2012 Q8

[neil-thomson]

All,

I'm looking for some clarification / discussion on the above question and I guess the definition of risk / hazards.

The first part of the question is leading you towards MVDCs, axle counters and GPS positioning (ETCS).

The second part asks for three hazards, causes and effects for each for 9 marks. This puzzled me. Am I right in thinking that safety hazards would be something like signal reversion, section showing clear when occupied and section showing occupied when clear?

I would also say if this is right then a large number of the effects will be protecting signals at red / SPADs / delays.

Thanks in advance

Neil

[Peter]

All,

I'm looking for some clarification / discussion on the above question and I guess the definition of risk / hazards.

The first part of the question is leading you towards MVDCs, axle counters and GPS positioning (ETCS).

The second part asks for three hazards, causes and effects for each for 9 marks. This puzzled me. Am I right in thinking that safety hazards would be something like signal reversion, section showing clear when occupied and section showing occupied when clear?

I would also say if this is right then a large number of the effects will be protecting signals at red / SPADs / delays.

Thanks in advance

Neil

The hazards that you have listed there would be fairly normal ones for TCs. I think that the question is looking for some hazards that are specific to the detection yep. For instance, axle counters have reset issues and do not provide any form of broken rail detection; a train based system may have issues with poor coverage, incorrect message identification, vulnerability to masquerade attacks. Think a bit wider than the traditional hazards of a TC not correctly performing its function.

Peter

[neil-thomson]

In which case i think the question could be worded more clearly. I took that as 'for each...describe three safety hazards' rather than 'describe three safety hazard for each'.

I may be reading into it too much...

[PJW]

I don't see the difference in your wording.....to me the word order does not affect the meaning.

I am sure that they want you to give a total of 9 hazards-
3 applicable for your example in (i),
3 for (ii) and
3 for (iii).
Further they want different hazards in each case and so if you want to get your full 9 marks for the section, then give them what they want which is at least one cause and one effect for every one of the 9.

Also note that whereas perhaps GPS can be used as one of the diverse means of determining speed and location of a train, do not simply equate train position reports in ETCS with GPS. The prime means is via reading track balise to get an absolute position fix and subsequently using odometry looking at wheel revolutions to estimate movement since passing the balise- generally doppler radar is used as a diverse input into the odometry and potentially GPS could be used for this.

So one might focus upon:

track circuits:
loss of train shunt due to rusty rails,
EMI from traction exceeding the immunity of detector / relay,
failed insulated block joint permitting voltage from one section to be applied to the receiver of the adjacent

axle counters:
following an axle counter section having become disturbed, the signaller in error resetting a different one that was actually occupied at the time,
a possession being surrendered with an engineering vehicle having being left on track by mistake,
axle counter head becomes detached from the rails

train position reports:
temporary loss of power supply at control centre resulting in uncertainty of how many trains are in the affected area and where precisely they are,
a failed balise having been replaced but having been incorrectly programmed for the position it was installed,
poor adhesion conditions leading to excessive wheel slip / slide

In which case i think the question could be worded more clearly. I took that as 'for each...describe three safety hazards' rather than 'describe three safety hazard for each'.

I may be reading into it too much...