[xplo42]

How are automatic announcements and information boards triggered by the approach of a train at a station?

What is the interface between the train and station equipment to inform the serving of a booked train or one that is not booked to stop?

Many of times have I noticed that platform information screens and announcements air "stand clear at platform x, the approaching train is not scheduled stop at this station" - only for either nothing to pass or a train does stop...!

I did read many years ago that in order to supply accurate train running information to stations it is mandatory for the train to actually be moving. For example. If a train is 5 minutes late and then stops another 5 minutes for an unknown reason - the station information will not be updated to show the train is now in fact now 10 minutes late until it restarts motion. Judging by this am I correct to guess that the track circuits are possibly involved in the delivery of train information to stations?

[causton]

It obviously depends on the area but my belief is that track circuits have a lot to play in it. The length of the track circuits around the station can sometimes limit/dictate the amount of warning that can be given of trains approaching/non-stop trains passing through. For example at Wembley Stadium station today, most trains passing through from Marylebone were announced a good 2-3 minutes before passing, a bit long IMO, but a train was sitting in the Chiltern depot. It came out and passed without warning until it was actually passing us, as the announcement system did not know the train was moving until it passed into the track circuit of the platform.

Likewise, when a train leaves a platform and is still displayed this is usually because it is still in the track circuit section of the platform. Once it passes the next signal/track circuit boundary it should disappear

[Class377/5]

Originally Posted by xplo42

How are automatic announcements and information boards triggered by the approach of a train at a station?

What is the interface between the train and station equipment to inform the serving of a booked train or one that is not booked to stop?

Many of times have I noticed that platform information screens and announcements air "stand clear at platform x, the approaching train is not scheduled stop at this station" - only for either nothing to pass or a train does stop...!

I did read many years ago that in order to supply accurate train running information to stations it is mandatory for the train to actually be moving. For example. If a train is 5 minutes late and then stops another 5 minutes for an unknown reason - the station information will not be updated to show the train is now in fact now 10 minutes late until it restarts motion. Judging by this am I correct to guess that the track circuits are possibly involved in the delivery of train information to stations?

It's all done by track circuits these days. However a train doesn't have to be moving these days for the station system to change the information displayed. The track circuits are used as timing points and the systems can be clever enough to see that a train hasn't moved and delay it by another minute. This is why sometimes you see the boards racking up the minutes, minute by minute. However my lot actually turns the board to "delayed" after 5mins not moving.

All TOC's have a system but there are various different systems which is why you get different behaviours, even within a TOC.

As for announcing stand clear for trains stopping, if the head code is different and it changes in platform then until the signaller changes the code then it will treat it to however the initial headcode is programmed to be seen.

The difference is all in the coding. There are various states in the CIS (Customer Information System/Screens), including P = passing, T = through/calling, E = empty. This determines which announce the system plays.

[Daz28]

My local station has announcements that are played out on the relevant platform only. "Please stand clear of the platform. The train approaching platform 1 is not for customer use." This plays all day, reliably, about 20 seconds before each train zips past.

A bit pointless as nothing is ever scheduled to stop on platform 1, and nobody is ever standing there. It only exists for use during engineering possessions or disruption and has no PIS display.

[louis97]

Its not really track circuit directly, the track circuit only says if the section is occupied, and the CIS equipment actually does not even see the Track Circuit. The information the station information screens and announcements use is the Train Describers (TD), this is how the CIS knows the location of every train using the "Headcode", and is the reason why the length of a delay is not known until the train is moving again. If the train is sat in a certain TD for a long length of time a good CIS will flash up 'Delayed' on the screens, and announcements will also reflect this, a poor CIS will add minutes, minute by minute.

Areas which don't have Train Describers are areas of semaphore signalling, and also single lines that use tokens. These have manual Trust reports and generally the screens and announcements work off timers, hence if a train is delayed where there is no TDs the screens can sometimes remove the train from the screens believing it is ontime.

