Rail decarbonisation: What are the solutions?

[Rail Blues]

The first priority should be to limit or remove diesel running through built up areas, especially in major covered stations.

I'm amazed that they've got away with running diesels in enclosed stations for so long, surely the air quality in somewhere like New St must be appalling. I remember going there in the 80s and my eyes streaming. It wasn't much better last time I was there a few years back with voyagers belting out fumes.

 

[Iliketrains123]

Battery trains on rural branch lines. Vivarail came up with an interesting battery concept.

 

[greatvoyager]

I'm amazed that they've got away with running diesels in enclosed stations for so long, surely the air quality in somewhere like New St must be appalling. I remember going there in the 80s and my eyes streaming. It wasn't much better last time I was there a few years back with voyagers belting out fumes.

As part of the direct award from last year, XC will trial batteries on Voyagers for use on approach and departure from stations, so hopefully that will aid this very issue.

 

[hwl]

Using "drop in" biofuels means that you can operate existing train fleets without modifications.

Biomass gasification followed by Fischer Tropsch Synthesis. Gives you diesel fuel with very high cetane and essentially zero sulphur. Incorporate carbon capture and you have carbon negative fuel.

This is what the aviation sector is looking at to produce 'green' Jet-A1.

It sounds like a lot of hardware and subsequent processing just to be able to continue running what are now diesel vehicles. That would only be justifiable if they were used on diagrams where there was no running under the wires. Just how much primary energy is required to produce the fuel?

DfT have indicated that Aviation will need all the advanced /F-T biofuels so none available for other sectors.

The reality might be small quantities but rail needs to get thinking and moving.

Both Germany pre '45 and South Africa (apartheid sanctions era) have extensive experience in producing liquid fuels via F-T from coal, it ain't cheap.

 

[AM9]

DfT have indicated that Aviation will need all the advanced /F-T biofuels so none available for other sectors.

The reality might be small quantities but rail needs to get thinking and moving.

Both Germany pre '45 and South Africa (apartheid sanctions era) have extensive experience in producing liquid fuels via F-T from coal, it ain't cheap.

So it seems that the DfT are likely to get tough on who uses what to play their part in carbon neutral transport. Today's announcement on advancing the decarbonising of the UK is hopefully an indication that things that need to be and will be done might affect the way that many people live.

 

[hwl]

So it seems that the DfT are likely to get tough on who uses what to play their part in carbon neutral transport. Today's announcement on advancing the decarbonising of the UK is hopefully an indication that things that need to be and will be done might affect the way that many people live.

If they didn't then everyone would assume they could use an easier liquid fuel option which would leave a mess to sort out later. Better to set a clear direction sooner.

It does of course put more pressure on DfT as "wait and see" on Hydrogen is now less of an option for rail or road HGV /coaches.

What price you put Carbon also matters, there is some what of a difference between ETS traded prices and marginal abatement cost curves...

DfT will be discovering that it is the later that matters.

 

[AM9]

If they didn't then everyone would assume they could use an easier liquid fuel option which would leave a mess to sort out later. Better to set a clear direction sooner.

It does of course put more pressure on DfT as "wait and see" on Hydrogen is now less of an option for rail or road HGV /coaches.

What price you put Carbon also matters, there is some what of a difference between ETS traded prices and marginal abatement cost curves...

DfT will be discovering that it is the later that matters.

I wasn't criticising the DfT (this time), it seems at last that there is a need to have a pecking order to conserve any limited supplies for those servces that really need it. It would be a farce if the availability of compliant liquid fuel was squandered as an excuse not to electrify even a rural branch line.

 

[XAM2175]

In the meantime, given the limitations of existing hydrogen and battery technology, has the option of Compressed Natural Gas (CNG) been explored as an alternative to diesel? The bus industry has made great strides with CNG engines. The CNG buses in Sunderland are markedly quieter than their diesel counterparts, and I believe emissions are significantly reduced.

