Certainly to me it definitely means occupied by rail vehicle and almost certainly by one of a type that one could reasonably expect to be detected. The definite inference is that the signal should have been at red and there is no suggestion that the train was authorised procedurally to pass it (because the driver's claim is of a proceed aspect).
Hence
# tree = NO
# supermarket trolley = NO
# car / lorry / bus etc = NO
# rail engineering trolley = assume not but could perhaps stretch it to include
# tamper = possible (a possible cause of the event could be the inability of the vehicle to present a sufficiently low shunt resistance and thus the track circuit remaining up)
# train = YES.
In general one should interpret the question as widely as possible, but since the wording was "occupied" rather than "obstructed" and the question is clearly focussed on whether a SPAD occurred or an invalid aspect was shown rather than the reason for the obstruction being there, then I would simply have stated as an assumption: "occupied section interpreted as meaning by a previously authorised train movement" which would still permit such causes as an axle counter having been reset invalidly with a vehicle left there after engineering work, yet discount the fallen tree, crashed road vehicle, barricade erected by vandals, herd of cows etc that I think lie outside the subject area of this question.
I think Jerry has responded to the other parts of the question; I'd just say that
a) the police are often first on the scene of an accident and are interested in a scene of crime and securing the evidence (even if they actually sometimes inadvertently destroy or fail to capture because of lack of technical understanding),
b) the RAIB then arrive and carry out investigations focussed on lessons to learn, looking at trends, investigating whole incident widely, not seeking to attribute blame. Reports take a long time to be published, but elements are often drip fed in advance and this can result in actions being taken and the various parties doing some associated inquiry,
c) generally is a parallel investigation- indeed this may have started under the auspices of the police prior to RAIB. Indeed it does depend on the seriousness of the incident- there may well not be an RAIB investigation at all. In this case for example there could have been no accident at all, the train may have passed the signal and stopped well short of the first train perhaps due to the action of TPWS, so the actual risk relatively low and there would be no involving of the police at all and the RAIB would probably only be interested in hindsight statistically unless they had reason to believe that this was not an isolated incident.
Hence does depend on circumstances.
d) eventually there may be a public enquiry for serious accidents and this is where the lawyers all get involved and therefore blame attribution is inevitable. Obviously to back up the respective cases of the parties involved other investigations etc can be initiated, which themselves can cast more light and thus be assimilated as another strand of evidence in the RAIB investigation. A case that springs to mind is Potter's Bar points; the information relating to a history of nuts working loose on adjustable stretcher bars at many sites over a significant time emerged quite late after the accident and I think as a result of certain parties defending their positions.
However whenever anyone is investigating any incident should always keep mind open and examine all the evidence and consider various possibilities- not just find a bit of evidence that seems to back up the initial assumption and consider that was definitely the cause. Obviously though one does focus attention- if there are several bits of evidence all pointing the same way and the most obvious alternative explanation all have evidence against them, then that is a reason for gradually excluding them and seeking to ensure that the incident can be fully explained by the scenario which is being considered the overwhelmingly most probable.
If you read almost any RAIB report you will see that they go much further- even if fully convinced that the incident is explained and various elements of the evidence gathered are not relevant to the actual occurrence of the accident, if they find other things that are not perfect (in the real world they almost certainly always ill if they look hard enough) then they will comment or even make recommendations about them even if it is clear that it had no bearing on the immediate cause, root cause, likelihood, severity, mitigation etc of what actually happened. The iceberg argument; whilst they have "lifted the lid" looking at a typical bit of the real world in microcosm, if they think there are other unrelated lessons to be learned then they will highlight them in that report.
Hence
# tree = NO
# supermarket trolley = NO
# car / lorry / bus etc = NO
# rail engineering trolley = assume not but could perhaps stretch it to include
# tamper = possible (a possible cause of the event could be the inability of the vehicle to present a sufficiently low shunt resistance and thus the track circuit remaining up)
# train = YES.
In general one should interpret the question as widely as possible, but since the wording was "occupied" rather than "obstructed" and the question is clearly focussed on whether a SPAD occurred or an invalid aspect was shown rather than the reason for the obstruction being there, then I would simply have stated as an assumption: "occupied section interpreted as meaning by a previously authorised train movement" which would still permit such causes as an axle counter having been reset invalidly with a vehicle left there after engineering work, yet discount the fallen tree, crashed road vehicle, barricade erected by vandals, herd of cows etc that I think lie outside the subject area of this question.
I think Jerry has responded to the other parts of the question; I'd just say that
a) the police are often first on the scene of an accident and are interested in a scene of crime and securing the evidence (even if they actually sometimes inadvertently destroy or fail to capture because of lack of technical understanding),
b) the RAIB then arrive and carry out investigations focussed on lessons to learn, looking at trends, investigating whole incident widely, not seeking to attribute blame. Reports take a long time to be published, but elements are often drip fed in advance and this can result in actions being taken and the various parties doing some associated inquiry,
c) generally is a parallel investigation- indeed this may have started under the auspices of the police prior to RAIB. Indeed it does depend on the seriousness of the incident- there may well not be an RAIB investigation at all. In this case for example there could have been no accident at all, the train may have passed the signal and stopped well short of the first train perhaps due to the action of TPWS, so the actual risk relatively low and there would be no involving of the police at all and the RAIB would probably only be interested in hindsight statistically unless they had reason to believe that this was not an isolated incident.
Hence does depend on circumstances.
d) eventually there may be a public enquiry for serious accidents and this is where the lawyers all get involved and therefore blame attribution is inevitable. Obviously to back up the respective cases of the parties involved other investigations etc can be initiated, which themselves can cast more light and thus be assimilated as another strand of evidence in the RAIB investigation. A case that springs to mind is Potter's Bar points; the information relating to a history of nuts working loose on adjustable stretcher bars at many sites over a significant time emerged quite late after the accident and I think as a result of certain parties defending their positions.
However whenever anyone is investigating any incident should always keep mind open and examine all the evidence and consider various possibilities- not just find a bit of evidence that seems to back up the initial assumption and consider that was definitely the cause. Obviously though one does focus attention- if there are several bits of evidence all pointing the same way and the most obvious alternative explanation all have evidence against them, then that is a reason for gradually excluding them and seeking to ensure that the incident can be fully explained by the scenario which is being considered the overwhelmingly most probable.
If you read almost any RAIB report you will see that they go much further- even if fully convinced that the incident is explained and various elements of the evidence gathered are not relevant to the actual occurrence of the accident, if they find other things that are not perfect (in the real world they almost certainly always ill if they look hard enough) then they will comment or even make recommendations about them even if it is clear that it had no bearing on the immediate cause, root cause, likelihood, severity, mitigation etc of what actually happened. The iceberg argument; whilst they have "lifted the lid" looking at a typical bit of the real world in microcosm, if they think there are other unrelated lessons to be learned then they will highlight them in that report.
(21-06-2012, 10:51 AM)ricky Wrote: The question states a train enters an occupied section.
Now I read this to mean that there was a train already in the section. However could this also be interpreted to mean perhaps there was a fallen tree or supermarket trolley etc. How would you interpret occupied? Is it a train being there, something being there or something detected as being there. If the tree falls and shorts the track is that different to not shorting the track? Or is this unnecessary nit picking?
PJW