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.
phatmanace said:
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.
They can well be signalling problems - possibly the heat is exacerbating the situation. - 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.
However, suicides in front of trains are also referred to as 'signal failures' - again - perhaps the heat is a factor.
It would be surprising if they were software related, although I am sure there have been times when the control offices have gone down. I have always assumed it is usually hardware related so a bit of kit that has failed, and that would appear more likely in extremes of temperature hence yesterday's issues.
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?
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?
A cynic might post this ...
Oct16 article said:
Analysis by the Labour Party found that between 2010 and 2015 Network Rail paid train operators £575 million for delays and cancellations caused by issues such as signalling problems and power failures, while the rail firms paid just £73 million in compensation to passengers over the same period.
... so it's in the interest of the train operator to give some spurious reason blaming Network Rail. My train this morning was "delayed because there is a delay" tog said:
Is theft of copper cabling still a problem?
Not in the areas with fibre optic cables !
bigandclever said:
A cynic might post this ...
You do know that not all train operators have passengers, don't you ?Oct16 article said:
Analysis by the Labour Party found that between 2010 and 2015 Network Rail paid train operators £575 million for delays and cancellations caused by issues such as signalling problems and power failures, while the rail firms paid just £73 million in compensation to passengers over the same period.
... so it's in the interest of the train operator to give some spurious reason blaming Network Rail. My train this morning was "delayed because there is a delay" 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?
alangla said:
Can anyone with a bit more info confirm if I'm on the right lines or expand a bit?
Pretty good explanation! As you have said the main ones tend to be:Track circuit failures (can be the supply, the relay, leakage due to wet or contaminated ballast, or something as simple as a rogue metal can, lipped rail joint etc bridging two sections and causing them to show occupied on the signallers panel. Once this happens the signaller can't route anything through until the fault team clears the fault.
Points failure - could be something stuck in the points, lack of lubrication, electrical fault, point heater failure in winter, or on some old-fashioned pneumatic points it could be loss of air supply. The points will try to move and if they are obstructed they will move back to where they were and the signaller gets an alarm to notify the fault team.
Power failure - most signalling (except some old rural stuff) is fed from backed up supplies - more often than not the cause lies with linesode power cables. On old systems these are fed from one end only so if you lose the first cable you lose about 5 miles of signalling. They are aluminium with smaller copper tails (16 or 35sqmm copper) at each end which makes it easier to terminate, but that means there are 2 joints per cable and after 40 years in service some of them are starting to go bad.
A lot of this stuff is old technology, but really fascinating to see. Recommend a video on YouTube called "Points and Aspects". All that gear being installed by men with mustaches and flares is still ticking away today.
Network Rail have recently had their boffins working on some remote monitoring systems which help to predict the type of failures listed above. These systems are now in widespread use and there are plenty of stories about averted failures - of course none of those make the news!
alangla said:
Can anyone with a bit more info confirm if I'm on the right lines or expand a bit?
Pretty good explanation! As you have said the main ones tend to be:Track circuit failures (can be the supply, the relay, leakage due to wet or contaminated ballast, or something as simple as a rogue metal can, lipped rail joint etc bridging two sections and causing them to show occupied on the signallers panel. Once this happens the signaller can't route anything through until the fault team clears the fault.
Points failure - could be something stuck in the points, lack of lubrication, electrical fault, point heater failure in winter, or on some old-fashioned pneumatic points it could be loss of air supply. The points will try to move and if they are obstructed they will move back to where they were and the signaller gets an alarm to notify the fault team.
Power failure - most signalling (except some old rural stuff) is fed from backed up supplies - more often than not the cause lies with linesode power cables. On old systems these are fed from one end only so if you lose the first cable you lose about 5 miles of signalling. They are aluminium with smaller copper tails (16 or 35sqmm copper) at each end which makes it easier to terminate, but that means there are 2 joints per cable and after 40 years in service some of them are starting to go bad.
A lot of this stuff is old technology, but really fascinating to see. Recommend a video on YouTube called "Points and Aspects". All that gear being installed by men with mustaches and flares is still ticking away today.
Network Rail have recently had their boffins working on some remote monitoring systems which help to predict the type of failures listed above. These systems are now in widespread use and there are plenty of stories about averted failures - of course none of those make the news!
paolow said:
They can well be signalling problems - possibly the heat is exacerbating the situation.
However, suicides in front of trains are also referred to as 'signal failures' - again - perhaps the heat is a factor.
However, suicides in front of trains are also referred to as 'signal failures' - again - perhaps the heat is a factor.
Never known a suicide to be classified as a signal failure, more a 'passenger incident' or 'person nit by train'. My lot call them a 'person on the track' as opposed to a 'tresspasser on the track' which is, err, a tresspasser on the track.
Also with my lot, a signal failure is a knackered signal or points but a 'signalling problem' tends to be a driver or signaller f
kup e.g a Spad.
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