MML Electrification - what hope of further routes being added going forward?

[Nicholas Lewis]

Moderator note - split from

MML Electrification: progress updates

There's an article about NR's plans in Rail this week (#765 p54). It seems that work on site will start in April 2015, the contractor being Carillion Powerlines. They will be using road-rail vehicles for the work, not a high-output system. The 125mph design isn't explicitly named but seems...

www.railforums.co.uk

Is there any news as to when work will start for RS2 – Wigston South to Syston?

Your not going to see any white smoke here until we have the spending review next month but after Heidi Alexanders appearance at the Transport Select Committee im feeling nervous that she doesn't see electrification as a priority as she waxed lyrical about going to Hitachi and the benefit of bimodes.

See below the question and answer given my emphasis in italics

Olly Glover: Thinking about other forms of transport, you have mentioned cars and vans and so forth. Turning to railways, the new German coalition Government agreement includes the following commitment, as published in Railway Gazette International last month: “The coalition now defines rail electrification as a measure to address climate change and will no longer use cost benefit ratios to determine whether wiring schemes will go ahead.” What are your thoughts on that policy? Should we have that in the UK as well?

Heidi Alexander: The electrification of the rail network is critical. Unfortunately, some of the plans that the previous Government put together have proved unaffordable. We are going through a process of reviewing that at the moment. We think that battery trains and electronic trains that can use overhead lines are the way forward. I was at Newton Aycliffe a couple of weeks ago, at the Hitachi factory there, looking at the production of their tri-mode trains, which can operate in diesel, with the overhead lines, and switch to battery as they are pulling into a station. Not only is that reducing carbon emissions, but it makes it quieter for people who live around the station. You are right to say that electrification is absolutely key. We will be looking at how we can incorporate that through the spending review in our plans for enhancements to the railway as we move forward.

 

[CdBrux]

Heidi Alexander: The electrification of the rail network is critical. Unfortunately, some of the plans that the previous Government put together have proved unaffordable.

I doubt that it was the previous government that caused them to be unaffordable, however let's see her plans to make them affordable which I would imagine is largely going to be finding ways to have the same outcome for less cost

 

[Nicholas Lewis]

I doubt that it was the previous government that caused them to be unaffordable, however let's see her plans to make them affordable which I would imagine is largely going to be finding ways to have the same outcome for less cost

The industry has caused it to be unaffordable and until there is an acknowledgement by senior leaders across the industry that we need to get a grip on costs i don't see much further progress being made. We are also at risk here of the skilled workforce dissipating again especially with the massive expansion being projected for the grid.

 

[Richard123]

The industry has caused it to be unaffordable and until there is an acknowledgement by senior leaders across the industry that we need to get a grip on costs i don't see much further progress being made. We are also at risk here of the skilled workforce dissipating again especially with the massive expansion being projected for the grid.

I think she was referring to the scale of undeclared funding gap across the entire government balance sheet that became apparent when the incoming government sought to understand the “start position.” (Overspends that hadn’t being declared and policies/schemes announced as in delivery that hadn’t been costed or funded).

Though your comments on U.K. electrification costs are equally valid.

 

[YorkshireBear]

The industry has caused it to be unaffordable and until there is an acknowledgement by senior leaders across the industry that we need to get a grip on costs i don't see much further progress being made. We are also at risk here of the skilled workforce dissipating again especially with the massive expansion being projected for the grid.

The industry has not caused it alone. One of the main reasons is the boom and bust cycle which leaves you with a lack of expertise in electrification and learning expensive mistakes every time.

The industry has a significant blame of course but it is not alone.

 

[GRALISTAIR]

The industry has not caused it alone. One of the main reasons is the boom and bust cycle which leaves you with a lack of expertise in electrification and learning expensive mistakes every time.

The industry has a significant blame of course but it is not alone.

And politicians constantly changing their minds

 

[Nicholas Lewis]

The industry has not caused it alone. One of the main reasons is the boom and bust cycle which leaves you with a lack of expertise in electrification and learning expensive mistakes every time.