Somewhat reduced, but will still emit significant CO2 from the exhaust.

The bus industry in Australia became very enthusiastic about CNG in the mid 1990s but I noticed that it's definitely waned on this side of 2010, when the total fleet across operators in Brisbane, Sydney, Canberra, Melbourne, and Adelaide was around 1700 vehicles. The main impetus was the marked reduction in particulate emissions, as well as a reduced fuel cost compared to diesel, but since the Euro IV restrictions entered force and low-sulphur diesel became more readily available the reduction in emissions is no longer as significant. With the loss of that big difference the higher costs involved in transporting and storing CNG and in maintaining engines that use it are harder to justify.

 

[HSTEd]

Ultimately, spend the money for mass electrification.

 

[RAGNARØKR]

Commonsense. Even assuming that CO2 emissions are the problem that is currently believed, then the CO2 put out by the railways is a tiny proportion of transport CO2, let alone total CO2. If the aim is to reduce CO2, then the railways should not be burdened with unnecessary costs. The main objection to diesel is local pollution in station areas, which could be dealt with by battery back-up. It would also be a good thing if the overall environmental impact of these "green" fuels was taken into account. I hope that there will be backtracking on what looks like a panic-driven fad.

There is also the option of external combustion technology which gets rid of NOx and particulates and can be achieved at relatively low capital cost.

 

[Roger B]

Ultimately, spend the money for mass electrification.

Rather, INVEST in electrification. It delivers an asset that will provide benefits for year to come rather, than spending money that just disappears into the ether!

 

[RAGNARØKR]

Investment in electrification is worth while if the traffic is sufficiently dense to make it worth putting up and maintaining the wires. Even then it leads a vulnerable system - as here in Sweden. Wires come down somewhere or other every few days. Otherwise electrification is poor value for money. 70% of UK route mileage, at most, is worth electrifying. That includes routes like Basingstoke-Exeter and the missing bits between Reading and Redhill which logically should be electrified on the third rail system, but that would be too dangerous.

 

[zwk500]

That includes routes like Basingstoke-Exeter and the missing bits between Reading and Redhill which logically should be electrified on the third rail system, but that would be too dangerous.

Small point, but logically we should convert the entire 3rd rail system to OLE. Not that it's going to happen but there you are, stuck hauling the legacy of our past.

 

[tbtc]

Was thinking about the earlier.

A small improvement would be minimising "diesel under the wires" unless there isn't a practical alternative.

For example:
-CrossCountry Birmingham-Stansted cut back to Cambridge (onward service provided by Greater Anglia)
-CrossCountry not North of Leeds/York (covered by TPE/LNER bi-modes instead)
-Northern Barrow/Windermere as shuttles only (or bi-mode stock)

That sort of thing.

(For example, I would keep XC to/from Manchester as Voyagers or future bi-modes due to the complexity of splitting the paths at Birmingham)

Agreed.

If we are serious about pollution/ carbon then we need to look into these kind of amendments.

Electrifying a thousand miles sounds great - but that's not going to happen for a few years - so what can we do in the short term?

Cut/tweak some services to permit an EMU to run where possible - e.g. pairing up diesel services like the Manchester Recovery Taskforce has been trying to do (minimising things like diesels under the wires to Manchester Airport - however much this might upset Angry Of Southport), cutting some through trains at times of the day (e.g. Lancaster - Skipton - Leeds)

But these kind of threads only seem to discuss spending money on things like electrification - if you are serious about cutting emissions then are you prepared to have a difficult conversation about services where passenger numbers are so low that the DMU is causing more pollution than if all people on board were to individually drive a typical car? Because sometimes it seems like "carbon" is just an excuse for people who like electrification to suggest that we electrify more lines.

As far as medium term improvements go, I'd focus on "electrification of key sections of line, around big cities" and "lots more bi-modes". There are plenty of lines where there's a frequent service out of the city but the branches mean that it's uneconomic to wire up every branch with just on for two trains per hour (or there are bridges/ tunnels that make electrification too difficult to do cheaply) - e.g. Edinburgh to Dalmeney, Manchester Victoria - Rochdale, Stourbridge - Birmingham - Tyseley.

