Comparison of safety between overhead line vs third rail electrification systems

[AM9]

max speed on third rail 110 if your lucky

109 was a class 442 record way back when they were new.

OHLE 325 KM in europe 140 mph here

186 mph (300kph) daily on HS1

 

[HSTEd]

max speed on third rail 110 if your lucky

The number of places with 125mph running that rae not already electrified, or committed to electrification at 25kV are rather small.

OHLE 325 KM in europe 140 mph here

186mph here.

transformer 3rd rail 1 per mile
ole 5 miles or more

The substation spacings are determined entirely by local demand conditions and it is extremely unhelpful to make simplistic distance comparisons.

economics power transfer and speed

Economics comparisons are normally based on previous estimates for 25kV that have proven not to be particularily accurate.
£2.5m track-km changes the figures rather drastically - ofcourse each project must be assessed based on the requirements for that scheme.

 

[yorksrob]

I think that we can all agree that if we were electrifying the nation from scratch, DC third rail would not be the first choice. However, whatever issues third rail has, cannot justify the ludicrous situation where sensible extensions to the existing third rail network cannot be contemplated.

We had a perfectly sensible convention where third rail was allowed in it's areas but overhead was the preferred system elsewhere for several decades. It's illustrative of the hubris of modern thinking that such a sensible compromise was abandoned to the detriment of the railway, it's customers and society in general.

 

[GRALISTAIR]

added to the sticky

 

[edwin_m]

I claim Fair Dealing on the following for educational and research reasons:

I made an FoI request for documentation from "Electrical Power Asset Policy Section 2 - Historical Analysis".
Total risk for third rail according to Network Rail's own analysis is roughly 8 Fatality Weighted Injuries on third rail, and 1 FWI for 25kV systems.

Roughly 1620km of third rail electrification route, 3250km of 25kV electrification route.
Which makes:
0.000308 FWI/km-year for 25kV electrification
0.004938 FWI/km-year for third rail electrification

So about 0.0046 FWI/km-year excess deaths on third rail electrification.
The value of prevented fatalty is something on order of £1.6m - whch means the excess safety costs of third rail electrification is ~£7,360/ route km-year

£7360/route km-year sounds like a lot
But at current costs of 25kV electrification it is effectively negligible.

Thanks for those figures. They indicate that the rate of equivalent fatalities for a section of third rail route is about 16 times higher than for a section of OLE route of the same length. People asserting that third rail is less dangerous need to think about this, though I doubt it will settle the debate in the absence of the base statistics which are still, as far as I can see, not in the public domain.

When assessing cost £7360/route km is indeed small compared to the 2009 projections of somewhat over £1m per route km of double track, let alone the inflated costs of actual recent schemes. Bear in mind however that you are comparing an annual cost with a fixed cost - the £7360 safety benefit needs to be brought down to a a NPV over (typically) a 60 year scheme lifetime and added on to the NPV of the energy saving from 25kV vs 750V which will be in the order of 25% of the energy cost.

However the VPF analysis is in itself suspect since it is a tool to be used, if at all, to assess whether a tolerable risk is reduced "as low as reasonably practicable". ORR regards the risks of significant extensions to third rail as intolerable so will only consider third rail under the more stringent test of any alternative being "grossly disproportionate". The detail of the reasoning behind ORR's view is again not publically available as far as I'm aware.

 

[yorksrob]

Thanks for those figures. They indicate that the rate of equivalent fatalities for a section of third rail route is about 16 times higher than for a section of OLE route of the same length. People asserting that third rail is less dangerous need to think about this, though I doubt it will settle the debate in the absence of the base statistics which are still, as far as I can see, not in the public domain.

When assessing cost £7360/route km is indeed small compared to the 2009 projections of somewhat over £1m per route km of double track, let alone the inflated costs of actual recent schemes. Bear in mind however that you are comparing an annual cost with a fixed cost - the £7360 safety benefit needs to be brought down to a a NPV over (typically) a 60 year scheme lifetime and added on to the NPV of the energy saving from 25kV vs 750V which will be in the order of 25% of the energy cost.