BR and its suppliers (BICC & Pirelli) had its own famine after Weaver Jcn-Motherwell was completed but managed to remobilise for BedPan and massively scale up its capability to deliver ECML at a very competitive rate. Yes life was simpler and the spec was lower but what we had then, which seems lacking now, is inspired leaders that drove projects forward and an in house engineering team that strove to fulfill the brief at the least cost. The industries reorganisation destroyed that ethos and im not sure we will ever restore it short of dragging a lot of retired folk back.

 

[QSK19]

Your not going to see any white smoke here until we have the spending review next month but after Heidi Alexanders appearance at the Transport Select Committee im feeling nervous that she doesn't see electrification as a priority as she waxed lyrical about going to Hitachi and the benefit of bimodes.

See below the question and answer given my emphasis in italics

I just cannot forget the fact that GBR HQ will be based in Derby and having 222s/810s running into the city on diesel isn’t a good look for a government which actively portrays its environmental credentials.

Surely wiring up to Derby would be seen as being of paramount importance not least for that reason. But, let’s see what the spending review is.

PS: made me laugh when I read “electronic trains”!

 

[Richard123]

I just cannot forget the fact that GBR HQ will be based in Derby and having 222s/810s running into the city on diesel isn’t a good look for a government which actively portrays its environmental credentials.

Surely wiring up to Derby would be seen as being of paramount importance not least for that reason. But, let’s see what the spending review is.

PS: made me laugh when I read “electronic trains”!

To be fair, the trains have relied on power electronics rather than just electric for forty years. More efficient and reliable.

So it wasn't that wrong.

 

[Nottingham59]

Surely wiring up to Derby would be seen as being of paramount importance not least for that reason.

Wiring up to Derby and Nottingham may make sense, but the business case for going any further north must be very weak, certainly until the future of Cross Country rolling stock is settled.

 

[edwin_m]

To be fair, the trains have relied on power electronics rather than just electric for forty years. More efficient and reliable.

So it wasn't that wrong.

So do some of the diesels including 810s and Voyagers. So they count as electronic trains too...

 

[Brubulus]

Wiring up to Derby and Nottingham may make sense, but the business case for going any further north must be very weak, certainly until the future of Cross Country rolling stock

The voyagers won't last forever, their replacements will be bi-mode at the very least. Add in whatever replaces the 158s on Norwich-Liverpool likely being bi mode, there is a strong case for Derby-Sheffield in the medium term.

 

[jontyasaurus]

First post from a local...I fear there will be a lot of trouble with the segment from Derby to Clay Cross:- the locals are currently in strong opposition to a project to build power lines through the Amber Valley and have just elected two Green councillors to preserve their local environment (aka preserve their house prices at all costs). Once it's past Toadmoor there are but a couple of footbridges and one or two road crossings which may cause minor issues.
As a Chesterfield resident, I've been hoping for wires my whole life!

 

[Nottingham59]

The voyagers won't last forever, their replacements will be bi-mode at the very least. Add in whatever replaces the 158s on Norwich-Liverpool likely being bi mode, there is a strong case for Derby-Sheffield in the medium term.

Sure, but if the voyager replacements and the 158 replacements are both bi-mode, then they can function perfectly well without wires. that undermines the financial case for electrification. The environmental case still stands, but that will apply equally to other places where electrification will bring cost savings and financial returns far greater than any that will come from electrifying the MML.

First post from a local...I fear there will be a lot of trouble with the segment from Derby to Clay Cross:- the locals are currently in strong opposition to a project to build power lines through the Amber Valley and have just elected two Green councillors to preserve their local environment (aka preserve their house prices at all costs). Once it's past Toadmoor there are but a couple of footbridges and one or two road crossings which may cause minor issues.
As a Chesterfield resident, I've been hoping for wires my whole life!

Welcome to the forum!

 

[Peter Sarf]

First post from a local...I fear there will be a lot of trouble with the segment from Derby to Clay Cross:- the locals are currently in strong opposition to a project to build power lines through the Amber Valley and have just elected two Green councillors to preserve their local environment (aka preserve their house prices at all costs). Once it's past Toadmoor there are but a couple of footbridges and one or two road crossings which may cause minor issues.
As a Chesterfield resident, I've been hoping for wires my whole life!

