2009 Main Line Layout

[PJW]

I don't think that you and I are actually disagreeing about what the exam SHOULD be; indeed I think we very much share the same opinion.

Where we differ, is our view about what the examiners are ACTUALLY looking for, which we can only surmise from the little indications which are given.

I base what I wrote on what has been said at Exam Reviews and indeed by the examiners when I was attempting to write the Study Pack. In several respects I feel that their expectations are frozen in time, but having this insight it seems reasonable to let candidates know my estimation of where the marks are.

I must confess that I have a difference of opinion here over the provision of AWS and TPWS on your layout.



Reuben

[Peter]

Sorry to be a pain on the 1.5 times the braking issue. I may be slow here, but from my reading of the GK/RT0075 standard, I can't seem to see where it says it's OK to exceed the min braking distance by more than 50% for mixed traffic on the same line. However, as pointed out, I guess this is one of those problems that arises in the exam because the deceleration rates for passenger and freight are equal, and this is not necessarily reflective of reality (though makes for simpler exam calculations).

I think this is covered in the exceptions in Table 1 entry d on page 10.

[reuben]

I don't think that you and I are actually disagreeing about what the exam SHOULD be; indeed I think we very much share the same opinion.

Where we differ, is our view about what the examiners are ACTUALLY looking for, which we can only surmise from the little indications which are given.

I base what I wrote on what has been said at Exam Reviews and indeed by the examiners when I was attempting to write the Study Pack. In several respects I feel that their expectations are frozen in time, but having this insight it seems reasonable to let candidates know my estimation of where the marks are.

I must confess that I have a difference of opinion here over the provision of AWS and TPWS on your layout.



Reuben

Sorry Peter, I had overlooked that you've got some extra steer upon the areas of interest from the examiners. In this context your advice to relegate AWS and TPWS to the poor-relations box is perfectly correct. If only the question said so....!

Reuben

[asrisaku]

Dear Professional Railway engineers

I had another go in this year. I have studied the attempt from Reuben with PJW's comments. Then I made it as a practice.

I would much appreciate it if I can get any comments and broaden my knowledge.

Note: I really have a problem about positioning signals at platform in station B. With min braking distance 760m from 4-aspect, it cannot be satisfied because of point work. I handled it with speed restriction and this might have an impact on headway speed. Actually this can be fixed if we don't position signals at platform as Reuben did. And I am really not sure the way to deal with it. It seems the train cannot stop at platform if I position the signal not in the platform. Any suggestion idea? Please share.

Best regards
Arnut

---

The last attachment.

[reuben]

Headway Calculation

The headway calculation is very well performed, one of the best I’ve seen.
Minor criticism – no braking distance calculated for 40 Kmh or 100 kmh.
It might be worthwhile to draw a simple diagram of two trains at the headway critical moment, to justify the equations used for 3 and 4 aspect headway time.
Although 1.33 was used in the past, 1.5 is usually used today as the maximum signal braking distance - adopting this more relaxed limit will always make your task of signalling the layout easier.
The stopping calculation is very well presented and concisely argued - this is essential in the limited time available.
The final graph is a good illustration. One error in the dimensioning is that you have marked 118.4 s (non stop HT) in place of 215s (stopping HT).

The layout
You need to state which network rules you have used - I assume “UK Main Line” ?
Query signal 101 is positioned as for a 3 aspect signal, but has a 4 aspect profile.
You would benefit from studying the methods which can be used to mitigate underbraked 3 aspect signals and to achieve transition 3 to 4 aspect. The two problems and their solutions are very similar. One solution involves applying MAR to the previous signal, when the underbraked signal is ON; the other method uses an additional distant signal for the underbraked signal. These methods would let you manage the transition from 3 to 4 aspect on both lines in this layout.

