London underground stop marker accuracy

[waterboo]

Obviously the deep tube lines that use these markers are running on ATO now. However, for when they were driven manually, I have the following questions:

- Does the viewing window have to land on the green bit exactly, or can it run into the black and yellow triangles?

- How often do drivers overrun/underrun these stop makers?

- Can normal station duties be carried out if these makers were undershot/overrun?

Check this pic if you do not know what I am talking about!
http://www.flickr.com/photos/juniper007/12874398743/


Any replies will be gratefully accepted, I can assure that you are supporting a future tube geek.

 

[Dstock7080]

That type of marker are provided for S7 and S8 Stock. Obviously "S7" "S8" for appropriate Stock, there are also "SS" (all S Stock) and "SR" S Stock reverse markers.
"The train should be aligned with:
the green section of the chevron marker visible through the front cab window aligned with the edge of the windscreen."
The tolerance is just 0.7m to get an accurate stop. This will only illuminate on the Signalling Interface Display (SID) once the train has come to a complete stop. The in-cab CCTV monitors will also illuminate.

Non-S Stock operated trains would use the traditional white diamond mark in the '4-foot', the cab needs to stop over these to obtain CSDE requirements.

 

[waterboo]

That type of marker are provided for S7 and S8 Stock. Obviously "S7" "S8" for appropriate Stock, there are also "SS" (all S Stock) and "SR" S Stock reverse markers.
"The train should be aligned with:
the green section of the chevron marker visible through the front cab window aligned with the edge of the windscreen."
The tolerance is just 0.7m to get an accurate stop. This will only illuminate on the Signalling Interface Display (SID) once the train has come to a complete stop. The in-cab CCTV monitors will also illuminate.

Non-S Stock operated trains would use the traditional white diamond mark in the '4-foot', the cab needs to stop over these to obtain CSDE requirements.

Ooooh, that sheds some light on things! Thank you very much. However when you say 0.7 m tolerance is that beyond the green section, in which it will be allowed.

 

[Peter Mugridge]

I think it's 0.7m from the vertical dashed line in the middle of the marker...

 

[Domh245]

I'm guessing it is +- 0.7m (0.7 either way) or is it 0.7 centred on the line (+-0.35)?