 

[HSTEd]

Ultimately "lots more bi-modes" is probably the answer.

But that is going to be rather expensive.

 

[Rhydgaled]

Unfortunately DfT is now obsessed with road

Perhaps that should be 'still' instead of 'now'; 'now obsessed with road' suggests that it is a new obsession - they've been obsessed with road for decades.

Another vote for a rolling programme of electrification.

In the meantime, given the limitations of existing hydrogen and battery technology, has the option of Compressed Natural Gas (CNG) been explored as an alternative to diesel?

I believe there's a trial ongoing with a class 180, but I'm not sure if that's LPG, CNG, LNG or some other gas and I think the alternative fuel might be blended with diesel rather than a full replacement.

Fair enough, I wasn't aware such a plan existed. Let's hope it can actually be implemented in a competent, timely and cost effective manner.

The fact is, there will be a large number of routes which simply aren't going to justify the cost of electrification for various reasons. It's very probable we'll need the 158s/159s for at least another ten to fifteen years, the Turbostars for another twenty and the 185s, 195s, 196s and 197s for the full length of their designed service life. To state a specific timeframe for the latter, I expect it'll be the mid-to-late 2050s before the Civity diesel units are withdrawn. However, by then I'll be in my 60s and would like to think we'll have sufficient electrification and know whether hydrogen or another alternative fuel source is a viable and sustainable alternative for routes which can't be electrified.

There is indeed a fair number of routes which don't justify electrification - I think I listed them all in this topic. However, since most of these lines see very little traffic they do not actually require all that many units to run them. Ultimately it adds up to less than 120 diagrams for units with a self-power capability in total - everything else can be an EMU. Within those 120 diagrams, most of the battery units would need a pantograph to charge the batteries on the wired sections of their routes (not sure how you charge the units used on the Cornish branches, which is why I think that's where some of the Civity DMUs would end their days if the TDNS is implemented).

That wouldn't be a dual mode unit though, it'd be a DEMU with provision to convert to dual mode or EMU built into the design. That's exactly what TfW Rail's 769s are.

Indeed, that is essentially what they TfW 769s are - but would a new-build DEMU with bi-mode/EMU compatibility built-in be significantly cheaper than a new-build bi-mode? It's still worth considering though, if a unit will initially run away from the wires all the time (as the TfW 769s will) it may well be better all round if the cost and weight of the transformer and pantograph are omitted at first.

Was thinking about the earlier.

A small improvement would be minimising "diesel under the wires" unless there isn't a practical alternative.

For example:
-CrossCountry Birmingham-Stansted cut back to Cambridge (onward service provided by Greater Anglia)
-CrossCountry not North of Leeds/York (covered by TPE/LNER bi-modes instead)
-Northern Barrow/Windermere as shuttles only (or bi-mode stock)

That sort of thing.

(For example, I would keep XC to/from Manchester as Voyagers or future bi-modes due to the complexity of splitting the paths at Birmingham)

Good point, but with most of your specific examples I think bi-modes are the answer (not brand new 125mph capable ones though - those routes that need 125mph should get bi-modes cascaded from GWR/EMR/ICWC as wires are extended on those routes. For XC, my current thinking is that both Manchester services should be concentrated onto the Reading/Southampton/Bournemouth route (as this is already wired north of Birmingham) so that it can go directly from Voyagers to EMUs by implementing the 'electric spine' 0 thus avoiding the need for a bi-mode intercity unit with third rail capability. I think there's only a need for 1 XC service each hour north of York/Northallerton though (which should be the Plymouth-Edinburgh services). The current Newcastle services (which would be switched to come from Cardiff or Bristol/Exeter/Paignton) should either terminate at York or be diverted to Scarborough or the Durham coast.

