The Anonymous Widower

Is The Battery Electric Multiple Unit (BEMU) A Big Innovation In Train Design?

By training I am an Electrical Engineer who specialised at Liverpool University and for a few years afterwards in the mathematics of the control of mechanical, electrical and other systems.

Over the last fifty years, I’ve liked to think of myself as scientifically green and in transport, I’ve come to the belief that we need to be as electric as possible, as this can produce a minimum of carbon dioxide and less noxious fumes and noise.

We may have produced a series of battery-electric vehicles for special purposes such as golf buggies, the electric milk floats of my childhood and light taxis and buses for historic city centres.


Electric Taxi In Malta

Electric Taxi In Malta


But where are the queues of stylish electric cars waiting for the charging points in my local car park in Dalston?

In my view, electric road vehicles with one or two rare exceptions, don’t really appeal to drivers, owners and users. You read reports that the economics are suspect without large subsidies. That’s as maybe, but having once owned a golf buggy, I can testify that battery life and performance wasn’t acceptable to the special needs on my farm.

So when Bombardier, Network Rail, Greater Anglia and others announced they were going to test a Class 379 4-carriage train as a battery-electric multiple unit (BEMU), I either thought they had more money than sense or there was something I’d missed.

Riding The BEMU

A desire to investigate found me on a cold morning in February boarding what looked to be a outwardly normal Class 379 train at Manningtree.

An Outwardly Normal Class 379 Train

An Outwardly Normal Class 379 Train

The only visible difference was the Batteries Included sign on the side. Inside nothing appeared to have been changed

A Very Familiar Interior

A Very Familiar Interior

Except for the destination display showing we were going the dozen miles to Harwich Town.

As we trundled away and breezed down and back up the Stour Estuary, I could detect no difference between the two runs and between train 379013 and its unmodified siblings, which I use regularly to Cambridge. The conductor assured me that they generally went one way under AC power from the catenary and the other on the batteries.


Returning from Harwich, I travelled with the train’s on-board test engineer, who was monitoring the train performance in battery mode on a laptop. He told me that acceleration in this mode was the same as a standard train, that the range was up to sixty miles and that only minimal instruction was needed to convert a driver familiar to the Class 379 to this battery variant.


It was an impressive demonstration, of how a full-size train could be run in normal service without connection to a power supply. I also suspect that the partners in the project must be very confident about the train and its technology to allow paying passengers to travel on their only test train. 

It’s All About The Rolling Resistance

The physics of rolling resistance, explain why I was wrong to be sceptical and had now been so surprised and delighted by the Class 379 BEMU.

Most of us have driven a car with soft tyres and know that you need more power to maintain speed, as soft tyres have a higher rolling resistance.

Generally the rolling resistance of a steel wheel on a steel rail is lower, which helps trains move heavier loads for less power than road vehicles with rubber tyres.

But also if you read about the mathematics of rolling resistance, you will find that if you increase the load on a steel wheel running on a steel rail you lower the rolling resistance, so you can move the train for less power. This helps explain the impressive performance of the BEMU.

You have the paradox, that optimally-located heavy batteries, in a steel-wheel-on-rail vehicle, reduce the rolling resistance and mean it needs less power.

One of the most important  rules of life is that you can’t disobey the laws of physics.

A Hybrid Train

In some ways to consider this train a battery electric multiple unit is wrong, as its nearest cousin is probably the hybrid bus, such as the New Routemaster in London. In the bus the battery is charged by a small diesel engine and final drive is all-electric.

In the rest of this article, I will continue to use BEMU, but hybrid electric multiple unit or HEMU might be better. It could be argued that the general public associate hybrid with something good, so there may be sensible public relations reasons for calling the trains HEMUs.

Using a BEMU

One of the main uses of a BEMU would be on a cross-country route that connects two electrified lines. The overcrowded Cambridge to Ipswich route would certainly be possible, as the gap between Haughley Junction and Cambridge is short of thirty miles and well within the capability of a BEMU.

Another use of  a BEMU would be to extend an electrified route  to an important town that needed a rail link bigger than can be provided by a two-coach diesel train of a certain age. London to Great Yarmouth via Norwich would be a typical route.

Branch lines off an electrified main line, such as the Felixstowe branch would be ideal for a BEMU.

The three East Anglian examples I have given could probably be served without spending a penny on infrastructure.

The Greater Anglia Involvement

Greater Anglia’s involvement in the project is significant as East Anglia has several routes suitable for a BEMU, in addition to those mentioned earlier.

The trains would also give the company the ability to extend some of the Liverpool Street to Cambridge services to perhaps Norwich, Newmarket and Bury St. Edmunds.

Some gaps like Ely to Norwich, might be stretching the range, but the trains could give the soon-to-be-two Cambridge stations much better access to a wider East Anglia from Peterborough and Wisbech in the West, Norwich and Cromer in the North and Yarmouth and Ipswich in the East.

East Anglia seems to suffer more than most from track and overhead wire problems and rebuilding. A BEMU would make a superb blockade buster and could even have been used to get passengers to Peterborough, when all the problems happened on the East Coast Main Line at Christmas, by jumping the gap from Ely.

