Would the slipping of coaches meet today's safety standards?

[infobleep]

Would the practise of slipping of coaches meet today's safety standards on the railways?

I'm ignoring the timetable issues here and just focusing on the practise it self. I'd assume the rolling stock wouldn't have slam doors.

 

[Clip]

Quite simply no.

 

[yorkie]

Clearly not, no.

Also, perhaps you could help people understand what the practice was, perhaps by linking to an existing explanation and quoting from it, for the benefit of anyone who doesn't know.

 

[John Webb]

Slip Coaches were a means of giving a service between a train's starting point and an intermediate station. They were designed to be detached from the rear of a train in motion as the station was approached. A guard in the slip coach then brought it to a halt in the station. The coach had to be equipped with a special coupling and brake pipe connections that could be separated without bringing the whole train to a halt, and larger air reservoirs carried by the coach enabled the guard to apply and release the brakes to bring the carriage to a halt as required. After passengers had disembarked the station 'pilot' loco would remove the slip coach from the main line.

The system was started by several railway companies around 1858, and the last slip coach was in 1960 at Bicester on the former GWR Paddington - Birmingham line. Special arrangements of tail lamps had to be used on the slip coach and the main train to indicate to signallers and other lineside staff the state of the train.

As far as safety goes, it violated the basic principle of the absolute block system of one train in the block section at a time. And in foggy or snowy weather the whole train had to stop anyway as slipping was not allowed in such conditions.

The needs of modern rolling stock for power for air conditioning, door operation and the like would cause considerable problems in present times, as well as the obvious safety concerns, in restarting slip coach operations.

 

[Lucan]

With self-driving cars on the horizon and driverless (and cab-less lorries) delivering on public roads ...
https://www.reuters.com/article/us-einride-autonomous-sweden/driverless-electric-truck-starts-deliveries-on-swedish-public-road-idUSKCN1SL0NC
... rail is being left behind. The advent of SD vehicles is another nail in the coffin because rail's advantages of a far lower driver-per-passenger or driver-per-freight-ton ratios than road, and the ability to transport people who cannot drive (or do not wish to), are shortly going to vanish.

The infrastructure for driverless trains is largely already in place (the steering problem is solved for a start) - yet we cannot handle a slip coach ?

 

[pdeaves]

In a modern transport system a slip coach is no use unless there is a means to pick up at speed to balance it. Ways could be found, I am sure, but satisfying the safety requirements will be challenging.

 

[Belperpete]

As pdeaves has just mentioned, slip coaches only solved the problem of intermediate stations in one direction. Coming back, the train needed to stop to collect the slip coach and returning passengers. Or the slip coach was worked to a station where the express stopped, to be rejoined there for the return journey.

Interestingly, the ETCS specs include provision for both dividing trains on the move (i.e. slipping), and also joining trains on the move. Whether they will ever be implemented is another matter. However, I suspect that it wouldn't have got into the specs if at least one country wasn't still doing it at the time, or at least thinking of it. Are there any other countries that still do slipping? Or attaching/detaching bankers on the move?

 

[tasky]

Seems like extremely limited benefit for quite significant costs and dangers

 

[30907]

Interestingly, the ETCS specs include provision for both dividing trains on the move (i.e. slipping), and also joining trains on the move. Whether they will ever be implemented is another matter. However, I suspect that it wouldn't have got into the specs if at least one country wasn't still doing it at the time, or at least thinking of it. Are there any other countries that still do slipping? Or attaching/detaching bankers on the move?

Detaching bankers is still practised. The Geislinger Steige (Incline) east of Stuttgart in Germany is one, and AFAIK the incline at Liege. This includes passenger trains at Geislingen occasionally, and possibly at Liege.

 

[smsm1]

With multiple units where both portions of the train are powered should make it easier, especially if you can have the train control systems talking to each other.

 

[Clip]

With self-driving cars on the horizon and driverless (and cab-less lorries) delivering on public roads ...
https://www.reuters.com/article/us-einride-autonomous-sweden/driverless-electric-truck-starts-deliveries-on-swedish-public-road-idUSKCN1SL0NC
... rail is being left behind. The advent of SD vehicles is another nail in the coffin because rail's advantages of a far lower driver-per-passenger or driver-per-freight-ton ratios than road, and the ability to transport people who cannot drive (or do not wish to), are shortly going to vanish.