* to get round the power:weight issue in diesel mode and provide longer trains I propose using all six diesel engines from pairs of 5-car 800s to create 8-car sets for XC (with GWR getting new EMU vehicles to utilise the otherwise redundant driving vehicles)

 

[RAGNARØKR]

Somewhat reduced, but will still emit significant CO2 from the exhaust.

C02 emissions from rail are a tiny fraction of total transport CO2 emissions and an even smaller fraction of total CO2 emissions. I have yet to see a plausible explanation of the so-called greenhouse effect allegedly caused by CO2, and it is not because I have not looked.

The best reason for getting rid of diesel is to clean up the air in and around stations. Paddington was cleaner in 1955 than it was until 2019 when they got rid of the diesels.

Perhaps that should be 'still' instead of 'now'; 'now obsessed with road' suggests that it is a new obsession - they've been obsessed with road for decades.


I believe there's a trial ongoing with a class 180, but I'm not sure if that's LPG, CNG, LNG or some other gas and I think the alternative fuel might be blended with diesel rather than a full replacement.


There is indeed a fair number of routes which don't justify electrification - I think I listed them all in this topic. However, since most of these lines see very little traffic they do not actually require all that many units to run them. Ultimately it adds up to less than 120 diagrams for units with a self-power capability in total - everything else can be an EMU. Within those 120 diagrams, most of the battery units would need a pantograph to charge the batteries on the wired sections of their routes (not sure how you charge the units used on the Cornish branches, which is why I think that's where some of the Civity DMUs would end their days if the TDNS is implemented).


Indeed, that is essentially what they TfW 769s are - but would a new-build DEMU with bi-mode/EMU compatibility built-in be significantly cheaper than a new-build bi-mode? It's still worth considering though, if a unit will initially run away from the wires all the time (as the TfW 769s will) it may well be better all round if the cost and weight of the transformer and pantograph are omitted at first.


Good point, but with most of your specific examples I think bi-modes are the answer (not brand new 125mph capable ones though - those routes that need 125mph should get bi-modes cascaded from GWR/EMR/ICWC as wires are extended on those routes. For XC, my current thinking is that both Manchester services should be concentrated onto the Reading/Southampton/Bournemouth route (as this is already wired north of Birmingham) so that it can go directly from Voyagers to EMUs by implementing the 'electric spine' 0 thus avoiding the need for a bi-mode intercity unit with third rail capability. I think there's only a need for 1 XC service each hour north of York/Northallerton though (which should be the Plymouth-Edinburgh services). The current Newcastle services (which would be switched to come from Cardiff or Bristol/Exeter/Paignton) should either terminate at York or be diverted to Scarborough or the Durham coast.

* to get round the power:weight issue in diesel mode and provide longer trains I propose using all six diesel engines from pairs of 5-car 800s to create 8-car sets for XC (with GWR getting new EMU vehicles to utilise the otherwise redundant driving vehicles)

Birmingham to Didcot should be high on the list for electrification. Reading to Basingstoke could be done using third rail which is a lot easier to install. That gives a complete electrified route from the WCML to the south coast. Then do Basingstoke-Exeter/Southampton-Bath on third rail.

 

[Bletchleyite]

Small point, but logically we should convert the entire 3rd rail system to OLE. Not that it's going to happen but there you are, stuck hauling the legacy of our past.

It's low priority because third rail still works fine for low to medium-speed commuter services even if it perhaps isn't ideal on safety grounds.

Ultimately "lots more bi-modes" is probably the answer.

But that is going to be rather expensive.

XC clearly needs bi-modes. The Voyagers are now about 20 years old - if we can get over the "all rolling stock shalt last 50 years" thing replacing them with 80x is not at all a bad plan.

Northern could do with a few for Barrow (Windermere needs wiring). A few more 769s would be OK, just put nice seats in them. I don't think anyone would be over-bothered about whether they had aircon or not.