Originally Posted by causton

For example at Wembley Stadium station today, most trains passing through from Marylebone were announced a good 2-3 minutes before passing, a bit long IMO, but a train was sitting in the Chiltern depot. It came out and passed without warning until it was actually passing us, as the announcement system did not know the train was moving until it passed into the track circuit of the platform.

This will be down to the placement of the Train Headcode into the Describer, trains entering depots have to have it manually placed by the signaller. Therefore the TD was obviously placed too late for the announcement to go off in time.

[tcm1106]

Originally Posted by causton

It obviously depends on the area but my belief is that track circuits have a lot to play in it. The length of the track circuits around the station can sometimes limit/dictate the amount of warning that can be given of trains approaching/non-stop trains passing through. For example at Wembley Stadium station today, most trains passing through from Marylebone were announced a good 2-3 minutes before passing, a bit long IMO, but a train was sitting in the Chiltern depot. It came out and passed without warning until it was actually passing us, as the announcement system did not know the train was moving until it passed into the track circuit of the platform.

Likewise, when a train leaves a platform and is still displayed this is usually because it is still in the track circuit section of the platform. Once it passes the next signal/track circuit boundary it should disappear

Far more complex than just track circuits. They do of course play a part but a larger system called Darwin takes data from multiple sources such as TD.net, Trust and line-side equipment and provides an output to the various CIS systems. A colleague of mine produced a very good explanatory diagram which I'll try and dig out when I'm back at work.

[causton]

Originally Posted by tcm1106

Far more complex than just track circuits. They do of course play a part but a larger system called Darwin takes data from multiple sources such as TD.net, Trust and line-side equipment and provides an output to the various CIS systems. A colleague of mine produced a very good explanatory diagram which I'll try and dig out when I'm back at work.

Oh indeed, I never intended for that to be anywhere near a complete explanation! I know Darwin and its many useful outputs, like the live departure boards and LDBCIS screens (seen at some help points and stations on computers etc) an example here!

(change the WIM to the crs code of your choice for any station's live departures!)
--- old post above --- --- new post below ---

Originally Posted by louis97

This will be down to the placement of the Train Headcode into the Describer, trains entering depots have to have it manually placed by the signaller. Therefore the TD was obviously placed too late for the announcement to go off in time.

Indeed, this is what I guessed however the train before it set off was only about 10-15 metres from the mainline so it's a very small distance to have a second TD to determine the halfway stage between standing on the depot line and passing the station!

[louis97]

Originally Posted by causton

Indeed, this is what I guessed however the train before it set off was only about 10-15 metres from the mainline so it's a very small distance to have a second TD to determine the halfway stage between standing on the depot line and passing the station!

There wont of been a second TD, there wont be any TD for standing at the depot, when the signaller noticed that the train is starting to leave the depot, he would of placed the Headcode into the TD which was relative to the next signal - which just happens to be the one relative to the platform.

[eMeS]

At Wolverton on the WCML there are announcements for the two slow platforms, and for the Up Fast which shares the same island as the Down Slow. I've never heard any announcements for traffic on the Down Fast, platform 1 if my memory is correct. The gap between announcement and train is just sufficient for my camcorder to be switched on, from cold - if only camcorders weren't programmed to go to sleep...

[James564]

If my memory serves me correctly, PA announcements are disabled on platform 1 at Kings Langley, Apsley, Tring, Cheddington, Leighton Buzzard, and Wolverton.

[causton]

Originally Posted by louis97

There wont of been a second TD, there wont be any TD for standing at the depot, when the signaller noticed that the train is starting to leave the depot, he would of placed the Headcode into the TD which was relative to the next signal - which just happens to be the one relative to the platform.

Indeed, that was what I was saying!

[HLE 13]

Originally Posted by causton

Oh indeed, I never intended for that to be anywhere near a complete explanation! I know Darwin and its many useful outputs, like the live departure boards and LDBCIS screens (seen at some help points and stations on computers etc) an example here!

(change the WIM to the crs code of your choice for any station's live departures!)

WOW, never knew how to do that!

Thanks,