Train stopping positions

[Deleted]

Hi guys, so I was wondering if we can discuss train stopping positions on the extension.

Under ATO, what determines the trains correct stopping position? Is it the CBTC (Communications Based Train Control) system that assumes it has stopped the vehicle in the correct position, or is it a proximity based induction loop system as found on some other LUL lines? Finally, do any of you know what allows the PED's (Platform Edge Doors) to be opened? Are there sensors on each platform that determine an accurate stop - if so, how accurately does the train have to be aligned?

The reason I ask is that the other day, when berthed at Canary Wharf after a seemingly normal deceleration and ultimate stop, the train stopping position was way off! The train had stopped at least 1ft past the PED opening threshold; anyone exiting the train not paying too much attention would walk straight in to the PED! This isn't normal and I'm surprised the train and platform systems allowed the doors to be opened at such an odd stopping location.

[rincew1nd]

Feb 27, 2017 20:16:22 GMT nnan said:

...or is it a proximity based induction loop system as found on some other LUL lines?

This would be CSDE, Correct Side Door Enable as explained by District Dave here. I would assume that this system is still in place on the JLE (Julbilee Line Extension) as I guess it's used on the outdoor Jubilee platforms - just with a small loop to give quite a tight range of stopping point .

[philthetube]

Feb 27, 2017 20:16:22 GMT nnan said:

Hi guys, so I was wondering if we can discuss train stopping positions on the extension.

Under ATO, what determines the trains correct stopping position? Is it the CBTC (Communications Based Train Control) system that assumes it has stopped the vehicle in the correct position, or is it a proximity based induction loop system as found on some other LUL lines? Finally, do any of you know what allows the PED's (Platform Edge Doors) to be opened? Are there sensors on each platform that determine an accurate stop - if so, how accurately does the train have to be aligned?

The reason I ask is that the other day, when berthed at Canary Wharf after a seemingly normal deceleration and ultimate stop, the train stopping position was way off! The train had stopped at least 1ft past the PED opening threshold; anyone exiting the train not paying too much attention would walk straight in to the PED! This isn't normal and I'm surprised the train and platform systems allowed the doors to be opened at such an odd stopping location.

If I saw this I would immediately report it to the Line Controller, it is a safety issue and shouldn't happen.  There must have been a fault somewhere but the driver should have noticed and not opened the doors, (assuming that the driver does still open them).

[br7mt]

All done using the TBTC signalling system - there is a specific sub-system for communicating between train and platform to open the Platform Edge Doors once the door open button is pressed. If I remember correctly the tolerance is +/- 0.25m for the PED equipped stations, so a range of 0.5m, which increases to +/- 0.5m and 1m respectively for non-PED stations.

The old CSDE was responsible for telling drivers that they had achieved an accurate stop and would communicate to the PED controller using trackside loops. This used the ATO controller fitted for the part-abandoned WestRace automatic control system.

Regards,

Dan

[Deleted]

Feb 28, 2017 9:42:48 GMT br7mt said:

All done using the TBTC signalling system - there is a specific sub-system for communicating between train and platform to open the Platform Edge Doors once the door open button is pressed. If I remember correctly the tolerance is +/- 0.25m for the PED equipped stations, so a range of 0.5m, which increases to +/- 0.5m and 1m respectively for non-PED stations...

Those tolerances seem fair and achievable (especially for an ATO system).

br7mt ,would I be right in assuming that the green portion of the stopping board must be in the cab side window when the Train Operator is seated in the normal driving position?
Stopping Board London Bridge Eastbound

Also, here is a pic I managed to snap of the overrun train (the angle of the photograph makes it look more acceptable than it should be IMO). 
Overrun Train Canary Wharf PM Peak
(One lady did walk straight in to the open PED as she disembarked, which is what drew my attention to it!)

...The old CSDE was responsible for telling drivers that they had achieved an accurate stop and would communicate to the PED controller using trackside loops. This used the ATO controller fitted for the part-abandoned WestRace automatic control system...

That explains why, since the upgrade, the door closing sequence has changed slightly. (The PEDs used to close immediately along with the audible warning chime).

As seen in this YouTube video from 2010

vs. the current closing sequence - there's a slight delay before the PEDs close. I know it's only a tiny difference but I've noticed it over the past few years.

[Deleted]

Feb 28, 2017 19:49:15 GMT nnan said:

br7mt ,would I be right in assuming that the green portion of the stopping board must be in the cab side window when the Train Operator is seated in the normal driving position?
Stopping Board London Bridge Eastbound

Yes that is the general idea

[tubetraveller]

With the exception of Westminster eastbound, the PED is always to the right hand side of the train and has a 'diamond' stopping mark on the driver's PED and a green 'chevron' on the left of the driver's window

Generally in PED equipped stations we're trained to go by the diamond in the window since it's a much more accurate indicator that you're lined up correctly within +/- approx 0.5m. Quite often, the chevron will be a little out depending on what position your chair is in, or fit entirely within the driver's side window with room to spare!

Generally as long as you are stopped on the 1m or 0m mark, TBTC will give you an accurate stop and allow you to open both train doors and PEDs though CSDE can be overridden in the event of a larger under/overshoot (as long as the doors are still reasonably well aligned)

[brigham]

I don't suppose that anyone thought to make the platform edge doors wider, to give some leeway?
Or would that smack of old-style 'common sense'?

[Chris M]

The platform edge doors are already wider than the train doors, to allow for the ±0.5m tolerance. If you make them too much wider you increase the risk of someone falling between the platform and train or getting trapped between the train and the PEDs - both more dangerous than on platforms without PEDs because of the reduced space and restricted visibility.

[norbitonflyer]

Mar 1, 2017 7:42:51 GMT tubetraveller said:

With the exception of Westminster eastbound, the PED is always to the right hand side of the train

What happens at North Greenwich?

[tubetraveller]

Mar 1, 2017 14:23:26 GMT norbitonflyer said:

Mar 1, 2017 7:42:51 GMT tubetraveller said:

With the exception of Westminster eastbound, the PED is always to the right hand side of the train

What happens at North Greenwich?

You're right! I forgot North Greenwich eastbound is different too!

If I remember correctly, Westminster and North Greenwich both have a chevron on the right and a diamond on the door to the left.
Personally, I still go by the diamonds

[br7mt]

Feb 28, 2017 19:49:15 GMT nnan said:

Also, here is a pic I managed to snap of the overrun train (the angle of the photograph makes it look more acceptable than it should be IMO). 
Overrun Train Canary Wharf PM Peak
(One lady did walk straight in to the open PED as she disembarked, which is what drew my attention to it!)

I've been on a train that has stopped like that right at the edge of the tolerance. As indicated by Chris M, there has to be a limit to the PED width otherwise you would be creating more risks than it solves. The main thing is that situations like this are outliers on a bell shaped curve (statisticians will understand this), which means it is very infrequent.

Regards,

Dan

[banana99]

Feb 28, 2017 19:49:15 GMT nnan said:

Also, here is a pic I managed to snap of the overrun train (the angle of the photograph makes it look more acceptable than it should be IMO). 
Overrun Train Canary Wharf PM Peak

I don't think that's a particularly egregious example and I have experienced similar encounters about a dozen times. I didn't observe anyone having a problem negotiating such an obstacle clear as day in front of them. I suspect you have unintentionally overstated the risk here...