As an alternative, rejig (once Windermere is wired) to all Windermere services operating through to Manchester, and have an hourly clockface Lancaster to Carlisle via Barrow connecting with it in both directions.

 

[zwk500]

Birmingham to Didcot should be high on the list for electrification. Reading to Basingstoke could be done using third rail which is a lot easier to install. That gives a complete electrified route from the WCML to the south coast. Then do Basingstoke-Exeter/Southampton-Bath on third rail.

Reading-Basingstoke will absolutely only be done as OHLE. It should be done as quickly as possible. However for Southampton - Salisbury there's an argument for 3rd rail, even if 3rd rail generally can cost a lot more over it's lifetime than OHLE. There's a reason OLE is the default standard all over the world and 3rd rail remains a niche thing for metros.

It's low priority because third rail still works fine for low to medium-speed commuter services even if it perhaps isn't ideal on safety grounds.

I'm well aware of the various arguments for and against it, both in absolute terms and in terms of converting to OLE.

 

[507021]

Indeed, that is essentially what they TfW 769s are - but would a new-build DEMU with bi-mode/EMU compatibility built-in be significantly cheaper than a new-build bi-mode? It's still worth considering though, if a unit will initially run away from the wires all the time (as the TfW 769s will) it may well be better all round if the cost and weight of the transformer and pantograph are omitted at first.

I really don't see the point in ordering (expensive) dual-mode units as diesel units, only to convert them to EMUs later, because it defeats the whole point of what dual-modes were designed for. If we're going to decarbonise, we should be looking at gradually and sustainably reducing the reliance on all use of diesel engines, dual- and tri-modes which are fitted with them included. Of course, you could convert them to battery and electric (essentially 756s without the diesel engines), but doing so would just add needless expense and complication to the whole concept.

It would be far cheaper, and in my view more logical, to procure DEMUs which are fitted with a transformer and pantograph well from the factory. That way, the units can still benefit from superior acceleration to standard DMUs until they're converted to EMUs when OHLE infrastructure allows. You also need to look at the conversion itself, because I'm pretty sure adding the transformer at a later date is going to be a lot more complicated and time consuming than only needing to remove the power modules and adding the pantograph.

 

[quantinghome]

I have yet to see a plausible explanation of the so-called greenhouse effect allegedly caused by CO2, and it is not because I have not looked.

Look harder.

 

[Western Lord]

Trying to solve tomorrow's problems with today's technology is a waste of time, unless you believe that we know everything that there is to know and that there will never be new discoveries and inventions. If you had put "top experts" in a room a hundred years ago and asked them what the implications of a UK population of 65 million by the early 21st century were for energy supply they would have told you that there would have to be a massive increase in coal mining.
It is entirely possible that future generations will look back at our attempts to run things on batteries with some amusement as they whizz around in cars, planes and trains powered by dilithium crystals.
Beam me up Scotty!

 

[Purple Orange]

So your plan is to do nothing with the technology we have today. I am sure future generations will applaud us for that.

 

[Rhydgaled]

Birmingham to Didcot should be high on the list for electrification. Reading to Basingstoke could be done using third rail which is a lot easier to install. That gives a complete electrified route from the WCML to the south coast. Then do Basingstoke-Exeter/Southampton-Bath on third rail.

I would agree that Reading-Basingstoke could be done using 3rd rail, but I doubt that would be the best approach. While we do have class 92s, and a rolling programme of electrification would hopefully result in procurement of new dual-voltage locomotives for hauling freight from Southampton, there will still be freight locomotives that are not 3rd-rail capable. Thus, Reading-Basingstoke-Salisbury-Southampton should be done with OHLE to allow electric freight using AC-only locomotives to use that route.

The only current unelectrified sections that absolutely make more sense as 3rd rail than OHLE are the Uckfield branch and Guildford-Reigate. Ashford-Ore could either be 3rd rail or extension of OHLE from Ashford and the other diesel island on the Reading-Reigate route could either be done with 3rd rail or with extension of OHLE from Reading (with a relatively short stretch at the Reading end converted from 3rd rail to OHLE).

