Seamless Interchangeability
At several places on the UK rail network, two trains running as a pair will split, with one train going to one destination and another going to another.
I wrote about trains splitting and joining in Trains Uncoupling and Coupling at Cambridge.
In the past, UK railways used to use the concept of slip coaches, so that coaches could be dropped from an express without stopping. But the last time it was used in the UK was in September 1960 at Bicester North station.
I have just read this article on the Rail Engineer web site, which is entitled Seamless Interchangeability.
The article talks about a concept of dynamic coupling, where trains are automatically coupled and uncoupled at line speed.
It also talks about the issues this would raise.
As a Control Engineer, I’m fairly certain, that it would be very easy to create a system, where say an eight-car Kings Lynn train could split just before Cambridge station, with the front four-car train going to Kings Lynn and the other four-car train stopping in Cambridge station.
It could either be done using two drivers or by driver-less trains. Although the unions would have a lot to say about the latter.
I also believe that if the trains could uncouple, then coupling at line speed would also be possible.
So what is the point?
An Example From The Brighton Main Line
To make full use of the capacity available, Southern serve Littlehampton and Ore, with a train that divides at Haywards Heath. It is a well-proven technique that has been used for decades.
Automatically splitting the two trains at line-speed, can give journey time advantages.
Take the 19:47 from Victoria, which arrives at Haywards Heath at 20:30 as an example.
The following is taken from the timetable.
- The front portion to Ore leaves at 20:34.
- The rear portion to Littlehampton leaves at 20:36.
- Stops at East Croydon and Gatwick Airport take about a minute.
This leads to the following, if the two trains split immediately after stopping at Haywards Heath and before the trains take different directions after Keymer Junction where the East Coastway Line divides from the Brighton Main Line, a few miles South.
- The Ore train performs a one-minute stop instead of one of four minutes, thus saving three minutes.
- The Littlehampton train performs a one-minute stop instead of one of six minutes, thus saving five minutes.
- The platform at Haywards Heath is only occupied for a minute, as opposed to six.
- The Littlehampton and Ore portions must be capable of providing enough capacity for their route.
For those worried about driver-less trains, the driver of the second train for Littlehampton, would probably step up at the previous stop at Gatwick Airport or at Haywards Heath.
But the outcome would be a small increase in capacity on the line, due to the platform at Haywards Heath being occupied for five minutes less.
Coming North, take the 09:47 from Littlehampton as an example.
The following is taken from the timetable.
- The first train arrives at Haywards Heath at 10:35 and leaves at 10:45.
- The second train arrives at Haywards Heath at 10:41.
The pattern of the trains would be different.
- Whatever was the front portion of the train would go through Keymer Junction first
- The train forming the rear portion would be the next train through the junction.
- The rear portion could catch the front portion and the two trains would be automatically coupled together before Haywards Heath.
- The joined train would stop at Haywards Heath for a minute.
- The driver of the second train could step-down at Gatwick Airport or Haywards Heath.
In some ways the mathematics involved in the coupling, are not unlike those for a fighter jet connecting with a tanker aircraft. Except that speeds are a lot lower and there is no need to control direction only closing speed.
Haywards Heath station would be occupied for up to nine minutes less, thus creating capacity.
This simplistic analysis, shows how automatically coupling and uncoupling trains at line speed can create capacity and decrease journey times.
- Journey time from Victoria to Ore would be reduced by three minutes.
- Journey time from Victoria to Littlehampton would be reduced by five minutes.
- In the Down direction the platform at Haywards Heath station would be occupied for just one minute instead of six.
- Journey time from Littlehampton to Victoria would be reduced by nine minutes.
- Journey time from Ore to Victoria would be reduced by three minutes.
- In the Up direction the platform at Haywards Heath station would be occupied for just one minute instead of ten.
Obviously strategies would have to be developed for various eventualities including.
- Unsuccessful coupling or uncoupling.
- Late trains.
- Signalling and train failures.
- Leaves on the line.
- Extreme weather.
But as during all coupling and uncoupling operations, both trains would have a driver in the cab, keeping an expert eye over the procedure and each train could be driven independently, I think all safety issues could be overcome, to the satisfaction of all parties.
If you read the full article, you’ll see that there are some much more exciting possibilities, than the simple ones I have outlined here.
But I do believe that line speed uncoupling and coupling of trains with a driver in the cab of both trains involved, can be a very powerful tool in creating capacity on the UK’s railways.
The Great Eastern Main Line
I know the Great Eastern Main Line well and several trains are coupled and uncoupled regularly on this line.
As Greater Anglia has ordered new five-car Aventra trains and nearly all platforms can take 12 -car trains, running these trains in pairs and coupling and uncoupling appropriately, is probably in their plans for the line.
As on the Brighton Main Line, could coupling and uncoupling at line speed, unlock capacity on the line?
A few weeks ago, I caught a train from Chelmsford to Manningtree, that divided at Colchester, with the front four-car train going to Clacton and the rear four-car train going to Harwich.
The 16:44 from Liverpool street is a train that divides at Colchester, when it arrives at 17:40. These timinings are from the timetable.
- The Clacton portion of the train leaves at 16:44.
- The Harwich portion of the train leaves at 16:47.
As the Sunshine Coast Line for Clacton leaves the Great Eastern Main Line immediately after Colchester station, it would appear that the two trains must uncouple during the stop at Colchester.
