The Anonymous Widower

The Part-Time Electric Train

Nearly all diesel trains are not pure diesel, where a large engine drives the wheels mechanically, but mostly diesel electric, where the diesel engine generates electricity and this is then used to drive electric traction motors that actually power the train. This may seem a bit complicated, but it isn’t really any less so than the transmission of a hybrid car, such as a Toyota Prius. It does have advantages though in terms of efficiency, acceleration and reliability.

When I went to Sheffield, I travelled in a train called a Class 222 or Meridian.  These are diesel-electric multiple units with one diesel engine, one generator and two traction motors in each coach, which are capable of 200 km/hr.

I found the train comfortable, but some have criticised them because of the vibration caused by the diesel engine underneath the coach floor.

It is often said that the best ideas come in the hardest of  times and Modern Railways this month had a long comment about converting these trains and the similar Voyagers to a bi-mode diesel-eletric/electric operation.

As on the southern part of their route north from St. Pancras to Sheffield and Nottingham, they run under the wires of the surburban electrics until Bedford, why not add an extra coach with a pantograph and the associated electrical equipment to each train.  This would bring a much-needed increase in capacity, but with several other advantages.

  1. As the train would be electrically powered at the southern end, there would be an increase in efficiency and a decrease in costs and direct carbon emissions.
  2. There would be considerable savings in the cost of maintaining the diesel engines as these have to be replaced regularly.
  3. There would be a certain amount of decrease in noise and vibration.
  4. As to passengers and most staff, they would just be a train that was one carriage longer, there would not be the same familiarisation process and working in, that usually accompanies any new rolling stock.

But the biggest advantage would come, if it was decided that London to Nottingham and Sheffield were to be electrified. As each new section of electric line is added, the trains could immediately use the new line, thus saving more in costs.

Ultimately, when the eletrification was to be complete, you would prefer to switch totally to either new or cascaded electric trains. But you actually have flexibility in when they are built and enter service, as they don’t have to be immediately ready, when electification is completed, but at the time that is optimum with respect to cost, passenger numbers and having a new use for the lengthened and modified Meridians.

So what might seem a crazy idea has a lot of things going for it!

If we do electrify substantial parts of the rail network, these bi-mode trains would not be short-term white elephants after being replaced by electric trains on the London to Sheffield route, as a similar progressive electrification could be applied on the services out of Paddington to Bristol, Cardiff and Swansea, as it has been stated that electrification on this route will be applied in stages.  Electrification is also starting between Liverpool, Manchester, Preston and Blackpool, so perhaps Trans-Pennine is another route, especially as at the eastern end it uses the East Coast Main Line.

It also has to be born in mind, that these trains would obviously be modified in the UK, so would create and sustain much-needed jobs.

There has been talk of replacing the HST with a bi-mode train, but the economics of that are very questionable, as that would be complete new trains, whereas the bi-mode Meridian/Voyager is a clever stop-gap. that makes electrification much more affordable.

Even after the electrification is substantially complete, the bi-mode trains would have substantial use on routes, which are effectively branches off the main electrified network, such as Bristol-Penzance, Doncaster-Hull, Peterborough-Ipswich,  Edinburgh-Aberdeen, Edinburgh-Inverness, Ely-Norwich etc., where extra capacity is much needed.

They could also be used to effectively prove if a route would benefit from modern trains or a frequent service, by running the trains in diesel mode only.

December 9, 2010 - Posted by | Transport |


  1. […] Severn Tunnel and many of the current trains can be converted to electric operation, as I posted here. I think it is mostly four track too, which helps with the […]

    Pingback by Midland Main Line To Be Electrified « The Anonymous Widower | July 14, 2012 | Reply

  2. […] idea is not new and I wrote about it in The Part-Time Electric Train, after a long editorial comment in Modern Railways in […]

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  3. […] idea is not new and I wrote about it in The Part-Time Electric Train, after a long editorial comment in Modern Railways in […]

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