The infrastructure for driverless trains is largely already in place (the steering problem is solved for a start) - yet we cannot handle a slip coach ?

Its an ineffective use of station capacity before you even think about the safety issues

 

[61653 HTAFC]

Detaching bankers is still practised. The Geislinger Steige (Incline) east of Stuttgart in Germany is one, and AFAIK the incline at Liege. This includes passenger trains at Geislingen occasionally, and possibly at Liege.

With the ETCS provisions outlined above, and a largely multiple unit railway, the process of "slipping" a unit in the future could well be easier and safer than in the past. For one thing, rather than dropping off unpowered vehicles that need a station pilot to clear them from a platform, a DMU can move under it's own power to sidings.

 

[Lucan]

With multiple units where both portions of the train are powered should make it easier

Slipping off one unit of a Portsmouth or Southampton-bound EMU at Woking (which has a London facing centre bay platform) comes to my mind. It would take five minutes off the journey time of the otherwise stopping Portsmouth train, which would also be saved from travelling half-empty beyond Woking (where a lot of commuters get off).

The problem is re-joining Up trains, but as I pointed out, with the advances in SD road technology in mind we ought to be applying some of that to railways too. Units joining up on the fly does not look like a difficult problem to me, if the regulatory bodies can get over it. It amazes me that SD tech is being at least partially implemented on public roads with hardly a murmur from the road traffic authorities.

 

[MarkyT]

I seem to recall historic operations on train ferries in Scandinavia included the splitting and joining of express units on the move as part of loading and unloading. It was all fairly low speed though, little more than walking pace, and presumably involved moving of points in front of moving trains as the idea was to accommodate the two portions of the train alongside each other on the train deck of a comparatively short vessel.

A modern implementation of splitting and joining on the move under ETCS would have to incorporate an effective 'virtual coupling' between the units involved that would have to remain engaged while the operation took place as long as the parts were less than a conventional braking distance apart. Virtual coupling is a concept being investigated anyway to allow multiple separately powered units to work together as a combined service without them having to be coupled together physically at all. That could be of great use on its own for speedy splitting and joining at stations, without the additional factors involved in accomplishing such operations on the move. Part of the virtual coupling concept is a real-time high-integrity wireless linking of the traction and braking control systems on the units working together. To be fully fail-safe the rear unit will have to engage an immediate full emergency brake application should the link fail or become compromised in other ways.

As a development roadmap, I'd suggest virtual coupling will be developed first for splitting and joining units while stationary at stations, with the possibility of allowing it to take place on the move being a subsequent refinement.

 

[Clip]

Slipping off one unit of a Portsmouth or Southampton-bound EMU at Woking (which has a London facing centre bay platform) comes to my mind. It would take five minutes off the journey time of the otherwise stopping Portsmouth train, which would also be saved from travelling half-empty beyond Woking (where a lot of commuters get off).

All well and good till someone is in the wrong portion and gets carried to here they dont want to go - hell it even happens now but at least people get a second bite at the cherry so it is to move.

 

[infobleep]

Clearly not, no.

Also, perhaps you could help people understand what the practice was, perhaps by linking to an existing explanation and quoting from it, for the benefit of anyone who doesn't know.

Good point:

A slip coach or slip carriage is a British and Irishrailway term for passenger rolling stock that is uncoupled from an express train while the train is in motion, then slowed by a guard in the coach using the brakes, bringing it to a stop at the next station. The coach was thus said to be slipped from its train. This allowed passengers to alight at an intermediate station without the main train having to stop, thus improving the journey time of the main train. In an era when the railway companies were highly competitive, they strove to keep journey times as short as possible, avoiding intermediate stops wherever possible.

https://en.m.wikipedia.org/wiki/Slip_coach

 

[duffield]

...

A modern implementation of splitting and joining on the move under ETCS would have to incorporate an effective 'virtual coupling' between the units involved that would have to remain engaged while the operation took place as long as the parts were less than a conventional braking distance apart. Virtual coupling is a concept being investigated anyway to allow multiple separately powered units to work together as a combined service without them having to be coupled together physically at all. That could be of great use on its own for speedy splitting and joining at stations, without the additional factors involved in accomplishing such operations on the move. Part of the virtual coupling concept is a real-time high-integrity wireless linking of the traction and braking control systems on the units working together. To be fully fail-safe the rear unit will have to engage an immediate full emergency brake application should the link fail or become compromised in other ways.
...

