Extra fact (that could be fiction): The policeman in rear of A.201 is there to protect the crossover in advance of OJ.13, from overrun since A.201 does not provide sufficient overlap, for a train travelling at line speed as far as I know
It's to protect a train standing at OJ13. There is insufficient overlap to protect a train in the section between A201 and OJ13 from a SPAD of A201 at full line speed.
If they do convert the Piccadilly line, I hope that they use the tried and tested traditional track loop based system, rather than the Radio based system for compatibility with the Northern and Jubilee Lines. The new fangled radio based system, unfortunately still needs physical hard wired Track Circuits as evidenced on the Victoria Line. (You can physically see the track circuit wiring leads on Victoria Line stations).
I wonder has the radio based system proved itself yet on a complex railway, using the traditional proven track loop system may be a better idea. The downside with radio based systems is that you still need Track Circuits (Hint = Victoria Line 2009 stock), which can be done away with in the track loop system.
The Thales system for SSR uses radio but does not use track circuits. RF tags each with unique IDs perform a function similar to JL/NL loop crossovers and there are axle counters at certain locations.
My questions (prompted by reading (possibly incorrect) reports that an emergency brake application caused a NYC subway train to derail recently as discussed in another thread):
What is the maximum safe braking rate of a tube train? Is '4 bar' the standard brake cylinder pressure that is applied across all LU trains during emergency brake applications?
How is the maximum safe braking rate determined?
What lead me to ask the question: The 'brake cylinder pressure gauge' (may not be right term) located under the seats at one end of each carriage on the central line seems to jump up to '4 bar' during emergency brake applications. The train comes to an abrupt halt.
On the metropolitan line recently, two failed signals between Liverpool Street and Moorgate required the driver to 'apply the rule' to pass the signals at danger. I observed that the brake cylinder pressure gauge jumped to '4 bar' as we came to an abrupt stop.
I know that on older trains, one door in each double leaf can be 'pushed back' a few centimeters to free small obstructions like a coat toggle which could still be trapped despite the doors being proved shut. The force required to push the door back has to be easy enough to overcome to free an obstruction, but not so easy that it would be pushed back by the forces generated by an emergency brake application. I recall that when the 2009ts was being designed, emergency braking could have caused spring loaded doors to 'push back' during maximum deceleration, so sensitive door edges was a solution to enable the doors to be locked tight shut but mitigate the risk of a passenger to be dragged.
I imagine that the rate of deceleration needs to balance the need to stop the train as quickly as possible, against the risk of damaging the wheels / injuring the passengers / keeping the train on the tracks?
The maximum safe braking rate on the S-Stock is dependant on what type of car it is (DM, M1 M2(D) etc), which end of the car and the passenger loading which is monitored by the load weigh system. There are set braking parameters which the train must be able to achieve, from tare weight to crush load.
Without going into too much detail, here are the figures for Emergency braking in tare conditions: DM - A end 4.01 - 4.39, D end 3.22 - 3.60 M1 - A end 3.38 - 3.75, D end 3.53 - 3.90 M2 - A end 3.04 - 3.42, D end 3.04 - 3.42 M2D - A end 3.12 - 3.50, D end 3.20 - 3.58 MS - A end - 3.25 - 3.63, D end 3.25 - 3.63
For crush load conditions in Emergency braking: DM - A end 5.58 - 5.96, D end 5.58 - 5.96
M1 - A end 5.23 - 5.61, D end 5.45 - 5.83
M2 - A end 5.06 - 5.44, D end 5.06 - 5.44
M2D - A end 5.21 - 5.59, D end 5.29 - 5.67
MS - A end - 5.09 - 5.47, D end 5.24 - 5.61
There are also figures for maximum service brake, under tare and crush load conditions.
The train has a EP (Electro Pneumatic) Valve of some sort monitoring each bogie and will determine the the rate of braking depending on the above factors.
On the S-Stock, the 'next station' message is cutting out much sooner than would be necessary for what you mention above.
I actually thought they were out of action because they stayed blank for so long.
A sensible solution to the 'no interruption' rule would be to have a shorter "Next Station Xxxxxx" message without all the ancillary detritus that would display, to avoid the long blank periods that are happening at the moment.
Or just cycle "Approaching Xxxxx" until the front of the train reaches the platform - there would be plenty of time for the 'approaching' to scroll out of the way before the train stopped.
The current method may well have been implemented for 'a good reason', but it is sub optimal and can leave passengers without information.
And, don't forget, these passengers are not aware of the 'good reason', and, if caught out, are probably thinking "why do these muppets stop the information just when you need it most?"
It's not particularly nice to be referred to as a muppet on here, but nevertheless I'll offer some more thoughts.
1. The visual message is not cutting out earlier than I described. Obviously if the train is held at the home signal after the approach message has started, the time duration of the blanking is extended, but the trigger point is as I described. 2. You queried why there is so much information in the approach message. Again, LUL specifies what is to be announced and in some cases when, also RVAR sets various similar but not identical requirements. To best comply with the RVAR requirement to announce the next station whilst 'at station' and before the doors close, the interchange and 'exit for' messaging is given in the approach message. LUL tries to keep to relatively short platform dwell times so as to be able to run its frequent services and indeed to allow the service frequency to be increased with the new signalling. 3. If you feel it is better to continue to repeat scroll the approach message and maybe just overwrite it potentially unfinished immediately when the 'at station' message should start, straight after the doors open, that is an alternative if LU accepted not completing a run through of the scrolling message. I suggest you raise it as a suggestion direct with LUL.
To be fair I don't think class411 meant to call you a muppet or suggest that you were one. I think his point was that, as the points you raise are not necessarily obvious to the travelling public, they might, on watching the S stock information displays, jump to the conclusion that it was a matter of poor design/poor standards and essentially conclude that it was a result of incompetence rather than actual good sense. Which is maybe not such a good look for LU.
Of course, having said that, the moderator team will continue to keep an eye and let's all of us remember that politeness and respect for each other is a requirement not an option.
Naturally, don't hesitate to get in touch if you're unhappy with the way you're being treated on the forum.
Alright that's enough, I think we've got the best out of this discussion now, class411 has contacted TfL and they'll deal with it in whatever way they see fit.
class411 , I'm sorry you and your fellow passengers didn't get the level of customer service you expect. Certainly the way you tell the story - and I've no reason to doubt things happened exactly as you describe - this looks like a pretty poor job on that occasion and that must be very annoying for those who were left behind by the Met service especially as they may have had a long wait for another train to their ultimate destination. And, if I may say so, I personally felt that aslefshrugged 's response didn't quite tackle some of the points that you raised. However, here you have a member of train crew trying his best to politely give some of the possible factors that can be at play in events like these and there was no need for you to take such an ungenerous interpretation of his contribution, or to use words like 'sickening' and oodles of sarcasm. You don't know what the driver was focusing on in his monitors, he's got 8 cars and 24 sets of doors to look after so he may not have clocked people making way for the CSA, however obvious to you that was for example, nor do you know what was said between the two members of staff when the CSA knocked on the cab door. Your post is laden with interpretation, such as that he looked sneeringly at the passengers. And for all I know your interpretation is exactly fair and hopefully TfL will respond positively to your complaint. But now the complaint is made there's not a lot more we can get out of it here and emotions are clearly running high.