The provision of ROL at signal 103 is inappropriate – only suitable where there is a convergence (or very occasionally opposing overlap limit) within the full overlap area. Remember that with 4 aspect signalling, the basic requirement is to have (1- 1.5 *) braking distance from YY to R. This means that it’s OK to have greater than 0.5 braking distance in one signal section, provided it’s made up for in the neighbouring sections. In your case, positioning signal 103 at dimension 0300 would give 1850m to signal 111- still less than your calculated 2015m maximum.
The down goods should probably only require 3 aspect signalling, due to the lower braking distance at 100 kmh.
107 signal requires an overlap towards the spur line – suggested position 1700m to include the diamond.
Diamond crossing Down Goods / spur line:
• Is fixed - you have added “switch diamond” symbols.
• Will require trap points on both sides, to protect passenger spur line movements from Goods incursions.
Down siding also requires a trap point for the same reason.
Spur Line: 4 aspect signalling is inappropriate (and overbraked for the low speed). Would be better to use one train working controlled by track circuit and/ or 2 aspect.
Signals 111/ 109 should be placed at 2100m to give full overlaps to the points.
Signal 109:
• MAR not required as both routes have same speed.
• Standard indicator more suitable

Signal 113 would be more appropriate as a shunt signal (run round moves only)
Signal 115 would be more appropriate as 3 aspect with standard indicator.
Route 115B appears to take the Up Branch and “skip” signal 151 - is this intended?, if so, a down direction signal required alongside 151 on the Up branch.
Ongoing signals 117 & 119 are unconstrained by layout features, so the signal spacing could be extended within the range calculated to reduce cost.

Up Siding E:
• No method has been provided to enter siding - requires down direction shunt signal at 1040m.
• Separate track circuit GA not required.
• Siding track circuit not named (but not required either)
Signal 122 should be placed at position 2850m to provide full overlap clear of points. See previous comments about ROL and 3 to 4 aspect transitions.
Note that platform end signals are not obligatory to instruct making a station stop - they often fall in this place to protect pointwork beyond the station only. You can therefore omit signals 110/ 108, and reposition 106/ 104 to position 0800m. this would then give correct 2050m braking from 122 (YY), via 116 (Y) to 106 ®
Subsidiary aspects/ call-on routes not required on 114/ 116 signals:
• Platform sharing not required by the spec.
• A goods train from 114 should not be called-on behind a passenger train at 110.
• The main class routes can be used for the “shunting” (but not necessarily shunt class) run-round movements.



Signal 151 inappropriately positioned with points in overlap – could reposition at 2950m to give 400m standage from Up Main and 100m reduced overlap – mitigated by 40kmh approach speed.
Signals 154 and 153 both inappropriately positioned to stop trains in the tunnel (also very difficult to sight). There’s actually no need for either of these signals:
• Since the “junctions” which they protect give no choice of route, signals are not necessary – any speed restriction through the points can be managed using permanent speed restriction arrangements.
• It is operationally inconvenient to stop trains in the single line section
• A better solution would be for 151 route to pass all the way to 155, and 156 all the way to 152
Signal 156 inappropriately positioned - see previous ROL comment.
Signal 152 better to use standard indicator.

Limit of shunt required on up branch at approx 2100m to terminate running-round locomotives.
Call-on class route required at 152 signal to allow run-round locomotive to rejoin train at 114.
Trap points required in Up Goods at 2450m.

Route tables could be done faster by only writing column headings once (“these are my column headings for all route tables”). Could reasonably omit for simpler signals such as 302, 301 etc.

Good provision of point positions and numbering.

Good provision of train detection and numbering.

Overall
Although I appear to have made a lot of comments, they are mostly “fine detail” in nature. The layout has been comprehensively signalled in accordance with principles and the spec. Coupled with the good headway calculation and points/ train detection provision, I think that this response would comfortably achieve a good “pass” grade. Not a lot of improvement would be needed for a “credit” to be feasible.

[asrisaku]

Dear Reuben

Thank you very much for your comments. Actually I cannot improve my knowledge without your comments. I am out of office and preferably print out your comments and take them into consideration carefully.

At the moment, I am very happy getting any comment. I have weak background in the railway. And I learned a lot from your attempts and others' attempt as well.

I'll be back with my query later after review.

Thanks again

Arnut S.

[asrisaku]

Headway Calculation

The headway calculation is very well performed, one of the best I’ve seen.
Minor criticism – no braking distance calculated for 40 Kmh or 100 kmh.
It might be worthwhile to draw a simple diagram of two trains at the headway critical moment, to justify the equations used for 3 and 4 aspect headway time.
Although 1.33 was used in the past, 1.5 is usually used today as the maximum signal braking distance - adopting this more relaxed limit will always make your task of signalling the layout easier.
The stopping calculation is very well presented and concisely argued - this is essential in the limited time available.
The final graph is a good illustration. One error in the dimensioning is that you have marked 118.4 s (non stop HT) in place of 215s (stopping HT).