Interesting; I can see this idea could potentially give considerable capacity increases on very busy sections of the network, e.g. 3x4 coach trains leaving a major station simultaneously to different eventual destinations, all sharing the same path as a single 'virtual train' and potentially 'virtually splitting' dynamically at junctions (I guess you'd need to split the virtual train dynamically into two portions occupying two paths as it approached the junction to ensure the points could be changed safely between the two portions). But with solid realtime comms between the parts of the virtual train all sorts of interesting possibilities would arise.

 

[hexagon789]

Are there any other countries that still do slipping? Or attaching/detaching bankers on the move?

Did any other countries ever have Slip Coaches?

 

[edwin_m]

They used to use slipping to test brakes on new wagons on the Down Slow north of Crewe in the 1980s - not sure if they still do. They had a dual-braked 47 and Mk1 coach modified so they could use vacuum brake during the tests with the air brake operational on the wagon under test. The wagon was slipped by a special coupling release handle which also started a distance counter - the loco and coach kept going and backed up when they were absolutly sure it had stopped, which wound the distance counter back to measure the stopping distance of the wagon.

 

[DerekC]

Interesting; I can see this idea could potentially give considerable capacity increases on very busy sections of the network, e.g. 3x4 coach trains leaving a major station simultaneously to different eventual destinations, all sharing the same path as a single 'virtual train' and potentially 'virtually splitting' dynamically at junctions (I guess you'd need to split the virtual train dynamically into two portions occupying two paths as it approached the junction to ensure the points could be changed safely between the two portions). But with solid realtime comms between the parts of the virtual train all sorts of interesting possibilities would arise.

Coventry University (sponsored by RSSB) did a study into just this concept a few years ago. See:

https://www.sparkrail.org/Lists/Records/DispForm.aspx?ID=24669

Seamless Interchangeability (DC NOTE: that's what CU called the concept) involves the running of a non-stop 'train', known as the 'prime train' between the terminal stations. To serve intermediate stations, autonomously powered carriages couple/uncouple from the front/rear of the prime train. This allows passengers to travel from an intermediate station and join the 'quicker' non-stop train,o giving passengers the option to walk through and change trains without stopping. The concept benefits were highlighted using a developed fictitious railway network simulation model, allowing today's operation to be compared to that of Seamless Interchangeability

Unfortunately the full report is only available if you have access to RSSB's SPARK database, but it's worth a read.

The difficult bit as with most things to do with the railway, isn't the technology as such - it's the rules (you would have to break some of the current safety rules during uncoupling and coupling) and the radical change in operational concept, which would be very hard to handle. A complete recast, not just of the timetable but of train service specifications at national level, would be needed.

 

[6Gman]

Interesting; I can see this idea could potentially give considerable capacity increases on very busy sections of the network, e.g. 3x4 coach trains leaving a major station simultaneously to different eventual destinations, all sharing the same path as a single 'virtual train' and potentially 'virtually splitting' dynamically at junctions (I guess you'd need to split the virtual train dynamically into two portions occupying two paths as it approached the junction to ensure the points could be changed safely between the two portions). But with solid realtime comms between the parts of the virtual train all sorts of interesting possibilities would arise.

Until a cow/ road vehicle/ suicidal person/ p way staff member appears in front of the leading train resulting in an emergency brake application ...

 

[infobleep]

Until a cow/ road vehicle/ suicidal person/ p way staff member appears in front of the leading train resulting in an emergency brake application ...

That must have happens when slip coaches were regularly used. I'm not saying it was right and it may even be a good reason for it not to return. I'm no expert but I am interested in it

 

[infobleep]

All well and good till someone is in the wrong portion and gets carried to here they dont want to go - hell it even happens now but at least people get a second bite at the cherry so it is to move.

Well they don't of they don't alight before the portions split.

 

[PeterC]

Even without dynamic slipping a virtual coupling would make portion working safer, and easier, as it wouldn't need anybody climbing between units to connect them.

