MRT odd happenings

last SG · 2010-12-29T23:01:27+00:00

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. Thi...

joeyfjj SG

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.

C751A 70049/70050 SG

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.

watson374 SG

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...

C751A 70049/70050 SG

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.

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.

watson374 SG

Yeala of course it's still got problems...

TIB1224Y SG

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.

From MRTC:

For ATP purposes the running line is divided into a series of ATP blocks by track circuits. The train is provided with two speed parameters:-

1. The Maximum Safety Speed (MSS), which is the maximum speed at which the train is permitted to travel within the ATP block it currently occupies.
2. The Target Speed (TS), which is the speed which either the manual driver or the automatic equipment should aim to achieve and which is generally the same as the Maximum Safety Speed for the next ATP block ahead.

If the train speed exceeds the Maximum Safe Speed, motoring is inhibited and an emergency brake application is made.

Adding on: Exceeding of Target Speed can be done, as long as you make it below the MSS before you hit the next block, if not EMG brake will be made upon your train.

Hope this clarifies.

E5 SG

That will be, wheel-lock.

http://www.youtube.com/watch?v=sAzK0HYrNNU

This video is sufficient to explain my stance with regards to wheelslipping during braking.

My sources tells a different story:

Some of the things there may not necessary applies to our system. As an example:

- Are the ATP block sign placed before the beginning of every ATP block to notify the TO that he/she has to stop/reach the target speed before that point?

langer68 SG

I only see a stopped train on the video

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