2015 Q7 SPAD mitigation/Cab Signalling

[dorothy.pipet]

An attempt for comments please.
This was done under timed conditions

[PJW]

Part a
Four good cause of SPADs and it was good that you included distractions but I think I’d have gone for a little more diversity to have included more varied consideration of the approach rather than the signal ittself; could the SPADs be anything to do with misleading changes of gradient profile, poor rail conditions, inconsistent signal spacing or issues with the visibility or interpretation of the signal in rear (for example “Colwich type” issues)?  This is module 1 so you should cast your net rather wider than pure signal engineering; the overall impression given by your first section was that it was a bit more of a mod 3 or 5 type answer. Also worth stating the assumption that these incidents are not being caused by signal reversions as a result of failures or signaller action [particularly where there are aspect sequence transitions from 4 to 3 aspects (or the infamous “double red” or other “signal requires following signal off” type controls the signaller can be misled how far back there will be implications from having cancelled a route that they thought would be a legitimate action].
Giving yourself a wider range of items would have enable a greater range of mitigations; one page to obtain 10 marks was probably not quite enough.

Part b
The question was about designing the DMI; some of your items only addressed this indirectly and some so tangentially (e.g. consideration of the Rule Book) that certainly seem a little off from the question actually asked; you may have meant that the Rule Book must define a procedural method of overcoming any failure of the DMI but you need to be far more explicit how the associated Rulebook amendment would influence the design of the system.  The last bullet point also looked as if it was going off-piste, but the phrase after the dash then saved the situation and transformed it (but quite how one would achieve for a meaningful cab-signalling installation for anything less basic than RETB which is unlikely to be able to replace colourlight signalling is rather impracticable as there is bound to be a need for odometry of better integrity than could be achieved by GPS and very likely to be associated with train protection and thus needing train systems interface rather than a free-standing display)

Part c
Agree that description must be brief as only got 7 marks available.
Seemed ok; may have been worth having specified in part b a little about system you were envisaging; contrary to the impression given at end of part b you now seem to be assuming (very reasonably) that are considering this in cab-signalling to be associated with ATP and indeed the last part of part c further assumes something like ETCS L3 that doesn’t have lineside train detection.

Overall
pretty good timed attempt; I felt that the first section was the weakest and it would have been better to have had a more concrete description of a in cab-system in mind of which the DMI was a part so that part b and part c seemed more consistent.
 

An attempt for comments please.
This was done under timed conditions