MRT odd happenings
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The other night (26 Dec 2010), I was on the MRT between Clementi and Jurong East, towards Joo Koon. For some reason, the train stopped on the viaduct, and there was this "tssh" that was repeated as if the air brake or something was being applied.
Earlier that day, the train stopped on the incline coming into Dover from Buona Vista. I was on the Dover WB platform waiting, and it just stopped just before the hump. The headlamps went out for a short while, then the train crawled into Dover, and the brake sound had no electrical whirring, just the mechanical brake's high-pitched squeak.
Weird? Any ideas why? (It was raining like s*** btw).
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Post in Train Happening or??...
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Mod Notice: Removed.
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there's a trains happening thread already.
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Please leave the moderating of the thread to the moderators.
The sound you probably heard when the train stopped should be a emergency brake application. This is a usual practise by train operators when they have to change from automatic mode (where the train drives itself) to CM (where the train operators drives the train himself).
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Originally posted by joeyfjj:
Please leave the moderating of the thread to the moderators.
The sound you probably heard when the train stopped should be a emergency brake application. This is a usual practise by train operators when they have to change from automatic mode (where the train drives itself) to CM (where the train operators drives the train himself).
+1. People have a strange habit of rent-a-modding here.
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Is the switch from ATO to CM so easy? The train only stopped for a few seconds, like 3-5.
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Maybe the train is too near to the one in front, so it stopped.
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Maybe, but I don't think so... It was about 9 plus on Boxing Day night; anyway trains are never less than 2-3min apart in SG...
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This was the same thing that happened that time, SmRT trains often stop in the middle of Pasir Ris and Tampines stns while commuters on board before moving again1. I used the same reason to explain the above. nowsadays, instead I would see a train stop suddnly while on a bus or car. The last time that happened was when I was taking a bus and while traveling below TPE, I saw the train sitting jjust above the train tracks.
1 The last time I was sitting on the train when this happened was in jan.
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Originally posted by joeyfjj:
The sound you probably heard when the train stopped should be a emergency brake application. This is a usual practise by train operators when they have to change from automatic mode (where the train drives itself) to CM (where the train operators drives the train himself).
Contrary to what you have posted, it works the other way round. There may be a downhill section along the route, so the train has coasted above the maximum speed of that section of the line (ie. overspeed) so the OCC will send a signal to the train causing it to apply the emergency brake to a halt for safety. However, to take this train out of this situation, the driver needs to change to CM mode to take the train to its next station in order for the signals to reset.
Changing modes does not require the TO to apply the emergency brake as the emergency brake is, as its name suggests, for emergency only.
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Originally posted by Interception_7:
Contrary to what you have posted, it works the other way round. There may be a downhill section along the route, so the train has coasted above the maximum speed of that section of the line (ie. overspeed) so the OCC will send a signal to the train causing it to apply the emergency brake to a halt for safety. However, to take this train out of this situation, the driver needs to change to CM mode to take the train to its next station in order for the signals to reset.
Changing modes does not require the TO to apply the emergency brake as the emergency brake is, as its name suggests, for emergency only.
I'm not really sure, in fact. It is said (that means I heard of it from other people) that this is done when the train is in AM and needs to switch into CM between stations. This, of course, might not be correct, as we do not have any sources to verify or refute this.
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Besides over-speed while coasting, I would suggest wheelslip or skidding; it was raining cats, dogs and the maharaja's elephants.
Possible?
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is this any freaky? where is the freaky part of it?
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Originally posted by joeyfjj:
I'm not really sure, in fact. It is said (that means I heard of it from other people) that this is done when the train is in AM and needs to switch into CM between stations. This, of course, might not be correct, as we do not have any sources to verify or refute this.
Try not to post anything that you are unsure of as this may lead to confusion.
Originally posted by watson374:Besides over-speed while coasting, I would suggest wheelslip or skidding; it was raining cats, dogs and the maharaja's elephants.
Possible?
Wheelslip only occurs upon departure, and yes it may be due to rain.
