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Author Topic: Train crash at Br^tigny-sur-Orge - multiple fatalities - 12 July 2013  (Read 35339 times)
SandTEngineer
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« Reply #15 on: July 14, 2013, 09:49:53 pm »

Very similar to the incident at Southall back in 2002 (not the train collision one) http://www.hse.gov.uk/press/2003/e03027.htm
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TonyK
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« Reply #16 on: July 15, 2013, 04:47:03 pm »

... they are often screened by an insulting barrier.

Ah, les Fran^ais - quelle finesse!

But seriously, ET, I appreciate the explanation. As a barrack-room electrician only, I had missed the blindingly obvious. It seems then that the main protection from shock is normally the physical separation of equipment from civilian.
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thetrout
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« Reply #17 on: July 15, 2013, 04:54:01 pm »

When I saw the news about this my initial thoughts on hearing the accident was related to a set of points was actually Eschede 1998 Accident There is a Seconds from Disaster Documentary here about the accident. I'm not a great fan of the way the program is delivered, and this one easily wins a place in the irrelevant stock thread in The Lighter Side, after using MkII ExGatwick Express Stocks as a substitute for an ICE!

Eschdele was the results of a defective wheel which lead to a chain reaction of unlikely, yet unfortunate and devastating events. This included knocking over a set of points to the wrong position. What struck me as similar was that part of the train travelled over the points successfully before being diverted off the running line and hitting a bridge. I guess that would have been different if it was the Power Car Wheel that failed.

However the similarities to Potters Bar are also frightening. Indeed the collision with the Station Canopy was another part of the Potters Bar Crash.

But what was of interest to me was that it was the third coach that derailed. Just like Eschede where the leading power unit didn't derail and a trailing carriage did, although the main causes of both accidents appear to be very different. It seems odd that it was the third coach. Also seems unusual that another Train travelled over the same track about 30 minutes before the doomed train did.

I guess we can be fortunate to say that there were no Diesel involved. I'm minded of the events of Ladbroke Grove where the OHLE Equipment set the Diesel Vapours alight during the 1997 collision. If that were the case here I fear the consequences could have been much, much worse!

I also think that the contrast to the safety of Aviation vs other transport modes is ridiculous. A Pilot told me you're more likely to die slipping over in the bath than on an Aircraft. Whilst statistically he may have been right. If I'm onboard a train that crashes, take Grayrigg Accident for example. Or an Aircraft Crash... Which one am I likely to survive the most? He couldn't didn't want to answer that one!
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bignosemac
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« Reply #18 on: July 15, 2013, 05:06:23 pm »

Points, switches, crossovers, call them what you will, are always going to be a weak link in the safe running, at speed, of trains.

That's why they need special attention, and regular inspection. And after any sort of maintenance they need to be checked, checked again and triple checked.
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« Reply #19 on: July 15, 2013, 05:09:51 pm »


I also think that the contrast to the safety of Aviation vs other transport modes is ridiculous.


How so? Are you saying that rail has nothing to learn from the excellent safety systems used in aviation?
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« Reply #20 on: July 15, 2013, 05:22:58 pm »

I also think that the contrast to the safety of Aviation vs other transport modes is ridiculous.
How so? Are you saying that rail has nothing to learn from the excellent safety systems used in aviation?

Oh gosh... I didn't word that very well at all!

No, I was saying that basing a safety record of aviation to rail is completely ridiculous. I certainly think that some aviation safety methods could work very well on the railway.

However by saying that Air Travel is statistically safer, is a little smug in of the Aviation industry in my opinion, as the methods, vehicles, training etc is very different from a Railway. If you look at the amount of times the average commuter flies every year vs the amount of trains and buses they catch every year, you may see what I'm getting at!

Also look at the amount of flights in/out of the UK (United Kingdom) every year vs the amount of timetabled trains run every year, it soon becomes apparent that you cannot base one from the other.
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TonyK
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« Reply #21 on: July 15, 2013, 06:00:17 pm »


I also think that the contrast to the safety of Aviation vs other transport modes is ridiculous. A Pilot told me you're more likely to die slipping over in the bath than on an Aircraft.

Uncannily, I once almost did both within 12 hours. The morning after successfully flying my first ever solo cross-country flight, I made a non-standard departure from the bath after my shower, suffering what physicists call a "rapid decrease in potential energy". I woke up sometime later, having stopped my fall with the edge of the toilet.

You are quite right about the comparison of risks in transport being futile. Walking is not without its perils, especially if done badly. The truth these days is that when we set off on a journey, it is always with the expectation of arriving safely. This is a fairly recent thing - there is still no news of John Cabot. Much of the English law relating to negligence and personal injury, and especially who is responsible for what, arose out of litigation after train crashes. That doesn't make rail travel any more or less dangerous than any other mode, just older than most. Until rail came, very few people could travel fast enough to damage themselves or others.

Air traffic control is not unlike block signalling in some senses. A piece of airspace has to be empty before another aircraft can enter it, although the majority of the sky above us is uncontrolled for small aircraft flying visually. Maintenance schedules are stringent - one of the first steps in planning a flight is to check the tech log to make sure you'll be home before the next 50 hour check is due. I assume rail operators and Network Rail have similar regimes in place. I'm struggling to think of any other similarities. Risk assessment has a dirty name these days, but it's what keeps us safe - mostly.
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« Reply #22 on: July 15, 2013, 06:15:31 pm »

I note that some tabloid reports are suggesting that passengers were electrocuted. Is that likely? Wouldn't the power have tripped out pretty quickly as soon as a derailing train shorted the circuit?