Thanks Reuben. The calculation was suggested by Peter in Mod2 2005 and I found the presentation for headway calculation and adopted that way to present it.
Next attempt, I'll try to use 1.5(maximum tolerable). I totally agree with you I had difficulty to use 1.33. 1.5 provides more margin.

Headway Calculation
The layout
You need to state which network rules you have used - I assume “UK Main Line” ?

Yes, actually I wrote it in the layout in the little box at the upper right corner. You might not see it.

Query signal 101 is positioned as for a 3 aspect signal, but has a 4 aspect profile.
You would benefit from studying the methods which can be used to mitigate underbraked 3 aspect signals and to achieve transition 3 to 4 aspect. The two problems and their solutions are very similar. One solution involves applying MAR to the previous signal, when the underbraked signal is ON; the other method uses an additional distant signal for the underbraked signal. These methods would let you manage the transition from 3 to 4 aspect on both lines in this layout.

Thanks for this useful info. I have read it in the study pack and did not implement into layout because I forgot this important principle.

The provision of ROL at signal 103 is inappropriate – only suitable where there is a convergence (or very occasionally opposing overlap limit) within the full overlap area. Remember that with 4 aspect signalling, the basic requirement is to have (1- 1.5 *) braking distance from YY to R. This means that it’s OK to have greater than 0.5 braking distance in one signal section, provided it’s made up for in the neighbouring sections. In your case, positioning signal 103 at dimension 0300 would give 1850m to signal 111- still less than your calculated 2015m maximum.

On the time at attempt I did not know that we can have the distance over 1.33(0.66+0.66) from YY to R and now you gave me the easier way to implement the layout. Thanks again.

The down goods should probably only require 3 aspect signalling, due to the lower braking distance at 100 kmh.

I must confess that I was not careful at the speed for the down goods and spur line until you pointed out to me. This helps a lot with next attempt.

107 signal requires an overlap towards the spur line – suggested position 1700m to include the diamond.
Diamond crossing Down Goods / spur line:
• Is fixed - you have added “switch diamond” symbols.
• Will require trap points on both sides, to protect passenger spur line movements from Goods incursions.
Down siding also requires a trap point for the same reason.
Spur Line: 4 aspect signalling is inappropriate (and overbraked for the low speed). Would be better to use one train working controlled by track circuit and/ or 2 aspect.
Signals 111/ 109 should be placed at 2100m to give full overlaps to the points.
Signal 109:
• MAR not required as both routes have same speed.
• Standard indicator more suitable

All comments I agree. But one question Signal 109 MAR not required as both routes have same speed. Could you please explain more? I think that by the nature of turnout we need to have delay time to proceed a train. Did I miss something?

Signal 113 would be more appropriate as a shunt signal (run round moves only)
Signal 115 would be more appropriate as 3 aspect with standard indicator.
Route 115B appears to take the Up Branch and “skip” signal 151 - is this intended?, if so, a down direction signal required alongside 151 on the Up branch.
Ongoing signals 117 & 119 are unconstrained by layout features, so the signal spacing could be extended within the range calculated to reduce cost.

Regarding the Route 115B, yes it is. I have one question. It has no possibility to have a train go to down branch from Signal 115 because of the point direction of switch diamond. It is not possible to have a route that 209A is normal and 209B is reverse. Am I right?

Up Siding E:
• No method has been provided to enter siding - requires down direction shunt signal at 1040m.
• Separate track circuit GA not required.
• Siding track circuit not named (but not required either)
Signal 122 should be placed at position 2850m to provide full overlap clear of points. See previous comments about ROL and 3 to 4 aspect transitions.
Note that platform end signals are not obligatory to instruct making a station stop - they often fall in this place to protect pointwork beyond the station only. You can therefore omit signals 110/ 108, and reposition 106/ 104 to position 0800m. this would then give correct 2050m braking from 122 (YY), via 116 (Y) to 106 ®
Subsidiary aspects/ call-on routes not required on 114/ 116 signals:
• Platform sharing not required by the spec.
• A goods train from 114 should not be called-on behind a passenger train at 110.
• The main class routes can be used for the “shunting” (but not necessarily shunt class) run-round movements.

