Balcombe Tunnel Flooded 20/12

[TrafficEng]

As someone who works in railway drainage & flooding prevention I can tell you that any work we do is simply to reduce the likelihood. You don't beat mother nature!

As a one-time drainage engineer I can only agree.

The problem is convincing people that flooding that happens from time to time, and that more money needs to be spent to increase capacity to accommodate the additional demands we place on the system, as well as properly maintaining what already exists. A bit like the railway network as a whole really.

 

[Dr Hoo]

Yes it does, but you can only bring it into use when the whole section of line is clear of trains, it’s part of the conditions imposed by the interlocking.

But since both lines were effected it would of made little difference anyway in this instance.

Thank you for this helpful explanation. It would seem to indicate a significant limitation on what I would loosely describe as 'working to point of obstruction' (as we often did with a pilotman in the old days with Absolute block signalling).

 

[YorkshireBear]

That's fair comment but I don't think it's unreasonable for a layman to be asking questions.

Not at all wasn't suggesting it was unreasonable.

 

[Mugby]

On level ground in a tunnel do you suppose that floodwater will stay neatly on only one of two tracks?

Isn't Balcombe Tunnel on a gradient?

 

[tsr]

Isn't Balcombe Tunnel on a gradient?

Very few bits of the railway in this area are completely level!

My route maps show the gradient climbs towards the London end of the tunnel.

 

[Chris125]

Thank you. Given that the work to improve drainage was so major, and so recent, it only took somebody to give a reasoned response as to why it still can't cope. Nobody has, as far as I know, suggested that the current level of rainfall couldn't have been foreseen just a few months ago.
Anyway, sorry to ask a simple question of a member of rail staff.

Don't forget that improved drainage can allow water levels to recede quicker, so even if flooding does occur the impact is reduced.

 

[Sunset route]

Thank you for this helpful explanation. It would seem to indicate a significant limitation on what I would loosely describe as 'working to point of obstruction' (as we often did with a pilotman in the old days with Absolute block signalling).

First of all comparing AB to TCB is like comparing apple as & pears. Bi-Di signalling is not for working to and from a point of obstruction, for that you would need to bring “Pilot working” under P2 of the rule book.

It is designed to send a train or trains against the normal flow of traffic but under controlled signalling conditions as in the signals will work for trains travelling in that direction. The nature of the beast is that it’s interlocked that once a train enters the area wrong direction with signals that all the apposing signals will be held at danger by the interlocking until the train or trains have cleared what is effect now a single line at the exit. If the interlocking didn’t behave that way, you run the potential of having trains run towards each other on the single line (that is in use) and at best having a Mexican stand off at worst (if things have really gone wrong) a head on. The same interlocking logic will prevent you from sending a train Bi-Di with a train in section running the normal (correct) direction.

With this in mind if a train has travelled right direction but can’t go any further (as in 9S00 at Balcombe today) has not met the conditions to free the interlocking ie cleared the exit then then the signals for the set back movement will be held at danger and as such the driver will need to be talked passed everyone of them at danger until the train has passed clear of the entrance to the Bi-Di signalled area. This is now when if required you instigate working by “pilot workingl” under rule book section P2 working to and from a point of obstruction.

 

[Raul_Duke]

Not sure what the exact level was, but I noticed that during the flooding around Sway on the SWML the other night, CrossCountry Voyagers were able to keep running at a reduced speed, it was only the SWR 3rd rail stock that couldn't run.

Sometimes this is due to the location of traction motors on the stock.

Voyagers/Meridians will quite happily go for a bit of a shallow paddle for example, whereas HST’s much prefer keeping their feet dry and out the water.