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Originally posted by Interception_7:
Contrary to what you have posted, it works the other way round. There may be a downhill section along the route, so the train has coasted above the maximum speed of that section of the line (ie. overspeed) so the OCC will send a signal to the train causing it to apply the emergency brake to a halt for safety. However, to take this train out of this situation, the driver needs to change to CM mode to take the train to its next station in order for the signals to reset.
Changing modes does not require the TO to apply the emergency brake as the emergency brake is, as its name suggests, for emergency only.
As far as I observed on JUR - CLE sector, there is a slop sector.
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Originally posted by langer68:
This was the same thing that happened that time, SmRT trains often stop in the middle of Pasir Ris and Tampines stns while commuters on board before moving again1. I used the same reason to explain the above. nowsadays, instead I would see a train stop suddnly while on a bus or car. The last time that happened was when I was taking a bus and while traveling below TPE, I saw the train sitting jjust above the train tracks.
1 The last time I was sitting on the train when this happened was in jan.
[Note: This is not related to the threadstarter's question, but clarifications for langer68's post.]
This is only caused when that train that stopped is waiting for one of the trains to clear the station. It happens 70% of the time during peak hours, and happens at Marina Bay and Joo Koon too.
Like for example, there's two trains in the station, the train could not enter the station as both platforms are filled. So this train (the train that's outside the station) waits for one train to depart before proceeding.
Another case is when there's one train departing Pasir Ris at platform A, this train (that's outside the station) would enter platform B, however, as the train at platform A has already set the route and is departing, the train outside would have to wait till the train crossovers, and after the signals and tracks have been set, then the train would proceed.
(Correct me if I'm wrong, cause I know my percentage is wrong,
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Originally posted by Interception_7:
Contrary to what you have posted, it works the other way round. There may be a downhill section along the route, so the train has coasted above the maximum speed of that section of the line (ie. overspeed) so the OCC will send a signal to the train causing it to apply the emergency brake to a halt for safety. However, to take this train out of this situation, the driver needs to change to CM mode to take the train to its next station in order for the signals to reset.
Changing modes does not require the TO to apply the emergency brake as the emergency brake is, as its name suggests, for emergency only.
Some things to clarify here;
ATO operation has failsafe algorithm in place to prevent overspeeding. If the train in ATO has indeed exceeded the speed limit (which is highly unlikely) specified within a section, it is actually ATP that was tripped to instruct the train to come to a complete stop using emergency brakes. The same goes to overspeeding in CM.
Emergency brakes is not only applied during emergencies, but also during non-emergency cases. A good example would be a misjudge of CSP which may result in overrun.
Originally posted by Interception_7:Wheelslip only occurs upon departure, and yes it may be due to rain.
Wheelslip occurs too during braking, not neccessarily only during acceleration.
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Originally posted by yellowflip999:
[Note: This is not related to the threadstarter's question, but clarifications for langer68's post.]
This is only caused when that train that stopped is waiting for one of the trains to clear the station. It happens 70% of the time during peak hours, and happens at Marina Bay and Joo Koon too.
Like for example, there's two trains in the station, the train could not enter the station as both platforms are filled. So this train (the train that's outside the station) waits for one train to depart before proceeding.
Another case is when there's one train departing Pasir Ris at platform A, this train (that's outside the station) would enter platform B, however, as the train at platform A has already set the route and is departing, the train outside would have to wait till the train crossovers, and after the signals and tracks have been set, then the train would proceed.
(Correct me if I'm wrong, cause I know my percentage is wrong,
.)This is actually a problem in termini in London, where you need to wait to enter. Are there any termini in Singapore that could use a 3rd platform?
BTW the Pasir Ris problem can be solved if you have a flying double crossover, and is caused by the use of a flat scissors crossover, right?
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Originally posted by E5:
Wheelslip occurs too during braking, not neccessarily only during acceleration.
That will be, wheel-lock.
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Originally posted by E5:
Some things to clarify here;
ATO operation has failsafe algorithm in place to prevent overspeeding. If the train in ATO has indeed exceeded the speed limit (which is highly unlikely) specified within a section, it is actually ATP that was tripped to instruct the train to come to a complete stop using emergency brakes. The same goes to overspeeding in CM.