Welcome to the forum.

It does feel like the UK will be the pioneer of trains relying on no OHLE simply because we have so little OHLE !. Battery technology might make longer and longer sections without OHLE possible but fundamentals like the Midland Main Line all the way to Sheffield should be kept simple electric. It would be battery powered gaps linking the MML Eastwards to the ECML and Westwards towards Manchester that are to be accepted.

Once Bi-modes are on Cross Country then Derby to Birmingham would be usefully electrified and Sheffield to Leeds/Doncaster. But in the meantime the core MML should be the priority.

 

[GraphitProjekt]

To what extent can nimby opposition directly push down on an electrification project? It's mostly alteration to the railway's land rather than long sections of new acquisitions as you need for new National Grid lines or new railways? Where so much new land is required seems to trigger a long series of public consultations. Does pure electrification cause the same? Only a few very small parcels of land get acquired mostly for temporary construction depots - and an even smaller amount of land for substations, both are small enough that the local council approves or disapproves it. Does every bridge alteration require a consultation? Surely the disruption is often mostly temporary.

The biggest blocker to MML is surely Treasury by way of DfT. I suppose if the nimbies make the voices very well heard by central government a political gain could be calculated by Westminster to *not* carry out the work on top of their own short termist financial assessments

80mph. There is very little over 100mph north of Derby.

there are some 110s for HSTs, could it not be made possible for other trains to use those speeds? What was the special ability of HSTs for them to be allowed faster?

 

[Nottingham59]

To what extent can nimby opposition directly push down on an electrification project?

The power to block comes from things like listed buildings consent. Like the local council did with Steventon bridge during Great Western Electrification. See here:

Steventon Bridge: Overcoming the Obstacle - Rail Engineer

Listen to this article In the complex story of the electrification of the Great Western main line, one name keeps cropping up – Steventon Bridge (issue 167, September 2018). This structure, and the problems it has caused, has been the subject of much media coverage, both technical and public...

www.railengineer.co.uk

there are some 110s for HSTs, could it not be made possible for other trains to use those speeds? What was the special ability of HSTs for them to be allowed faster?

There's a 110mph section from Wingfield Tunnel to Clay Cross, and also a bit just north of Derby. I assume other trains can use those speeds. But the point I'm making is that north of Derby, the MML is not a 125mph mainline, which would help to justify electrification.

 

[edwin_m]

there are some 110s for HSTs, could it not be made possible for other trains to use those speeds? What was the special ability of HSTs for them to be allowed faster?

A train requires enhanced braking to use the HST speeds. However, 22x stock are able to use HST speeds and I believe the same will be true of 810s and probably of whatever eventually replaces the Voyagers.

 

[swt_passenger]

there are some 110s for HSTs, could it not be made possible for other trains to use those speeds? What was the special ability of HSTs for them to be allowed faster?

Better braking characteristics came with HSTs, so speed could be increased without changing existing signalling, but bear in mind that since then HST speeds also apply to many other classes, eg 220/221, 222, 80x, some older DMUs including EMR’s 158s and 170s.

 

[GRALISTAIR]

First post from a local...I fear there will be a lot of trouble with the segment from Derby to Clay Cross:- the locals are currently in strong opposition to a project to build power lines through the Amber Valley and have just elected two Green councillors ……..

Welcome to the forum

 

[deltic08]

Welcome to the forum.

It does feel like the UK will be the pioneer of trains relying on no OHLE simply because we have so little OHLE !. Battery technology might make longer and longer sections without OHLE possible but fundamentals like the Midland Main Line all the way to Sheffield should be kept simple electric. It would be battery powered gaps linking the MML Eastwards to the ECML and Westwards towards Manchester that are to be accepted.

Once Bi-modes are on Cross Country then Derby to Birmingham would be usefully electrified and Sheffield to Leeds/Doncaster. But in the meantime the core MML should be the priority.