However the VPF analysis is in itself suspect since it is a tool to be used, if at all, to assess whether a tolerable risk is reduced "as low as reasonably practicable". ORR regards the risks of significant extensions to third rail as intolerable so will only consider third rail under the more stringent test of any alternative being "grossly disproportionate". The detail of the reasoning behind ORR's view is again not publically available as far as I'm aware.

It's a shame the ORR doesn't assess the risks of people falling under buses and cars, then perhaps they might have a more realistic basis on which to compare alternative forms of public traction.

 

[edwin_m]

It's a shame the ORR doesn't assess the risks of people falling under buses and cars, then perhaps they might have a more realistic basis on which to compare alternative forms of public traction.

This information is very readily available.

https://www.gov.uk/government/statistics/transport-statistics-great-britain-2016 (and linked tables):

Rail: 45 fatailities for 64.4 billion passenger-km, so 1.4 billion passenger-km per fatality.

Road: 1,732 fatalities including pedestrians and cyclists, for 707 billion passenger-km, so 4.1 million passenger-km per fatality. The "actual" figure would be higher, because some casualties would be in HGV accidents so not really attributable to passenger transport, but I don't think this would bring it close to the rail figure.

What I suspect you are actually after is how these figures would change if cheaper methods of electrification (in this case, and on the questionable assumption that third rail is actually cheaper) made rail more attractive and generated modal shift from less safe modes. That is a far more difficult thing to establish and I'm not aware of any research in this area.

 

[nomis1066]

If 3rd rail is unsafe then rip it all up and replace it with OH. Will they do that. Of course not. 3rd rail is as safe as people allow it to be. If they - non railway people - are dumb enough to trespass on a 3rd rail powered railway then they are twice as idiotic. Take it to it's logical conclusion - roads are dangerous so shouldn't we be closing pavements or installing lengthy stretches of fencing?

The South East has three isolated pockets of diesel operation surrounded by hundreds of miles of 3rd rail. All three justify electrification and for standardisation and rolling stock considerations, they should all be juiced with 3rd rail.

Just get on with it.

 

[yorksrob]

This information is very readily available.

https://www.gov.uk/government/statistics/transport-statistics-great-britain-2016 (and linked tables):

Rail: 297 fatailities for 64.4 billion passenger-km, so 21.5 million passenger-km per fatality.

Road: 1,732 fatalities including pedestrians and cyclists, for 707 billion passenger-km, so 4.1 million passenger-km per fatality. The "actual" figure would be higher, because some casualties would be in HGV accidents so not really attributable to passenger transport, but I don't think this would bring it close to the rail figure.

What I suspect you are actually after is how these figures would change if cheaper methods of electrification (in this case, and on the questionable assumption that third rail is actually cheaper) made rail more attractive and generated modal shift from less safe modes. That is a far more difficult thing to establish and I'm not aware of any research in this area.

So these statistics are saying that there is less chance of a fatality on the roads, where any Tom, Dick or Harry can wander into the road whenever they like, and that road transportation is safer on an accidents per km of travel basis, than a controlled railway system where people are generally segregated from the permanent way. If this is the case I suspect it has less to do with safety and more to do with peoples propensity to choose the railway as a form of suicide.

Me thinks these statistics quoted do not tell the whole truth.

 

[HSTEd]

Thanks for those figures. They indicate that the rate of equivalent fatalities for a section of third rail route is about 16 times higher than for a section of OLE route of the same length. People asserting that third rail is less dangerous need to think about this, though I doubt it will settle the debate in the absence of the base statistics which are still, as far as I can see, not in the public domain.

When assessing cost £7360/route km is indeed small compared to the 2009 projections of somewhat over £1m per route km of double track, let alone the inflated costs of actual recent schemes.
Bear in mind however that you are comparing an annual cost with a fixed cost - the £7360 safety benefit needs to be brought down to a a NPV over (typically) a 60 year scheme lifetime and added on to the NPV of the energy saving from 25kV vs 750V which will be in the order of 25% of the energy cost.