Emergency brakes is not only applied during emergencies, but also during non-emergency cases. A good example would be a misjudge of CSP which may result in overrun.
Wheelslip occurs too during braking, not neccessarily only during acceleration.
My sources tells a different story:
If the driver exceeds the speed limit for a section, the train will brake automatically until it is both below the limit and the driver presses a flashing "Alarm" button.
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Originally posted by watson374:
This is actually a problem in termini in London, where you need to wait to enter. Are there any termini in Singapore that could use a 3rd platform?
BTW the Pasir Ris problem can be solved if you have a flying double crossover, and is caused by the use of a flat scissors crossover, right?
no. The only termini I could think of is..... Paya Lebar CCL or Promenade CCL, which is potential but not real termini. Well, the stations are constructed so narrow that employs a island platform and cutting through in (Imagine Woodlands got a middle track due to an extension from its sidings) is impossible, even it had the station closed for years.
Building through its side like JEMP sounds possible (Even if the disruptions is acceptable), but there again, one must consider that building such crossover from the side will cause "wide crossing" (Such as changing 2 lanes or more in normal vehicle) in any case (Either before terminating OR when the train sets to depart) unless you stack it up for above ground or stack it below for underground terminus but then the gradient is most likely unacceptable.
Apart of that, one has to remember that in between stations has only and will only features 2 platforms for each direction only with some notable exceptions of 3 or 4 platforms because they are interchange / potential future interchanges from an extension line out of it and hence terminate in a 3rd platform will not help much at all.
Hence, the solution is to use Spanish solution such as one used to be (Now rarely seen for various reasons) employed in Harbourfront where Platform A is used to disembark the pax and Platform B is used for passenger boarding so that the train generally park them in the overrun sector (Due to generally the use of scissors crossover such as one in Dhoby Ghaut CCL) and Platform B for a quicker access to trains and paxes in an orderly manner.
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Wei, that isn't Spanish solution; Spanish solution is doors open on both sides, one to alight and one to board.
But yeah I get what you mean. If properly run, scissors style can be very good, like Brixton on the Victoria line in London.
And by third platform, I mean convert 2-platform terminus. Like say too many trains liao coming into Marina Bay cos got AMK, Yishun and Jurong East trains running, so build 3rd platform so can reverse more.
If you get me drift...
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Originally posted by watson374:
Wei, that isn't Spanish solution; Spanish solution is doors open on both sides, one to alight and one to board.
But yeah I get what you mean. If properly run, scissors style can be very good, like Brixton on the Victoria line in London.
And by third platform, I mean convert 2-platform terminus. Like say too many trains liao coming into Marina Bay cos got AMK, Yishun and Jurong East trains running, so build 3rd platform so can reverse more.
If you get me drift...
A bit la, forget the real term. If you say like that, then only AMK LTE is Spanish.
Ok, but if you need more platform on terminus so that the train no need to wait outside, then you have to do it either on the side on above / below the station and not just slotting one more platform inside it for obvious reason. If you put it on the side, then the crossover from the side to the other direction bound will require many crossovers (2 at least) and a longer travelling distance of crossing over, which can be both jerky and time consuming due to low speed and means, trains might still have to wait outside while crossing over.
If you build it above / below the existing station, crossing over impact when compared to the side is still there, but not that much, but the problem is more on the gradient which is either unacceptable steep or longer distance involved which faces space constraint. In any case, that wont work and effectively kills provision to extend it (Tuas extension from Joo Koon, olden days Yishun extend to Woodlands etc).
Hence the solution is to use one like HBF, but now it is seldom (Or even none) practiced due to someone tried to see and verified that the crossover after HBF is a scissors with power supply intake / staircase access to that area which effectively kills any southern extension out of it, which I had imagined NEL extending to Pulau Semaku when the rubbish had land filled it by 2050 which according to them (Government), by then it would be a recreational area during my tour to there as part of Social Studies back then.
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Yeala of course it's still got problems...