If you've just swapped the wires leading to two aspects, then a wire count won't show anything amiss.
a wire count should be to diagram and tags should be used if cables were unidentified which is probable given vintage of trackside installation
for sure if the cable and coupler could be withdrawn from the affected track area so the no physical cable cores were being disconnected.
Keep in mind the following:
Indeed, looking at Google Maps it doesn't appear to have a TPWS fitted.
That would only be true if the error was made on the signal side of the ATPLITs (the current sensing component of an ATP system) or where the input to the TPWS was terminated. If the error was made on the relay/module side then either the ATP would behave in accordance to the signal lamp actually illuminated and the TPWS would not receive the input to command it to energise its loops.
If it was plug coupled both ends, and if the couplers were able to pass through any glands or trunking needed to move the cables clear of the works.
I believe assessments are 3 yearly now. If you only make minor errors then you don't need to do the full training again, you can be mentored and then have a second attempt at the assessment. If you fail that as well then you need to go on the full training. A full training course is required if you make major errors.
S&T often use the term ‘wire count’ to mean rather more than just counting the number of wires, but what is actually involved includes a CORRELATION CHECK (checking that the equipment to the wiring diagrams) and a check to confirm that each individual wire is uniquely labelled. Hence why if two wires are swapped, this check should pick it up.
I recall that the RAIB have previously taken interest on contractors staff relating to checks on how many hours are being worked, so could be relevant, sorry cannot find relevant report to link to.
Which is the whole point of the person testing the work to be independent of having carried out the work. Which is the principal of SMTH that is discussed above. Assuming there were no existing installation errors, for an unsafe error to have been missed, it means that the person doing the work must have made an error, and the person testing must have either not done the checking and testing, or made multiple serious errors.
If signalling equipment was disconnected by removing wire(s) or cable(s), SMTH is very clear that checks and testing is required. If things were running behind the planned timings, the signal should never have been returned to service until all checks and testing had been completed.
Multiple errors would indeed have had to be made. If the cause was indeed a cross in the wires, the opportunities for this to be prevented by following the proper procedure would have included:
Quite, Clapham happened due to an overworked member of staff and potentially that's happened again which is frankly ridiculous.
Please do not hold your breath waiting for them to pay any attention to this.
Yes they both work to the same standards but contractors need to earn money to stay solvent and too many self certify their own staff with insufficient external checks and audits done to ensure they are compliant. Fortunately the vast majority know that any disregard of the processes to ensure competent staff are employed could mean they lose their NR certification to supply staff, and thus their solvency, so are very rigorous.
Your suggestion is fine in principle, but not in practice. All that happens is that the risk of error is moved to the manufacturer. So if testing either by the manufacturer is inadequate or the testing when the item of equipment is changed is inadequate, an unsafe situation could still occur. Items of signalling equipment that suffered from manufacturing faults have been found before.
Maybe the model of using multiple small contractors isn’t ideal. When I started in the industry there were just three big contractors, GEC-General Signal (my first employer), ML Engineering in Plymouth (nearly my second employer), and Westinghouse (where I worked until I retired). Looking from the outside today I am truly mystified at how the signalling industry works today.
would the signaller be aware that this had not been done and should track be accepted back after a possession in this case?
Like yourself Tim M, my involvement in the industry was similar (and as long) as yours but working in reverse order for the big two, i.e. GEC last (now called Alstom).
for some interface design as you had previous knowledge of that specific area.I don't know for certain, but the impression I get as a layperson who reads RAIB reports is that the person who hands the track back after a possession is asserting to signaller that it is in a safe condition for trains to run.
Correct the SMTH competent person books the equipment off with the signaller then books it back on when installation and testing complete. The signaller should observe the correct function of equipment for the passage of first train. In this situation that would have been track circuits showing occupied as no signal indications provided to the panel / VDU.
This is a key point. I did some routine replacements last night and as the work was wholly within the possession the signaller knew we'd done some work to the points as we asked them to be operated at the end, but they have no details of what was done. It's not the signaller's job to check up on what people are doing.
not on this occasion as it was an auto signal
And it's just a click on a computer mouse these days.
If they are asked to operate some equipment (points, signals, etc) then the signaller on duty at the time of the testing will know that work of some sort has taken place that affected/has the potential to affect that specific equipment but not necessarily the details. The signaller on duty at the time or testing may or may not be the same signaller who is on duty when the possession is given up and/or the first trains after the possession operate.
Not for older installations/systems. It could be, depending on the technology and design:
Not necessarily.
