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Old August 5th, 2013, 01:13 AM   #1941
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Quote:
Originally Posted by Silly_Walks View Post
If we stick to your roof analogy: if my neighbor's roof collapses because of 3 missing bolts, then I certainly WILL check my roof for 'similar safety gaps', as 33Hz was saying.
And DO YOU have anything to check?
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Old August 5th, 2013, 01:43 AM   #1942
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And DO YOU have anything to check?
Just my mental health
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Old August 5th, 2013, 02:09 AM   #1943
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Anyway, I´d rather slow it down a bit, the thread.

There´s too many posts about the accident lately, and not that much real info about the matter, which is HSR in Spain.

In the meantime, I have a thing or two to say about HSLs in construction in Spain (precisely the one of the accident is one of them).

I´ve refrained for days because of the tragedy. But life goes on, you see.

Can I say what these news are about, or will you still keep on mourning the dead for a few more weeks?
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Old August 5th, 2013, 02:43 AM   #1944
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shit ALWAYS will happens
I bet you also dismiss phobia-stricken folk ... why didn't you just dance with the fellow back there?

It must be creepy crap when a reach from abroad tries snaring him, the poor driver ... and it hadn't taken long to set beacons with needed signaling there after all either (right?)
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Old August 5th, 2013, 09:31 AM   #1945
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Originally Posted by 437.001 View Post
Can I say what these news are about, or will you still keep on mourning the dead for a few more weeks?
If you have something cool, interesting or fun to share about Spanish HSR, please do! A change of subject never harms in a thread like this one.
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Old August 5th, 2013, 11:12 AM   #1946
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Quote:
Originally Posted by 437.001 View Post
Anyway, I´d rather slow it down a bit, the thread.

There´s too many posts about the accident lately, and not that much real info about the matter, which is HSR in Spain.

In the meantime, I have a thing or two to say about HSLs in construction in Spain (precisely the one of the accident is one of them).

I´ve refrained for days because of the tragedy. But life goes on, you see.

Can I say what these news are about, or will you still keep on mourning the dead for a few more weeks?
Go ahead.

As for the accident I agree fully with 33Hz - life goes on and we will still ride trains, but we also need to learn from every accident and ensure that EXACTLY the same thing doesn't happen again somewhere else.
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Old August 5th, 2013, 01:48 PM   #1947
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The problem is that there already was a thread for rail accidents, but no one used it...

I will still refrain for a few more hours to see if this can divert the accident-related posts to the other thread.
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Old August 5th, 2013, 02:22 PM   #1948
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Quote:
Originally Posted by 437.001 View Post
The problem is that there already was a thread for rail accidents, but no one used it...
It's a phenomenon happenning on forums from all over the world.
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Old August 6th, 2013, 01:31 AM   #1949
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Please go ahead and post new news...
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Old August 6th, 2013, 02:35 AM   #1950
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Quote:
Originally Posted by webeagle12 View Post
Do you know if your roof is 100% stable and it's not going to fall on you any minute? When you walk on intersection, do you know 100% that driver brakes will work?

Your demands are useless. Get over it, shit ALWAYS will happens. You fix one thing, something else will go wrong, either driver or mechanical.
Not quite so. To run safely high speed trains, safety measures with a degree of redundacy must be implemented. There are standards and formulas to calculate these safety measures , which were not implemented in this case.

Perhaps this was an oversight on the part of the company responsibile for the infrastructure safety.

To slow down a train from 200km/h to 80km/h it takes a certain distance ,which also varies according to the weight of the trains, and according to its percentage of braking force/weight. Also, in the calculation of the deceleration curve some allowances/ margins have to be made for slight delays in response.


The train was supposed to slow down from 200 km/h to 80 km/h, in a 4 km section, and no safety measures were in place, in case of overspeeding on the slowing down section.

At 200 km/h it takes only 60 seconds to travel 3.33 km..so there is very little margin for error.

The deceleration section was too short ,and not protected by any automatic train control system.

Also the train driver was alone in the cabin, and the train was travelling at 200- 190 km/h, just few seconds before slowing down, at the beginning of the curve.

It was an accident waiting to happen.


Have you asked yourself what would have happened if the train driver had an heart attack, and therefore had been unable to slow down the train, from 200-190 km/h to 153km/h, as he did?

The accident would have been much more catastrophic. In order to slow down, from 200-190 km/h to 80 km/h in just 4 kms, an automatic control system must be in place, and this control system must be able to stop the train automatically, if the driver does not implement the correct procedure, or does not acknowledge the acoustic alarm, or press the "dead man button" , or start immediately to slow down the train.

The very fact that shortly after the accident some beacons have been installed in this section, suggests that the company responsable for safety has acknowledge to have made a mistake, or that it was just a technical oversight, on the part of ASFA.

With regard to the driver, and on the bases of the news reported in this topic, I felt distressed by the fact that, immediately after the accident, the train driver has been described by the press (and by Renfe /ANSFA) like a sort of "irresponsible joy raider".
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Old August 6th, 2013, 02:38 AM   #1951
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redundance makes failures more improbable, not impossible
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Old August 6th, 2013, 03:09 AM   #1952
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redundance makes failures more improbable, not impossible
I do not know of any safety system which is 100% safe. In this case the addition of 3 more beacons on the 2 km section, and the reduction of speed to 160 km/h just to 2 km before the curve, and then to 30 km/h just before negotiating the curve, will allow for a safer approach to the said station .

