The Anonymous Widower

Has Thameslink Got The Wrong Length Of Train?

The Train And Half-Train Philosophy

If you look at some recent train orders and one successful old one, they seem to suggest a train and half-train philosophy.

  • Great Western Railway’s order for Class 80x trains.
  • Virgin Trains East Coast’s order for Class 80x trains.
  • Greater Anglia’s order for Aventras.
  • South Western Railway’s order for Aventras.
  • Southeastern’s Highspeed Class 395 trains.

In all these fleets, it would appear that two half-trains can be used to create a full length train, when needed. This coupling and uncoupling is done throughout the day and often on an automatic basis in around a couple of minutes.

This video shows Javelins at it.

Impressive isn’t it? The second train left Ashford station thirty seconds after the first.

In a few years time, all trains will be able to couple and uncouple automatically like this.

Thameslink’s Class 700 Trains

Thameslink’s Class 700 trains only come in lengths of eight and twelve cars.

The eight-car train is needed for short platforms on the Sutton Loop Line.

But eight-car trains have disadvantages compared to say a six-car train.

  • Two trains can’t be joined together to make a full-length train.
  • Sixteen-car trains would be just too long for operational reasons.
  • An eight-car train uses one of the valuable twenty-four hourly paths through the central core of Thameslink, just as a twelve-car train does.

The train length seems to be inefficient.

I can’t think of a train operator, who has two similar train fleets longer than five-cars, where one fleet is not half the length of the other.

Maximising Capacity In The Core

The capacity of the central core of Thameslink, depends on how many trains go through in an hour.

Current proposals given in Wikipedia are as follows.

  • 14 x 12-car trains
  • 10 x 8-car trains

If the 8-car trains were replaced with 12-cars, this would give a sixteen percent increase in capacity in the central core.

The Sutton Loop Line

The Sutton Loop Line could be run by using six-car trains that split and join in the area of Streatham station.

This map from shows the track layout at Streatham, at the start of the loop.


  1. Streatham South Junction is the gateway to the Sutton Loop, with the tracks to the West going via Tooting station and those to the South via Mitcham Eastfields station.
  2. There is a lot of spare land in this area.
  3. Transport for London keep talking about creating an interchange at this point.

I think, if and when the interchange is built, it could be designed, so that it increased traffic around the Sutton Loop Line.

  • Two six-car trains running as a twelve-car could split at the interchange.
  • One train would go round the loop clockwise and the other anti-clockwise.
  • The trains would rejoin together at the interchange.

The same procedure could be done at Streatham, without creating the interchange, but it would block the station, if trains got delayed on the loop.

Currently, two trains per hour (tph) are proposed to run in both directions on the Sutton Loop Line.

This requires four eight-car trains and four paths through the central core.

If four six-car trains were to be used, running in pairs splitting at Streatham or a new Streatham Common interchange, there would still be two tph in both directions round the Sutton Loop, but only two paths would be needed in the central core.

Travellers to and from stations on the loop would see six-car, rather than the proposed eight-car.

If the number of six-car trains were to be doubled and four paths used in the central core, the Sutton Loop Line would see four tph in both directions.

But this might be two much traffic for Platform 9 at Wimbledon station.

Splitting Trains At The End Of A Route

It is not beyond the bounds of possibility for two six-car trains to do the following.

  • Start independently in the North.
  • Join at a convenient station.
  • Pass through the Snow Hill Tunnel  as a twelve-car train.
  • Split at a convenient station.

The two six-car trains would then continue to two separate destinations.

One possibility would be to do the following.

  • Start at Peterborough and Cambridge.
  • Join at Hitchin.
  • Split at Three Bridges
  • Finish at Horsham and Brighton.

Between Hitchin and Three Bridges, the train is twelve-cars, whereas at other times they are six-cars.

Hopefully train length could be geared to passenger traffic.

I don’t think there are many opportunities at the current time.but as Thameslink develops, with perhaps more stations and electrification, the use of this technique might increase.

Although, It should be noted that the current eight-car trains are not suitable.

Eight-Car Trains Across The City

Three of the services through the core are as follows.

  • Cambridge North and Maidstone East.
  • /Luton(Peak)/Kentish Town(Off Peak) and Orpington
  • Welwyn Garden City and Sevenoaks

All services are served by eight-car trains, with the first two services running all day.

In the May 2017 Edition of Modern Railways, there is an article entitled Kent Capacity Constraints Highlighted.

Reading this article, gives the impression that several stations served by Thameslink in the Southeastern area have platforms that are a tad short.

So perhaps this is the reason for the short trains.

But would using two six-car trains joining at a station like Bromley South, enable another twelve-car train to go through the central core.


Six-car trains instead of eight-car trains on Thameslink, may increase capacity.

According to Wikipedia, the formation of the two trains are as follows.


It would appear that the 12-car trains have two extra MSO cars and two extra TSO cars.

If all the TSO and MSO cars are identical, I wouldn’t be surprised that to lengthen the trains from eight to 12 cars, is just a cut-and-shut job, as it is with the London Overground’s Class 378 trains and Crossrail’s Class 345 trains.

With sixteen percent extra capacity by lengthening all trains to twelve cars, I would expect that this capacity will be claimed when needed.

An alternative could be to shorten the sixty eight-car trains to six-cars, which would release sixty each of MSO and TSO cars. Sixty new PTSO and DMCO car could be added and there would be another thirty six-car trains, making ninety in total.

I suspect Siemens could add automatic coupling and uncoupling.

These six-car trains would give the following.

  • Twelve-car trains through the core.
  • Better use of valuable paths through the core.
  • Six-car trains on the Sutton Loop Line, by splitting and joining in the Stratham area.
  • The ability to split and join trains to serve new destinations.

Thameslink’s train problem is not insoluble.




May 14, 2017 - Posted by | Travel | ,


  1. […] I wrote more about the problem in Has Thameslink Got The Wrong Length Of Train?. […]

    Pingback by Gibbs Report – Depot Issues « The Anonymous Widower | July 9, 2017 | Reply

  2. […] In Has Thameslink Got The Wrong Length Of Train?, I showed how if the trains were twelve- and six-car units and the latter had the ability to split and join automatically, this would lead to the following. […]

    Pingback by Observations On Thameslink Between Brighton And Cambridge « The Anonymous Widower | March 13, 2018 | Reply

  3. […] In Has Thameslink Got The Wrong Length Of Train?, I proposed the following. […]

    Pingback by Thoughts On The Sutton Loop Line « The Anonymous Widower | March 14, 2018 | Reply

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