Shapps wants ‘earlier extinction of diesel trains’: suggestions welcome on how to achieve this

[trebor79]

How many bridges would have to be almost completely rebuilt with more clearance, and how much does it cost per bridge to do that.....?

Isn't a lot of that because the clearances required have been made a lot greater in recent years? Meanwhile all the legacy electrification carried out by BR with much less structure clearance seems to operate just fine. Funny that.
Almost as if the regulations are overkill and seeking to eliminate perceived rather than actual risk. A bit like the Azuma inter-carriage "ladder" (non)issue earlier this year. What was the actual solution to that, does anyone know?

 

[johnnychips]

Not doubting that at all, and evidently diesel trains are not a ‘good thing’ but compared to the stuff given out by diesel cars, vans, lorries and industrial machines, the amount given out by trains will be tiny.

 

[tpjm]

There's also a bit of a problem that TPE and Northern are currently taking delivery of brand new diesel-only trains

TPE aren’t in quite as much trouble as Northern as none of their new trains are fixed as diesel.
Class 397 is electric, Class 802 is bi-mode and the MkVa coaches could in theory be hauled by modified Class 88s in an electric world.

 

[Mikey C]

Not doubting that at all, and evidently diesel trains are not a ‘good thing’ but compared to the stuff given out by diesel cars, vans, lorries and industrial machines, the amount given out by trains will be tiny.

But if in 10 years time governments REALLY start cracking down on petrol and diesel road vehicles, it will look embarrassing and hypocritical to have diesel trains chugging away

Leaving aside "Failing Grayling" and his hopelessness, the environmental issue has moved on significantly, even over the last year or so. I'd be very surprised to see any further orders for pure diesel DMUs (other than perhaps small top up orders) from now on as the leasing companies will be really worried about how long they will be in service for. The next Chiltern franchise (or whatever it will be) will be VERY interesting.

 

[GRALISTAIR]

They need to get on with the rolling electrification programme cut by Grayling.

Precisely- this would be the biggest and best contribution to his goal.

 

[GRALISTAIR]

Tfl should be given powers to surcharge operators arriving at electrified terminals with diesel trains imho. Give the likes of Great Central, Virgins successor and Hull Trains 5 years notice of a £25 per seat Ultra low Emission Charge for Diesel Trains arriving in London.

Or going through Birmingham New Street

 

[deltic08]

Absolute load of politicised electoral guff. Not going to happen. What’s going to replace the 60s?. A load of battery powered wagons ? Total and utter tosh. Network Rail can’t even afford to finish the jobs it has at the moment. Let alone electrify everywhere else. Or he intends having 200tonnes of batteries lugging around 120 tonnes of ironing board seated coaches. Maybe he’s going to be hauling the 442s to Weymouth

If a route is regularly operating class 60s then it needs electrifying and new electric locos building. There are already electric locos that can run to Weymouth if need be. They are called 92s! Don't exaggerate.

I don't want clagtastic 37's and 56's off the rails in 20 years, they've been around as long as I remember and it would be crap to think they aren't running at all anymore

You may not want to lose 37s/56s but everyone else will want to. They don't last forever.

Although I'm starting to feel more optimistic that maybe we will start to see much more electrification, I'd be astonished if you can electrify the entire remainder of the network for £20bn.
How many bridges would have to be almost completely rebuilt with more clearance, and how much does it cost per bridge to do that.....?

Don't forget that as in-fill electrification progresses more routes become viable to electric traction especially freight, reducing the need for diesel. Sort of diminishing returns in reverse.
According to Bald Rick it can cost upwards of £3m per bridge for a full deck lift, but there are new ways being developed that are cheaper.

 

[AM9]

As the carrots for moving away from CO2 producing traction dry up, so the stick for not moving away will get more and more painful. Those who insist continuing to operate cars, buses, trains and even some boats that produce climate damaging pollution, will find that their competitiveness rapidly disappears, so either they will be flushed out of the gene pool, or they will see the error of their ways and join the less selfish operators.

 

[Comstock]

Although I'm starting to feel more optimistic that maybe we will start to see much more electrification, I'd be astonished if you can electrify the entire remainder of the network for £20bn.

How many bridges would have to be almost completely rebuilt with more clearance, and how much does it cost per bridge to do that.....?

Would you need to run wires under the bridges? Surely with battery technology we could settle for just electrifying the rest of the route?