Very unlikely in my view that anyone on the train could have been electrocuted.
Whilst it is entirely possible that displaced and still live OHLE came into contact with the train, this is unlikely to be dangerous.
For electricty to be dangerous, current must pass through the body, for example by touching a live conductor whilst in contact with earth.
Someone on a train that is in contact with live wires should be safe as all parts of the train would be at same voltage.
I consider it much more likely that those on the train were killed by impact, crush injuries etc.

For someone on the platform the position is very different, a person standing on the ground could well be killed by contact with displaced overhead line equipment that remained live, even briefly.

It should be noted that overhead line failures (without any other accident) occur regretably often in the UK (United Kingdom), often resulting in the wires contacting the train, I have never heard of anyone on the train getting an electric shock in such circumstances.

Bystanders and trackworkers would be at some risk in such circumstances.
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A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU (Diesel Multiple Unit) is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
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« Reply #23 on: July 15, 2013, 06:18:36 pm »

The morning after successfully flying my first ever solo cross-country flight,

Being that it was cross-country, were there plenty of toilets, but all smelling worse than a downtown Kolkata sewer? Did you turn up expecting a seat but had to fight for one because the reservation system had gone t*ts up? Did the on-board catering consist of nothing more than a melting Kit-Kat and a warm can of Carling, delivered to you by a trolley dolly who turned up 3 minutes before your destination?

That's my experience of travelling solo cross-country.
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« Reply #24 on: July 15, 2013, 07:25:48 pm »

For someone on the platform the position is very different, a person standing on the ground could well be killed by contact with displaced overhead line equipment that remained live, even briefly.

Four of the six people killed were on platforms, though I've not found out whether this was by impact with the train, a cable or other infrastructure, or by electricity. And several people were thrown from the train as windows smashed and in some cases carriages broke up. All told, I am still amazed so few passengers were killed.

There were two SNCF (Societe Nationale des Chemins de fer Francais - French National Railways) staff on the platform who saw a carriage coming towards them, sideways on, at high speed. They threw themselves on the ground and the carriage was launched into the air over them and onto the canopy. Now that is really scary - others sadly were not so lucky.

At 1500 V, one ohm circuit resistance, hence 1500 A, the power (in simple terms) is 2.25 MW or about 3000 HP. That's about one train (at full power). If a supply has to cope with several trains, it has to supply a total circuit resistance of well under one ohm. So it will take a very firm contact with the ground (or grounded metalwork) to produce such a low resistance to Earth, and carry a big enough over-current to then trip the supply.
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« Reply #25 on: July 15, 2013, 08:07:17 pm »

Looking at the electrocution question again, I recall hearing that DC (Direct Current) is more dangerous than AC, because the latter causes muscle spasm, meaning that one is likely to be thrown away from the danger. No-one on the train would be in danger in any case, but people on the platform may, sadly, have been. It remains a moot point only. Being crushed or electrocuted is unimportant compared to being killed or seriously injured.
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TonyK
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« Reply #26 on: July 15, 2013, 08:08:26 pm »

Being that it was cross-country, were there plenty of toilets, but all smelling worse than a downtown Kolkata sewer? Did you turn up expecting a seat but had to fight for one because the reservation system had gone t*ts up? Did the on-board catering consist of nothing more than a melting Kit-Kat and a warm can of Carling, delivered to you by a trolley dolly who turned up 3 minutes before your destination?

That's my experience of travelling solo cross-country.

For the record, the onboard catering consisted of a packet of mint Imperials that I forgot all about once I left the ground. Toilet facilities consisted of waiting until I landed. I did have a seat, however; the left-hand one.
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stuving
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« Reply #27 on: July 15, 2013, 08:34:59 pm »

Looking at the electrocution question again, I recall hearing that DC (Direct Current) is more dangerous than AC, because the latter causes muscle spasm, meaning that one is likely to be thrown away from the danger. No-one on the train would be in danger in any case, but people on the platform may, sadly, have been. It remains a moot point only. Being crushed or electrocuted is unimportant compared to being killed or seriously injured.

I think it is the other way - DC produces strong constant muscle contraction, but AC produces more of a twitch, though it can be very strong. The extra danger was supposed to be when you are gripping something and cannot let go, since hand muscles only pull one way (to grip). In other parts of the body muscles oppose each other, so the effect is less predictable.

If this effect is important, it might show up in the advice on how to rescue someone from the third rail. However, I rather think the actual advice is to keep clear, and a very out-of-date version that advised some action would be of dubious scientific basis.

Either way, what kills you is ventricular fibrillation due to the small part of the current that goes near your heart.
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Electric train
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« Reply #28 on: July 15, 2013, 09:01:05 pm »

... they are often screened by an insulting barrier.

Ah, les Fran^ais - quelle finesse!

But seriously, ET, I appreciate the explanation. As a barrack-room electrician only, I had missed the blindingly obvious. It seems then that the main protection from shock is normally the physical separation of equipment from civilian.
That's correct for OLE (Overhead Line Equipment, more often "OHLE") systems place out of reach; ac protection against shock is also by equipotential bonding and for dc screening and insulation, conductor rail systems are just dangerous!!!!

It is unlikely that anyone was electrocuted, as soon as the wire hit the ground or a return path (earth) fault clearance and limitation of rise of earth potential are governed by EN50122-2

I can not recall an incident where a passenger in a train has been electrocuted by the passage of OLE fault current through a train. 
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TonyK
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« Reply #29 on: July 15, 2013, 09:12:52 pm »

[I can not recall an incident where a passenger in a train has been electrocuted by the passage of OLE (Overhead Line Equipment, more often "OHLE") fault current through a train. 

Neither can I. The "Faraday Cage" effect would see any current running to earth around passengers, rather than through them. I have twice, in former times, seen Blackpool trams - both double-deckers - "brewed up" by a catastrophic short circuit. No passengers were harmed, although many were shaken by the sight and noise, and even more were inconvenienced.
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