That's a fair point. However I wonder whether you would lose some flexibility compared to an entire fleet of five car EMU's that can be doubled up during periods of high demand.
How fast can a class 88 go? Assuming that it can operate at 125 mph I would be interested to know how its acceleration would compare to an 125 mph EMU with distributed traction.
The 88 was more of an example as it's only rated to 100mph and, of course, there is now plenty of 110mph+ on the MML so I can't see it being deployed on the MML.
It would be very interesting to see how a modern 125mph compared with a modern 125mph EMU. I suspect that the EMU would win!
I can't say much for a modern electric locomotive hauled train against a multiple unit equivalent, but I can provide a bit more insight
Traction being centralised (locomotive) or distributed affects the acceleration of a train by affecting both how much the driving wheels of the train can adhere to the rails (adhesion).In short, the more distributed the traction is, the more of the train's weight is over powered axles and the more adhesion the train has, hence the more force can be applied before wheel-slip.
While top speed and gearing of the train do also affect acceleration, they can actually be ignored when analysing the effects of acceleration to due traction distribution. There's actually a fairly simple calculation that can be done to work this out.
I'd need more information on the 88 to be able to fully analyse is, but I have previously analysed an Intercity 225 (class 91, nine mk4s and a DVT) and a 9 car Pendolino. Assuming zero gradient, mediocre rail conditions (coefficient of friction of 0.35 for anyone who's interested in that) and zero air resistance.
- An Intercity 225 has sufficient adhesion to accelerate to 50mph in 39.472 seconds.
- A Pendolino has sufficient adhesion to accelerate to 50mph in 19.528 seconds.
If anyone's interested I can message you the calculations, but generally the effect of distributed traction is roughly double the potential maximum adhesion-based acceleration limit. However, I don't believe either train ever accelerates to 50mph in anything less than 40 seconds (do correct me if I'm wrong!), so the reasons why an Intercity 225 cannot achieve this rate of acceleration would be down to reasons other than it being a locomotive hauled train. What's also interesting is that the Pendolino can never achieve its figure of 19.528 seconds, as the total power output of its motors limits its minimum time to 50mph to 22.82 seconds.
In fact, if any drivers on this forum would be happy to tell roughly how long you take to accelerate your train to 50mph then I'd be very interested to hear!
