2012 Q6 permissive moves

[Hort]

Hi, I have attempted Q6 from last year's paper.

[PJW]

Hi, I have attempted Q6 from last year's paper.

I shall attempt to comment shortly but in the meantime note that this question
Discuss the risks associated with allowing a second train into an occupied platform and the measures that may be taken to reduce these risks. Your answer should include the situations when this feature would be used and any assumptions made about the signalling system.

has some similarity to the 2006 question which was attempted recently: http://irseexam.co.uk/thread-1436.html

A suburban terminal station has platforms that can accommodate trains up to nine cars long. The service is operated by multiple unit trains of either four or five car lengths. All cars are 20m long. At peak times units may be coupled together in the platforms to form trains of up to
nine cars long. Describe with the aid of a diagram:
• The indications shown and the controls on the incoming signal when the platform is clear and when it is occupied.
and
• The arrangements to ensure, that if the platform is already occupied, a train will not be signalled into that platform if the platform cannot accommodate the combined length of the two trains.

The 2012 question seems to require an answer based on GK/RT0044 fom a UK perspective whereas the 2006 question clearly intended one based on "Lime Street controls" but these are far less applicable nowadays than they were historically.

[PJW]

First beware; the question asked for RISKS and you have described HAZARDS. I think the examiners would expect you to have continued by describing the Hazards, but you should have demonstrated that you knew the difference.

So start with the RISKS, perhaps
1. Death / injury of driver, passengers on trains or event on the platform
2. Rolling stock / platform / track damage.
3. Potential subsequent event such as fire or oil spillage harming environment
4. Immediate disruption to train services (at least one platform will be out of use for an extended period whilst incident is dealt with / investigated, may actually tie up rather more of the station and could even close the line to certain destinations)
5. Chance of further risky incidents occuring as a result of needing to operate the railway in degraded mode- handsignalling errors etc
6. Chance of incidents occuring whilst the initial incident is being resolved- rescue workers (both rail and emergencies) put at additional risk as a result.
7. Longer term impact of having a couple of trains no longer available for service until they can be repaired and re-certificated- may lead to loss of capacity due to cancelled or short-formation trains, also consequent over crowding.
8. Adverse publicity to the travelling public and via coverage in the press leading to poor public perception, loss of confidence in the railway. The company bosses may even lose their annual bonus (I suppose that this may actually be a gain for the railway if the money is kept in the coffers rather than being paid out, but we'll leave politics out of this! Certainly a "loss" for the affected individuals).


I think that you should include some suggestions that reduce CONSEQUENCES but probably most of them will be to reduce LIKELIHOOD and that is your lead-in to discussing the various HAZARDS which could lead to the accident occuring.

You made a mistake initially in just stating that the train would be brught to a stand at the signal and that a specific aspect would be given; it would have been better to have started off without these assumtions that can then later be introduced as "mitigations" of the risk (e.g. the slow speed is a mitigation of the consequence of a collision). Just because "everyone knows this is what we do", don't ignore such- this comment is actually quite widely applicable when answering IRSE questions.

Your "risks" were too verbose descritions of the events- need to be more punchy and concentrate on the specific hazards and suggest a bullet point list would suffice. In fact you may prefer a table if you think that against each there is a measure (or two or three) that could be taken and a situation in which applicable.

For example:
{I can't get columns to align when submitting this post, so actually show each column supposed to be on the one row as separate lines here}

Col1. HAZARD Poor adhesion

Col2. OCCURS WHEN
a) leaf fall in area approaching station
b) oil leaks from diesels whilst waiting for periods in platform
Col3. MITIGATION
a) Vegetation management
b) Better train maintenance
all- Wheel slip Protection
all- Defensive driving- low max speed, early braking
.
I have probably been a bit too minimalistic above to get to fit per line, but you get the general idea.
Marks are for lots of separate ideas, not the number of words.

Overall though the content of your answer was reasonable; I interpret that your hazards were:
1. Driver distraction
2. poor wheel rail adhesion.
3. Poor visibility approahing platform so driver doesn't see 1st train soon enough
4. Driver misinterprets the routing of entry signal and is incorrectly assuming that will need to stop by a certain place and driving accordingly, but is actually being sent to a different platform
5. Driver follows first train out of the platform [either SPADing or taking the exit signal before it has reverted to danger to protect the first train (due to delayed replacement controls)]
6. Combined length of two trains exceeds that of platform- some doors not adjacent to platform and station operability compromised by train trailing out into junction area prior to the platform.

The mitigations seem fine, but should consider that often more than one is applicable to each and would be needed to reduce risks to ALARP- don't just think of one and stop.

Some items which you haven't mentioned for example-
a) crash resistance of rollingstock and the internal design to minimise injuries in the event of a collison,
b) the "PL and MARI" as opposed to "yellow and SARI",
c) mid-platform signals to make the platform into two separate block sections so no permissive working actually needed (unless the need is to join separate trains to form one),
d) platform stop markers,
e) driver brefing and training,
f) operaing procedures which require a train which is to join another to first stop well clear (50m I think) the driver to make an announcement to the passengers, the first train also to have its passenger doors closed and then the 2nd train driven to auto-couple with the first.

Even though this is a mod3 rather than a mod1 or mod 7 question, still worth casting your net wider than "pure signaling" and incorporate more "railway domain" knowledge.

Hi, I have attempted Q6 from last year's paper.

[Hort]

thanks PJW, some good points raised.

[BHAR6026]

Hi PJW
So in this case do we have to explain risks in the beginning(which you have suggested) , then hazards leading to it and risk mitigations in the end ?

[PJW]

My view is that the question asked for RISKS and therefore you should start with these.
Since risks result from HAZARDS it seems reasonable that these are identified as part of "discussing the risks".
To mitigate risk than it is always best to eliminate the hazard, or failing that to reduce the hazard and failing that to mitigate against the likelihood by adding some barrier to escalation or otherwise adding something that would serve to reduce the consequences which could be expected to result.
Therefore this would be the approach I would normally adopt for all such questions, but precisely how you tackle it is up to you and the context of the question; it could sometimes be best to deal with all the risks, then all the hazards and then all the mitigations but other times it may be more appropriate to deal with a risk, the related hazards and the relevant possible mitigation before moving on to the next risk and doing similarly.
Depends on how separate each set are / how much overlapping there is.
Alternatively use a tabular approach and then it could be read either way.

Hi PJW
So in this case do we have to explain risks in the beginning(which you have suggested) , then hazards leading to it and risk mitigations in the end ?