To me, Electric to at least MetroCentre but possibly Hexham would be the target, with batteries then beyond and the unit can Top Up in the bay at Carlisle. OLE as far as Ashington would be nice, but might not need to be all the way with a BEMU. Although going all the way to Morpeth is only going to make sense if the line is in passenger service
AIUI the Sunderland line has some level of provision for future conversion to 25KV, although it's not 25KV-ready I don't think. I have no idea if Metro units would need more work to be 25KV compatible, I imagine they'd need something at least.
I wonder what that level of provision is? Correct clearances for all modified structures seems likely? With SFC technology you may be able to re-use the grid connections used for the DC substations. Seems unlikely that they'd do anything else to help a conversion back in 2002.
Yeah i think this is where it all goes wrong. They are not compatible and I don't actually think passive provision was provided, I mean - it's a bit ambiguous whether it was, but you do need a different kind of pantograph for 25kV AC either way. Also, it's kind of a grey area to me whether it's worse having T&W provide bi-modes, or having it on the National Rail side of things.
The class 555s have no inbuilt provision for 25kV AC, as battery was the desired option. That said, Stadler would be able to add an extra car with a second pantograph and the required equipment fairly easily - they're specialists at this.
The passive provision on the Sunderland line for conversion to 25kV AC is very minimal - mostly just structure clearance and mast design.
Running 555s to Ashington wouldn't need wires with the 555's potential battery upgrade capacity, but having some way to charge at the northern terminus would be wise.
To be fair the Class 156's are pretty awful nowadays really. Outdated, noisy and some of them cramped. There's just worse around aka. Class 150's which make them more bearable.
The 156s are no more cramped or outdated than the 158s, especially when refurbished. The noise is about the same externally too, it's just that the 158s are much better insulated and don't rely on opening the windows for cooling the saloon down.
Both are fine for the Northumberland Line until something better is procured, though decisions will need to be made soon about the future. At least we're not still dealing with the 142s, as that certainly wouldn't have helped attract people to the line.