IMO▸ opinion bi-mode is a waste of money.
140 mph 4 MW electric loco push pull change to 2MW diesel at end of wires.
As the wires expand less diesel running.
I tend to agree with you. Everything else being equal, I would favour diesel loco drags beyond, Cardiff, Bristol or wherever the electrification ends on the S Wales and
BRI» routes. Your suggested power requirements seems about right too. A slightly slower speed and acceleration to Swansea and Weston-SM would be OK because of line speed issues and stopping patterns anyway and overall journey times might still be lower if the electrified line speeds are decent.
For the route to Plymouth/Penzance, the fraction likely to be electrified is relatively small, so I think it could be diesel all the way.
BUT there is a wrinkle regarding making the
MML» Meridians bi-mode. Although I am not generally in favour of bi-mode I think that this project might make some sense. Is this proposal not at least as much about finding a use for Meridians after the MML is electrified and also about increasing capacity as it is about getting a bi-mode vehicle for its own sake? The average Meridian is too short. There are too many Meridian cab-vehicles and not enough intermediate vehicles. MML has tried to remarshall its fleet, but the trains are still to short for the predicted future capacity to places like Cardiff. You would be right in calling, bi-mode vehicles a waste of money if we were building them from scratch, but we are not, the Meridians are already available (in fact if the MML is electrified they will be redundant) and if adding pantograph vehicles provides bi-mode AND extra capacity at a sensible cost it might be the best option.
Isn^t the current government^s cut-back scheme a sensible incremental approach?
AIUI▸ , the far-west is to be served by refurbished
HSTs▸ . That can only be a temporary solution because those trains cannot last for ever. One day they will need to be replaced and the candidate train to replace them is surely the bi-mode meridian displaced from the SW line which by that stage (2025-ish) will be electrified to Swansea one hopes.
By sticking new electric on the lines to Bristol and the MML, making far west refurbed HSTs and S Wales bi-mode Meridians which can transfer to far west in due course when S Wales goes all electric, the plan does have advantages of requiring only one new train design (the all electric train) which is much simpler than the EIP proposals.
As for making the Meridians Bi-mode it is my understanding that this is relatively simple because the train is already a
DEMU▸ . A new pantograph trailer is, one hopes not that much more heavy or complicated or expensive than a new trailer vehicle and I suspect that it might actually be cheaper than a new Meridian vehicle with an engine in it.
If the lengthening of the Meridians is a sensible thing to do in its own right. And I would argue that it is on capacity grounds alone, then we need to ask what do we lengthen them with. The options would be: 1) a new Diesel-engined vehicle, 2) a new trailer or 3) a pantograph trailer.
Option 1 would be expensive and would result in a fleet with different engine ages in the same unit.
Option 2 would be cheap but would give a performance penalty especially in terms of acceleration.
Option 3 might be the best overall. Hopefully no more expensive than option 1, and although there would be a performance penalty as with option 2 it would only apply away from the wires (which are likely to be lower line speeds anyway) so would be less of an issue.
DaFT» seems to have
Finally realised that electrification isn^t really about electrification. It is about provision of rolling stock.