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2009 Q2 DEGRADED MODE OPERATION OF SINGLE TRACK BRANCH
#1
(19-05-2010, 02:04 PM)Hort Wrote: Hi Peter,

I have been accepted to sit Mod 1 and 5 this year. Please see attached my attempts at questions 2, 5 and 7 of last year's Mod 1 paper.

Regards

Gethin

Question 2.

I don't see what the "one train" non compliant option was really worth much of a mention; perhaps it would have been better included at the end as the least risk option permitting the points at B to be secured in one lie and the rain effectively operated under what used to be called "One Engine in Steam". I don't think it was good to start with it particular as it was worded as if the only option. Also didn't understand why with one train the points at B would be operated locally.
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You talked about provision of Ground Frame and token; were you meaning that such a degraded mode facility should have been included as a fall back facility when line originally signalled just in case of such a failure- would a line like this justify such?
To me the question was more about how to operate the line given the sudden occurrence of a fault and therefore should have concentrated on purely operational issues without specific facilities.
If you did mean having GF and tokens as a degraded mode facility, how would this be integrated with the normal means of operation of the line? What would enable token working to be brought into use at a time that communication had been lost? How would normally electrically operated points become operated by a GF; I suppose the most practicable solution would have been to have a form of switch panel that could be switched in and take over the control function and the points remaining power operation. You need to explain your assumptions.
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Yes you could provide point indicators but again you ought to explain what role these would have when the line were operating normally.

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Your suggestion of having two separate trains both doing a shuttle service down part of the line seems far better to me and what the question was really about. You ought to have said something re how the points would be secured and how they would be known to be in that state; also the operational procedure under which each of the trains would be authorised to make a movement and then return back along the line in the opposite direction. This is here you need to demonstrate knowledge of your railway's operational rules. One thing you could do is appoint two pilotmen, one for each section but this is expensive in manpower but given the likely duration of the failure then would probably be the solution. If it existed for a longer duration then there would be the issue of how the B-C train could be extricated to be able to be maintained, refuelled, toilets emptied etc.

I know there is no hint of mark allocation, but remember that this is a Module 1 question, so your answer should really focus on safety and risks. You really didn't put a lot in about this. The need to override / isolate any form of train protection is certainly an important point, but with the railway operating as two single lines with all points secured and the overrun paths to arresting devices I don't see much of a risk.

You didn't state the form of train protection but in the UK context it seems reasonable to assume TPWS. What protection does that normally give re overspeed approach to points? It does however protect against bufferstop collisions (so we


Attached Files
.doc   2009 Mod1 Q2 Hort.doc (Size: 22 KB / Downloads: 106)
PJW
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