Would platform screen doors ever work on the Thameslink Core?

[SouthEastBuses]

As Thameslink now runs solely with a fleet of class 700s, I was wondering:

Would platform screen doors aka platform edge doors (like those used on Crossrail and the Jubilee Line extension) ever work on the Thameslink Core stations - ideally installed at Blackfriars, City Thameslink, Farringdon and St Pancras Int'l (Low Level platforms A and B).

Or would it be a waste of money?

Would be interesting to see what you all think.

 

[zwk500]

Short answer is yes they could be made to work.

The question about whether it would be a waste of money depends on a number of things. As both 12- and 8-car trains run through the core, it will need a system to make sure it doesn't open the wrong doors for the shorter train (might be simple, but needs to fail safe). Also at the moment level access is provided through harrington humps, so the doors would need to be rejigged for the humps or the platforms rebuilt (again, may not be too bad). The benefit for PEDs is primarily in safety and therefore reducing delays from incidents on the track. How often do trains get disrupted in the core for incursions on the track?

 

[Bald Rick]

They might, actually, be quite difficult to implement. Platform screen doors need a relatively straight alignment, horizontally and vertically. All the core platforms have elements of tight curves, tight vertical curves, or both. South end of St Pancras, and almost all of Farringdon in particular.

Very few track incursions in the core. The biggest impact would be eliminating issues where people drop shoes /phones / teddy bears etc on to the track.

 

[Failed Unit]

They often speed up boarding on the Jubilee as the passengers know exactly where to stand.

 

[Bald Rick]

They often speed up boarding on the Jubilee as the passengers know exactly where to stand.

In the core that is done by specific markings on the platform edges for where the doors will be. Same on the Victoria line (which is more intensive than the Jubilee).

 

[SouthEastBuses]

They might, actually, be quite difficult to implement. Platform screen doors need a relatively straight alignment, horizontally and vertically. All the core platforms have elements of tight curves, tight vertical curves, or both. South end of St Pancras, and almost all of Farringdon in particular.

Very few track incursions in the core. The biggest impact would be eliminating issues where people drop shoes /phones / teddy bears etc on to the track.

I'd say, yes, platform screen doors are less of an issue at Blackfriars and City Thameslink and more at Farringdon. St Pancras is generally fine with the exception of the south end of the station.

 

[SouthEastBuses]

They might, actually, be quite difficult to implement. Platform screen doors need a relatively straight alignment, horizontally and vertically. All the core platforms have elements of tight curves, tight vertical curves, or both. South end of St Pancras, and almost all of Farringdon in particular.

Very few track incursions in the core. The biggest impact would be eliminating issues where people drop shoes /phones / teddy bears etc on to the track.

And I guess they can also have advantages with overcrowding - the doors reduces the risk of people falling off to the tracks whether by accident or intentional.

 

[adamedwards]

Could you gain much of the benefit by simply fencing off the edges of the platform between the locations where the doors are?

 

[zwk500]

Could you gain much of the benefit by simply fencing off the edges of the platform between the locations where the doors are?

You'd have about 80% of the cost for 20% of the benefit.

 

[Bletchleyite]

You'd have about 80% of the cost for 20% of the benefit.

Some countries do have this, so clearly it is not as clear cut as you think.

 

[JonathanH]

How would the cost of something simple like railings fixed to the platform cost 80% of the cost of sophisticated platform edge doors? I appreciate they would need to be solid and not deform under pressure.

 

[Ianno87]

Could you gain much of the benefit by simply fencing off the edges of the platform between the locations where the doors are?

Although "unintended consequences" may mean that the 'security' of the fence may encourage people to stand closer to the gaps, thereby inducing a safety issue.

 

[Bald Rick]

You'd have about 80% of the cost for 20% of the benefit.

Not sure about that. The expensive bit of PEDs is the door mechanism and particularly the safety critical comms links that make the doors open / close only when commanded, and only when a train is there. Having panels with gaps would be the cheap bit.

 

[Jim the Jim]

Short answer is yes they could be made to work.

The question about whether it would be a waste of money depends on a number of things. As both 12- and 8-car trains run through the core, it will need a system to make sure it doesn't open the wrong doors for the shorter train (might be simple, but needs to fail safe). Also at the moment level access is provided through harrington humps, so the doors would need to be rejigged for the humps or the platforms rebuilt (again, may not be too bad). The benefit for PEDs is primarily in safety and therefore reducing delays from incidents on the track. How often do trains get disrupted in the core for incursions on the track?

Would it need to fail safe? Platform doors opening when there isn't a train behind them doesn't really create a scenario which is any more dangerous than not having platform doors at all.

 

[Bletchleyite]

Would it need to fail safe? Platform doors opening when there isn't a train behind them doesn't really create a scenario which is any more dangerous than not having platform doors at all.

