements are being improved significantly at the moment

 

[A0wen]

Because I understand given the catastrophic failure of the 25kV programme to deliver acceptable economic performance, its third rail or no electrification.

I don't think there has been a "catastrophic failure" at all - there have been cost over-runs, but the benefits of electrification, namely faster journeys, lower CO2 output etc still stand.

You're confusing project costs with economic performance - the two are quite different. The question ought to be why these projects exceeded their forecast costs and as a project manager I can safely say there are very few reasons why this can happen - specifically

- poor business case construction with flawed costs
- poor cost forecasting
- poor scope management

Every time there was a cost variance of + 5% against a line item there should have been a change request raised in order to secure the funds and ensure stakeholders were aware of the final cost position. I suspect what happened here is people kept on going on the grounds the project was "within financial authority" but it meant the project would run out of money later on. It's the wrong way to manage such things.

And given the climate imperative, that probably means line closures.

Scaremongering nonsense. This is often the problem with the environmental lobby - incessantly painting 'worst case' scenarios to scare people. You're no better than the boy who cried wolf.

At the end of the day, third rail is only responsible for a tiny handful of FWI per year.
If doubling the number of FWI caused in third rail related electrocution incidents cut road fatalities by 0.5% by making practical high intensity services that cut road traffic - that would still be an equal trade!

Comparing apples with bananas again - and you do yourself no credit for putting forward such a ludicrous proposal.

Each transport's safety case is built in relation to that mode of transport - quite rightly. Making 'x' safer is a net off for 'y' is not a place to go. Though if you'd like to, I'll happily point out that air travel is far safer than pretty much every other form of transport for distance covered, so perhaps we should all be flying more.

The issue with 3rd rail needs to be looked at - it was a system devised in the late 1800s and was rolled out in about 100 years ago by the Southern railway (and one of its predecessors) because it was cheaper than the alternatives. Safety wasn't a particular concern or focus. The reality is nowadays the risks of having exposed HV power supplies aren't acceptable. Arguing "well it only results in a tiny handful of deaths" isn't a good argument, particularly if an alternative can be seen to be safer - which with OHLE it is.

There is a role for 3rd rail - but extending it, particularly when alternatives such as battery are now becoming viable and don't have the same risks seems reckless. And if you look at the two obvious candidates - Uckfield and Ashford-Hastings - in the case of the former it's a 40 mile round trip in the case of the latter its 30 miles each way and has 3rd rail at each end. If you take the Viva Rail battery units as an example, they're quoting a 60 mile range with 7 minute recharge times. I'm not saying D train derivatives are the solution per se, but the technology exists such that a battery unit could cover these lines, recharge at Oxted in the case of Uckfield or either end in with Marshlink without the need to lay an additional mile of 3rd rail.

 

[hwl]

Some data from the tables to inform discussion:

(Average) Events per year​	OHLE​	3rd rail​	3rd rail : OHLE ratio​
Passenger stock @ station​	0.0667​	1.7109​	25.65​
Workforce arcing​	1.0857​	2.4216​	2.23​
Workforce shock​	1.4417​	3.7937​	2.63​
Adult trespasser​	1.6​	9​	5.63​
Child trespasser​	1.5429​	1​	0.65​
Other Public​	0.4286​	0.1077​	0.25​

Risk weighted FWI (average/year)​	OHLE​	3rd rail​	3rd rail : OHLE ratio​
Passenger stock @ station​	0.0075​	0.8477​	113.03​
Workforce arcing​	0.0237​	0.0528​	2.23​
Workforce shock​	0.2582​	0.3922​	1.52​
Adult trespasser​	0.6533​	6.2097​	9.51​
Child trespasser​	0.2462​	0.4024​	1.63​
Other Public​	0.0474​	0.0681​	1.44​

Passengers @ stations and adult trespassers show the biggest OHLE vs 3rd rail differences

 

[edwin_m]

The sum of all the FWI in the conductor rail column is ~8, as can be seen on the next page.

As I tend to look at things from a position of societal utility, the number of incidents is less important to me than the consequences.
Turns out OLE is not so much safer in FWI terms than conductor rail for staff as it is overall- despite the lower unmber of incidents the FWI figure is much closer due to the much greater consequences of a 25kV shock.

But the equivalent figure for OLE is ~1.2!

Taking trespassers out of the equation, as some would argue they brought it on themselves, the total FWIs are 0.3368 for OLE and 1.3608 for third rail.