Heck in some routes with only a handful of bridges the train could probably just coast through them?

 

[The Ham]

As only 1.6% of the total diesel and motor spirit used by roads and railways is used by trains, this seems to me to be tilting at windmills...

...still, it signals his virtue.

The amount of CO2 and other crap given out by diesel trains is minuscule compared with other stuff.

Not doubting that at all, and evidently diesel trains are not a ‘good thing’ but compared to the stuff given out by diesel cars, vans, lorries and industrial machines, the amount given out by trains will be tiny.

Although the amount of reduction compared to road traffic is small there's two things to consider:

We need to cut our CO2 emissions and there's benefit in every tiny bit that we can do fairly easily (and compared to road rail is easier to decarbonise). As such we need to look at everything we can do and not at what could cut the most.

Secondly, the sparks effect could increase the numbers using trains rather than driving, in which case you've reduced the impact of both, which may mean instead of cutting 1-2% of fuel use it could be 2-4% of fuel use (and no you wouldn't need to double passenger numbers on the currently diesel trains to double the fuel savings as trains are more efficient than cars).

On an unrelated point, no we wouldn't just be shifting the pollution to the coal powered power stations, as last year we only used coal for 5% of our electricity production, with use of gas for electricity also fallen since 2010 and renewables creating more electricity than predicted to be the case for 2020 (predictions made in 2010). In addition we now use the least amount of electricity since 1994 and on a per person basis the least amount since 1984 (this means that 5% of coal use isn't 1/6th the coal use for the 30% of coal use in 2014, although only marginally less it's still better than the % figures indicate).

The above is important, as a lot of the comparisons on train Vs cars are now based on a very much higher carbon producing electricity grid than is currently the case. This means that trains are a LOT better, I think that is something like 5 times less emissions for the average train passenger compared to the average car traveler.

 

[TheEdge]

OK Shappy my boy, I look forward to your announcement of wholesale electrification of the network starting Monday.

Oh, you just wanted to virtue signal becuase it makes you look good politically and base it all on the nebulous "new tech" rather than spending a government penny now. Gotcha.

 

[class26]

OK Shappy my boy, I look forward to your announcement of wholesale electrification of the network starting Monday.

Oh, you just wanted to virtue signal becuase it makes you look good politically and base it all on the nebulous "new tech" rather than spending a government penny now. Gotcha.

Give him a chance !

 

[rickerby1]

The hard work on electrification is done, the WCML and most of its branches, the ECML and the main spine of the GWML to Cardiff. On top of that most of the London commuter network is done and the MML is scheduled as far as Market Harbrough in the near future. What’s left is really infill, a lot of it granted. But a proper 20 year rolling programme should be feasible, perhaps looking at Danish State Railways approach as a model. This combined with advancing battery technology on lightly used routes should sort it

 

[DerekC]

Interesting debate and for me it doesn't matter whether Grant Shapps said his line as distraction technique or not - it is a real and urgent issue - and it is inconceivable that rail would be running large diesels around the place if road has adopted alternatives by 2040. No surprise on this forum that we have consensus that electrification of the main line network is a good thing - and sometimes to get what you want you have to applaud people you don't like. So as an industry we should tell Grant Shapps that what he needs to do is commit to a rolling electrification programme now. Then he can do what he probably had in mind - fund a few high-profile hydrogen and battery research projects with good photo-ops attached - to map out alternative energy options for secondary routes.

 

[Ianno87]

TPE aren’t in quite as much trouble as Northern as none of their new trains are fixed as diesel.
Class 397 is electric, Class 802 is bi-mode and the MkVa coaches could in theory be hauled by modified Class 88s in an electric world.

And Northern have a large proportion of routes that have limited prospect of ever being electrified.

 

[AndrewE]

I agree completely, but we also need a solution for the routes where electrification doesn't have a business case - otherwise @158756 will be right!

The point about a "business case" [edit: or any other cost-benefit analysis] is that the outcome/decision depends on the weighting given to the factors considered within it.
Today's news item about increased strokes and heart attacks on days of higher pollution (https://www.bbc.co.uk/news/health-50119981) provides a good reason to ramp up the weighting given to simply reducing emissions because of the wider health benefits. As any rolling electrification scheme progresses the costs of maintaining and managing the ever-smaller and more isolated islands of diesel working will rise too, so the case for complete elimination (at least across big areas of the country) gets stronger still.
Add to that a government looking at a major recession, especially in the manufacturing sector, so a big infrastructure project which plays into professed environmental objectives and with overwhelming public support and immediately obvious benefits becomes all the more attractive.