People will lean on them.

 

[Bald Rick]

Would it need to fail safe? Platform doors opening when there isn't a train behind them doesn't really create a scenario which is any more dangerous than not having platform doors at all.

It needs to be fail safe. 99.9999% of the time when the doors open there’s a train there - people are conditioned to that - then one day the 0.0001% happens and the door opens and no train - someone will walk through...

(And in terms of numbers, in normal service on Crossrail, a failure rate of 0.0001% means one door opening with no train every week...)

 

[Dr Hoo]

Blind and partially-sighted passengers might not be able to detect that there was 'no train' beyond the door that they had just heard and felt open for them.

 

[Dent]

It needs to be fail safe. 99.9999% of the time when the doors open there’s a train there - people are conditioned to that - then one day the 0.0001% happens and the door opens and no train - someone will walk through...

(And in terms of numbers, in normal service on Crossrail, a failure rate of 0.0001% means one door opening with no train every week...)

A mechanism to ensure the doors only open when the train is there is not difficult or expensive. Various methods to do this for lift doors have existed for over a century.

 

[Bald Rick]

A mechanism to ensure the doors only open when the train is there is not difficult or expensive.

Well we’ll have to disagree on that.

 

[swt_passenger]

Well we’ll have to disagree on that.

Didn’t the change of train length on the Jubilee line have to be done in a “Big Bang” primarily because it was decided they couldn’t safely run two different train lengths through the PED fitted stations even for a short period? I’m fairly sure that was the excuse given at the time, but it’s distant memory now…

 

[Journeyman]

Didn’t the change of train length on the Jubilee line have to be done in a “Big Bang” primarily because it was decided they couldn’t safely run two different train lengths through the PED fitted stations even for a short period? I’m fairly sure that was the excuse given at the time, but it’s distant memory now…

Yes, it was a significant factor in the decision to do the whole lot at once during a closedown.

 

[Dent]

Well we’ll have to disagree on that.

It's certainly well tried and tested, considering that it is a standard part of any passenger lift.

 

[Ianno87]

Didn’t the change of train length on the Jubilee line have to be done in a “Big Bang” primarily because it was decided they couldn’t safely run two different train lengths through the PED fitted stations even for a short period? I’m fairly sure that was the excuse given at the time, but it’s distant memory now…

Yes, the doors couldn't cope with a mix of train lengths (I assume that to do so would have been an extensive programming change not really worth it for a temporary situation).

 

[Bald Rick]

It's certainly well tried and tested, considering that it is a standard part of any passenger lift.

I’m not arguing that. Although lifts operate in a rather different environment.

AIUI, when MTR installed PEDs on existing lines on the HK Metro they insisted on every door having 10,000 consecutive fault free cycles before being brought into operation.

 

[Gareth]

Could you gain much of the benefit by simply fencing off the edges of the platform between the locations where the doors are?

I think the Seoul Metro has this at some stations; although I can't find any photos of it. They may have been upgraded to proper PSDs in the meantime.

 

[Bletchleyite]

I think the Seoul Metro has this at some stations; although I can't find any photos of it. They may have been upgraded to proper PSDs in the meantime.

I've seen it in a number of places. The KL Monorail has them too though that's partly to protect against a bigger drop than a typical railway platform has. They do have value but you have to take care not to engineer other accident possibilities such as people getting trapped between them and the train.

DB uses an interesting variant on platforms where 200km/h+ trains pass through non-stop, which wasn't previously allowed but was introduced for the WCML-PUG1-like upgrade of the Hamburg-Berlin route. They have fences on the platform but they are a metre or so back from the edge, and you're meant to stay on the "safe" side of them until your train stops. Because they're back from the train they don't need to match door positions. Something like this could work on Manchester Piccadilly P13/14, say.

 

[ashkeba]

I think the Seoul Metro has this at some stations; although I can't find any photos of it. They may have been upgraded to proper PSDs in the meantime.

They can be seen in pictures on http://urbanrail.net/as/kr/seoul/seoul.htm

 

[Gareth]

Thanks, ashkebad. Daegu also appears to have them...

http://www.urbanrail.net/as/kr/daegu/daegu-subway1.jpg

 

[Dent]

I’m not arguing that. Although lifts operate in a rather different environment.

What material difference would make doors that only open when a train is there impossible while doors that only open when a lift is there have been successfully employed all over the world for over a century?

 

[JonathanH]

What material difference would make doors that only open when a train is there impossible while doors that only open when a lift is there have been successfully employed all over the world for over a century?

Presumably there is a direct mechanical interlocking on lift doors between the lift car and the doors. That isn't really possible with a moving train and it has to be done with electronic means.