The absolute FWI for workforce is still greater for third rail than for OLE. However if these figures are to be normalised, the appropriate unit for workforce figures would be route or track miles, and as the 25kV network is significantly larger this would probably eliminate the discrepancy. The other interesting figure would be individual risk per worker, but that would be difficult to establish as we don't have figures for the number of track workers on each system, and even if we did they would be complicated by factors such as workers who visit the track only occasionally and (with track workers often ranging over a wide area) those who visit OLE track and also third rail track.

 

[hwl]

Taking trespassers out of the equation, as some would argue they brought it on themselves, the total FWIs are 0.3368 for OLE and 1.3608 for third rail.

The absolute FWI for workforce is still greater for third rail than for OLE. However if these figures are to be normalised, the appropriate unit for workforce figures would be route or track miles, and as the 25kV network is significantly larger this would probably eliminate the discrepancy. The other interesting figure would be individual risk per worker, but that would be difficult to establish as we don't have figures for the number of track workers on each system, and even if we did they would be complicated by factors such as workers who visit the track only occasionally and (with track workers often ranging over a wide area) those who visit OLE track and also third rail track.

Excluding trespassers it is 4.04x.
Worker metrics are around 2x (but could have improved since as we don't quite know quite how old the figures are), the big difference is still passengers at stations in terms of de-risking opportunity after stripping out tresspassers.

 

[O L Leigh]

There is a role for 3rd rail - but extending it, particularly when alternatives such as battery are now becoming viable and don't have the same risks seems reckless. And if you look at the two obvious candidates - Uckfield and Ashford-Hastings - in the case of the former it's a 40 mile round trip in the case of the latter its 30 miles each way and has 3rd rail at each end. If you take the Viva Rail battery units as an example, they're quoting a 60 mile range with 7 minute recharge times. I'm not saying D train derivatives are the solution per se, but the technology exists such that a battery unit could cover these lines, recharge at Oxted in the case of Uckfield or either end in with Marshlink without the need to lay an additional mile of 3rd rail.

It might be slightly off-topic, but as a driver I’m a little nervous about some of the claims for battery units. Given that you’re relying on battery power for all systems, including A/C where fitted, I’d also like a little comfort about how long the charge can last off the juice as much as how far it can travel. The instance that I’m concerned about being a stranding due to, say, signal failure or an obstruction on the line.

I don’t know where Vivarail have been conducting their tests, but the only battery electric trial that I’m aware of happening on the mainline under mainline running conditions was carried out using a Cl379 on the Manningtree branch. As well as that train performed, it was never away from the OLE at any time and could simply raise it’s pan if it ran into trouble. What happens if you’re off the juice halfway down the Marshlink and you’ve got to wait a couple of hours while our orange friends get to and deal with a fallen mature tree blocking the line?

 

[A0wen]

It might be slightly off-topic, but as a driver I’m a little nervous about some of the claims for battery units. Given that you’re relying on battery power for all systems, including A/C where fitted, I’d also like a little comfort about how long the charge can last off the juice as much as how far it can travel. The instance that I’m concerned about being a stranding due to, say, signal failure or an obstruction on the line.

I don’t know where Vivarail have been conducting their tests, but the only battery electric trial that I’m aware of happening on the mainline under mainline running conditions was carried out using a Cl379 on the Manningtree branch. As well as that train performed, it was never away from the OLE at any time and could simply raise it’s pan if it ran into trouble. What happens if you’re off the juice halfway down the Marshlink and you’ve got to wait a couple of hours while our orange friends get to and deal with a fallen mature tree blocking the line?

Fair shout - but what happens with an electric unit where you're waiting for the orange army to deal with a fallen tree? Presumably the juice has to be turned off when they are dealing with such things, so if you're on an EMU then it's dead or has emergency power only ?

If you take Marshlink, surely the correct thing would be to reverse back to the previous station? The stations are at the most about 5 miles apart and it would allow passengers who wished to detrain and make alternate arrangements to do so.

 

[O L Leigh]

Returning back to your previous stopping point isn't routinely done even where it may be possible. But while that may help the passengers (and I stress the word "may", as the previous stopping point may not present many options for alternative travel) it doesn't help the train. Going back adds to the total journey distance between charges without reducing the time between charges. If there isn't sufficient capacity to permit this within the battery system then you just end up with a dead train failed in the section.

An EMU may indeed find itself off the juice under these circumstances, although it may not necessarily be stopped in the isolated section, but at least it can just carry on as normal once the power has been restored.