Spotted this news article the other day and two statements jumped out at me...

"It was later found that sand applied to the rails to regain traction had interfered with the signals and given the City Rail train a false clear indication."

"The coroner also found that it was likely that a passenger on the 3801 had applied a handbrake on the third carriage that prevented the steam train from restarting."

I'm wondering how the sand could have interfered with the signal..and why is the coroner the one to determine the cause of the accident ?

https://www.abc.net.au/news/20...30-years-on/12205622

 

 

 

Last edited by G-Man24
Original Post

In Australia, as in the UK, they hold what is called a Coroner's inquest that when deaths are involved they call witnesses with the intent of figuring out the cause. They use it to determine something like if a death was an accident, suicide or murder, and in the case of an accident like this they will call experts in and the Coroner will determine from that testimony what the root cause was. Ultimately the call is with the experts, the coroner's judgement in most cases is pretty much a rubber stamp from what I know of it. 

As far a sand causing trouble with the signals, only thing I can think of is it somehow insulated the wheels enough from the rail that it didn't complete the circuit that would indicate the block was occupied,from what I recall of train signals it works exactly like a detector track on 3 rail, that if you get continuity between the 2 outer rails it causes the signal to indicate red. I don't think sand could interfere with more modern signal detection, but maybe one of the experts on here knows more, I am just guessing. 

Sand can still cause trouble with modern day signals. the relay coil is wired to the rails and is held in for a clear signal, when an axale bridges the two rails the current takes the path of least resistance  and the relay looses power and the signal drops to red. sand can change the resistance enough to keep the relay energized in the green or clear position. i think most of the class one railroads equipment is new enough where this dosen't happen. the short line I worked on although modern and up to date had signal equipment from many different eras 1920's and up. the gates on one crossing we had would do this if you sanded thru it. the system works opposite what we model guys use when there is no power on the relay the signals go red and the crossings the gates go down (failsafe). hope this helps a little.  Rick

Interesting information, thanks.

I'm kind of surprised they don't use a weight activated switch or transducer in the rails to activate a crossing or block signal. In fact for most of my life I just assumed that's how they worked.  I'm sure there are people a lot smarter than me designing these systems and they have very good reasons for doing it the way they do. 

Last edited by G-Man24

Since the very low voltage track circuit works by two wheels and an axle shunting from one rail to another, yes, sand can cause problems with shunting if a very short train (and here I mean a one or two-unit light engine) is stopped on heavily sanded rail.  Please note the emphasis.

Since the change from pole line signal coding to electronic coding in the rail, there have been rare instances in which a short train of light equipment did not adequately shunt the signal system and road crossing warning devices. However, this is only a rare problem with trains consisting of very few axles.  Most railroads have a rule that, unless a train or light engine exceeds a certain number of axles.  That equipment must move only under positive protection of an absolute block established by the Train Dispatcher.  Such a train may move on the main track within the absolute block, but must approach crossings protested by active warning devices (i.e., flashers, gates, etc., not just signs) prepared to stop until it is seen that the warning devices are functioning as intended.  To avoid all of this, the usual remedy is for there to be sufficient axles in a train, even if the train has to tote a few extra cars.

Don't be fearful that this is something that can happen often or easily.  It has happened on a tiny number of occasions, and warrants this abundance of caution because trains must be able to rely completely upon the block signal system.

Last edited by Number 90

Amtrak has to have so many axles per train on some routes.

That is a requirement of the host railroad, necessary to activate signals and crossing protection devices.

  Sand or some other issue?

Nothing to do with sand.

 

@Number 90 posted:

Since the very low voltage track circuit works by two wheels and an axle shunting from one rail to another, yes, sand can cause problems with shunting if a very short train (and here I mean a one or two-unit light engine) is stopped on heavily sanded rail.  Please note the emphasis.

Since the change from pole line signal coding to electronic coding in the rail, there have been rare instances in which a short train of light equipment did not adequately shunt the signal system and road crossing warning devices. However, this is only a rare problem with trains consisting of very few axles.  Most railroads have a rule that, unless a train or light engine exceeds a certain number of axles.  That equipment must move only under positive protection of an absolute block established by the Train Dispatcher.  Such a train may move on the main track within the absolute block, but must approach crossings protested by active warning devices (i.e., flashers, gates, etc., not just signs) prepared to stop until it is seen that the warning devices are functioning as intended.  To avoid all of this, the usual remedy is for there to be sufficient axles in a train, even if the train has to tote a few extra cars.

Don't be fearful that this is something that can happen often or easily.  It has happened on a tiny number of occasions, and warrants this abundance of caution because trains must be able to rely completely upon the block signal system.

I have older ETTs in my possession which caution that "Budd cars (RDCs) may not shunt crossing circuits." I presume this is a similar problem, caused by light equipment on rusted, wet or otherwise contaminated rail.

@Number 90 posted:

Since the very low voltage track circuit works by two wheels and an axle shunting from one rail to another, yes, sand can cause problems with shunting if a very short train (and here I mean a one or two-unit light engine) is stopped on heavily sanded rail.  Please note the emphasis.

Since the change from pole line signal coding to electronic coding in the rail, there have been rare instances in which a short train of light equipment did not adequately shunt the signal system and road crossing warning devices. However, this is only a rare problem with trains consisting of very few axles.  Most railroads have a rule that, unless a train or light engine exceeds a certain number of axles.  That equipment must move only under positive protection of an absolute block established by the Train Dispatcher.  Such a train may move on the main track within the absolute block, but must approach crossings protested by active warning devices (i.e., flashers, gates, etc., not just signs) prepared to stop until it is seen that the warning devices are functioning as intended.  To avoid all of this, the usual remedy is for there to be sufficient axles in a train, even if the train has to tote a few extra cars.

Don't be fearful that this is something that can happen often or easily.  It has happened on a tiny number of occasions, and warrants this abundance of caution because trains must be able to rely completely upon the block signal system.

To add more to Tom's quote, MOW has a rough time staying connected because of there lite weight, causing signals to drop in and out. Add a little rust to the rail head and all kinds of issues occur. Fairmont actually insulated there axles to prevent signal activation on there speeders. even the heaviest of there speeders the A-8 was insulated. One of there ops manuals actually explained why they did it and not to over ride it.

 

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