2010 Q3 Track Circuit SCWO

[PJW]

At Reading Study Group we discussed a couple of Mod 1 questions, of this this was one.
As a one off experiment, I thought I'd see how much I could actually get down on paper in the time now permitted. I gave myself a strict 18 mins to do all that you see attached (i.e. including heading info) just to see how it went when against the clock.

Of course I had all the decided advantage of having discussed the question in class a few days earlier; I certainly doubt whether I could done so well if I had been completely cold into the exam with only 10 minutes to select the questions and think of an outline. I felt that I would only have permited myself 10% of the 20 minutes to plan before commencing writing, so hence the 18min allowance I set. I suppose that I am not as "young and fit" as those who sit the exam but don't feel that I am too much into my dotage yet, although noticeably slowing down.

I have got to say that I think it is too tough; very difficult to have done 3 questions within the hour to any reasonable level.

Note that I knew I was fighting time so it is a bit of a scawl and generally terse; also gaps left in case I had time to go back and flesh out- which I of course didn't end up having the luxury to do.

Having to move straight on to the next one to do in the same fashon and then another one- umm.

Personal conclusion: asking candidates to attempt 3 questions within the hour was probably a mistake. I accept all were in the same boat and it was certainly possible to pass (hats off to those who succeeded), but I can see why the scores were all low across the range.
"I think we'd better think it out again".

[hiteshp]

PJW,

Thanks for attempting to complete this question under exam conditions. I took this paper and failed. It's reassuring to know that it was difficult to obtain a pass. I will attempt to take it again this year along with mod 2 and 3.

What are your thoughts about the format of the exam this year? Will the IRSE revert back to a 2 questions paper or will they keep the 3 question format and increase the time allocation?

Hitesh

[PJW]

To be honest, I don't think they know yet!

I think though that it is likely stay as 3 questions from what I have heard.

However I think that the "reading time" for possibly all papers may be reduced to 5 mins, or even eliminated altogether, in order that the module 1 paper can be extended to be 90 mins without making the overall day longer.
Associated with this, it may be that the nominal time for each of the modules will actually be extended slightly but without allocated "reading time", thus leaving each candidate to deploy the total time available as they see fit.

The reading time was originally introduced to give people time to become familiar with the nuances of the questions without feeling the pressure to start writing- a period of calm in which to choose their questions wisely. The perceived problem was that candidates were launching straight into "writing mode" before engagng brain.
It doesn't actually seem to have worked and the feeling from those who invigulate is that most candidates just appear to idle the time away.

Quite what it would do to those exam centres that have in recent years been given 20mins rather than 10mins reading time per paper, is just one of the "open points" within the proposals which seem to be under discussion........

When there is an official announcement, or when I hear more on the grapevine then I'll share on this Forum. Of course when applying for the 2011 exam you could always explicitly ask for confirmation re the length of the paper / number of questions you'll registering for!

PJW,

Thanks for attempting to complete this question under exam conditions. I took this paper and failed. It's reassuring to know that it was difficult to obtain a pass. I will attempt to take it again this year along with mod 2 and 3.

What are your thoughts about the format of the exam this year? Will the IRSE revert back to a 2 questions paper or will they keep the 3 question format and increase the time allocation?

Hitesh

[PJW]

Further to previous, this evening I was speaking to someone who did pass mod1 although he believed that he hadn't. He felt that the time pressure made it the hardest exam he had done in his life!

He put his success down to having practiced very many questions (albeit 30mins rather than 20mins). Tended to use a question answer posted on this forum as the trigger for attempting, and then compare answers and any comments given. Admitted that he probably should have shared his own attempt and I agreed that he indeed should, but it does show that even those who prefer to work privately can get a measure of how their output compares with what the examiners will expect.

PJW,

Thanks for attempting to complete this question under exam conditions. I took this paper and failed. It's reassuring to know that it was difficult to obtain a pass

Hitesh

[dorothy.pipet]

An attempt for comments please

- not timed

[PJW]

An attempt for comments please

- not timed

2010 Mod1 q3 DAP

OK as far as it went, but somewhat too brief for 30 minutes (but reasonable if you had allocated 20 minutes as indeed candidates had to do in that year), though I note that you didn't actually time yourself.