As far as I can tell, actually costs for a twin-track 25kV scheme are on order of £3-5m/route-km, which makes £7360 pale into insignificance.
Although it does not include an NPV calculation, even over 60 years it only adds up to ~£440k/route-km.
Which is going to be a very small portion of the price of the scheme in all reasonable scenarios.

The energy cost situation is not as simple as it appears - the 25% loss scenario only applies in a certain case of a heavily used route with a certain infrastructure.

Such things can only be assessed reliably on a scheme by scheme basis.
There are also ways to use modern power electronics to reduce these figures drastically in potential future schemes, if other issues can be overcome (and I am confident that they could be with a suitable development programme).

However the VPF analysis is in itself suspect since it is a tool to be used, if at all, to assess whether a tolerable risk is reduced "as low as reasonably practicable". ORR regards the risks of significant extensions to third rail as intolerable so will only consider third rail under the more stringent test of any alternative being "grossly disproportionate". The detail of the reasoning behind ORR's view is again not publically available as far as I'm aware.

But as far as I can see, this 'intolerable' risk is actually rather small.
And as such is an unreasonable restriction that does much to prevent the electrification of the railway.

This is before we could go into ways to use modern power electronics to reduce the risk further, for example by having a section of normally dead rail in the centre of platforms, which would only be activated by a plunger by the stop board if the train happened to stop gapped (due to length issues or having lost a shoe). Or by simply tying the platform rail to the right-away indicator.

 

[edwin_m]

So these statistics are saying that there is less chance of a fatality on the roads, where any Tom, Dick or Harry can wander into the road whenever they like, and that road transportation is safer on an accidents per km of travel basis, than a controlled railway system where people are generally segregated from the permanent way. If this is the case I suspect it has less to do with safety and more to do with peoples propensity to choose the railway as a form of suicide.

Me thinks these statistics quoted do not tell the whole truth.

Please read it again. The figures are kilometres per fatality, so the bigger the figure the safer it is. The figure I quoted for deaths on the railway excludes suicides.

 

[edwin_m]

As far as I can tell, actually costs for a twin-track 25kV scheme are on order of £3-5m/route-km, which makes £7360 pale into insignificance.
Although it does not include an NPV calculation, even over 60 years it only adds up to ~£440k/route-km.
Which is going to be a very small portion of the price of the scheme in all reasonable scenarios.

The energy cost situation is not as simple as it appears - the 25% loss scenario only applies in a certain case of a heavily used route with a certain infrastructure.

Such things can only be assessed reliably on a scheme by scheme basis.
There are also ways to use modern power electronics to reduce these figures drastically in potential future schemes, if other issues can be overcome (and I am confident that they could be with a suitable development programme).



But as far as I can see, this 'intolerable' risk is actually rather small.
And as such is an unreasonable restriction that does much to prevent the electrification of the railway.

This is before we could go into ways to use modern power electronics to reduce the risk further, for example by having a section of normally dead rail in the centre of platforms, which would only be activated by a plunger by the stop board if the train happened to stop gapped (due to length issues or having lost a shoe). Or by simply tying the platform rail to the right-away indicator.

I agree the costs can only be assessed on a scheme basis - however if we start picking and choosing voltages for each scheme we end up with an unworkable mishmash.

I'm beginning to think that no more 25kV should be authorised until costs have been brought back down to a reasonable level - someone has to understand and challenge why they have got so high rather than just accepting it as a fact. And you are ignoring the point that, if OLE costs have gone up so much after we did very little of it for 20 years, how much will third rail costs have gone up when we've done hardly any for even longer? There is also the risk that novel power electronics will start raising all kinds of safety approval issues as well as increasing equipment costs.

One those considerations have been taken into account the £440k per route-km might become quite a significant proportion of the scheme cost.

The 25% energy saving would probably be higher on a lightly-used route because the substations will be further apart so the voltage drop losses will be proportionately more. However I agree with the point I think you are trying to make, that the absolute losses will be less because the total consumption is also less.

