2011 Mod 3 Control Table attempt

[alexkwan]

Dear Sir/Madam,

I have attempted 2011 Mod3 Q1 as attached.
Grateful if any comments could be given.
Thanks in advance.

Regards,
Alex

[reuben]

Dear Alex

I've had a quick look at 133 points - which reveal in some cases that my "model answer" was wrong and you were right!

it's inevitable in the exam that you will find lots of routes calling and locking each point - often in "groups" from one signal with similar characteristics. Although this would not be done in real work, i think it's an acceptable shorthand for the exam to write "34A(M/C)/ B(S)/C(M/C" as a single entry instead of putting each true route name on a separate line. this will save you both time and space, which are both in short supply!

You have indicated that routes 352A and 348A call the points reverse - this is not the route option required - see the notes next to the route boxes on the plan

you've missed calling reverse by routes from 212 signal

There are also possible swinging overlap conditions associate with routes from 327 & 343 signals, but these start to get very difficult to spot, let alone express!

Overall, you have well captured the main conditions calling and locking the points. Take care to look for information on the plan regarding the "alternative route" which is intended.

I've started to look at the routes and remembered how my head hurt last time I looked at these - so will defer comment until later.

best wishes

Reuben

[alexkwan]

Thanks very much for your comment, Reuben.
I indeed miss the route from 212.
But I think 352A and 348A should be there.
The notes beside the route boxes are via 133R.
And I wonder if swinging overlaps have to be included in the point control table and also the format.
I have no idea of the way of writing them.
Thanks.

Regards,
Alex

Dear Alex

I've had a quick look at 133 points - which reveal in some cases that my "model answer" was wrong and you were right!

it's inevitable in the exam that you will find lots of routes calling and locking each point - often in "groups" from one signal with similar characteristics. Although this would not be done in real work, i think it's an acceptable shorthand for the exam to write "34A(M/C)/ B(S)/C(M/C" as a single entry instead of putting each true route name on a separate line. this will save you both time and space, which are both in short supply!

You have indicated that routes 352A and 348A call the points reverse - this is not the route option required - see the notes next to the route boxes on the plan

you've missed calling reverse by routes from 212 signal

There are also possible swinging overlap conditions associate with routes from 327 & 343 signals, but these start to get very difficult to spot, let alone express!

Overall, you have well captured the main conditions calling and locking the points. Take care to look for information on the plan regarding the "alternative route" which is intended.

I've started to look at the routes and remembered how my head hurt last time I looked at these - so will defer comment until later.

best wishes

Reuben

[reuben]

Oops, my mistake re routes via points R!

Peter's diagnosis of my error was perfectly correct. I lose track of the times I've reminded others to beware of the upside-down route boxes......

I do think this peculiar practice of CIW-land is very sensible - once you get used to it!.

Reuben

[reuben]

Hi again Alex

Sorry for the slow reply- here are further comments on your route control tables:

Route 216A(M)

Route controls:

Good- opposing routes handled correctly.
Selection of available swinging overlap also correct.
I know what you’re trying to express, but it’s not the custom to state “OFZ-BA free”, as this assumes you have a separate control table expressing how OFZ-BA operates. In practice, you need to end up writing a very complex expression to express how “OFZ-BA” is free, in terms of other routes, track circuits and points – see my model answer. Realistically, you won’t have time in the exam to handle this, and the examiners are unlikely to award many marks for it - you’re better applying effort to the easier stuff.

Signal controls
Also good, but there’s no need to check OFZ-BA to be free: the setting of this route should impose locking to prevent other conflicting routes/ overlaps being set, expressed on the CTs for the other routes.
You missed the flashing yellow condition in the aspect sequence.
It might also be worth adding the “stick unsetting” conditions – this has to be a special control as there are no columns provided.