Thanks for platform signal solution. I always position a signal at platform at the beginning and this is the case that I cannot have it. I will follow your suggestion when it is underbraked.

Signal 151 inappropriately positioned with points in overlap – could reposition at 2950m to give 400m standage from Up Main and 100m reduced overlap – mitigated by 40kmh approach speed.
Signals 154 and 153 both inappropriately positioned to stop trains in the tunnel (also very difficult to sight). There’s actually no need for either of these signals:
• Since the “junctions” which they protect give no choice of route, signals are not necessary – any speed restriction through the points can be managed using permanent speed restriction arrangements.
• It is operationally inconvenient to stop trains in the single line section
• A better solution would be for 151 route to pass all the way to 155, and 156 all the way to 152
Signal 156 inappropriately positioned - see previous ROL comment.
Signal 152 better to use standard indicator.

I always aware that it is better to avoid to position signals in tunnel and viaduct area. Speed restriction as you proposed it can deal with it. I’ll use this technique if I have difficulty to place signals in that area.

Limit of shunt required on up branch at approx 2100m to terminate running-round locomotives.
Call-on class route required at 152 signal to allow run-round locomotive to rejoin train at 114.
Trap points required in Up Goods at 2450m.

Route tables could be done faster by only writing column headings once (“these are my column headings for all route tables”). Could reasonably omit for simpler signals such as 302, 301 etc.

Good provision of point positions and numbering.

Good provision of train detection and numbering.

Overall
Although I appear to have made a lot of comments, they are mostly “fine detail” in nature. The layout has been comprehensively signalled in accordance with principles and the spec. Coupled with the good headway calculation and points/ train detection provision, I think that this response would comfortably achieve a good “pass” grade. Not a lot of improvement would be needed for a “credit” to be feasible.

All in all, thanks for your time and your contribution. This can actually shorten my time studying railway layout and it helps a beginner like me to develop skills.

[reuben]

Hi Again

to answser your specific questions:

Q- But one question Signal 109 MAR not required as both routes have same speed. Could you please explain more? I think that by the nature of turnout we need to have delay time to proceed a train. Did I miss something?

A - The normal way of warning of a speed restriction (turnout, curvature, poor track quality, whatever) is by lineseide signage , driver instructions (The sectional appendix), and driver training, collectively known as "route knowledge". therefore a signal such as 104, which leads from a 100 kmh line, via 40 kmh turnout, to a 140 kmh line , needs neither a route indicator nor MAR approach release condition. The driver approaching this signal, even if it is green, or if did not exist at all, would know that the maximum safe speed is 40 kmh , and adjust speed accordingly.

Usually where there is a turnout and choice of route, there is a "faster" and "slower" option, such as 111. if the driver sees only yellow or green in this signal, they control the train speed within the higher speed profile (140kmh). the route indicator is used to inform the driver that a lower speed profile applies - in this case 40 kmh for the turnout. Because the speed differential is very great, approach release from red (MAR ) is also require to enforce this speed reduction.

Now, in the case of 109, the approaching driver knows that the highest speed profile available is 40 kmh through points 206, regardless of the final train destination. Therefore, MAR is not needed to force this reduction (just like 104 signal). Route indications are still required to confirm (in case of misrouting for example) the actual route, and since there is no "fastest" route, an indication would be used for both options.

Q Regarding the Route 115B, yes it is. I have one question. It has no possibility to have a train go to down branch from Signal 115 because of the point direction of switch diamond. It is not possible to have a route that 209A is normal and 209B is reverse. Am I right?

A - the switch diamond cannot allow any movement from 115 to 151 - it only allows "straight across" moves. My point is that, when the move from 151 to 153 passes on the Up Branch, the driver will be confused that there is a Down Direction Signal 151 to be ignored, but no signal to obey - this is the "parallel lines" rule. the confusion is removed by providing an extra down direction signal on the Up branch, alongside 151.

Hope this helps

best wishes

Reuben

[asrisaku]

Thanks a lot. Reuben, that's clear.

[dorothy.pipet]

Another attempt for comments please.