2010 Q2 Rolling Stock length change

[greatnessjason]

An attempt for comments please

[PJW]

Yet to find the time to dig out the question paper and read carefully, but a skim read suggests that it is of a sensible length, clearly laid out and certainly starts off well.

Possibly you should have made more of the effects on signal sighting re cab sight lines if the train just fits between signals but not with the ability to stand sufficiently far from the signals to give good sighting- perhaps co-actors would provide mitigation.

Could have mentioned that there are sometimes "measuring tracks" and the longer trains could defeat.

Similarly longer trains could give problems if they have electrical connections to a common busbar as could short across between different traction power supplies or liven up sections that are supposed to be isolated. Longer trains may also draw more power and this in turn could give problems with the operation of track circuits or even axle counters.

The tabular presentation looked good although I haven't yet read the detail, but as far as initial impressions go it looks a good answer- provided of course you have really answered the question the examiners asked!

An attempt for comments please

[greatnessjason]

Hi PJW,

Thanks for your comments. I agree could make a mention of signal sighting re cab sight lines, but I would think this statement would not be specifically addressing any part of the question - it could be a statement that affirms the examiner that I actually do understand the issue? In the exam scenario do you think any marks would be given for making such a statement?

For your convenience I attach the question here:

A railway operates an urban and inter-urban rail service utilising lineside signals at speeds up
to 100MPH (160km/h). It is proposed to replace the current 144m long trains with trains of
184m length.

Identify three issues of infrastructure compatibility which need to be considered. [3 marks]

At stations, the stopping positions are going to be closer to the existing signals. The
administration is considering moving the signals or extending the platforms in the rear.
Describe the advantages, disadvantages and commercial implications of the two options.
[10 marks]

At two locations it is not possible to relocate the signal or extend the platform, requiring the
train to stop approximately 1.5m from the signal. Describe two possible solutions to enable the
train driver to be fully aware of the signal aspect taking account of modern multiple unit design
features such as restricted visibility. (Novel, practical solutions will achieve extra credit).
[12 marks]

[PJW]

Hi PJW,

Thanks for your comments. I agree could make a mention of signal sighting re cab sight lines, but I would think this statement would not be specifically addressing any part of the question - it could be a statement that affirms the examiner that I actually do understand the issue? In the exam scenario do you think any marks would be given for making such a statement?

For your convenience I attach the question here:

A railway operates an urban and inter-urban rail service utilising lineside signals at speeds up
to 100MPH (160km/h). It is proposed to replace the current 144m long trains with trains of
184m length.

Identify three issues of infrastructure compatibility which need to be considered. [3 marks]

At stations, the stopping positions are going to be closer to the existing signals. The
administration is considering moving the signals or extending the platforms in the rear.
Describe the advantages, disadvantages and commercial implications of the two options.
[10 marks]

At two locations it is not possible to relocate the signal or extend the platform, requiring the
train to stop approximately 1.5m from the signal. Describe two possible solutions to enable the
train driver to be fully aware of the signal aspect taking account of modern multiple unit design
features such as restricted visibility. (Novel, practical solutions will achieve extra credit).
[12 marks]

Now I have looked at question and seen the marking scheme then I actually think that you went into too much detail for the first 3 marks.
You could have been more brief re item 1, item 2 about right and I suggest that for item 3 rather than list what the question is going on to tell you anyway then the traction power supply issue might have been a better one to mention.

Whenever looking at advantages and disadvantages of a pair of options, try not to waste time by saying that A has an advantage and then B has the equivalent disadvantage. Better to have a first column explaining the issue and then Advantage and then Disadvantage columns and enter in these option 1 or option 2 accordingly. So for example if need to reposition other signals for braking is being considered, then the disadvantages are for 2 and you can list them but just put 1 in the corresponding advantage column since it does not suffer these.


I think you should certainly have pointed out that if the stopping position is to be closer to existing signals then the likelihood of SPAD would be increased and therefore safety risk would be increased.

Similarly you haven't mentioned that if move signals then need to reconsider the train protection arrangements. Also if there are any raised sections of platform to ease wheelchair access, then if train stopping position altered these will no longer line up with the doors!

It does depend on the site of course, but actually the construction of extended platforms may often be less disruption to travelling public; different situation though if in tunnel etc!


The last part of the question had a large number of marks allocated to it, but don't think you'd have got many of them. You didn't seem to focus on means of the driver being aware of the signal aspect when stopped very close to it.
In fact I can't see what I'd write on this subject for so many; I think therefore I'd have avoided the question and chosen another. There is something about the last sentence that suggests the examiner is faced with this as a real life problem that they don't know how to solve and wants a candidate to suggest a possible solution for them!

[Alan Beavers]

Yes PJW I realised that when I was practising and got to part 3! It's deceptive, on initial glance I thought I'd be able to answer it decently. I could only think of one thing and that was a sideways-on co-acting signal (Nottingham station). Or maybe an in-cab display but as the question asked for novel, PRACTICAL solutions I couldn't say that.

[PJW]

Yes PJW I realised that when I was practising and got to part 3! It's deceptive, on initial glance I thought I'd be able to answer it decently. I could only think of one thing and that was a sideways-on co-acting signal (Nottingham station). Or maybe an in-cab display but as the question asked for novel, PRACTICAL solutions I couldn't say that.

At Penzance there is (I assume still; certainly there was) a miniature LED signal hung underneath the main aspect to enable a view from almost beneath.  Not a co-actor as such (it was not proved in the same way) but I think just paralleled off the main aspect feed and called something like a "Close-up viewing repeater" to differentiate; it appeared in IRSE News possibly 10-12  years ago as an "interesting signal" .  Perhaps this could count as one of the options and your co-actor at right angles as another.

I suppose another option could be a colour CCTV monitor on a mast some 25m beyond the signal which displayed a live picture of the signal itself so that the driver could be said still to be able to observe it even when too close to it to directly observe. 

Of course on the roads it is not unusual for there to be temporary traffic lights to implement some alternate single line working when one carriageway is blocked by roadworks and for the lights to be hard on the obstruction but a "When Red Light Shows STOP HERE" sign somewhat on the approach.  It is not something that I believe has ever been done on the railways [having said that I think that the Swiss often do not have separate signals for each platform at a passing loop on a single line but make do with a single signal beyond the convergence and display a different aspect on it to signify from which line a movement is being authorised] and I am sure it would need a specific sign and Rule Book amendments, but potentially at least the signal could be relocated further ahead (whereas the question said not possible, this would have been assuming the signal would have to denote the stopping position and this option would remove that constraint) and the relevant sign placed where it used to be.  I suppose that this sign might best take the form of a STOP Board with wording "untli signal XYZ displaying proceed aspect".   Perhaps the "signal" itself could be built into a modified form of hollow sleeper with the LED aspects shining out of a raised portion of the sleeper within the height envelope of an AWS, angled say 45 degrees upwards to the driver's cab when stopped at the STOP Board.  

In former times there were "standing out" signal indicators, but I think these tended to be indicators on the rear face of the signal so that the driver could lean out from the footplate and look back along the platform; whereas these may have been the solution in days of steam, don't see they'd work when there may not even be as much as an opening cab window which could be leant out from.

I noted that at the recently lengthened platform at Waterloo there are co-actors which are not parallel with the main signal but significantly beyond them; these needed a derogation to standards....

Not sure that any of these ideas are very good, but I technically all would be quite possible; gaining acceptance might in practice not be too easy!