Why ‘make trains longer’ isn’t that simple

When faced with a overcrowded peak hour train, “why don’t they add another carriage” sounds like a obvious fix – but unfortunately the answer isn’t always that simple.

Craigieburn line at Newmarket station - no hope of fitting on this train!

To start with, the ‘extra carriages’ have to exist. In the case of the Melbourne suburban fleet, trains are formed into fixed 3-carriage sets.

3-car X'Trapolis passes over the Richmond Flyover bound for the eastern suburbs

With a drivers cab at either end and electrical equipment scattered between the different cars, these 3 car long trains can’t be broken up into single carriages and then added to other trains to make them longer, at least without lots of modification to make it all work. The same applies to many other rail networks – you can’t just mix and match carriages to make a train.

Once you get the extra carriage sorted, you need a platform long enough for passengers to board.

X'Trapolis train arrives into Parliament station platform 4

It doesn’t make sense to build platforms longer than the longest train, so once you start adding carriages, you also need to start extending platforms – a difficult enough activity in busy urban areas, which becomes incredibly expensive if you are dealing with underground stations.

Now that the passengers can board the train, your troubles aren’t over – you need to get those trains running.

Comeng departs North Melbourne platform 5, as a Siemens train waits for the signal to clear

Signalling systems are used to keep trains a safe distance apart. They do this by dividing the tracks into a series of blocks, where only a single train is permitted, and a ‘clear’ zone behind each train to provide a safety margin.


Diagram by the UK Parliamentary Office of Science and Technology

Once you start making trains longer, they can start to overlap the signalling blocks, which doesn’t affect safety, but does reduce the capacity of the railway, thanks to longer than required gaps being left between trains. The only solution – twiddle with the existing signalling system to allow for longer trains, or upgrade to a moving block signalling system to run even more trains on the same tracks.

You also need to supply more electricity to power these bigger trains.

Comeng passes the Campbellfield substation on an up Upfield service

So upgrades to the traction power system might also be needed.

Now that the trains are moving, those extra passengers need to go somewhere once they arrive at their destination. Are there enough escalators linking platforms to the station concourse?

Passenger congestion for the escalators from platforms 9 and 10 at Southern Cross Station

Are there enough ticket gates to let these extra passengers exit the station?

Wow - the morning queues at Flagstaff are getting even worse!

And are there wide enough footpaths around railway stations so they can get to their workplace?

Pedestrian congestion outside Flagstaff station on William Street

I said it was difficult, didn’t I?

And two bonus issues

The problems don’t end when the passengers leave the train – trains have to be parked somewhere between runs, usually in sidings designed to accept trains of a given length.

Comeng, Siemens, Comeng, Siemens, Comeng, Siemens... 8 trains stabled at Melbourne Yard, and all alternating like so!

The same considerations apply to maintenance facilities and workshops.

Siemens in the shed at Newport

Once you start extending trains you either need to break up trains into smaller sections to make them fit existing sidings, or extend the sidings as well.

One dirty hack

One way to make longer trains work on constrained rail networks is selective door operation – leave the infrastructure as is, and only allow passengers to use part of the train at short platforms. This only avoids the need to lengthen platforms, but doesn’t address any of the other issues I’ve listed above, and can result in a net loss of capacity, as platform dwell time blows out due to passengers passengers crowding the doors that are in use.

Coming soon: how is Melbourne getting around these problems?

Melbourne currently has new 7 car long ‘High Capacity Metro Trains’ on order – one carriage longer than our existing trains. How will they fit onto our existing network – a future post will cover this.

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12 Responses to “Why ‘make trains longer’ isn’t that simple”

  1. Andrew says:

    Melbourne has extended trains (and platforms) twice already.

    When Melbourne’s suburban network was electrified just after WWI, the maximum length train was six cars (MTMTTM). The electrification was so popular and patronage grew so much that commencing around the mid ’20s the VR purchased new trailer cars and moved (slowly) to seven car trains (MTTMTTM). This required platform extensions, and lines were slowly converted over about eight years.

    In the late ’60s, patronage growth on the outer suburban lines was again causing congestion, and the VR undertook a program of extending the seven car Harris trains to eight cars. Again, this required a program of platform extensions – and these can still be seen at many locations where the platforms are now much longer than required (Windsor is a good example). The first eight car trains were introduced in 1967, and conversion was line by line. The Camberwell group was first, and then, from memory, the Frankston line.

    • Marcus Wong says:

      Thanks for the extra history Andrew – I’ve been slowly trawling thorough ‘The Electric Railways of Victoria’ by S.E. Dornan and R.G. Henderson, with a post on this topic coming at some point in the future.

  2. James Stewart says:

    What about double decker trains? Are they suitable in Melbourne or not?

  3. Kevin says:

    The photo of the electrical substation is along the Upfield Line just north of Camp Rd, right? I wonder what will happen to it with the level crossing removal works happening. Or would it only be affected by duplication? Or a new Campbellfield station? I believe power is being upgraded down around Brunswick.

    • Marcus Wong says:

      Spot on for guessing the substation location.

      Level crossing removal works at Gardiner, Bentleigh, Ginifer and Blackburn left their substation as-is, with just the traction feeder cables relocated, so Campbellfield might get left alone as well.

      • Kevin says:

        That is good news Marcus! If it remains there, then there would obviously be enough room for a desperately-needed bike path. At least until duplication occurs.

  4. Jordan says:

    what about v/line services, aren’t they able to run 7-9 car trains as many platform extensions have occurred over the past few years

  5. Tom the first and best says:

    The previous extensions to suburban platforms, to 7 and then 8-car trains, were for shorter carriages. After the lengthenings commenced in 1967, new train designs had longer carriages (except for the double-decker train, which had the old length because the end only door model of the double-decker trains needs shorter carriages).

    • Marcus Wong says:

      Spot on – Melbourne’s early suburban trains were all ‘short’ carriages:

      – Swing Door: 17.4 metres (57 ft 1 in)
      – Tait: 18.8 metres (61 ft 8 in)
      – Harris: 19.20 metres (63 feet)

      The first ‘long’ carriages were the prototype Harris trailers at 22.86 meters (75 feet).

      The Hitachi and Comeng trains that followed were the same ‘long’ size, plus or minus a metre.

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