It is an extraordinary neat attempt and a real joy to read; I just don't think that you could do like this in exam conditions when it needs to be fast and therefore more of a scribble.
Similarly it was clearly set out in text book fashion; you do need to show the logic but in the exam you won't have time- hence need to be more brief rather than waste time repeating too much of the question.
The examiners are always wary of the use of DGR, but your diagram is very clear to explain this initially. However it is at stage (v) when you divide DGR by B and come to the answer N=1.9 that they will object- what is the significance of N they ask? Whatdo you think you are doing when you divide a conceptual distance DGR by the braking distance; it is a ratio yes, but what is the significance of the number one gets? You need to relate this back to signalling principles (see later).
You then draw a diagram showing 4 aspect signals spaced at D4 which you then claim must lie within the range 0.5B to 0.75B; also that D4<= GDR/3. There is absolutely nothing wrong with these as conclusions, BUT you really have not explained well eenough WHY!!
I did quite like your diagram of the usable range within which a signal can be positioned and satisfy the constraints- however I wouldn't call it a "safety band". The min signal spacing is a safety constraint arissing from needing the relevant BRAKING DISTANCE, but the maximum signal spacing is an OPERATIONAL CAPACITY constraint arsing from the need to achieve the specified headway.
I did not agree with "enable 4-aspect signalling for a more frequent and economical services".
Basically if you position 3 aspect signals as close as you can safely do, they will be 1975m apart on this layout. However as you have shown (well nearly) if you spaced them like this then the smallest headway distance you could achieve would then be 1975x2+389+180+180 and that does not satisfy the headway requirement.
Hence you have to incur a lot more cost and provide many more signals using 4 aspects that can be as close as 988m. However by spacing these out as far as you can such that the signalling only just achieves the headway requirementt, then the solution is as economical as it can be whilst satisfing the other constraints.
NOW LETS LOOK AT THE ACTUAL QUESTION ASKED
a) Determine minimum braking distances for the permissible speeds and braking
characteristics of the traffic on offer.
b) Determine graphically, or by calculation, the headway at minimum signal spacing and the
given speed for:
i) A fast passenger train following another fast passenger train; AND
ii) A fast passenger train following a stopping passenger train.
All calculations and graphs must be shown [20 Marks]
You did a) in your section (iii)- may have been a good idea to have annotated accordingly to show the examiner that you have done it.
I don't think that you actually did b)i).
What you did do was broadly related to it (and indeed very important for the rest of the question when placing signals on the layout), but you did not explicitly answer the actual question the examiners asked in the 2008 question paper.
Obviously you have not attempted b)ii) as only claiming to be doing the non stop headway at present.
There were 20 marks available and you need to aim to get these in less than 18 minutes.
Let's guess that the marks are actually split between the sections as 6+7+7.
You'd have got the first 6.
You'd have got perhaps 3 of the next 7.
You'd have got none of the next 7.
Hence let's say a total of9; the question is: did it take you more than 8 minutes to achieve them- I bet it did!
The analogy is that it was a very smooth sedate ride in a lovely car and hence pleasurable. However not so good if one particularly anxious to get to the destination by a specific time; the car is using so much petrol that it will be ceertainly out of fuel before getting half way there.
So for the exam, think a little less about quality, more about the need to get a good "marks per minute" rating.
Similarly it was clearly set out in text book fashion; you do need to show the logic but in the exam you won't have time- hence need to be more brief rather than waste time repeating too much of the question.
The examiners are always wary of the use of DGR, but your diagram is very clear to explain this initially. However it is at stage (v) when you divide DGR by B and come to the answer N=1.9 that they will object- what is the significance of N they ask? Whatdo you think you are doing when you divide a conceptual distance DGR by the braking distance; it is a ratio yes, but what is the significance of the number one gets? You need to relate this back to signalling principles (see later).
You then draw a diagram showing 4 aspect signals spaced at D4 which you then claim must lie within the range 0.5B to 0.75B; also that D4<= GDR/3. There is absolutely nothing wrong with these as conclusions, BUT you really have not explained well eenough WHY!!
I did quite like your diagram of the usable range within which a signal can be positioned and satisfy the constraints- however I wouldn't call it a "safety band". The min signal spacing is a safety constraint arissing from needing the relevant BRAKING DISTANCE, but the maximum signal spacing is an OPERATIONAL CAPACITY constraint arsing from the need to achieve the specified headway.
I did not agree with "enable 4-aspect signalling for a more frequent and economical services".
Basically if you position 3 aspect signals as close as you can safely do, they will be 1975m apart on this layout. However as you have shown (well nearly) if you spaced them like this then the smallest headway distance you could achieve would then be 1975x2+389+180+180 and that does not satisfy the headway requirement.
Hence you have to incur a lot more cost and provide many more signals using 4 aspects that can be as close as 988m. However by spacing these out as far as you can such that the signalling only just achieves the headway requirementt, then the solution is as economical as it can be whilst satisfing the other constraints.
NOW LETS LOOK AT THE ACTUAL QUESTION ASKED
a) Determine minimum braking distances for the permissible speeds and braking
characteristics of the traffic on offer.
b) Determine graphically, or by calculation, the headway at minimum signal spacing and the
given speed for:
i) A fast passenger train following another fast passenger train; AND
ii) A fast passenger train following a stopping passenger train.
All calculations and graphs must be shown [20 Marks]
You did a) in your section (iii)- may have been a good idea to have annotated accordingly to show the examiner that you have done it.
I don't think that you actually did b)i).
What you did do was broadly related to it (and indeed very important for the rest of the question when placing signals on the layout), but you did not explicitly answer the actual question the examiners asked in the 2008 question paper.
Obviously you have not attempted b)ii) as only claiming to be doing the non stop headway at present.
There were 20 marks available and you need to aim to get these in less than 18 minutes.
Let's guess that the marks are actually split between the sections as 6+7+7.
You'd have got the first 6.
You'd have got perhaps 3 of the next 7.
You'd have got none of the next 7.
Hence let's say a total of9; the question is: did it take you more than 8 minutes to achieve them- I bet it did!
The analogy is that it was a very smooth sedate ride in a lovely car and hence pleasurable. However not so good if one particularly anxious to get to the destination by a specific time; the car is using so much petrol that it will be ceertainly out of fuel before getting half way there.
So for the exam, think a little less about quality, more about the need to get a good "marks per minute" rating.
(16-07-2013, 01:13 PM)s.sathish08 Wrote: Hi Everyone...
Herewith i have attached 2008 Module 2 Non stop headway calculation,
Please check and review it ..
Your corrections and suggestion is required please...
Thanks
Sathish
PJW