 

[mpthomson]

They need to get on with the rolling electrification programme cut by Grayling.

Sadly, given Network Rail’s wholesale project management incompetence in delivering anything remotely near budget and timescales then that was the right decision at the time. Get that sorted out first and then restart the programmes.

 

[coppercapped]

Although the amount of reduction compared to road traffic is small there's two things to consider:

We need to cut our CO2 emissions and there's benefit in every tiny bit that we can do fairly easily (and compared to road rail is easier to decarbonise). As such we need to look at everything we can do and not at what could cut the most.

Secondly, the sparks effect could increase the numbers using trains rather than driving, in which case you've reduced the impact of both, which may mean instead of cutting 1-2% of fuel use it could be 2-4% of fuel use (and no you wouldn't need to double passenger numbers on the currently diesel trains to double the fuel savings as trains are more efficient than cars).

On an unrelated point, no we wouldn't just be shifting the pollution to the coal powered power stations, as last year we only used coal for 5% of our electricity production, with use of gas for electricity also fallen since 2010 and renewables creating more electricity than predicted to be the case for 2020 (predictions made in 2010). In addition we now use the least amount of electricity since 1994 and on a per person basis the least amount since 1984 (this means that 5% of coal use isn't 1/6th the coal use for the 30% of coal use in 2014, although only marginally less it's still better than the % figures indicate).

The above is important, as a lot of the comparisons on train Vs cars are now based on a very much higher carbon producing electricity grid than is currently the case. This means that trains are a LOT better, I think that is something like 5 times less emissions for the average train passenger compared to the average car traveler.

A point of order!

The electrification of the Euston - Manchester - Liverpool route in 1966 generated a considerable increase in the number of passengers carried and so the increase was labelled the 'sparks effect' it was in fact a misnomer as accelerated diesel powered services also generated increases in passenger numbers.

The reason for the traffic increases were in fact down to a combination of faster and of more frequent services. There certainly will be a slight increase in passenger numbers following electrification, largely because of the novelty effect of something new, but of itself, electrification will not attract significantly more passengers. This will only happen if the service offered is attractive. In many areas this will mean expansion of the infrastructure to accommodate more frequent trains and different routings. This will be the expensive part - modal shift will not occur due to electrification alone.

 

[AM9]

... The reason for the traffic increases were in fact down to a combination of faster and of more frequent services. ...

Faster trains are easier to provide and cheaper to run once the electrified infrastructure is in place than with diesels. Similarly, more frequent services using electric trains are cheaper to provide than with diesels. That's all before the travelling public realise that electric railways of almost any age are cleaner for both themselves and the environment than even the newest diesel operated line with the same service density.

... There certainly will be a slight increase in passenger numbers following electrification, largely because of the novelty effect of something new, but of itself, electrification will not attract significantly more passengers. This will only happen if the service offered is attractive. In many areas this will mean expansion of the infrastructure to accommodate more frequent trains and different routings. This will be the expensive part - modal shift will not occur due to electrification alone.

I dispute that assertion, - see my comment above. You are also blurring the discussion by bringing in other route enhancements. Taking an existing route run with current diesel trains and compared to the same route run with equivalent age cascaded electric trains, there would be an uplift in patronage.

 

[Kingspanner]

https://www.rssb.co.uk/en/Research-...isation-our-final-report-to-the-Rail-Minister

The above link is (or was, because of course the minister was different then) the RSSB's analysis from June this year. Handles all the arguments about what can and cannot be electrified, and what is or isn't possible on branch lines.

 

[DynamicSpirit]

https://www.rssb.co.uk/en/Research-...isation-our-final-report-to-the-Rail-Minister

The above link is (or was, because of course the minister was different then) the RSSB's analysis from June this year. Handles all the arguments about what can and cannot be electrified, and what is or isn't possible on branch lines.

Thanks, that looks informative.

On a quick glance, I think the key conclusion from an electrification POV is this:

The economic modelling work that has been undertaken as part of the T1145 suggests that, to remove diesel-only passenger trains from the railway by 2040 and to achieve 80% carbon reduction on 1990 levels by 2050, it may be necessary to electrify about an additional 4,000 route km. By comparison, the modelling suggests that, to achieve net zero carbon, is likely to be only about 250 route km more than that. If the outputs of this high-level modelling are proved correct in more detailed analysis, the marginal additional electrification is so limited that it almost makes sense on this basis alone to decide now on a net zero carbon target by 2050.

