Distance between trains

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Kevin Wilson-Smith

Distance between trains

Post by Kevin Wilson-Smith »

This morning for the second time I saw something I have seen once before.

On the Metro line near me (a very busy line in the morning) I was watching the Metro trains going though - these are made up in rakes of 12 (as follows if anyone is interested - PCCCCCCCPCCP >) adn behind me I heard an unusually long train. I turned arounf=d and saw that the one set had passed me, followed by a second at A COACH LENGTH - speed was probably in the region of 20 km. About three trains latter, this happened again.

Is this safe? Is this allowed? Is there a rule that covers this?
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Steve Appleton
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Location: Johannesburg, South Africa

Re: Distance between trains

Post by Steve Appleton »

I would hardly think that is safe, certainly not that close and at that speed.

In terms of the normal rules, a controlled stop signal at danger may only be passed under very specific circumstances, such as when a Train Control Officer gives permission and an authority number. The driver otherwise may never, ever, pass such a signal, no matter how long it stays red, or remains unlit if faulty.

The only signal at danger that a driver may pass without a TCO's authority is an automatic or 'T' signal (marked with a 'T' on the post), but then only after stopping and following a defined proceedure. If, after a defined time (several minutes) the signal does not clear, the driver must attempt to contact the TCO. If he cannot make contact with the TCO, after yet another defined time (minutes, cannot remember how many) and again failing to contact the TCO, he may then proceed "on sight" to the next signal, travelling at such a speed that he can stop short of any possible preceeding train or obstruction in the section. The time delay inherent in applying this rule would certainly not put two trains that close unless the preceeding train had failed.

So, I can only assume that either:
a) the signalling was out and the trains were passing signals on authorities which included a provision to drive "on sight", or
b) there is a special local working rule allowing such trains to pass certain signals (probably only automatic 'T' signals) at danger and drive "on sight". This is speculation on my part, but such a rule might be in place to permit higher train densities on the route at certain times than would otherwise be possible in a strict 'one train per block' scenario. Essentially because the signalling blocks are too long for the traffic density.

What is a "T" signal? I hear you ask.
This is a signal that protects the block ahead and which is operated automatically soley by the occupancy of the track circuit ahead. Unlike a conventional stop signal, such a signal is not 'controlled' by the CTC. 'T' signals may be passed at danger under circumstances as described above. This is acceptable because, on unidirectional line, there can be no conflicting train movements - all trains are moving in the same direction over a single line without turnouts, turnins or junctions to create possible conflicts.
By contrast, all signals protecting points, junctions, as well as entrance to bidirectional single or double line sections are always 'controlled' signals. These may never be passed at danger without an authority because of the danger of a possible conflicting movements by other trains.
"To train or not to train, that is the question"
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Mike Haslam
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Location: Vermont, USA

Re: Distance between trains

Post by Mike Haslam »

Steve has said it. There are rules to follow. There is even a rule which states that in circumstances when following another train, sufficient distance must be allowed to stop the train without collision. Following a train at 20km/hr at a distance of a coach (approx 21m) is not in my opinion a safe distance.

When arriving at a T signal at "danger", the TCO should be contacted immediately. If the TCO does not respond then wait three minutes and try again. If the TCO still does not respond, then the driver may proceed "on sight" to the next signal.

Otherwise, unless under special circumstances (like assisting a failed train), or authorised by the Chief Executive, two trains may not be in the same section.

As Steve says. There may be some local working rule - but it seems vary odd in terms of safety.
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Kevin Wilson-Smith

Re: Distance between trains

Post by Kevin Wilson-Smith »

I will go to the same spot and watch again and see if I can get it on video!

There is a high density of traffic - sometimes a train every two or three minutes, as there is a junction and a flyover. The spot is just past Langlaagte heading towards Roodepoort. Very busy normally at peak hours.

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As a separate issue, where can I get a guide that explains the SA signaling practice - and the types of signals in use? Have asked this before, but no-one has come up anything concrete.......
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Steve Appleton
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Joined: 23 Jan 2007, 14:14
Location: Johannesburg, South Africa

Re: Distance between trains

Post by Steve Appleton »

I would like to see that! Perhaps this is an issue for the authorities such as the Metrorail and the RSR to look into. It would be instructional if the types, layout and positioning of the appropriate signals was annotated as well. Plus, documented proof that trains are passing such signals at danger or not.
In terms of signalling literature; this is contained in course material that FOTR provides to its aspirant guards, train assistants and drivers as part of the training courses it runs for particpating members. Another reason to join FOTR -- you get to know how the various train systems work!
"To train or not to train, that is the question"
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