XC clearly needs bi-modes. The Voyagers are now about 20 years old - if we can get over the "all rolling stock shalt last 50 years" thing replacing them with 80x is not at all a bad plan.

Bi-modes yes but not brand-new ones unless they fitted with unit end gangways which obviously will restrict their use to routes that don't need 125mph stock.

I believe Great Britain already has at least 186 units of classes 800/802/805/810 in service or on-order. That's significantly larger than XC's entire current fleet and a large proportion of the 80x are working routes that should be priorities for electrification. Building new 80x for XC will make it harder to get the current bi-mode routes wired up.

50 years is more than most units manage. A few years ago, my rule of thumb was 30 years for something powered by diesel and 40 for electrics and loco-hauled coaching stock. Now, having seen many Sprinters pass their 30th birthday without any plans for replacement and one of the ROSCOs (Porterbrook I think) using 35 years I have increased the mental yardstick to 35 years for diesel stock but wouldn't be too worried about diesel stock going after 30 as long as the lowest-quality units (150s) go first and none of the replacements are diesel-only units.

While we don't need stock to last 50 years, the embeded carbon involved in building new stock is significant. Unfortunately, I don't know exactly how long a train has to last to avoid wasting the embeded carbon.

Northern could do with a few for Barrow (Windermere needs wiring). A few more 769s would be OK, just put nice seats in them. I don't think anyone would be over-bothered about whether they had aircon or not.

Windermere is down for battery operation in the TDNS; electrification for Barrow.

I really don't see the point in ordering (expensive) dual-mode units as diesel units, only to convert them to EMUs later, because it defeats the whole point of what dual-modes were designed for.

What were dual-modes designed for?

If we're going to decarbonise, we should be looking at gradually and sustainably reducing the reliance on all use of diesel engines, dual- and tri-modes which are fitted with them included.

Agreed, the problem is that the life-expiry dates of current DMUs running on lines that should be electric in future do not coincide with when we are able to electrify them. We need to replace a large number of DMUs in the next 10 years with something that is able to run on non-electrified routes. However, building straight DMU replacements means we are stuck with DMUs for another 30-35 years - which for a new fleet delivered in 2024 would mean electrification is delayed until 2054 to 2059. Building a new DEMU (prefrably with reconditioned rather than brand new internal combustion engines) that we can remove the engines from at a later date means we can get rid of the diesel engines sooner without scrapping all the steel/aluminum in the bodywork before the train is life expired. Remember that steelworks are far from zero-carbon and I expect aluminum smelters are similarly polluting.

It would be far cheaper, and in my view more logical, to procure DEMUs which are fitted with a transformer and pantograph well from the factory. That way, the units can still benefit from superior acceleration to standard DMUs until they're converted to EMUs when OHLE infrastructure allows. You also need to look at the conversion itself, because I'm pretty sure adding the transformer at a later date is going to be a lot more complicated and time consuming than only needing to remove the power modules and adding the pantograph.

I'm still not seeing the difference between what you are suggesting here (a DEMU with provision for a pantograph) and a bi-mode/dual-mode unit with the pantograph left off at first. How is one far cheaper and more logical than the other? Is the debate simply whether or not you install the transformer from new?

 

[507021]

What were dual-modes designed for?

I think it's pretty obvious what dual modes were designed for, and it isn't ordering them as DMUs and converting them to EMUs later.

However, building straight DMU replacements means we are stuck with DMUs for another 30-35 years - which for a new fleet delivered in 2024 would mean electrification is delayed until 2054 to 2059. Building a new DEMU (prefrably with reconditioned rather than brand new internal combustion engines) that we can remove the engines from at a later date means we can get rid of the diesel engines sooner without scrapping all the steel/aluminum in the bodywork before the train is life expired.