348C(M)
144 points missed.
Route controls also require 321 normal - single line release- this is effectively a “directly opposing route”
Route controls also need to treat 343A(M) as an indirectly opposing route – if a train has arrived at 347 signal safely, 131 points will be locked under the train, but if the train SPADs at 347, 131 points will release and the SPAD, while still in the overlap will lose its opposing locking protection.
Foul track circuit FG missed from signal controls

349D© (route to platform 2)
You have provided controls for route 349C(M) - platform 1 instead. However, they look correctly handled.
The route controls need to specify that the platform should have at least one occupied track circuit at time of route setting.

We don’t know how the examiners treat this situation.
• Certainly you won’t get any direct credit for a correct answer to the wrong question.
• One school of thought argues that if 25% of the question is not answered, the maximum you can score is 75%, even if the remainder is answered perfectly
• An alternative argument could be that you have already demonstrated knowledge of how to specify all the different control functions in other parts of the question, only leaving features unique to the part you missed – such as controls unique to call-on class routes. In this case, you might be able to score 90% (say) despite your omission.

I suspect that the actual view taken in marking is somewhere between the two extremes expressed above.

In summary, your tables have correctly captured most of the features, including complex features such as indirectly opposing routes and swinging overlaps, so this answer would score well in the exam.

You annotations seem to show that you spent over 30 minutes on the three route control tables, and presumably another 10-15 on the points. Therefore, some care is needed to budget time fairly in the exam and strictly move on when the 30 minutes per question is up. the time is always better spent scoring the "easy firsy 50%" marks of two long answer questions.

Good work - good luck for the exam!

Reuben

[PJW]

Reuben Thanks for sharing the load and responding to this thread!

Just one comments and this applies to anyone claiming to do the Control tables to NR current standards; 11202 was reissued a couple of years ago now and yes for SSI it does mandate a sub-route / sub-overlap releasing table and then route tables that only declare the relevant sub-route. The change was to make the CTs more aligned to the data structure and also give testing efficiency and open the door to have CTs matching the functionality of different interlocking systems suh as SIMIS-W that operate rather differently.

I don't suggest this approach for the IRSE Exam, but candidates do not claim to be doing Control Tables to "NR current standards" unless you really are!- similarly if you don't want to get involved with complicated post SPAD aspect reversion, better to say "Network Rail standards c2000".

Route controls:

Good- opposing routes handled correctly.
Selection of available swinging overlap also correct.
I know what you’re trying to express, but it’s not the custom to state “OFZ-BA free”, as this assumes you have a separate control table expressing how OFZ-BA operates. In practice, you need to end up writing a very complex expression to express how “OFZ-BA” is free, in terms of other routes, track circuits and points – see my model answer. Realistically, you won’t have time in the exam to handle this, and the examiners are unlikely to award many marks for it - you’re better applying effort to the easier stuff.

Reuben

[PJW]

I think you are about right. My information is that "it depends"

I understand that if the route were similar in nature and it was thought to be a genuine mistake, the examiner may mark the paper twice
a) on the assumption the answer was for the requested route, and
b) on the basis that the route which had apparently been done had been the one requested.
Initially mark a) would be utilised when calculating the candidate's overall score, but if a borderline F/NM or NM/P then mark b) would be looked at to see if this move the candidate over the threshold.
However a lot would depend on whether the wrong route seemed to be the sort of error that can occur in exam conditions and therefore whether it was considered reasonable to give the candidate the benefit of the doubt. Clearly if there was something specific about the route that had been asked for, such as a flashing aspect, which did not apply to the route actually undertaken, then those potential marks would just have to be regarded as lost.

Moral is always to double check!

We don’t know how the examiners treat this situation.
• Certainly you won’t get any direct credit for a correct answer to the wrong question.
• One school of thought argues that if 25% of the question is not answered, the maximum you can score is 75%, even if the remainder is answered perfectly
• An alternative argument could be that you have already demonstrated knowledge of how to specify all the different control functions in other parts of the question, only leaving features unique to the part you missed – such as controls unique to call-on class routes. In this case, you might be able to score 90% (say) despite your omission.

I suspect that the actual view taken in marking is somewhere between the two extremes expressed above.

Good work - good luck for the exam!