Surely, an improved and well-designed automatic uncoupling system could separate the trains faster, saving minutes on both services.
Towards London, two trains leave Harwich and Clacton at 07:16. The timetable shows.
- The Harwich train arrives at Colchester at 07:47 and leaves at 07:54.
- The Clacton train arrives at Colchester at 07:50 and leaves at 07:54.
Surely, an improved coupling system, could join the trains faster, saving minutes on both services.
The time savings will not be as great as those at Haywards Heath, but automatic coupling and uncoupling must be a worthwhile feature of the new trains.
|As Bombardier are adding automation to the Aventra, could they be adding the ability to automatically couple and uncouple trains, both in the station and at line speed?
The West Coast Main Line
I have seen Class 221 Trains, join at Crewe, but I don’t think this is done any more.
However, with the need for direct services from London to places like Blackpool, Burnley and Huddersfield, the ability to be to couple and uncouple trains quickly must be something that would be useful to make optimal use of the valuable train paths on the line.
The East Coast Main Line, Midland Main Line, Great Western Main Line And South West Main Line
If the West Coast Main Line could benefit, then surely these lines could as well.
Class 800/801 Trains
The Class 395 train is very much related to the Class 800 and Class 801 trains, that are being built by Hitachi for the East Coast Main Line, Great Western Railway and other routes.
In The Impressive Coupling And Uncoupling Of Class 395 Trains, I talked about the design of the coupling system for the Class 395 trains.
I would be very surprised if this feature was not incorporated in the Class 800 and Class 801 trains.
So will we be seeing two five-car Class 800/801 trains dividing and joining at a convenient station and then running as a ten-car train to and from London?
Class 385 Trains
What about the Class 385 trains for Scotland?
- These are another version of Hitachi’s A-Train, like 395s, 800s and 801s.
- These will come in two lengths; three-car and four-car.
- Edinburgh-Glasgow services will need at least two units to be coupled together.
- The trains are being introduced from Autumn next year.
It seems to me, that Scotrail are acquiring a very flexible fleet that can run in various lengths.
Will they have the ability of the 395s to couple and uncouple in under a minute?
And if they do, will Scotrail use this ability to adjust train formation to the traffic?
Aventras
There are three definite orders for Bombardier’s new Aventra train at the present time.
- Class 345 trains for Crossrail.
- Class 710 trains for London Overground.
- Five and ten car units for Greater Anglia.
All trains are fixed formations in a mixture of lengths.
Will Aventras have similar coupling and uncoupling performance to Hitachi’s Class 395 trains?
I suspect normally, the Crossrail trains will never be coupled together, as where are platforms for a four-hundred metre long train?
But suppose a train fails in the central tunnel, will the quickest way to remove it, be to attach it to another train and drag it out?
The routes where the London Overground trains will run, are currently served by a mixture of four-car and eight-car trains. So will London Overground, adjust train length to the known traffic patterns?
Greater Anglia do couple and uncouple trains at present to serve Harwich. So I suspect, we’ll see use of an automatic and fast coupling and uncoupling feature to create a more efficient timetable.
Cross City Lines
There are several cross-city lines in the UK.
- Cross-City Line – Birmingham
- Crossrail
- North Berwick Line – Edinburgh
- Northern Line – Merseyrail
- Snow Hill Lines – Birmingham
- Thameslink
One of the characteristics of cross-city lines, is they are busiest in the centre of the city, where passengers tend to use the trains for short hops , as well as longer distances. Then in the suburbs, outside of Peak hours the trains could run almost empty.
Crossrail’s trains are designed so that hopefully they could cope with the variable traffic, but would it be possible to have half trains, which join and split at outer stations.
Thameslink
I think that Thameslink could be the line that might benefit most, as it would probably want to serve more places.
In All Change On Thameslink, I detailed the current proposed schedule of trains.
- 4 trains per hour (tph) – Sutton to St. Albans (2 tph via Wimbledon, 2tph via Mitcham)
- 2tph – Brighton to Bedford
- 2 tph – Three Bridges/Gatwick Airport to Bedford
- 2 tph – Brighton to Cambridge North
- 2 tph – Horsham to Peterborough
- 2 tph – Maidstone East to Cambridge
- 2 tph – Sevenoaks to Blackfriars
- 2 tph -Orpington to Kentish Town/West Hampstead
- 2 tph – Rainham to Luton (via Dartford and Greenwich)
- 2 tph – East Grinstead to Bedford
- 2 tph – Littlehampton to Bedford
This makes a total of twenty-four tph, which is the design limit for the central tunnel.
In this schedule 4 tph go to Cambridge and 2 tph go to Peterborough. Suppose, it was decided that Peterborough needed 4 tph.
The path limit of 24 tph through the central tunnel makes this impossible, but if Peterborough and Cambridge services joined and split at perhaps Stevenage, then both Cambridge and Peterborough would get 6 tph through the core tunnel.
It would need new six-car trains, that could couple and uncouple quickly.
Conclusion
I believe that improving the coupling and uncoupling of all modern trains to the standard of that of the Class 395 trains could be very beneficial, to train operators, staff and customers.
If coupling and uncoupling could be done at line speed, this might bring extra benefits.
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The Anonymous Widower 
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