(24-09-2011, 01:13 PM)Hort Wrote: Hi,
I have had a go at this one. I have little experience in Operations but I thought that it would be worth having a go since the answer is mostly in the Rule Book!
Indeed.
I thought your answer was pretty good.
A small item is that a signal can only be plated passable if, as well as what you describe, there are no opposing direction moves that could be being made at the time when a driver could arrive at the red signal. In a module 1 question, this is a small detail; rather more important to get it right for mod2 or mod3. Note that it is possible to plate intermediate signals on long single line sections as passable, provided that the whole length of line acquires a "directionality" as soon as a train is signalled into it from one end or the other.
Another issue in your first section is that a verbally authorised can be made over points with failed detection once the signaller has had them operated and secured into the correct position and someone has "walked the route" to confirm.
It would also have been worth mentioning that Single Line Working could be planned to enable an engineering possession of the other line. It is not something which frequently happens on NR (although the story has been that it will be making a come back) but it used to be very common, sometimes for the last few trains on a Saturday night so that work could start on one line several hours before the end of service, sometimes it would continue throughout Sunday. By doing so it would have shown that you had fully addressed the wording re "intrusive maintenance" within the question.
Also should have mentioned the handsignalman would be displaying flags and have put detonators on the track.
Overall though a good attempt; given it was a Mod 1 question I think it would have been good to work a little more in re hazard, likelihood, severity, human error.
i.e. a signalman can institute "Temporary Block Working" along a significant length of uni directional railway, arranging for each driver to be given a ticket telling them which signals to pass and at which one they are to stop, but the risk associated with head-on collision is greater and therefore the additional mitigation of appointing a pilotman. Note however certain single lines are authorised to institute modified block working to keep the traffic flowing even before it is possible to get a pilotman there- it is a short term expedient (therefore hopefully limited likelihood of an incident) and to institute this requires escalation to a senior Ops manager who independently confirms the position of all trains and acts as a detached second person as a cross check on the actions being undertaken on site.
