I think that, if we are using "green" arguments to justify electrification, we'd be a lot better off focussing on core sections of busy lines and using bi-modes
We can't wire everything up, we have to prioritise, and (whilst some bits of route are cheaper/more expensive than others to wire) every mile of low frequency branchline that you want to wire up comes at the cost of wiring up some main lines elsewhere
So, in the West Midlands, do Dorridge to Stourbridge (since the reduced frequency to Stratford/ Worcester would mean a lot more wiring, the marginal benefits become smaller the further out you go) - that way you could have the frequent DMUs through central Birmingham replaced by EMUs but then run them on batteries for the far ends of their services...
...same with the proposals for Edinburgh to Dalmeny (you
could go all the way through Fife, but then you could use the money for Maryhill/ Kilmarnock etc instead)
Focus on improving air quality in city centre stations, introduce fast accelerating EMUs for the frequent stopping sections, let batteries (or diesel) take the strain for the extremes - we know that bi-modes work, we know that battery technology will work on shorter sections (but we are reluctant to trust long services entirely to them - however running most of the journey under the wires would give sufficient opportunity to charge the batteries) - and focussing on the central sections would enable big improvements whilst allowing scope for future expansions
If you can deliver over 80% of the benefits for half of the total cost then why would you use finite budgets to wire bits of route with an hourly train at best, when that money could be used for other busy sections
Bi-modes are the future
Uckfield line. Just electrify the Southern diesel islands & get rid of the 171s in one fell swoop!
If one metric is "DMU carriages freed up per mile electrified" then Uckfield has to be one of the highest scorers
(usual proviso re battery operation etc etc)
Uckfield seems to justify ten coach trains, and the ten coach trains spend half the route on electrified sections, whereas Marshlink is more about two coach DMUs which don't spend much of their time on electrified sections... Uckfield is a much bigger priority than Marshlink IMHO
Avanti don't seem to show interest in diverting that way
Yet again, because someone doesn't do something, it must be because they aren't interested (rather than working out that running WCML trains to Glasgow via Newcastle/ Edinburgh would take around three hours longer than the regular route, whereas sticking them on a coach up the M74 is fairly competitive time wise, or that they don't have enough trains for the long diversion via Newcastle/ Edinburgh, even assuming that there were paths through Edinburgh for them) - easier to dismiss it as them just not being bothered I guess!
The Manchester - Warrington Central - Liverpool route. Like the Shotts route it is a basic 2 track railway with a couple passing loops [plus some sidings at Warrington] so no complex junctions. Plus the wiring is already done at the Manchester end for Trafford Park and very nearly connects at the Liverpool end [for access to the depot]. The sort of route which could probably be closed for a couple months to do the wiring in one big bang
Would allow the stoppers to run as EMUs with the fast services run to Manchester Airport rather than being long distance services which poor time keeping (so the Cleethorpes & Nottingham trains can terminate in the main train shed at Piccadilly)
That looks like a priority - all of the complicated stuff has already been done (the city centres/ the junctions) - if you terminated all Hope Valley services in the main shed then that would allow 13/14 at Piccadilly to be operationally independent of the Stockport (etc) lines which would improve reliability across greater Manchester and beyond