2012 Q9 Hazards & risks of facing points beyond signal

[Hort]

Thanks for previous comments. I have now attempted Question 9 on the 2012 Mod 3 paper.

[PJW]

I actually think this question is a bit too limiting and therefor difficult to get good marks.

Item 1 is the obvious one; items 2 &3 are fundamentally the same as each other, the only difference whether or not it involves a SPAD and potentially therefor potentially a slower speed incident. Your 4th is about trailing points which are outside question scope- however it did add value since it is the only time you mentioned operational impact and damage in addition to collision / derailment (which are really the events which lead to the risks including the above, injury, death etc.)

I think that to try to get some more content that I'd have looked at the various scenarios; e.g. perhaps the signal is a platform starter (often is as generally try to avoid placing points immediately beyond signals but this is a circumstance when unavoidable)
a) booked train may not have departed on schedule, signaller may then have replaced its signal to danger but without reaching a proper understanding with the driver who had previously seen it off and was about to move,
b) diesel / oil on rails from leakage from previous trains meant that the rails were slippery and a driver running into the station intending to stop then suddenly encountered low adhesion so overshot a short distance and encountered points,
c) driver given "right away" by guard / platform dispatch staff who had failed to check signal was cleared for train departure and driver also fails to check aspect,
d) driver of through train but to take the lower speed diverging route is expecting the signal to be approach released as gets close to it as previous experience suggests it will, only today it does not.
Hence already we have 3 type different forms of SPAD and for which the later part of the question can discuss interlocking / procedural controls.
You may feel that I am talking more about SPAD than the points, but isn't this the risk scenario; otherwise we are really restricted to discussing signalling wrong side failures (or of course the situation in which such locking is not regarded as necessary).....whereas these should be mentioned of course, I doubt whether it would be easy to get the marks for the question mainly from this. Detection of points in line of route is really a "given" so that would itself be holding the signal to red, hence the only "engineering judgement" type debate is about detection of points within the overlap, application of "time of operation locking" etc. and there is not much here to talk about I feel).

To me it is the existence of the set of points immediately beyond the signal that converts what might otherwise be a relatively low risk event into something potentially much worse.

Your answer re item 1 was OK; useful had you pointed out that the provision of flashing aspects could be helpful in reducing the risk associated with the driver making the incorrect assumption of last minute approach release and indeed explaining that current practice for MAR is to release as soon as possible given route indicator sighting rather than perpetuating previous practice of trying to hold signal at danger until train speed had been reduced to junction speed.

Items 2&3 reasonable but would have been better to tie more closely with the various different find of SPAD scenarios.

Operational impacts.
Reasonable and yes I think it was a good idea to illustrate with mechanical signalling as well as RRI since it does serve to expand the question. I can assure you that with ticket working that it is even more restrictive, with people needing to secure and padlock points on site before any inolvement authority given and that takes a very long time!
Of course item 4 is out of scope.

Thanks for previous comments. I have now attempted Question 9 on the 2012 Mod 3 paper.

[AdrianM]

Hi,

See my attempt attached. Exam conditions, ran over my 30 minutes while I thought about the 20 marks allocated to the first part.

I have to say I struggled to come up with a range of different hazard that I could then follow up with good examples of control.

Also, I've probably overdone the last part. I should probably have spoken in general about the impacts rather than taking each one in turn (which is what I would do if it was worth more marks)

Little time left but any thoughts appreciated

Adrian

[PJW]

Forum has been very quiet this year, but actually I have had a lot of attempts from a range of individuals, particularly recently; everyone seems very shy in sharing their work......
However I have permission to put some attempts on which I have commented on the Forum, so here is one of them attached with some comments written on and others below.

2012 Q9:

Again this was good; I very much liked the presentation style.
A few things that space on paper did not allow me to write:

• You should when asked for a HAZARD always try to write it in the form
  “IF <inappropriate / unfortunate / careless action>
  WHEN <particular circumstances exist>
  THEN <specific accident> might occur. 
  Your answer did infer this quite often, but could have been worded better.  Remember that a HAZARD is “an accident waiting to happen” and an ACCIDENT always involves a loss (of life, of health, or equipment, of money, of environment, of reputation)
  
  
• Note that for signals it is generally the READABILITY rather than VISIBILITY which is important.  Driver might be able to see a signal in the distance but may well have to be closer to know if it really is at single or double yellow, whether that is the PLJI position 1 or position position 6, whether the one he can see is for the Fast line rather than the Slow line etc. 
  Also that MAR is not controlling the speed of train to match the turnout (it WAS this perhaps 40 years ago, but nowadays it is about making sure don’t mislead the driver by them thinking they are routed differently than actually are- hence the important thing is that they are braking at th previous signal and the junction signal does not clear before, in totality, it is readable (unless has had a Flashing Yellow or Splitting Distant on the approach)
  
  
• Swinging overlaps are provided to give layout flexibility, broadly to allow the signaller the choice of which of several potential conflicting movements they want to make at the time when bringing a train to a red signal and have the option of then changing the allocation once a movement has been made to then swing overlap to alternative position to be able to free up another bit of the layout for another movement.  You are entirely right that when the train is close to exit signal and therefore there is a chance of a SPAD that we would need to prevent such swinging for a while by imposition of Time of Operation locking, this is in case points were moving just at the time the train did SPAD and therefore may be encountered mid-stroke.  Generally facing points are not called when route is set, it is the trailing points beyond it which are called- but iif they are locked or there is an opposing overlap which conflicts, then it is the facers which are called to select the other overlap.
  
  
• For the last part I think worth saying that inclusion of any extra controls can only hamper system availability- the more there is the more that can fail.  Obviously if derailment at trap points, this is not itself risk free; there will certainly be delays and loss of availability of layout and if that is at entrance to a train depot the entire train service may be affected if the trains cannot get out onto the running line.  Most of the other controls do also have a downside (hopefuly small compared with their advantages, but still negatives.  A very slight overrun at traps will break the TCI and could therefore cause disruption for hours until rectified; during that time the line would either be closed or hand signalled and there are other risks that result from either (overcrowding , more people on busses etc;  or accident following hand signalling error).
  

[Alan Beavers]

Thanks Peter, I have certainly been using the forum to go through past reviews and in cases where the review looks of decent length (like all yours!) I have had a practice first, then looked at the attempt and the review.
I did post a couple (only ones started by me on the first page), practised in a similar way, which were supposedly 'good' examples from the IRSE website; I actually thought they'd have been lucky to have passed.