So, again from the report, we have 19291 single-track miles of track, of which 8106 is already electrified. So from a quick calculation, they are saying that we need to electrify about 38% of the remaining non-electrified track to get to zero-carbon, with the remainder presumably running hydrogen and battery-powered trains.

 

[Rhydgaled]

They need to get on with the rolling electrification programme cut by Grayling.

We need a rolling electrification programme full stop. I'm not sure if the programme cut by Grayling really was a rolling one, it was GWML, MML, electric spine (whose cancellation wasn't even announced) and north-west + TPE. A fairly extensive programme to be sure but there was no authorisation or funding promised for any routes for the wiring teams to move onto once that lot was done.

Unless he's going to announce funding to make the UK a world leader in battery technology what this really means is Beeching Mk2.

Not necessarily, he might be looking at the two pilot hydrogen trains (one 319 and one 321 if I recall correctly) with a view to adopting this technology for lightly used lines.

The amount of CO2 and other crap given out by diesel trains is minuscule compared with other stuff.

At the moment that is true. However, how will that change once sales of petrol and diesel cars have been banned? Anyone asking pepole to give up their electric cars and shift mode to (diesel) trains would be eyed with suspicion; indeed are electric cars more environmentally friendly than diesel trains? In that case, we may indeed be looking at 'Beeching 2' if the likes of the Heart Of Wales aren't equipped with hydrogen or battery units by about 2050.

On the other hand, the way the political climate is changing, I could well imagine the idea of diesel trains could become politically totally unacceptable well before 2040. I wouldn't be surprised if by about 2030-2035, we'll tend to be thinking of diesel trains in much the same way that most people today think of - say - smoking in public, or fox hunting.

Well said. That's one reason why building all those new (Civity) DMUs (see also this topic) doesn't seem sensible. Northern's 195s were a necessary evil to replace the Pacers, and hopefully the next franchise can find something cleaner and nicer to replace them on Northern Connect (cascading the 195s as 150/1 replacements), but the TfW new fleet is just a short-sighted "let's try to make ourselves look good by replacing the entire fleet for the sake of it". That may well come back to bite the Welsh Government in a few years, but by then it will be too late to do anything about it without scrapping kit that is far from life expired. They won't even have the battery-hybrid technology of the 230s as far as I'm aware.

It's probably not too different from the amount put out by cars and buses per passenger-mile travelled. And diesel used in transport has a particularly serious problem of producing all the particulates right where many people live and go to work/go shopping.

That is an interesting point. Presumably the new Civity units would have to adhere to the lastest EU emmisions regulations, meaning less dangerous particulates in Birmingham New Street than with the current class 158s. However, technology that produces cleaner exhausts has in the past increased fuel consumption, so increasing CO2 emmisions (and damaging the case for electrification due to having new DMUs to find a home for) while reducing the immediate health risks. The answer I feel might be an immediate ban on new diesel units (to cover the TfW units but not the 196s for West Midlands which have commenced construction) and on new bi-modes capable of more than 100mph (slightly different to the other in that orders already placed but not yet under construction would be exempt).

Hydrogen seems to be sexier for some reason, but it still has some way to go to demonstrate real practicability and cost-efficiency.

I'm not sure about 'sexier'. Hydrogen seems to be more difficult than batteries, but does it have advantages over batteries? Would a hydrogen unit be lighter than a battery unit? And how does the range between refuelling/recharging stops compare? What was the range of the class 379 'IPEMU' trial unit? Would the battery tech available in 2030 be suitable for full battery operation of the Heart Of Wales, Far North and West Highland Lines? I doubt it, which means we have two options: hope hydrogen trains work out or settle for battery-diesel hybrids like the proposed Transport for Wales class 230s until the early 2050s and hope something else has been dreamt up by then to avoid having to close those routes.

Myself? Pretty much blanket OHLE electrification[1] of any line with at least, say, 1tph, and alternative power (e.g. batteries or hydrogen) for lines where this cannot be justified.

[1] For smaller lines light-rail-ising may be a possible cheaper consideration, i.e. 750VDC overhead and tram style vehicles.

