Slightly interesting story...

[Deathbyteacup]

I was on the Tram from Bury to Manchester today when I noticed we were doing a very slow speed towards a signal at clear.

Anyway the signal started to behave erratically switching to Danger, then back to clear and back to danger a couple times, and sitting at the front since I'm sad like that, I then notice the driver's tram phone ring and heard the entire conversation between him and the depot (evesdropping, I know but my curiosity was peaked at this point....)

Anyway the conversation between those two was basically the driver telling the depot what the Signal was doing for a short while then they told the driver to stand by....

At this point everyone near the front as I was started looking a bit nervous but after a minute he was called back and basically was told he was given the all-clear to proceed through this signal and the next signal at danger since they are not functioning correctly at reduced speed being ready to stop for obstructions....

....having read that website I posted about the Class 47's where almost the exact same words were used I was a little nervous and admittedely intregued at this point since that particular story ended in a accident.

Anyway the driver warned everyone that he was about to pass a signal at danger and that the brakes might automatically apply so they should brace.

Sadly they didn't nor did anything interesting happen after passing the two signals at danger so this is a story with an anti-climax and I don't know why I wrote it but it was an interesting part of my day I felt like sharing.


Uh....that's all. Although I do wonder what would cause a signal to act like a disco light.

[richard thompson]

I think i would have opted for a boring end rather than a mention on the news.
Richard

[Deathbyteacup]

Originally Posted by richard thompson

I think i would have opted for a boring end rather than a mention on the news.
Richard

Trust me I wasn't looking for the news item spot.

I've never seen a train or tram's brakes apply automatically due to TPWS is it? Not sure what the system is on Metrolink but I hear it's quite violent breaking.

Naturally I wasn't interested in the collison part.

[Foghut]

Well passing a signal at danger (WITH AUTHORITY) is a fairly regular occurance on the railway, although that's not to say that it's taken lightly. Since the signalling system is designed to be Failsafe, then any sort of problem would/should result in an errant signal staying at danger - hence the signaller authorising you to pass it at danger. There is a whole wodge of Rulebook dedicated to this since you've now abandoned the safety of the system.

I've had a moderately similar experience to the one mentioned above a while ago. I was waiting at a junction signal. After a train went past on the adjacent line which I was expecting cross over onto, my signal went to yellow, then red, then two yellows, then red, then two yellows again. This is classified an irregular signal sequence since a signal should never revert to a lesser aspect (unless of course the signaller 'puts back' on you for an emergency).

So I called the signaller and he said..
"O yes that's quite alright, I know what's causing that, don't worry"
To which the reply had to be
"Well I do, would you care to share it with me"

He explained that there was a problem with the points 'bouncing'. He was using ARS (Automatic Route Setting) and the computer had set the route as quickly as possible after the other train cleared the overlap. Points and signals are interlocked, so that the signal can't clear until the route is set and checked. As soon as the proving on the points saw them reverse it set the signal, but when the points bounced a bit the proving was removed and so the system put the signal back to danger. This happened several times quickly but there's always a little delay in the system so that I was treated to a bit of a light show.

This proving is an arrangement whereby the signalling system gets confirmation that things are how they should be. So there are sensors on the points to confirm that they are in the right postion. Similarly many colour light signals have proving on their bulbs. If a bulb burns out the signal in its rear will automatically step down to a single yellow at best, so that you automatically bring the train to a stand at the signal which isn't diplaying any aspect.


And finally we come to the reason for all this blather...... if a signal has an intermediate fault on the proving circuit, that can cause the signal to return to danger every time the proving is lost. But that's OK, as we all know that any signal which isn't showing a steady proceed aspect is automatically defined as being at danger.

Phew, HTH
Foggy

[Foghut]

Originally Posted by Deathbyteacup

I've never seen a train or tram's brakes apply automatically due to TPWS is it? Not sure what the system is on Metrolink but I hear it's quite violent breaking.

Speaking about trains only now - I wish it was violent. Don't believe what you see on the telly. TPWS will put the brakes into emergency, which on our units is 12%G. It's a bit of a lurch, but wouldn't put your nose against the windscreen. There's no point in braking too hard as the steel wheel on a steel rail would just lock up and be inefficient, even with wheelslide protection (the railway equivalent of ABS).

(As an aside, when they first mentioned the revised braking forces they had a typo in the document which said that we would be experiencing 12G - now THAT really would be classed as violent )

[pavorossi]

With regards to the brakes coming on when you pass a signal at danger, it can be quite violent, certainly it seem to be more so than the emergency braking on the East Lancs.

[Foghut]

Originally Posted by pavorossi

With regards to the brakes coming on when you pass a signal at danger, it can be quite violent, certainly it seem to be more so than the emergency braking on the East Lancs.

I'm not quite sure what you're referring to here. You haven't mentioned any specific traction type. Are you comparing disc brakes of modern stock with vacuum brakes of heritage traction ? If so there's bound to be a difference.


1) I wonder under what circumstances they use emergency braking on the East Lancs ? Running brake tests are usually carried out at full service brake or considerably less, as you're only looking for retardation. Emergency braking often causes wheel flats, especially on stock not fitted with wheelside protection (the railway eqiuvalent of ABS on cars) .

2) Where are you passing signals at danger ? And hopefully this is with the signaller's authority (though you don't say ) ?

TIA,
Foggy

[Deathbyteacup]

2) Where are you passing signals at danger ? And hopefully this is with the signaller's authority (though you don't say ) ?

I'm sure he nor anyone else is SPAD'ing just for a giggle.

I'm not an expert so most of your post went over my head but I hope I've not started something with this thread.

[Foghut]

Originally Posted by Deathbyteacup

I'm sure he nor anyone else is SPAD'ing just for a giggle.

No, I'm not suggesting that.

I'm not an expert so most of your post went over my head but I hope I've not started something with this thread.

No problem, I don't mean to be contentious. I'm just a little curious.

[Deathbyteacup]

Originally Posted by Foghut

No, I'm not suggesting that.
No problem, I don't mean to be contentious. I'm just a little curious.

It's alright, I wasn't suggesting you was being contentious, I'm just being silly.

I'm interested in these conversations even though I don't entirely "understand" everything as it stands but I like to pick stuff up and learn so it's all good.