 

[Bald Rick]

Please read it again. The figures are kilometres per fatality, so the bigger the figure the safer it is. The figure I quoted for deaths on the railway excludes suicides.

The 297 figure you quoted includes 252 suicides.

 

[DerekC]

The 297 figure you quoted includes 252 suicides.

And presumably the road figures do too, although on the road suicides must be harder to distinguish from plain stupidity.

 

[Bromley boy]

Are there any official figures for deaths/injuries from OLE v third rail? I seem to remember some being posted previously showing that 3rd rail was only marginally more dangerous.

Personally, being used to it, I'm very comfortable around the third rail. It won't do you any harm unless you do something very silly or fall onto it.

I've certainly been made aware of a few incidents. I believe a train cleaner sadly lost his life at my TOC by falling out of a set of doors in a depot and landing on the third rail. I believe he wasn't discovered for some hours by which time he was deceased. Another was apparently seriously injured or killed when jet washing a shoe fuse - not a sensible thing to do - warning stickers are now being applied to said shoe fuses.

Then again I'm not sure I'd want to be anywhere near OLE if the wires had come down. I'm aware there have been a few nasty incidents where this has happened. 25kv AC can jump and is a great deal more lethal than 750v DC, as has been mentioned previously.

EDIT:

Sorry I just sad HSTed's figures posted previously. As I expected, 3rd rail is only marginally more dangerous. I suspect many of these additional deaths/injuries come to people who shouldn't be on the railway in the first place, rather than PTS trained staff going about their business.

 

[Bromley boy]

If 3rd rail is unsafe then rip it all up and replace it with OH. Will they do that. Of course not. 3rd rail is as safe as people allow it to be. If they - non railway people - are dumb enough to trespass on a 3rd rail powered railway then they are twice as idiotic. Take it to it's logical conclusion - roads are dangerous so shouldn't we be closing pavements or installing lengthy stretches of fencing?

The South East has three isolated pockets of diesel operation surrounded by hundreds of miles of 3rd rail. All three justify electrification and for standardisation and rolling stock considerations, they should all be juiced with 3rd rail.

Just get on with it.

Well said that man!

 

[JamesRowden]

I agree the costs can only be assessed on a scheme basis - however if we start picking and choosing voltages for each scheme we end up with an unworkable mishmash.

I'm beginning to think that no more 25kV should be authorised until costs have been brought back down to a reasonable level - someone has to understand and challenge why they have got so high rather than just accepting it as a fact. And you are ignoring the point that, if OLE costs have gone up so much after we did very little of it for 20 years, how much will third rail costs have gone up when we've done hardly any for even longer? There is also the risk that novel power electronics will start raising all kinds of safety approval issues as well as increasing equipment costs.

One those considerations have been taken into account the £440k per route-km might become quite a significant proportion of the scheme cost.

The 25% energy saving would probably be higher on a lightly-used route because the substations will be further apart so the voltage drop losses will be proportionately more. However I agree with the point I think you are trying to make, that the absolute losses will be less because the total consumption is also less.

Network Rail seems to presently be limiting its assumptions regarding the cost of electrification when one considers the relative range it gives for the cost of each option for electrifying the Marshlink:

Option 1 - dc electrification £100-250M
Option 2 - ac electrification £250-500M

Even with such wide error margins the result of the study suggests that dc electrification of this line would involve less capital investment than ac electrification (assuming that the maximum/minimum possibilities of dc/ac cost are mutually exclusive since some random factors would increase/reduce the cost of both options).

 

[HSTEd]

And you are ignoring the point that, if OLE costs have gone up so much after we did very little of it for 20 years, how much will third rail costs have gone up when we've done hardly any for even longer? There is also the risk that novel power electronics will start raising all kinds of safety approval issues as well as increasing equipment costs.

Well there was a major third rail electrification scheme in the 90s, not long before the last major BR-era schemes of 25kV, (Ellesmere Port actually commisioned after privatisation commenced IIRC).

