2007 Q7 Features of Signalpost Telephone system

[JPM]

I have attempted here question 7 from the 2007 paper.
I welcome comments.

[PJW]

I have attempted here question 7 from the 2007 paper.
I welcome comments.

My initial view was that there is not much content for a 30 minutes question; however I would agree that have basically addressed the various elements of the question.
I suppose it is psychological that since there are 4 marks than merely including reference to each of 4 items ought to give you full marks; had the question been marked out of 100 rather than 20 then instead of 4 marks per section there would have been 20 each and you may have felt inclined to write somewhat more explanation!
As it is, remember that marks can be awarded in fractions so there is no real difference; for other modules where a whole question is scored out of 25 then I think "a mark a minute" is a good benchmark (since in a 30 min slot there are only really 25mins active writing by time done thinking/ admin / intro / summary); in mod 7 I suppose it would be "a mark per 1.25mins".

Obviously marks are only awarded for what is relevant and for quality rather than quantity, but you can't expect to score fully for much less.
Hence I think you either need to expand the number of the points made in the various sections (breadth) or give a more detailed explanation, particularly of the WHY.

However I can't say that I can readily think of very more elements and overall the answer was pretty good as far as it went, so definitely a sound pass but to get higher marks you do need to flesh it out a bit.

For example you mentioned the preferred positioning of the SPT, but not what can be done when this can't be achieved. Diamond signs, NRN phone number of the signaller, denotion of "limited clearance" phones both on site and on signaller's concentrator, provision of "call-back" lights so that signaller can indicate to the driver that traffic on adjacent line has been stopped and thus safe to access SPT etc.

One of the primary areas that you didn't explore was the fact that the SPT system only permits the signaller to be speaking to one driver at a time and that (you made this point only for the radio as if it was different) there is an indication to the signaller re the origin of that call so that the verbal exchange between driver and signaller is only part of the assurance that each party is talking to the person they think they are.

For the advantages of the radio you didn't mention the fact that the signaller can more readily contact the driver and may have the option of a) individual non urgent contact (used when train at a stand only- can pass on messages for the driver to contact the TOC control for example)
b) group broadcasts of "advisory only" messages to trains within an area (perhaps there has been a report of suspected trespassers on the line that doesn't require trains to be formally stopped and cautioned but for which the ALARP solution is to attempt to make drivers aware before entering the area)
c) emergency stop messages to all trains within an area (e.g. after a SPAD, report of bridge strike etc.)

You could then have gone on to explain the advantages not only for safety but also in avoiding delays (BTW generally drivers do not now wait 3 minutes when held at a red signal- there can be plates advising at each site what time to wait, but recently the default has changed to be zero). Indeed although not specifically in the question I might also have mentioned one potential disadvantage as well (e.g. in an area where the signalling is in-cab using radio there is the chance that the same failure condition causing loss of signalling could also cause the loss of the voice communications as well and thus some limited provision of lineside phones may still be sensible).

I hope this gives you some hints of the sort of information that you should have added to flesh out you basically sound skeleton without just adding fat (superfluous not strictly relevant information) or skin (glossy surface presentational woffle).

[PaulJenkins]

I agree with Peter, this looks a bit thin. Cab radio has some further advantages: not least that the signaller can call the driver at any point along the route! Cab radio can also be used for many more things than an SPT: telemetry off the train, broadcast and group calls, shunting, etc. Reduced trackside equipment to maintain and avoidance of safety risks assoociated with maintenance. Cab radio tends to get used more promptly at red aspects, especially when its raining! - reducing delays.
We should make clear that the formal voice protocol must be used, in accordance with the rule book. This is an important safeguard in both SPT and radio systems.

[dorothy.pipet]

Another attempt for comments please. I'm not a telecoms person so I may have missed some of the points.