East Putney Signal Failure

I hesitate to keep doing this but, while the points would need to be secured on LU, the points would not be secured on Network Rail.

For those interested, suppose it was necessary to authorise trains to pass signal W360 at danger. W360 is the junction signal on the Up line which authorises trains to proceed either to the LU station or onto the National Rail lines to Point Pleasant Junction and Clapham Junction. A diagram is available on the main site

For the purposes of this explanation we shall ignore the ground frame as, I believe, it has been abolished. We shall authorise a District Line train to pass the signal at danger and proceed into the LU station.

Before authorising the signal to be passed at danger you would:

Make sure that the line is clear and safe to run on up to and including the overlap of the next signal, W356. This you would do by observing your overview diagram (see photos.signalling.org/picture?/12306/category/1194-2007 ) and ensuring that all track circuits are clear. If, for example, you have a track circuit showing occupied when clear due to a failure you'll need to do a bit more work, but we won't worry about that.

Make sure all points are in the required position. To do this you would get out your route card which will show you all of the point ends that need to be set and in what position they must be in. In this case your route card will tell you that W698 points must be in the normal position (set for the LU station). You would place these points in the normal position by operating the individual point switch. The individual point switches are the black knobs that you can see above the route-setting panel in this picture photos.signalling.org/picture?/12107/category/1194-2007 You must ensure that the yellow light with the N next to it (N for normal) is lit. This is showing you that the points are detected and locked in the normal position. If you do not have that light you will need to get them secured on the ground. You must carefully observe this indication. You must place a reminder appliance on this switch to prevent you from mistakenly operating it. If possible you will then close the book containing your route cards and ask a colleague to come over and check your route setting. You will get them to get the route card out themselves and not give them the route card you were using (in case you were using the wrong one) and you will ask them to make sure everything is set correctly. If you do not have a handy colleague you will shut the book and then start again yourself as if you were checking somebody else's work.

You will place reminder appliances on the route setting buttons controlling any conflicting routes to prevent you from clearing conflicting signals. In this case there aren't any, but if we were authorising the train to proceed to the National Rail lines then W359 would be a conflicting signal and we would place a reminder appliance on that signal's control.

Now we are ready. If possible we will now call the route on the route setting panel. If the route calls then we know that we've set the route correctly. If the route fails to call (for example because we have set the points incorrectly) then it will show us we've made a mistake. Calling the route will give us back the benefit of the interlocking and will also prevent us from signalling conflicting moves. However it may not be possible to do this. If we have a track circuit failure we won't be able to call the route. Also, for example, if we were authorising a train to enter a possession. If it is not possible to call the route we must stop trains on any opposite or adjacent line that could be fouled by the movement if the route is set incorrectly. So in this case we would have to stop trains on the Up District Line at W359. We would place a reminder on W359. This is because, if we have set the route wrong, the Up Line would be fouled by our train turning right and going towards Point Pleasant Junction. When one train has passed safely over the route it will not then be necessary to stop trains on opposite or adjacent lines when authorising subsequent trains to pass W360 at danger as we know the route is correctly set. If, however, we then alter the route we will again need to stop trains on opposite or adjacent lines, though only the first time. But every time we alter the route, we must stop trains on opposite or adjacent lines that could be fouled for the first train.

Now we are ready. As Colin says the conversation with the driver should go something like this:

Due to a signalling equipment failure I am unable to clear W360 signal. Please repeat this message back to me.

Driver repeats.

That is correct driver. So, when authorised, I will require you to pass W360 signal at danger, proceed cautiously through the section and then obey all other signals. Please repeat this message back to me.

Driver repeats.

That is correct driver. I can now authorise you, the driver of *train* to pass W360 signal at danger.

Other scripts are available, but what you're supposed to get in the conversation is:

Why the signal is to be passed at danger.

How far the movement can proceed.

Instructions for infrastructure where applicable (mainly level crossings and SPAD indicators, neither of which are relevant here).

Proceed at caution.

Times when it will be necessary to secure points when passing signals at danger are during temporary block working (all point ends), emergency special working (points which do not have detection only) and if you have mechanical point detection and no FPL is fitted (or you cannot be sure that it has correctly engaged).

However I don't think that's really what brigham was getting at there. The point I'm sure he was making is that we have here a situation where the driver is authorised to pass a signal at danger and yet a safety device designed to intervene when a signal is passed at danger without authority is still intervening to bring a train full of passengers to a sharp and potentially rather violent stop. This should not happen, I agree with him. I'm the last person in the world who would want more of a train to be a computer, but it does seem that whereas this was necessary in the past, on a modern train like an S Stock it should surely be possible to install an override button or switch to prevent the emergency brakes kicking in when a train passes a signal at danger with authority. Whether an automatic speed limit of 10 mph should then be imposed is another matter that has already been discussed. But it shouldn't be necessary for the train to be brought to a sudden stop.

In this case I cannot disagree with you in the slightest. On no account should the train stop be pegged down for the duration of the failure. As you say there would then be no protection against a train SPADing W361. We would then have a situation where a train would be given a full main aspect yellow at the previous signal (W359 or W353) and could then proceed normally without any warning towards W361 at danger. In this case the train stop should be operative. That's what it's there for. The train stop should intervene to stop a train which has a bona fide SPAD at the defective signal. Probably this would apply even more in this case as, with trains working through a failure, there is a greater likelihood that a train will be not far ahead. The signal being defective is no excuse at all to disable the safety system all the time. No no it should intervene to stop any train which passes W361 at danger without authority.

What we might have to agree to disagree about is whether the train strop should intervene to stop trains which pass W361 at danger with authority. This is not only clearly "non-optimal" on the face of it, but it is a safety risk. Bringing even a lightly loaded train to a sharp stop is not but a little thing (hence the PA drivers have to make to warn passengers when applying the rule). If the train is crush-loaded it really isn't good. Not at all.

I also don't find the potential for misuse particularly compelling. You could say that about any number of the cut-out switches on trains. But that's why you train and recruit the proper people for the job. That's the point of having the people in the first place to be trained to apply the proper procedures when things are going wrong. It's a standard feature of main line TPWS and a good and useful one at that. Indeed if the TPWS train stop override is not used when passing a signal at danger with authority then the forms will come out of the folders!