I agree that OHLE should be erected as much as possible before battery power is relied upon for short distances only.
Brand new all electric buses introduced on the Leeds-Harrogate-Ripon route in March have already had a bus run out of battery power in service far from a charging point after only 5 weeks. Battery propulsion is not infallible it seems. Grand Central beware.

 

[Brubulus]

Out of the entire route, the section least likely to be electrified is Wigston-Syston, given the clearances. Derby to Sheffield will get done, simply because of the high traffic density, the lack of other electrification in the region, therefore enabling battery trains on local routes and the potential for HS2 to use the route eventually from the Birmingham-Derby line if that is also electrified. (I understand capacity constraints make that difficult). The only way in which I see Wigston-Syston electrified is if Felixstowe-Nuneaton is electrified, which is unlikely to happen in the short to medium term.

Battery trains are much less likely to run out of battery than battery buses, given the fixed distances on the railway and reduction in variables. I would assume each trains battery would be range tested in the cold at full load to provide it's official service range, with a buffer, such that the train could actually go much further, as seen with the Merseyrail 777s.

 

[Peter Sarf]

Out of the entire route, the section least likely to be electrified is Wigston-Syston, given the clearances. Derby to Sheffield will get done, simply because of the high traffic density, the lack of other electrification in the region, therefore enabling battery trains on local routes and the potential for HS2 to use the route eventually from the Birmingham-Derby line if that is also electrified. (I understand capacity constraints make that difficult). The only way in which I see Wigston-Syston electrified is if Felixstowe-Nuneaton is electrified, which is unlikely to happen in the short to medium term.

Battery trains are much less likely to run out of battery than battery buses, given the fixed distances on the railway and reduction in variables. I would assume each trains battery would be range tested in the cold at full load to provide it's official service range, with a buffer, such that the train could actually go much further, as seen with the Merseyrail 777s.

I think in terms of batteries we need to think of two types.

1. Trains with enough battery to get them past dead sections (eg 777/0s) up to perhaps the end of a short branch (eg 777/1s).
   
   
2. Trains with enough battery to get them on a significantly longer non-electrified route with perhaps less then 50% of their total journey having electrification available. That would include Wrexham to Bidston, Liverpool/Manchester to Anglia and Cross Country (a long way off). We are probably not there for a while yet so thing Bi-Modes (diesel & electric).

With Cross Country I wonder if the critical mass of already approved/existing electrification is any where near there yet ?.
The worst/longest hurdles are the ends of the NE-SW route such as beyond Bristol and beyond the Central Lowlands of Scotland. Their existence makes filling in Derby to Birmingham, Sheffield to Leeds/Doncaster and worse still Bromsgrove (Birmingham) to Filton (Bristol) perhaps seem less attractive. Especially if it is felt too tenuous to order new trains that are Bi-Mode for a route with too little electrified sections.

Que Cascade.
Of course if fewer Bi-Modes were needed out of Paddington and Kings Cross those Bi-Modes could end up on Cross Country.
So lets get on with finishing GW electrification properly (Swansea, Oxford, Bristol via Bath and beyond to Plymouth.
Electrify the MML thoroughly.
Then buy (lease) some more straight electric trains for those routes.

Realistically this won't happen until after the current GW Bi-Modes are life expired.

I wonder if we are at risk of using half baked compromise solutions on our mainlines so what is left for the lesser main lines ?.

(bit of a rash brainstorming but hopefully food for thought).

 

[Nottingham59]

I think in terms of batteries we need to think of two types.

1. Trains with enough battery to get them past dead sections (eg 777/0s) up to perhaps the end of a short branch (eg 777/1s).
2. Trains with enough battery to get them on a significantly longer non-electrified route with perhaps less then 50% of their total journey having electrification available. That would include Wrexham to Bidston, Liverpool/Manchester to Anglia and Cross Country (a long way off).

I agree.