That's why I've suggested modular DEMUs rather than standard DMUs, or unicorn BMUs without the electrical apparatus. Why do you want to build units which have provision for both diesel and electric propulsion if you're so against the former?

I'm still not seeing the difference between what you are suggesting here (a DEMU with provision for a pantograph) and a bi-mode/dual-mode unit with the pantograph left off at first. How is one far cheaper and more logical than the other? Is the debate simply whether or not you install the transformer from new?

Hang on, you said in this post you'd initially leave the pantograph and transformer off. Which is it?

My point is that adding the traction motors and transformer from the factory has initial and long term benefits. The initial benefits are, as I said, better acceleration across the board which means that they'll consume less fuel from a standing start, which is where all ICEs use the most fuel. In the future, removing engine modules and adding a pantograph is going to be far easier and less time consuming than having to add purchasing and then fitting a transformer to that list as well.

As for cost, a DEMU is cheaper to purchase than a BMU.

 

[HSTEd]

How many diagrams are likely to exist on the railway that never go near overhead wiring or third rail?

Some diagrams in the North of Scotland?

 

[Bletchleyite]

I really don't see the point in ordering (expensive) dual-mode units as diesel units, only to convert them to EMUs later, because it defeats the whole point of what dual-modes were designed for. If we're going to decarbonise, we should be looking at gradually and sustainably reducing the reliance on all use of diesel engines, dual- and tri-modes which are fitted with them included. Of course, you could convert them to battery and electric (essentially 756s without the diesel engines), but doing so would just add needless expense and complication to the whole concept.

It would be far cheaper, and in my view more logical, to procure DEMUs which are fitted with a transformer and pantograph well from the factory. That way, the units can still benefit from superior acceleration to standard DMUs until they're converted to EMUs when OHLE infrastructure allows. You also need to look at the conversion itself, because I'm pretty sure adding the transformer at a later date is going to be a lot more complicated and time consuming than only needing to remove the power modules and adding the pantograph.

Regarding the TfW 769s, they are bi-modes, the pantograph has just been taken off (a bit like the shoes from the 350/1s) to remove the need to maintain it. It can always be put back.

Not so easy with the transformer as if you removed it you'd have to ballast the vehicle (or change the suspension to a different spec) so it might as well stay.

I would agree that the current 195/196/197 build should be the very last mechanical DMUs built, with everything else being built with 25kV capability even if it has something else as well.

 

[greatvoyager]

How many diagrams are likely to exist on the railway that never go near overhead wiring or third rail?

Some diagrams in the North of Scotland?

Do the Devon Metro or local Cornwall services count?

 

[507021]

Regarding the TfW 769s, they are bi-modes, the pantograph has just been taken off (a bit like the shoes from the 350/1s) to remove the need to maintain it. It can always be put back.

Not so easy with the transformer as if you removed it you'd have to ballast the vehicle (or change the suspension to a different spec) so it might as well stay.

I would agree that the current 195/196/197 build should be the very last mechanical DMUs built, with everything else being built with 25kV capability even if it has something else as well.

Are they really dual-modes if they can't actually switch from one form of propulsion to another though?

They're dual-mode capable, absolutely, but I think a more accurate classification would be "DEMU with dual-mode provision". In a somewhat similar vein, I'm still struggling to understand why Porterbrook are marketing the 769/5s and 769/9s as tri-modes, when they're actually dual-voltage dual-mode units.

 

[Bletchleyite]

Are they really dual-modes if they can't actually switch from one form of propulsion to another though?

I think that's getting a bit pedantic, to be honest. The pantograph has been taken off but they are otherwise fully equipped 25kV units. To use them as such just requires putting it back on.

I do agree that tri-mode for diesel + 2 voltages of electricity is a bit odd. A tri-mode would be something like diesel, battery and electric, to me, as after all a dual-voltage EMU is not called a bi-mode. "Dual-voltage bi-mode" would probably be the correct description of a unit that can do 25kV AC, 750V DC and diesel.