Scenario 2 also requires some rail break /poor series bonding of jumpers etc. somewhere along the track between the train axle and AA relay end(or a poorish train shunt that means with two track feeds in parallel the remaining rail to rail voltage is such that AA relay does not actually drop- however this partially duplicates scenario 1) because a short on the track is still a short wherever the feed has come from.

Scenario 3.  Probably needed more explanation (similar to 2) why the train shunt would not still short out; think best to talk about traction return large currents producing a dc offset down the length of a long section, the fact that one rail is effectively earthed by virtue of the traction return etc.

It is of course a mod1 question so I wouldn’t have expected to have had to go into the technical reasons for interference in great detail in this module.  In fact II think that it would therefore have been better to have amalgamated your scenarios 2 &3 and choose a more different one for the third.  

For example you hadn’t included considerations of physical stagger between IBJs and non-compliance with minimum length of track sections so certain wheelbase / inter-bogie spacing vehicles could escape detection since axles not actually in a location that does short out the track circuit.  This would both avoid the detail (which does not seem very applicable to the module and I don’t think is your strong point either) and open up to be more inter-disciplinary; a track circuit that used to be OK might fail to detect a vehicle that had not previously had cause to be utilised in the area.

Distinct reasons would then be:
1. Train shunt ineffective at rail interface
2. Undesired voltage presented to track relay
3. Dimensional incompatibility between vehicles and infrastructure
Each could have had sub-bullets (first one: wheel-wheel resistance, weight distribution on vehicle, wheel profile, rusty rails, icy rails, leaf fall mulch, surface contamination such as coal dust, sand applied to improve adhesion etc.)


However, going with what you selected, I thought page 2 was fine but you could have include what could be done in the wider signalling system to mitigate the consequences. Slow to pick TPRs (equivalent in SSI track special) is standard.  When ac vane tracks needed to be immunised for Eurostar, the the VT1(SP) was invented to add more “slow to pickness” in the location.  In ARS areas in particular, the interlocking utilises “15 sec track bob protection” for route holding if next track not occupied.  For lines were directionality can be reversed, then the long section route locking demands all tracks clear for 15 seconds in addition to the usual sectional route release. In leaf fall areas the interlocking can be configured to add extra delay in aspect clearance after any track has just picked.  Control systems such as IECC give “track out of sequence” alarms to the signaller.  I am sure that you know all this but you didn’t include anything of this ilk.

Initially I was reading the last para as part of item 2, but then realised that you must have intended it to have been 3.

You seemed only to be addressing the question from the perspective of a new works scheme, pre-commissioning; this is unduly limiting the question and constraining the scope of your answer.  So if you had considered the situation that a commissioned track was then discovered to be failing wrong side, that gives you more to discuss about the potential mitigations.  Certain rolling stock types could be temporarily prohibited from the route, or perhaps trains normally consisting of just single vehicles (e.g. a class 150) would be permissible if working in multiple so that there was a longer formation/ more axles.  Perhaps the risk of the possible WSF could be adequately mitigated in the short term by issuing signaller's instructions to disable ARS, key points into the required lie when routing over them and / or implementing a form of “double block working”.  

I think you were answering too much from just a signal engineering design perspective and not displaying a more holistic railway understanding. More consideration of the broad spectrum of how to manage the associated risk would have both given you more material and would have better aligned the answer with module 1 syllabus. Even just making clear which of your proposals were addressing the likelihood and which the consequences of the risk would have helped give the examiner the impression that you were very conscious of the syllabus of the module in whose context the question was asked.

It wasn’t a bad answer; I think that it should have passed but certainly wasn’t one of your better ones. Perhaps for the first 12 marks you’d have got: 2+2+2 and for the next 8 you’d have got 2+2+2 making it 12/20 (when I added the separate scores felt these overall didn’t reflect the subjective feel of the answer and then I realised that question in 2010 was out of 20 rather than 25); primarily because too focussed on the technical and not enough “management of safety”.  However note that 2010 was the year when candidates expected to do three questions in an hour and thus had to answer each in 20 minutes; this proved virtually impossible so that is why module 1 finally became like the other written papers regarding the number of questions and time allowance.