The whole issue highlights the urgent need for a national strategy for batterification. Without it, we are likely to waste huge sums on current electrification schemes like MML and TRU, with bridge raising and other clearance costs which turn out to be unnecessary. I would propose the following standards for the GB network:

SELF-RESCUE
At the very least, all electrification schemes should be designed on the assumption that all new traction will be capable of self-rescuing from stationary within extended neutral sections. 810s and bimode 80x already have this capability,

• on level track, all traction should be able to move itself 5km, against any headwind, from stationary. 802207 had a range of 43 miles on a 500kWh battery, so this suggests a minimum traction battery of around 50kWh on a 5-car passenger unit - very easily achieved.
• on a rising 1% gradient, the train should be able to move itself 500m uphill. For a freight locomotive hauling 4000t, this requires 200MJ of energy, around 60kWh - again possible with a battery or more likely with a diesel bimode locomotive.

BATTERY EMU
Electrification schemes should be designed on the assumption that all new passenger trains will come with variants with traction batteries sufficient to give 100km of range on level routes in all weather conditions. This suggests that gaps between electrification schemes should be 50km, so that trains can reverse in emergencies without getting stranded.

Alternatively, a tri-mode standard that included a small diesel range-extender for emergency use would enable a national electrified network to be designed with 100km gaps, so you only need half the number of electrified islands to get to the extremities like Penzance and Cleethorpes.

 

[Brubulus]

I agree.

The whole issue highlights the urgent need for a national strategy for batterification. Without it, we are likely to waste huge sums on current electrification schemes like MML and TRU, with bridge raising and other clearance costs which turn out to be unnecessary. I would propose the following standards for the GB network:

SELF-RESCUE
At the very least, all electrification schemes should be designed on the assumption that all new traction will be capable of self-rescuing from stationary within extended neutral sections. 810s and bimode 80x already have this capability,

• on level track, all traction should be able to move itself 5km, against any headwind, from stationary. 802207 had a range of 43 miles on a 500kWh battery, so this suggests a minimum traction battery of around 50kWh on a 5-car passenger unit - very easily achieved.
• on a rising 1% gradient, the train should be able to move itself 500m uphill. For a freight locomotive hauling 4000t, this requires 200MJ of energy, around 60kWh - again possible with a battery or more likely with a diesel bimode locomotive.

BATTERY EMU
Electrification schemes should be designed on the assumption that all new passenger trains will come with variants with traction batteries sufficient to give 100km of range on level routes in all weather conditions. This suggests that gaps between electrification schemes should be 50km, so that trains can reverse in emergencies without getting stranded.

Alternatively, a tri-mode standard that included a small diesel range-extender for emergency use would enable a national electrified network to be designed with 100km gaps, so you only need half the number of electrified islands to get to the extremities like Penzance and Cleethorpes.

I would generally agree. However the standards should be adjusted down by 20% to reflect that batteries would be at 80% given the increased degradation caused by being at 100%. On the other hand, BEMUs should have a service range of 50 miles, so an actual range of slightly over 60 miles in poor conditions at full loading. With some infill electrification, 95% of vehicles can be EMU or BEMU. The remaining 5% can be range extended BEMU, though these should have a shorter electric range, since the engine can replace a battery pack. 50 mile gaps in electrification are reasonable for trunk routes, while dissel can be used on secondary routes such as the Settle and Carlisle.

Anywhere which sees high speed service will need relatively continuous electrification though, the potential for which should be left open on the MML.

 

[brad465]

Once Bi-modes are on Cross Country then Derby to Birmingham would be usefully electrified and Sheffield to Leeds/Doncaster. But in the meantime the core MML should be the priority.

The Tamworth corridor is a must-do IMO: if coupled with electrification south west of Birmingham you can get EMUs on XC regional services (or at least BEMUs), plus improve the case for bi-modes on XC intercity services, which both provide more passenger capacity potential. Then more bi-mode/electric freight options enable better freight path utilisation on this intensive corridor.

 

[Brubulus]

The Tamworth corridor is a must-do IMO: if coupled with electrification south west of Birmingham you can get EMUs on XC regional services (or at least BEMUs), plus improve the case for bi-modes on XC intercity services, which both provide more passenger capacity potential. Then more bi-mode/electric freight options enable better freight path utilisation on this intensive corridor.

