Some more examples from an S&T perspective to highlight the difference between areas. First, my previous section, bit of a mix of urban and rural on the Western route, then my current city location in Scotland.
We could quite easily be an hour's drive from one end of the section to another. It wasn't a particularly rural section, and a large part of it followed the M4. One week, every day when we got to the outskirts of the western-most town to attempt to do our planned maintenance we got called to the junction at the eastern border of our section. Other times we'd be mid-way through a walk through doing maintenance when the phone rang, so we'd first have to walk back to the van. Back when S&T was afforded the luxury of three person teams we'd nominate someone to drive round and pick us up at the other end (or at an intermediate access point if a fault came in), so in theory we'd never be more than halfway from our van. Once they took us down to two person teams that option disappeared, so you had to walk all the way out and all the way back, and if a fault came in when you're at the far end... tough! One location we did as a two mile walk out, cross the line at the public crossing, and then a two mile walk back to catch the locations on the other side of the track. It never happened, but you'd be looking at potentially over an hour for us just to make it back to the van. I did once even ask if we could split that maintenance over two days and claim a half hour bus journey back to the van to reduce the risk of that situation, but was told no.
We only had one team the vast majority of the time, who covered maintenance and faulting. Some times, mostly nights, we'd also have a dedicated pointcare team, but I can count on one hand the number of times I can remember them attending faults. We theoretically also had a maintenance team, but with staff shortages and sickness they functionally didn't exist. I'm not sure if that team still exists even on paper post-modernisation. This meant that there was generally a choice between faults or maintenance getting done, and a high chance that the fault team would be partway through maintenance when called out rather than at a central location.
We weren't a section that covered a larger area at night, but it wouldn't be that unusual to have to travel to neighbouring sections to assist with cable faults. As teams are required at both ends of a cable for testing, at least four people are required. More might be needed if a large cable had to be run out as you need bodies to physically pull it along the track. Other times we might be needed for something urgent when they couldn't cover it themselves because of illness or lack of competency. One time they ended up with the lone person remaining from their depot, two of us, and four of the next section all down there for a signal failure. I have no idea why they decided to send the third section (and ultimately they weren't very helpful as they took a wrong turn and got the van stuck in a field before reaching us...) but someone made the call to risk leaving their section exposed to any failures. Another time I was nearly asked to go to a fault two sections away and about two hours down the motorway in the middle of the day because there was no one more competent any closer on Western route. There probably would have been if they'd looked outside the route, but there wasn't any mechanism for that back then, and I'm doubtful if there is now, even post-"modernisation". Fortunately for me it turned out I wasn't competant on that exact variant.
The geographic spread of the section also meant that if a part was required that we didn't have in the van it could be a significant distance to travel to obtain a spare. We experimented with "squirrel stores" in strategic locations a few times but it never stuck.
On other hand, as our section was largely a two track railway with minimal loops and alternative routes, if that fault phone rang we'd be straight in the van and on the way because we knew that we'd be afforded access to get in. There would usually be at least 5-10 minute margins we could use between trains, even during the day, and even if we needed longer the impact of the fault on services usually meant that it would be beneficial to hold a train to grant us access. Point failures typically meant that a train would be stuck until we got there, so we'd be getting in, no doubt. I hated it when we started using an iPhone as the fault phone as the sound of someone else's ringtone used to trigger a "OK got to go" reaction even when I wasn't on shift.
My current location operates quite differently in a lot of respects as it's much more urban.
The section is geographically denser. Typically we can be anywhere within the section within 20-30 minutes, unless it's at a particularly bad time for road traffic. The frequency of train services mean that access for maintenance during train running times is practically nothing, so teams are normally on standby in a central location rather than out doing maintenance during the day. Spare parts are also a lot closer to hand, or often there's another team available to drop whatever it is off to us.
We have at least one maintenance shift out every night, so that maintenance can still be carried out if there are faults, or if more than one team is required to attend to urgent faults or faults which need more personnel that one team can provide there's that flexibility. It's much less likely that we will need to draw resources from neighbouring depots, and although sometimes we have to assist them due to staff shortages it doesn't leave us totally uncovered. It does still happen, especially post-modernising maintenance, but far less than in sections with fewer teams. Our location also means that teams are much closer to each other than elsewhere. I've been to other sections to help out a couple of times and still never been more than an hour's travel from the opposite end of my own section. The density of depots is also useful if there's a shortage of spares; it can be collected by road in short order rather than having to arrange someone putting it on a train for an hour or two's journey and hoping it arrives safely at the other end!
The big difference in response times though—and this was a struggle for me to adjust to—is that the density of the network normally means that faults have less impact. The vast majority of the time we'll call the signaller before leaving and be told to leave it until after traffic as they can work round about it. There's only really a few point failures that will make us rush because we know they have no alternative options for those. Faults typically just get noted during the day and then mopped up by the night shift fault team instead of being fixed as and when they come in. The delays that would be caused by granting us access are greater than those that will be directly caused by the fault itself.