And there was the significant work resulting from the ELL reconstruction that lead to new third rail being brought into use.

There isnt really that much of a time advantage in favour of 25kV

Whilst power electronics might present challenges with approvals and similar - this is work that is eminently applicable in numerous other situations involving light rail in the future.
The same techniques that make third rail better make tramways better.

The 25% energy saving would probably be higher on a lightly-used route because the substations will be further apart so the voltage drop losses will be proportionately more. However I agree with the point I think you are trying to make, that the absolute losses will be less because the total consumption is also less.

Lightly used routes will tend to have shorter trains - and since the same conductor rails will likely be used in all new schemes (high conductivity aluminium types for example), the voltage drop per km will drop precipitously.

You can't get more than about 25% losses without massive amounts of parallel aluminium cables, becuase you will likely exceed the 120V touch potential in the running rail before that happens.

BUt absolute costs are the ones that actually matter in this context, as you say.

 

[HSTEd]

Network Rail seems to presently be limiting its assumptions regarding the cost of electrification when one considers the relative range it gives for the cost of each option for electrifying the Marshlink:

Network Rail Figures

Even with such wide error margins the result of the study suggests that dc electrification of this line would involve less capital investment than ac electrification (assuming that the maximum/minimum possibilities of dc/ac cost are mutually exclusive since some random factors would increase/reduce the cost of both options).

That is an interesting change in Network Rail's position - which means that ORR might actually have to justify its position on third rail.
Which would be nice, rather than simply having a blanket prohibition we might actually get some sort of discussion about the relative risks etc.

 

[yorksrob]

Please read it again. The figures are kilometres per fatality, so the bigger the figure the safer it is. The figure I quoted for deaths on the railway excludes suicides.

So it does !

I must have been under a mental fug yesterday evening

 

[A0wen]

Are there any official figures for deaths/injuries from OLE v third rail? I seem to remember some being posted previously showing that 3rd rail was only marginally more dangerous.

Personally, being used to it, I'm very comfortable around the third rail. It won't do you any harm unless you do something very silly or fall onto it.

I've certainly been made aware of a few incidents. I believe a train cleaner sadly lost his life at my TOC by falling out of a set of doors in a depot and landing on the third rail. I believe he wasn't discovered for some hours by which time he was deceased. Another was apparently seriously injured or killed when jet washing a shoe fuse - not a sensible thing to do - warning stickers are now being applied to said shoe fuses.

Then again I'm not sure I'd want to be anywhere near OLE if the wires had come down. I'm aware there have been a few nasty incidents where this has happened. 25kv AC can jump and is a great deal more lethal than 750v DC, as has been mentioned previously.

EDIT:

Sorry I just sad HSTed's figures posted previously. As I expected, 3rd rail is only marginally more dangerous. I suspect many of these additional deaths/injuries come to people who shouldn't be on the railway in the first place, rather than PTS trained staff going about their business.

My understanding is if an OLE wire comes down, doesn't it trigger a cut-out automatically? Therefore there should only be a very short window where that's a risk?

 

[Paul180]

My understanding is if an OLE wire comes down, doesn't it trigger a cut-out automatically? Therefore there should only be a very short window where that's a risk?

In theory yes but you should never assume. there was an incident a while ago were a driver was electrocuted after coming in contact with some downed wires (he survived).

 

[HSTEd]

It should be noted that the figures I quoted earlier were dominated by tresspassers (~6.5 FWI out of 8 in the third rail case, ~0.8 out of 1 in the 25kV case) - and that might inform discussions.

A passenger on the railway last year IIRC were just as likely to be killed by a station sign falling on their head as they were to be fried by the third rail.

 

[swt_passenger]

Well there was a major third rail electrification scheme in the 90s, not long before the last major BR-era schemes of 25kV, (Ellesmere Port actually commisioned after privatisation commenced IIRC).

And there was the significant work resulting from the ELL reconstruction that lead to new third rail being brought into use.

