signalling problems - what *really* are they?
Discussion
After todays problems at Cannon Street, I'm just curious (as someone who is an electrical engineer by training and IT by profession) - what , normally, really are 'signaling problems'?
- Hardware failures on the indicators that the drivers look at and/or sensors in the track?
- Software failures/bugs or machines running out of disk space or something arcane like that?
Really not mean to be a rant, I'm genuinely curious and hoping someone who works in the industry can share some insights.
- Hardware failures on the indicators that the drivers look at and/or sensors in the track?
- Software failures/bugs or machines running out of disk space or something arcane like that?
Really not mean to be a rant, I'm genuinely curious and hoping someone who works in the industry can share some insights.
alangla said:
As I understand it (I don't work on the railway!) they fall into a few basic categories:
Sensor failure as previously described - the lines have either track circuits or axle counters to detect trains - typically either the axle counter will get confused & think there's something there when there isn't or the track circuit will be shorted or the relay at the far end fails, again indicating something is there when it isn't.
Machinery failure - the motor or hydraulics that operates a set of points fails to make the points move, or the sensor attached to the points is unable to confirm if the points are properly positioned to run a train over them. Also failures of things like level crossings or their attached detection/CCTV etc.
Communications failure - often the equipment runs off what's basically a remote controlled signal box, sometimes the communication between the remote location & the manned signal box that supervises it is lost. I guess you could also get problems with communications between boxes, so trains move from one box to the next, but the next one has no idea what the train is.
Power failure - everything goes a bit dark. AIUI, signalling systems have separate power from the power at the stations, so the signals might work but the station lights could be out or vice versa, same with the overhead lines/3rd rail.
In areas with mechanical signalling, you can get things like snapped metal rods/wires that operate the old style semaphore signals/points as well, also the telegraph (yes, telegraph) between boxes can fail.
Can anyone with a bit more info confirm if I'm on the right lines or expand a bit?
Great post. Thanks for that.. Sensor failure as previously described - the lines have either track circuits or axle counters to detect trains - typically either the axle counter will get confused & think there's something there when there isn't or the track circuit will be shorted or the relay at the far end fails, again indicating something is there when it isn't.
Machinery failure - the motor or hydraulics that operates a set of points fails to make the points move, or the sensor attached to the points is unable to confirm if the points are properly positioned to run a train over them. Also failures of things like level crossings or their attached detection/CCTV etc.
Communications failure - often the equipment runs off what's basically a remote controlled signal box, sometimes the communication between the remote location & the manned signal box that supervises it is lost. I guess you could also get problems with communications between boxes, so trains move from one box to the next, but the next one has no idea what the train is.
Power failure - everything goes a bit dark. AIUI, signalling systems have separate power from the power at the stations, so the signals might work but the station lights could be out or vice versa, same with the overhead lines/3rd rail.
In areas with mechanical signalling, you can get things like snapped metal rods/wires that operate the old style semaphore signals/points as well, also the telegraph (yes, telegraph) between boxes can fail.
Can anyone with a bit more info confirm if I'm on the right lines or expand a bit?
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