The important thing is that Renfe /ADif/ Ansf have quickly learnt from the previuos, unfortunate, mistake.

In these cases, we humans, can only review our decisional criteria and change our parameters/ criteria after an accident has occurred.
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Old August 6th, 2013, 01:53 PM   #1953
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Quote:
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redundance makes failures more improbable, not impossible
In safety systems a distinction is made between safe and unsafe failures. Most failure modes just cause inconvenience, but do not cause a hazardous situation.

Train protection/control systems in Europe must meet the SIL4 safety integrity level. That means the probability of an unsafe failure must be once every 11500 years or better. And yes, that means the failure could happen in 2 seconds from now, but also not for another 100000 years. But every way you put it, winning the grand prize in a lottery remains more likely, then the occurance of an unsafe failure in a SIL4 system.

And for the record: I would board a train without a protection system without a second thought, because pretty much anything you'll do in your daily life will be less safe then riding a train.
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Old August 6th, 2013, 08:52 PM   #1954
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how are the years measured? because I'm sure that if we sum up the usage of those systems, we have more than a year of usage each single day.
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Old August 7th, 2013, 08:33 AM   #1955
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The failure rate is calculated over all the relevant parts of the safety system of one safety loop, so in this case it's the failure probability of one train and the track side equipment it encounters.

There are several methods how this is measured. You could take a certain number of samples and test the time untill the first one fails and calculate from there, but because of the system complexity in a lot of cases it comes down to calculating failure rates of individual components and then entering that data in a formula to calculate the overal result.
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Old August 7th, 2013, 09:49 AM   #1956
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ok... if it's the failure of one train and the track side equipment...

There are ~5000 trains running per day in Spain

Let's say (random, but I think it's bellow the reality) that they are working 20% of time (4 hours and 48 minutes)

We have then... 1000 days of trains running per day, that's 2.74 years.

That means that having in mind that a safety failure might occur in one of those 5000 daily trains each 4197 days or 11.5 years...

Am I right?
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Old August 7th, 2013, 10:31 AM   #1957
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Sounds a lot how risk management in the finance world is done. They basically set a required confidence interval.

How do they model the different components of the system. And what if one component is not modeled and the risk is underestimated. This will affect the whole chain of components? Do they do worst case scenario's?
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Old August 7th, 2013, 12:32 PM   #1958
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Quote:
Originally Posted by OriK View Post
Let's say (random, but I think it's bellow the reality) that they are working 20% of time (4 hours and 48 minutes)

We have then... 1000 days of trains running per day, that's 2.74 years.
The FIT (Failure in Time) already includes the time, you don't divide trough time again.

You can inform yourself here:
http://en.wikipedia.org/wiki/Safety_...ntegrity_Level

http://www.schischek.com/certificati...asis-info.html

And while it is true that it is impossible to make everything fail-safe, it is not impossible to make certain things fail-safe.
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Old August 7th, 2013, 12:37 PM   #1959
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Originally Posted by Ribarca View Post
Sounds a lot how risk management in the finance world is done. They basically set a required confidence interval.
There is a lot of the SIL norm that was defined from insurance companies. Insurance companies need to know the risk for failrues.
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How do they model the different components of the system. And what if one component is not modeled and the risk is underestimated. This will affect the whole chain of components? Do they do worst case scenario's?
There is a Siemens table for elecronical components. For each component the FIT is defined. Similar FIT tables are there for other components.

Once you know the FIT for each component you calculate the FIT of a system by adding up FITs of each component. If you have redundency the FIT of the system can be smaller then the FIT of the components.

The calculation is quite systematic with the exception of common cause failures. Common cause failerures are failures in several components that are caused by the same error. The common cause failures are only estimated. It is the weak point of the whole calculation.
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Old August 7th, 2013, 01:27 PM   #1960
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Am I right?
Your calculation looks right to me, but according to what I've been taught about statistics you can't apply large sample probabilities to a single event like that. Unfortunately I can't exactly explain to you why you shouldn't do that.

Also: Have you accounted for the fact that in the majority of cases even failures that are classified as dangerous failures do not lead to accidents.

Quote:
Originally Posted by Ribarca View Post
Sounds a lot how risk management in the finance world is done. They basically set a required confidence interval.

How do they model the different components of the system. And what if one component is not modeled and the risk is underestimated.
There is one big difference with the finance world: In this case every component must be included. I also forgot another important method: Proven in use. For example: There are 1000 systems in use and over 10 years there has been 1 dangerous failure. You can calculate you probability from that.

The major problem that remains is that in the majority of cases problems are not caused by a direct failure of a safety system, but by a situation that wasn't accounted for in the safety assement. In short: You should not worry about the safety system itself and more about how it's used. In this particular accident is was used wrong and therefor couldn't protect against what happened (there were beacons announcing the speed reduction, but they didn't actually require the driver to act accordingly)
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