Agree. The Southern region power supply upgrades (for service capacity) that have been going on almost continually since the decision was made to replace the Mk 1 stock have also generally been achieved by installing new intermediate substations and these will have also required upgrades to the private distribution network to the substations where necessary. Building a substation on a greenfield site alongside the railway won't change much depending on whether it is a strengthening supply or a brand new supply.

Virginia Water to Reading is another very recent strengthening project.

Installing the physical third rail is a well-known procedure, (because it's a standard activity during normal track renewals).

I can't quite see why edwin_m thinks DC installations are a perishable skill...

 

[HSTEd]

I am not currently advocating mass adoption of third rail schemes, however we have two significant areas of third rail operation in Britain (Merseyside and the South East) and I think funding at least one scheme would be justified - if for no other reason to see if we have decent cost estimations.

There are several schemes that might prove suitable:
Uckfield, Marshlink, Borderlands Line, or even things like Wigan Wallgate extensions

 

[edwin_m]

The 297 figure you quoted includes 252 suicides.

Oops. Teach me to try to follow statistics with three or four windows open at once. In my defence it's not totally clear in the document, though I should have twigged that 297 was a big number for accidental fatalities on the railway.

Original post corrected.

 

[edwin_m]

I can't quite see why edwin_m thinks DC installations are a perishable skill...

Until recently lots of people thought that AC installations weren't a perishable skill.

 

[keith1879]

Are there any official figures for deaths/injuries from OLE v third rail? I seem to remember some being posted previously showing that 3rd rail was only marginally more dangerous.

Personally, being used to it, I'm very comfortable around the third rail. It won't do you any harm unless you do something very silly or fall onto it.

I've certainly been made aware of a few incidents. I believe a train cleaner sadly lost his life at my TOC by falling out of a set of doors in a depot and landing on the third rail. I believe he wasn't discovered for some hours by which time he was deceased. Another was apparently seriously injured or killed when jet washing a shoe fuse - not a sensible thing to do - warning stickers are now being applied to said shoe fuses.

Then again I'm not sure I'd want to be anywhere near OLE if the wires had come down. I'm aware there have been a few nasty incidents where this has happened. 25kv AC can jump and is a great deal more lethal than 750v DC, as has been mentioned previously.

EDIT:

Sorry I just sad HSTed's figures posted previously. As I expected, 3rd rail is only marginally more dangerous. I suspect many of these additional deaths/injuries come to people who shouldn't be on the railway in the first place, rather than PTS trained staff going about their business.

If you look at HSTed's figures again - (they are analysed at post 35) they show that third rail electrification is not just "marginally" more dangerous but 16 times more dangerous (happy to be corrected).

 

[swt_passenger]

Until recently lots of people thought that AC installations weren't a perishable skill.

I don't disagree about AC. But at the same time when did we last hear of a DC upgrade going wrong in any way at all? If any have run seriously late they haven't had much publicity...

 

[Chester1]

I am not currently advocating mass adoption of third rail schemes, however we have two significant areas of third rail operation in Britain (Merseyside and the South East) and I think funding at least one scheme would be justified - if for no other reason to see if we have decent cost estimations.

There are several schemes that might prove suitable:
Uckfield, Marshlink, Borderlands Line, or even things like Wigan Wallgate extensions

Borderlands will be one of the last lines to be electrified unless the Welsh Government decided to fund it which is highly unlikely. It has been talked about for decades without any real progression. Wigan Wallgate to Skelmersdale and or Kirkby would be better as AC. While linking Skelmersdale with Liverpool is the primary object of the new line plan it would be odd to rule out services to Manchester. Merseyrails new rolling stock has been designed to be converted to dual mode and half of services from Liverpool would terminate at Kirkby in the event of either simple electrification to Wigan or building the Skelmersdale link. The main limitation to AC conversion on Merseyside is the loop and link tunnels height. I wouldn't guarantee that the existing Merseyrail network will stay 3rd rail let alone be expanded. Liverpool South Parkway to Hunts Cross would very likely be converted to AC if the CLC is electrified. Merseyrail would either have to use dual mode trains or stop serving Hunts Cross.