 

[anme]

With self-driving cars on the horizon and driverless (and cab-less lorries) delivering on public roads ...
https://www.reuters.com/article/us-einride-autonomous-sweden/driverless-electric-truck-starts-deliveries-on-swedish-public-road-idUSKCN1SL0NC
... rail is being left behind. The advent of SD vehicles is another nail in the coffin because rail's advantages of a far lower driver-per-passenger or driver-per-freight-ton ratios than road, and the ability to transport people who cannot drive (or do not wish to), are shortly going to vanish.

The infrastructure for driverless trains is largely already in place (the steering problem is solved for a start) - yet we cannot handle a slip coach ?

Apart from other issues, this ignores an obvious advantage of railways. It would be impossible for all London commuting to be done by car, self driving or otherwise. The road capacity is simply not available. Self driving cars may make congestion worse, if the cars are shared and have to drive between set down and pick up points, or to car parks, or if they drive around to avoid paying for parking.

 

[Clip]

Well they don't of they don't alight before the portions split.

They do because the doors open again if done as arrival> open> split> doors open

This was the way it happens on on SET if they still do it at Faversham

 

[61653 HTAFC]

Apart from other issues, this ignores an obvious advantage of railways. It would be impossible for all London commuting to be done by car, self driving or otherwise. The road capacity is simply not available. Self driving cars may make congestion worse, if the cars are shared and have to drive between set down and pick up points, or to car parks, or if they drive around to avoid paying for parking.

Though self-driving road vehicles would be able to be packed far closer together than is safe with a meatpuppet behind the wheel...

 

[Eddd]

Until a cow/ road vehicle/ suicidal person/ p way staff member appears in front of the leading train resulting in an emergency brake application ...

The system would rely on continuous, dependable, low-latency communication between the units involved. The emergency brakes would apply on all units simultaneously.

 

[Lucan]

It would be impossible for all London commuting to be done by car, self driving or otherwise.. ... Self driving cars may make congestion worse

Indeed. Commuter railways are not under threat from SD vehicles, but other railways (including all freight) are. If SD cars are used for commuting into cities the problem remains, as now, of parking them during the day. SD cars will "solve" this either by being sent all the way back home empty, to be recalled in the afternoon, or else they will be programmed to drive in circles round the block all day. So even more congestion.

Keeping moving in most cities is cheaper than parking (if parking can even be found). Yet another reason to replace the greater part of VED by road pricing per mile.

Though self-driving road vehicles would be able to be packed far closer together than is safe with a meatpuppet behind the wheel...

Cars are already driven by the meatpuppets far closer together than they should be, and in towns they are often moving so slowly that the officially recommended spacing is small anyway. In fact a frequent criticism of SD cars is that they will be programmed to keep recommended spacing (it cannot be otherwise) and will therefore reduce the road carrying capacity by this factor alone. Or are SD vehicles going to be exempt from the requirement to leave spacings at least greater than the stopping distance, while the requirement remains in force for trains?

 

[Killingworth]

What a superficially attractive idea, but the practical difficulties are immense and probably insurmountable.

Here's a hypothetical example, and with a degree of fine tuning might work - but in one direction only. The much discussed Liverpool-Nottingham-Norwich, Class 158 operated service. Not a fully slipped proposition, but on similar lines.

Starts from Liverpool 6 cars. 3 sections to be clearly indicated. After leaving Chinley it's made very clear that anyone wanting Sheffield (or Dore) should ensure they're in the rear 2 coaches that are slipped after leaving Totley Tunnel. First 4 carry on to Chesterfield via Dore curve.

At Chesterfield front 2 carriages detach and all are made aware that they will carry on to Nottingham and Norwich.

Rear 2 carriages continue via Derby to Leicester.

That could work coming the other way for a joining at Chesterfield by utilising Platform 3. Joining those 4 to a Sheffield portion between Dore West and Manchester would be a little more tricky!

In practice dealing with portions that are on time could probably be achieved, but having to wait for sections that are even a few minutes late (currently they can be 20, 30 or more minutes late) makes the idea unworkable. The possibility of 3 separate trains having to be found crews and emergency paths would be a total nightmare.

It could make a good comedy show. "Oh Mr Porter what do I do now, I wanted to go to Leicester but slept in until Ely!"