For passenger services, I feel that any line that carries at least five coaches per direction per hour (either 1tph with 5-car units or more-frequent shorter trains) should be automatically included in the rolling electrification programme. Less than that is more of a case-by-case basis based on how suitible the alternatives would be for the route. I like the idea of using tram-style OHLE for low-speed lines, but the 3rd rail network is 750VDC and tram-style vehicles are not required. So I'd go with EMUs similar to those used on other routes but with the ability to use 750VDC overheads, unless the route is a short one suitable for trams.

20 years would be plenty of time to electrify the majority of the UK network if desired. There's roughly 9,000 single-track km (stk) of non-electrified passenger railway in the UK so over 20 years that's 450stk per year. Quite a lot, but no more than was achieved in the 50s and the 80s and at the peak of the recent Great Western electrification. It would perhaps cost £1bn a year based on recent projects, maybe much less if efficiencies can be achieved through a rolling program of work. Especially if you assume a reasonable length of minor line stk could be met by hydrogen or batteries or light rail style electrification, it seems perfectly doable. Is rail electrification enough of a priority for the next 4-5 governments to commit a billion pounds or so every year for the next 20 years? Probably not based on past form, but it is definitely feasible.

There's a graph somewhere on the internet that shows UK new electrification against Germany. The UK has had two short periods of over 400 stkm and one year (probably 2017) at over 800 stkm of new electrification and many years of nothing in between. By contrast, Germany has averaged around 200 stkm per year since about 1970. If we adopted a rolling programme at 200 stkm per year that could be 6,000 stkm of new electrification by 2050. By your figures that would leave 3,000 stkm unelectrified, at 1,000 of which are probably routes with less than 5 coaches per hour for which battery/hydrogen is probably the only solution. The question is, what are the other 2,000 stkm?

(stkm = single-track km)

From what I've read, the comparatively high cost of the GWML was a bit of a one-off due to circumstances specific to the Western Region, so it mightn't be as expensive elsewhere.

I'd guess that it was at least in part due to being asked to implement so much electrification in such a short timescale. The old adage is that you can't have something done well, cheaply and quickly - you must choose two of those. GWML was done 'well' in that it was designed to be very robust (at the cost of ugliness) and they tried to do it quickly (yes they were late, but the original target of 2016 was aimed for for quite some time) so it cost loads. Hence why I suggested a target of 200 stkm per anum above, asking for it to be done too fast will increase costs.

Absolute load of politicised electoral guff. Not going to happen. What’s going to replace the 60s?. A load of battery powered wagons ? Total and utter tosh. Network Rail can’t even afford to finish the jobs it has at the moment. Let alone electrify everywhere else. Or he intends having 200tonnes of batteries lugging around 120 tonnes of ironing board seated coaches. Maybe he’s going to be hauling the 442s to Weymouth

The target was mentioned in relation to the removal of petrol and diesel cars. That suggests the minister may only have passenger traffic in mind, if I recall correctly the Scotish government's rail decarbonisation by 2035 target was specifically decarbonisation of passenger services. Maybe that is what Shapps really means, given that (unlike cars) there is no plan to ban diesel lorries (yet). That said, a rolling programme of electrification focused on the busiest routes would probably catch most of the main freight routes anyway; class 92s could perhaps replace most of the 60s then. Or, keep the 60s but stick a 92 on the front allowing the 60 to travel dead-in-train ready for the last mile.

 

[Bletchleyite]

With regard to existing DMUs, 15x might as well go for scrap, and by the time we reach this deadline 17x/175/180 and 22x will be close to it. But given that all a DMU requires for power input is a rotating shaft of a specified speed and torque range, why couldn't that rotating shaft be provided by something other than a diesel engine? After all, people fit different engines to the likes of Land Rovers all the time. So surely the likes of 185s, 195s etc could be converted?

 

[Rhydgaled]

With regard to existing DMUs, 15x might as well go for scrap, and by the time we reach this deadline 17x/175/180 and 22x will be close to it. But given that all a DMU requires for power input is a rotating shaft of a specified speed and torque range, why couldn't that rotating shaft be provided by something other than a diesel engine? After all, people fit different engines to the likes of Land Rovers all the time. So surely the likes of 185s, 195s etc could be converted?

Given enough money then maybe, but wasn't 'Project Thor'/E-Voyager promoted because it was eaiser to modify a DEMU to take power from OHLE than a purely mechanical DMU?