Reuben

[taxcel]

Dear Reuben

I also attempted 2011's control table, and I noted you mentioned you have a "model answer", may I know where it is posted? I couldn't find it on this website.

In addition, would you explain what is "OFZ-BA "

[PJW]

I can't help with the first part, so will leave that to Reuben

OFZ-BA is the nomenclature that is uused in SSI data to teflect the element of locking imposed when a route is et which has its overlap extending over track section FZ; it is called a "sub-overlap".

Just as route locking in RRI is either in the Up or Down direction, there is a need to specify the directionality. The various ends of the track section are given a reference in alphabtical order in a clockwise direction- on plain line sections there are directions AB, BA; for a section with a single point end there could be dirctions AB, BA as well as AC, CA and if there is more than a single point end then there can be even more ends and corresponding numbers of sub overlaps.

The most recent form of NR control tables for SSI and SSI derivative interlockings use such nomenclature. However would not follow this approach for IRSE Exam CTs as can only use this short cut on point and signal control tables if provide another type of Control Table regarding the route locking and you won't have time to do so.

Dear Reuben

I also attempted 2011's control table, and I noted you mentioned you have a "model answer", may I know where it is posted? I couldn't find it on this website.

In addition, would you explain what is "OFZ-BA "

[arunkumar]

Hi again Alex

Sorry for the slow reply- here are further comments on your route control tables:

Route 216A(M)

Route controls:

Good- opposing routes handled correctly.
Selection of available swinging overlap also correct.
I know what you’re trying to express, but it’s not the custom to state “OFZ-BA free”, as this assumes you have a separate control table expressing how OFZ-BA operates. In practice, you need to end up writing a very complex expression to express how “OFZ-BA” is free, in terms of other routes, track circuits and points – see my model answer. Realistically, you won’t have time in the exam to handle this, and the examiners are unlikely to award many marks for it - you’re better applying effort to the easier stuff.

Signal controls
Also good, but there’s no need to check OFZ-BA to be free: the setting of this route should impose locking to prevent other conflicting routes/ overlaps being set, expressed on the CTs for the other routes.
You missed the flashing yellow condition in the aspect sequence.
It might also be worth adding the “stick unsetting” conditions – this has to be a special control as there are no columns provided.

348C(M)
144 points missed.(EVEN Points 135, 139, 132, 137, 126 & 127 are to be added)
Route controls also require 321 normal - single line release- this is effectively a “directly opposing route”
Route controls also need to treat 343A(M) as an indirectly opposing route – if a train has arrived at 347 signal safely, 131 points will be locked under the train, but if the train SPADs at 347, 131 points will release and the SPAD, while still in the overlap will lose its opposing locking protection. (though train spads at 347 overlap point setting would be 132R. but, for 348C(M) 132 is required to be normal. so, 343a(m) may not be required to lock).
Foul track circuit FG missed from signal controls

349D© (route to platform 2)
You have provided controls for route 349C(M) - platform 1 instead. However, they look correctly handled.
The route controls need to specify that the platform should have at least one occupied track circuit at time of route setting.

We don’t know how the examiners treat this situation.
• Certainly you won’t get any direct credit for a correct answer to the wrong question.
• One school of thought argues that if 25% of the question is not answered, the maximum you can score is 75%, even if the remainder is answered perfectly
• An alternative argument could be that you have already demonstrated knowledge of how to specify all the different control functions in other parts of the question, only leaving features unique to the part you missed – such as controls unique to call-on class routes. In this case, you might be able to score 90% (say) despite your omission.

I suspect that the actual view taken in marking is somewhere between the two extremes expressed above.

In summary, your tables have correctly captured most of the features, including complex features such as indirectly opposing routes and swinging overlaps, so this answer would score well in the exam.

You annotations seem to show that you spent over 30 minutes on the three route control tables, and presumably another 10-15 on the points. Therefore, some care is needed to budget time fairly in the exam and strictly move on when the 30 minutes per question is up. the time is always better spent scoring the "easy firsy 50%" marks of two long answer questions.

Good work - good luck for the exam!

Reuben