Hacker News new | past | comments | ask | show | jobs | submit
1718627440 | on: What we know so far about Spain train crash
Sorry, but ordering trains to drive manually after the system locks itself down, is the proper procedure. Of course you are still supposed to only send trains to free sections, but the error is in that step, not that they ordered a train to drive on it's own.

Also the fallback procedure is also aided by automatic systems and a sizable number of accidents in the past were caused by that information being faulty.

julik | parent | next
It is the proper procedure, and it does come (in a lot of countries, AFAIK) with a lot of guardrails:

There will be a so-called "train order" allowing passage of a specific section ignoring the safety system warnings, which has strict validity limits both in time and in the area where it applies, usually denoted by specific hectometric mileposts

When cab signaling is involved (LZB is one of these) and it malfunctions, the entire system normally changes to "driving on sight only" - which indeed limits the train to 40, 30, 20, sometimes - 15 km/h (see https://fr.wikipedia.org/wiki/Marche_%C3%A0_vue) or the line gets switched to lineside signaling - if it is available.

I don't know how you could violate all of those rules - both from the driver's side and from the traffic control side - but it sounds absolutely horrible. Like an override of at least 2 (if not 3) very explicit safety margins.

1718627440 | root | parent | next
(The following is speculation:) The issue is that there was still a fallback system operating (ASFA), so they likely assumed that there is still a safety system running, while actually it needed to be ignored, because due to virtual blocks of LZB there is then more than one train in a ASFA block. This means that the next signal shows you "clear", so you accelerate thinking you are back into normal operation, but there is actually a train in front of you, just not in the next block, but in your very own block, which is a situation that is not supposed to happen. So the issue is kind of different train control systems interacting disagreeing with each other. Ironically it would have been actual if there would not have been another safety system, because then they would have known, that they need to operate manually right away.
loading story #50301610
dist-epoch | root | parent
There are audio recording from this incident where you can hear the "train orders" being given and acknowledged.

They were the wrong orders apparently.

AdrianCX | parent | next
Why is that?

I remember a long time ago I was stuck in a train in a field a considerable time because of a similar failure and conductor just wouldn't move unless green

I was expecting the same here, conductor is the first to die so just refuse until the idiots fix their system

1718627440 | root | parent | next
> Why is that?

What exactly?

A conductor always just gets a movement order. They are not able to assess whether the track is clear, that's the reason why the signalling system exists in the first place. How they get that movement order doesn't necessarily tell what the security steps were to back it.

Of course an attentive conductor can notice and mention there something being weird ("Doesn't the other train normally arrive first?"), but that's a rare lucky occasion, nothing to be relied on. And they just need to swallow the answer ("No, you go first today...") anyway.

> and conductor just wouldn't move unless green

The conductor won't ever move unless they get a movement authority, which most of the time is a green signal.

loading story #50287382
robhlt | root | parent
Many train systems have a trip-stop on signals that will automatically activate the trains's emergency brake if one passes a red signal.

It cannot be bypassed, if an operator must go through a red they have to manually reset the e-brake on each car once it passes the signal.

_trampeltier | parent
Yes, but just with max. 40km/h
wafflemaker | root | parent | next
So that's why my train slowed to 40kmph when the Norwegian Telecom died for a few hours 3 weeks ago.
_trampeltier | root | parent
Yes, 40km/h is for driving on sight in most Europa. I think in France it's even 30km/h.
masfuerte | root | parent
In the UK at night it's walking pace. Literally. The guard gets out and walks and the train follows. (At least that was the case 25 years ago when I had a very slow train journey.)
1718627440 | root | parent
Depends. For example German Zs1 (https://en.wikipedia.org/wiki/Railway_signals_in_Germany#Zs1...) would give them the full clear outside of stations.
sehansen | root | parent
If you're referring to "If the main signal is a (train station's) exit signal ("Ausfahrsignal"), this speed limit applies until the last set of points/switch has been passed by the complete train, after which regular speed is permitted.", I think that means "once you see a normally working signal again, if it's of a specific type (the exit signal), you still have to stay at 40 km/h until you have passed all switches.". As far as I understand the article, Zs1 is mostly intended for very local speed reductions, the kind of speed caution relevant to this discussion sounds more like the Zs7 signal.