 

[Bletchleyite]

Given enough money then maybe, but wasn't 'Project Thor'/E-Voyager promoted because it was eaiser to modify a DEMU to take power from OHLE than a purely mechanical DMU?

Yes, it would be. Adding a pantograph etc would be harder, but I think we're talking alternative self-powered technologies here?

 

[tbtc]

They can't make promises for five days time! Still, electrifying the majority of the UK rail network in 20 years would be practical and achievable and the total cost would be less than 1% of one year's GDP, spread over two decades, with hopefully significant benefits for many lines even ignoring CO2. If they're really serious about decarbonising transport, they would probably achieve more, more quickly for less money by investing in cycling infrastructure and buses and cracking down on private cars. Electrifying railways is relatively uncontroversial though (with the public and opposition parties). It's one of the few things they could just 'get done', or at least get started (or rather get un-stopped).

I'm all for rail investment but "1% of the country's GDP" is still a lot of money, especially considering that 90-95% of people don't take trains regularly. Though I'm not sure that we are going to manage to electrify the GWML in twenty years, the way things are going...

If we want to decarbonise transport then we should focus on bi-modes on the busiest corridors - e.g. we could insist on no diesel trains in central London/ Glasgow and through Birmingham New Street / Manchester Victoria/ Manchester Piccadilly/ Edinburgh Waverley/ Leeds etc in five/ten years time (but it'd be too much to completely wire every branch line and diversionary route).

Although if we want to decarbonise transport then we also need to look at lines where the average number of passengers could fit onto a minibus and wonder whether heavy rail is the most efficient way of transporting them.

But then, if we are getting into a debate about electrifying the majority of the UK rail network then we are doing what Shapps wants us to, and being distracted from what else the Government is getting up to - this was never a serious policy from 'The Artist Formerly Known As Michael Green and Sebastian Fox' - it wasn't even anything scribbled down on a fag packet - just a bit of well intentioned blue sky thinking he could throw to a compliant press to generate a short term boost in the headlines (and give the Tories some positive stories in one of the few areas where Labour have a more popular policy).

 

[Mikey C]

Faster trains are easier to provide and cheaper to run once the electrified infrastructure is in place than with diesels. Similarly, more frequent services using electric trains are cheaper to provide than with diesels. That's all before the travelling public realise that electric railways of almost any age are cleaner for both themselves and the environment than even the newest diesel operated line with the same service density.

I dispute that assertion, - see my comment above. You are also blurring the discussion by bringing in other route enhancements. Taking an existing route run with current diesel trains and compared to the same route run with equivalent age cascaded electric trains, there would be an uplift in patronage.

It does depend on what's being replaced. I doubt replacing HSTs with 80xs on the GWR to Cardiff will have much of a "sparks" effect by itself for example

I think modern DMUs are definitely closer to the EMU passenger ambience than older ones too. A 150 is significantly inferior to the equivalent EMU like a 317 or 455, whereas the same can't be said of a Turbostar when compared to an Electrostar.

 

[Bletchleyite]

I think modern DMUs are definitely closer to the EMU passenger ambience than older ones too. A 150 is significantly inferior to the equivalent EMU like a 317 or 455, whereas the same can't be said of a Turbostar when compared to an Electrostar.

And while you can tell the difference between a 195 and a 331, it's not that pronounced at all.

 

[trebor79]

Sit anywhere other than next to the power unit on a 755 and you'd think you were on an EMU.

 

[JKF]

But if in 10 years time governments REALLY start cracking down on petrol and diesel road vehicles, it will look embarrassing and hypocritical to have diesel trains chugging away.

Setting aside the issue of CO2 emissions, the main issue with diesel emissions from road transport is the direct impact on pedestrians that share the same transport corridor as them - i.e. people walking on pavements adjacent to roads inhaling particulates. Given rail transport away from stations doesn’t generally run along pedestrian routes then rail emissions are somewhat less important in improving public health.

Maybe there is an argument here for an interim solution using small battery units (or even OHLE) to power trains on departure when the most fumes tend to be generated next to platforms and humans, with a switchover to diesel once running at speed away from population centres, analogous perhaps to plug-in hybrid cars with a short range, where urban trips are done on electric but longer trips on trunk roads use the engine. Maybe on routes where hybrid trains are proposed (e.g west of Cardiff) the wires can terminate a few miles past the last electrified station to cover the acceleration away.