I imagine if the power goes down and comes back, axle counters are more of a pain than track circuits, you have to start afresh working out where the trains are.
The type of axle counter equipment on my area has battery backup. But the battery capacity will only supply the systems for about between 30 and 60 minutes. That’s normally more than enough time for the 650V generator set to come on line. But of no use if a fuse, MCB or other power fault occurs down stream of the generator, as there is no way that staff can get to site before the batteries run out of energy.
And, yes, when a group of axle counters does fail, it causes operations big, big headaches for operations, especially if it’s a junction area and therefore locks the points on / at the junction.
That’s true. However, off the top of my head I’d say the power requirements for axle counters would be rather lower than a track circuit equivalent scheme. As mentioned above it can be easier to concentrate axle counter equipment too. These factors can make it more cost effective to provide local UPS backup and reconfigurable power cable routing, improving security of supply. That mitigates the risk of ‘blind’ axle counters somewhat.
That very much depends on which track circuit type you are comparing and to which type of axle counter system. Remember, low voltage DC track circuits can operate for months from a primary (non-rechargeable) cell. And the axle counter evaluators that are on my area are in REB equipment buildings, which require air conditioning units (some need two of these) to keep the temperature in the room cool. When the air conditioning fails, on a hot summer day, it increases the risk of the axle counter evaluators failing.
It is possible for track circuits to have battery backup. But it’s not normally considered to be necessary because a normal track circuit will recover seconds after the power is restored.
Equally you could argue similarly for multiple section track circuits. They can be an absolute nightmare trying to race around all the relay ends to identify which section is at fault, and sod's law will say that either it's the opposite end to where you started or it rights itself before you manage to get to all of them. One blessing about axle counters is that even if they get restored they still give you information on the nature of the problem on the download.
Either track circuits nor axle counters are perfect. On irritating track circuit faults I've heard people say "I wish we could just rip it out and stick an axle counter in" and on axle counter faults I've heard the opposite. Axle counters aren't the demon I thought they were when they were first introduced here though.
Multi-section track circuits do cause problems. But in my experience, this was only an infrequent problem, and mostly only affected track circuits on plain line in the countryside or similar long stretches. On, or near junctions, most track circuits were single sections, or two or three fairly short sections, where you could walk from end to end in less than ten minutes (if that).
But with the axle counter installations, some that cover junctions are miles and miles away from the REB with the evaluator. Of course, a lot of this is down to how good or bad the scheme design is.
There is no doubt that axle counters have a lot of advantages. Long sections, no problem with traction return conductor rails / return current on OHL areas. Not affected by rusty rails. No butt to butt IRJ failures in summer. Plus many others. But they also have various disadvantages that appear to be overlooked at times.
Didn’t they get a bad reputation after a failure/incident in the Severn Tunnel? Maybe they just weren’t rugged enough for that purpose, at the time, and that view clouded everyone’s opinions for quite a time afterwards?
That was not really the fault of the axle counters, but more railway poor procedures and poor design of the interface to the rest of the signalling system. That axle counter system did not have isolation links. And at the time, the remote control system (TDM system) was failed, so the signaller could not see on their panel the state of the real railway. It’s still unclear on what exactly happened, but somehow the axle counter section went clear while a train was in section. And because the protecting signal had not been restricted to red, once the axle counter section went clear, the through-routes/emergency override system in use, caused the protecting signal to automatically clear to a proceed aspect...
Now axle counters are provided with disconnection links, so that they can be worked on with no risk of a similar problem occurring (assuming that procedures are followed).
I’m not pro or anti axle counters or pro or anti track circuits. But I do hate stupid designs and less than practical scheme designs.