The big prize would be to get HS2 services to Derby/Sheffield via this route, using the capacity unlocked by electrification. Also you could fit 2tph Birmingham-Leeds.

 

[Peter Sarf]

I agree.

The whole issue highlights the urgent need for a national strategy for batterification. Without it, we are likely to waste huge sums on current electrification schemes like MML and TRU, with bridge raising and other clearance costs which turn out to be unnecessary. I would propose the following standards for the GB network:

SELF-RESCUE
At the very least, all electrification schemes should be designed on the assumption that all new traction will be capable of self-rescuing from stationary within extended neutral sections. 810s and bimode 80x already have this capability,

• on level track, all traction should be able to move itself 5km, against any headwind, from stationary. 802207 had a range of 43 miles on a 500kWh battery, so this suggests a minimum traction battery of around 50kWh on a 5-car passenger unit - very easily achieved.
• on a rising 1% gradient, the train should be able to move itself 500m uphill. For a freight locomotive hauling 4000t, this requires 200MJ of energy, around 60kWh - again possible with a battery or more likely with a diesel bimode locomotive.

BATTERY EMU
Electrification schemes should be designed on the assumption that all new passenger trains will come with variants with traction batteries sufficient to give 100km of range on level routes in all weather conditions. This suggests that gaps between electrification schemes should be 50km, so that trains can reverse in emergencies without getting stranded.

Alternatively, a tri-mode standard that included a small diesel range-extender for emergency use would enable a national electrified network to be designed with 100km gaps, so you only need half the number of electrified islands to get to the extremities like Penzance and Cleethorpes.

Self rescue - that would also give more resilience at times of power supply failure or in 3rd rail land when someone "trespasses" on the track.

Electrification islands may not be that useful. The electrification island needs to be long enough and durable enough to charge the batteries. It is not just about battery range but also about how long it takes to re-charge the battery. So a 150 km section with 50 km in the middle electrified might not work. Certainly needs fast charging which is harder on the batteries and surrounding electricity supply. I wonder how Bristol to Penzance could shape up (probably mainly electric to Plymouth for a start).

Where to locate electrification islands ?.
One idea would be where there is a decent sized town with local services into/out-of it.
Perhaps Exeter and any nearby branches for example.
Being 25kV AC an island would not be small given that the grid feeder would be able to supply a large area and its significant cost is important it will not be justified for short sections.

I think in an ideal world we would continue electrifying main lines until we reach the point where only sub 50 km bits remain between main lines. I am thinking of either side of the MML (Midland Main Line).

The outer reaches of the UK are a different thing.
GW electrified to Swansea would make battery trains for services local to Swansea possible (except we will be relying on cooperation between TfW and DfT).
GW electrified SW beyond Bristol is a big step.
Aberdeen and Inverness might stand more chance !.

In the heart of the UK.
GW to Oxford and beyond might stand more chance as it gets tantalisingly close to Birmingham especially if it benefits the Chiltern route.

I would generally agree. However the standards should be adjusted down by 20% to reflect that batteries would be at 80% given the increased degradation caused by being at 100%. On the other hand, BEMUs should have a service range of 50 miles, so an actual range of slightly over 60 miles in poor conditions at full loading. With some infill electrification, 95% of vehicles can be EMU or BEMU. The remaining 5% can be range extended BEMU, though these should have a shorter electric range, since the engine can replace a battery pack. 50 mile gaps in electrification are reasonable for trunk routes, while dissel can be used on secondary routes such as the Settle and Carlisle.

Anywhere which sees high speed service will need relatively continuous electrification though, the potential for which should be left open on the MML.

I do think that high speed lines should avoid electrification gaps so that changeovers are not an issue.

For other routes it would be nice to get to the point that only batteries are required to make Bi-Mode. Otherwise longer gaps will make diesel tempting. I am thinking diesel will be heavier, messier (in the train) and less ecological.

 

[zwk500]

Self rescue - that would also give more resilience at times of power supply failure or in 3rd rail land when someone "trespasses" on the track.

