Can you tell me what failures aren't critical please? I'd like to know. All failures are critical and require additional concentration for my work. The delays will simply mount and the recovery to the service will never occur because the faults will never be fixed.
It is sometimes more convenient, for both the signaller and faulting staff, to leave failures until a quiet period where it is easier to work around and temporarily live with the fault than find a way to grant staff access to rectify it.
To give an example from last week: struggling to get reverse on a set of points. Not needed in reverse very often, but trains very frequently passing over them in normal. We arrived on site, contacted the signaller to see about taking a blockage to access the points. The signaller laughed, informed us there was no chance of us getting in—maybe we could get 2 minutes at most—and he said he'd maintain them normal if we would pass it on to the night turn for them to come out.
That was a fairly straightforward place to get to, with the points being accessible without a blockage and only one line required for the investigation. Other places might be even more complex, needing 4 or 5 lines blocked just to access, and then 2 or 3 blocked for the investigation. Doing that
would cause delays, but it might be possible to work around the fault and still run a normal service as long as nothing else fails nearby.
It does of course depend very heavily on the type of failure, the availability of margins, and the location. A busy area with multiple routes from A to B (e.g. a large station throat) is likely to have more redundancy in routes and it might be common for failures to be left until the night unless they're causing a real headache. A single or two track railway is unlikely to have that flexibility and failures are more likely to need attending there and then because that is the most efficient for that location. Even then though there are some failures that might still be left until later if the blockage required to investigate is too onerous at that time, e.g. a TPWS failure on a reversible signal.
Every failure is different and therefore handled differently. An agreement has to be made between the signaller/fault teams/control that benefits the railway best, within the balance of probability. As much as I might be itching to get in and fix a fault, it's no good to anyone if I was to insist on blocking half a major station during rush hour, or trying to fault find in 3 minute blocks. I don't like it, I want to get in and fix things, it's what I love most about my job, and I don't like that it's becoming more common even in the quieter areas with the ban on red zone working/walking, but I have to see the logic and toe the line that has been drawn by the ORR.
That said though, you can't predict what failures will happen or when, and I do agree that people need to be available to respond incase there is a real showstopper.
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