Here’s a train.
Specifically, it’s a D train as used on some London Underground lines. The Underground is doing a fleet replacement at the moment and for the sake of standardisation they’re going to replace all of the old and varied stock even if (like the D train) it’s still serviceable.
Here’s another train, a little one this time. It’s one of a variety of Pacers, bus-derived rolling stock which has to be retired by 2020 as they’ve been deemed not up to modern standards. If you’re a train company thus equipped you’re going to need something else then.
Fortunately, there’s a major electrification programme underway in the UK so there should be a steady supply of newly obsolete but still usable diesel stock which you can use to replace your old Pacers. Unfortunately, the pace of electrification has been less than, er, electrifying so something else needs to be done. The surplus, electric D trains are of course no use because they need a supply of electrons. Or are they?
Enter the proposed Class 230.
It looks remarkably like the underground train. Which it should, because that’s what it is. It’s still powered by its original traction motors, but now the electrons are supplied by 3.2 litre Ford engines (used on upmarket Rangers and North American Transits) which run generators which power the motors. Not a particularly efficient way to provide power but I suppose it saves having to source transmissions.
How the D train will react to the unaccustomed sunlight hasn’t been revealed.