Electrification islands may not be that useful. The electrification island needs to be long enough and durable enough to charge the batteries. It is not just about battery range but also about how long it takes to re-charge the battery. So a 150 km section with 50 km in the middle electrified might not work. Certainly needs fast charging which is harder on the batteries and surrounding electricity supply. I wonder how Bristol to Penzance could shape up (probably mainly electric to Plymouth for a start).

Where to locate electrification islands ?.
One idea would be where there is a decent sized town with local services into/out-of it.
Perhaps Exeter and any nearby branches for example.
Being 25kV AC an island would not be small given that the grid feeder would be able to supply a large area and its significant cost is important it will not be justified for short sections.

'Island' is, IMO, a misleading term. What the conceptual idea should be is BEMUs 'hopping' between properly electrified areas, rather than isolated sections of electrification. The Electrified network should be largely homogenous for the obvious efficiencies. The obvious application of the operation would be radial routes that cross several electrified main lines, like Norwich-Liverpool, the North Downs, or Oxford-Cambridge (although Oxford-Cambridge is going to be at speeds and frequencies that would justify full electrification).
Bristol to Penzance would primarily have an electrified London-Plymouth route via the B&H, and BEMUs would be used to 'bridge the gap' between Weston SM and Cogload Jn or thereabouts. After Plymouth, there wouldn't be any wires and fast-charging would be needed top up the batteries.

I think in an ideal world we would continue electrifying main lines until we reach the point where only sub 50 km bits remain between main lines. I am thinking of either side of the MML (Midland Main Line).

Agree.

The outer reaches of the UK are a different thing.
GW electrified to Swansea would make battery trains for services local to Swansea possible (except we will be relying on cooperation between TfW and DfT).

Battery to Camarthen is possible, but I expect the deepest West Wales services would need top-ups to be Battery operated.

GW electrified SW beyond Bristol is a big step.

I can see Bristol-Weston SM but not beyond in the medium term. XC are going to need bi-modes of one flavour or another anyway.

Aberdeen and Inverness might stand more chance !.

Inverness would be a purely political decision. Aberdeen has more of a chance at making it's own case.

In the heart of the UK.
GW to Oxford and beyond might stand more chance as it gets tantalisingly close to Birmingham especially if it benefits the Chiltern route.

GW to Oxford once the current set of works is complete is an absolute no-brainer to me. I'd also start the Chiltern route at the Snow Hill end first, to get Stourbridge or Kidderminster to Stratford and Leamington on full EMUs. Worcester might need to stay with BEMUs for the moment, but the fact we have a metro-frequency line running short DMUs in the second larges city in the country is bonkers.

I do think that high speed lines should avoid electrification gaps so that changeovers are not an issue.
For other routes it would be nice to get to the point that only batteries are required to make Bi-Mode. Otherwise longer gaps will make diesel tempting. I am thinking diesel will be heavier, messier (in the train) and less ecological.

Agree here. A massive benefit not often mentioned about eliminating diesel is that it eliminates all the environmental and fire hazards of having to handle diesel fuel. Having a fleet of purely electrics means no need for fuelling points, tanks, spill bunds, etc. No tanker deliveries to depots, etc, etc.

 

[GraphitProjekt]

With Cross Country I wonder if the critical mass of already approved/existing electrification is any where near there yet ?.
The worst/longest hurdles are the ends of the NE-SW route such as beyond Bristol and beyond the Central Lowlands of Scotland. Their existence makes filling in Derby to Birmingham, Sheffield to Leeds/Doncaster and worse still Bromsgrove (Birmingham) to Filton (Bristol) perhaps seem less attractive. Especially if it is felt too tenuous to order new trains that are Bi-Mode for a route with too little electrified sections.

Worth remembering that most of the wires Cross Country trains run under are currently at electrical capacity and would be unable to take anymore trains (especially brand new 125mph sets) without upgrades to the supply and feeding equipment probably including new grid connections. The most constrained sites are around the north of the ECML and the lines through Birmingham.