Slip coaches

[Falcon1200]

DItto Inverness to Far North services, Georgemas Junction has for years been the split for Wick and Thurso.

Pedant alert; No splits at Georgemas Jc for many years, Far North trains are now a single Class 158 which serves both Thurso and Wick.

Still in Scotland however the Caledonian Sleepers split (and join) at Carstairs and Edinburgh.

 

[AndrewE]

I expected someone to have pointed out our devotion to Absolute block by now. Lots of accidents with slip coaches resulted from the slipped portion "overtaking" the train, and it is difficult to see how the situatin just after the slip had happened could be brought within the regulations now. Even modest extensions of 3rd rail are "too difficult" - and that would give operational and CO2 emissions savings!

 

[Sun Chariot]

Pedant alert; No splits at Georgemas Jc for many years, Far North trains are now a single Class 158 which serves both Thurso and Wick.

My fat thumb typed has instead of had!
Yes, absolutely, the days of 156 splits - and, before that, the Mk1s splitting - are a fond, but distant, memory.

 

[edwin_m]

I expected someone to have pointed out our devotion to Absolute block by now. Lots of accidents with slip coaches resulted from the slipped portion "overtaking" the train, and it is difficult to see how the situatin just after the slip had happened could be brought within the regulations now. Even modest extensions of 3rd rail are "too difficult" - and that would give operational and CO2 emissions savings!

Conceivably it could be done with some sort of vital communication system that slams on the brakes of the slip portion if the main portion slows down for any reason immediately after slipping. This is similar to the "virtual coupling" principle proposed for gadgetbahns and sometimes for railways, where two vehicles run very close together but aren't actually coupled. Joining two moving portions would be considerably more risky, as the time in proximity would have to be longer and speeds would need matching very closely.

 

[Belperpete]

I expected someone to have pointed out our devotion to Absolute block by now. Lots of accidents with slip coaches resulted from the slipped portion "overtaking" the train, and it is difficult to see how the situatin just after the slip had happened could be brought within the regulations now. Even modest extensions of 3rd rail are "too difficult" - and that would give operational and CO2 emissions savings!

ETCS includes provision for both dividing on the move, and joining on the move. Whether any railway has actually implemented these options is another matter!

 

[Pigeon]

I expected someone to have pointed out our devotion to Absolute block by now. Lots of accidents with slip coaches resulted from the slipped portion "overtaking" the train, and it is difficult to see how the situatin just after the slip had happened could be brought within the regulations now.

Level 1 slipping: slip follows the main train then slows down and stops.

Level 2 slipping: slip slows down while the main train goes through on the fast, then points are changed to divert the slip into the platform road.

Level 3 slipping: main train stops at station after slipping and points are changed quickly to allow slip to overtake it and run into another station.

 

[AndrewE]

Level 1 slipping: slip follows the main train then slows down and stops.

while train runs through platform road (with waiting passengers) at line speed

Level 2 slipping: slip slows down while the main train goes through on the fast, then points are changed to divert the slip into the platform road.

as long as the slip has enough momentum to reach platform, or has power and can wait while the track section knows it hasn't been over-run and then changes the points ahead of the slip section

Level 3 slipping: main train stops at station after slipping and points are changed quickly to allow slip to overtake it and run into another station.

good luck getting a risk assessment approved for any of those!

 

[edwin_m]

s long as the slip has enough momentum to reach platform, or has power and can wait while the track section knows it hasn't been over-run and then changes the points ahead of the slip section

And also is slow enough with enough braking to stop at a suitable signal short of the points if they don't go fully over. This is probably unachievable in practice due to the short time interval between the main train and the slip portion, hence why at stations with platform loops either the main train ran through the loop or the slip coach stopped before the loop and was picked up by the station pilot.

 

[AndrewE]

And also is slow enough with enough braking to stop at a suitable signal short of the points if they don't go fully over. This is probably unachievable in practice due to the short time interval between the main train and the slip portion, hence why at stations with platform loops either the main train ran through the loop or the slip coach stopped before the loop and was picked up by the station pilot.

exactly... hence why I said "Good luck getting a RA approved!"
If it was actually a powered portion I suppose it could be slipped, come to a stand and then set off for the platform loop again, but signal spacing/ braking distances are such that you couldn't do this within one signal section - unless there was one extraordinarily long one just for the purpose, which would then impact headways for the rest of the services..

 

[Gloster]

Level 1 slipping: slip follows the main train then slows down and stops.

Level 2 slipping: slip slows down while the main train goes through on the fast, then points are changed to divert the slip into the platform road.

Level 3 slipping: main train stops at station after slipping and points are changed quickly to allow slip to overtake it and run into another station.

Just think what would happen if the points don’t go right across quickly enough or get caught half-way: one slip coach splitting the points or all over the place making a bit of a mess. Changing points in front of moving vehicles within their braking distance is probably not going to be acceptable to whoever makes the rules and I don’t blame them. It smacks of the Victorians and their blind faith in technology: we should know better.

 

[norbitonflyer]

while train runs through platform road (with waiting passengers) at line speed

Why would any passengers be waiting? The slip coach won't be going anywhere further.

 

[AndrewE]

Why would any passengers be waiting? The slip coach won't be going anywhere further.

people might have arrived in good time for the following train? Unless you find a member of staff to prevent access until the fast train has passed. Of course, there's always plenty of staff around for extra jobs like this (not!)

 

[Sun Chariot]

In the forum thread Realistic AI Railway Images, I envisioned a BR Sectorisation-era slip.

Show off your realistic AI railway images!

That is quite a success. Captures the Plymouth I remember from the 2000s. It has put Harriet a little close to the yellow line, but I suppose her and Dave are rebels.

www.railforums.co.uk

 

[Pigeon]

Just think what would happen if the points don't go right across quickly enough or get caught half-way: one slip coach splitting the points or all over the place making a bit of a mess. Changing points in front of moving vehicles within their braking distance is probably not going to be acceptable to whoever makes the rules and I don't blame them. It smacks of the Victorians

You didn't think I'd come up with the idea myself, did you?

and their blind faith in technology: we should know better.

...whereas in fact we're even worse.

 

[edwin_m]

One of the few possible benefits of some sorts of gadgetbahn is that if their "points" don't have moving parts on the ground, then a stream of closely-spaced vehicles can be split out down different paths, for example into a multi-platform station.