The rail network in East Anglia also suffers from periodic overcrowding, especially in the summer, so extra carriages on many services would be welcome to Greater Anglia and users alike.

East Anglia for so long a rail backwater would love these trains.

Advantages To Network Rail

Network Rail is an infrastructure company so why is it getting involved in the design of trains?

Network Rail has some problems with electrification due to well-publicised issues and in some cases the large quantity, they are being tasked to install, which puts pressure on manpower and resources.

In some sensitive areas, there may be planning issues with putting up the overhead wires. A simple example in Suffolk illustrates the value of a BEMU. It is unlikely the Gainsborough Line will ever be electrified, as it runs through the Stour Valley and the Nimbys would have a field day if Network Rail decided to put overhead line gantries on the iconic listed Chappel Viaduct, which is the second largest brick structure in England. But as the line is only a dozen miles long, running a BEMU on the line would be a sensible idea.

There are probably a lot of places where using a BEMU, rather than electrifying saves Network Rail a lot of installation costs and lawyers fees. Passengers would get a brand new and probably larger electric train, from the day they can be delivered and after the train crew has been trained.

Electrification of passenger services is a proven revenue generator, but predicting how much electrification will increase traffic, is one of the blackest of black arts. The difficulty is illustrated by the North and East London Lines, which were built to run the three-car trains that were thought to be required for the level of traffic. London Overground is now going through the second train lengthening process to cope, which is also requiring various infrastructure changes. If London can’t get this right with their massive journey databases, how can you predict traffic on a branch line in say Dorset or Norfolk? A shiny modern BEMU could be a valuable tool for assessing the increase in traffic, by trialling one for a period to ascertain what needs to be done to improve a service. The solution could be anything from bringing back the terrible diesel multiple unit, through using a BEMU on the line to full electrification.

I think it is true to say, that Network Rail could probably cut the cost of electrification and line improvements, by better planning of the work.

There are also innumerable lines in the United Kingdom, where the distance is less than sixty or seventy miles and both ends of the line are electrified, which are possibilities for running BEMUs.

  • Hurst Green to Lewes via Uckfield and the Marshlink Line in Sussex
  • The Tyne Valley Line between Newcastle and Carlisle
  • Many lines that link to electrified hubs like Liverpool, Manchester, Birmingham and Leeds.
  • Lines in Scotland that link to the current electrification. This could include the new Borders Railway which is only thirty miles long.
  • Any branch from an electrified main line.

Unfortunately for everybody concerned, the hundred miles between Salisbury and Exeter is probably just too far to run on batteries at present. But this could be possible in a few years, as the technology develops.

Many routes with minimal partial electrification could accept a BEMU tomorrow, which could be a more affordable alternative to full electrification.

  1. Full electrification often needs a lot of bridge and tunnel reconstruction to give sufficient clearance to the wires. With a BEMU, this is unnecessary.
  2. Deployment of BEMUs, could also release much-needed modern diesel trains for use on lines away from electrification.

I would argue it’s better to spend the money on rolling stock, rather than use it to enlarge bridges and tunnels.

The Biggest Advantage To Rail Companies And Users

The biggest advantage of the technology is a truly unusual one, which is akin to putting the cart before the horse.

It’s that the new BEMUs start to run as soon as they are delivered and even before the electrification is complete.

Suppose you are possibly going to electrify a line like Carlisle to Newcastle, where both ends are already wired.

Traditionally, you can’t run any electric trains, until the electrification is complete.

But if you used BEMUs to operate the line, you can actually deliver the trains and bring in the new service pattern before you electrify using the power at both ends to charge the batteries.

After electrification, you might replace the BEMUs with a non-battery sibling and move the BEMUs to another line to repeat the process.

So the passengers benefit earlier from new trains. The train company should also benefit, as hopefully all the publicity of better and possibly longer trains generates extra journeys.

Instead of the speed of the electrification works governing the pace of line modernisation, the limiting factor is how fast trains can be built and any necessary much smaller infrastructure improvements like platform extensions are completed.

A Possible Production BEMU

The partners in this project seem to have come up with some fairly tight performance objectives for the train.

  1. A sixty plus mile range. This seems to bridge a lot of network electrification gaps and the length of out and return on the average branch line – Achieved
  1. Performance similar to the standard Class 379 and enough to work the average secondary or branch line – Achieved.
  1. No change of passenger experience to a standard Class 379 – Achieved
  1. Identical Driving Characteristics to a standard Class 379 – Achieved
  1. An overall experience better than a Pacer or a Sprinter – Achieved by a wide margin. I’ve also ridden modern Class 171 and Class 172 diesel multiple units lately and the Class 379 BEMU was certainly better in terms of ambient noise.

Bombardier could just create a Class 379 BEMU, but I suspect that the upcoming Aventra train chosen for Crossrail would be used. After all, why would you use a boring old train, when you could have a sexy new one? Especially one that is lighter and more energy efficient.  You could even borrow the use of a small on-board engine to charge the battery from the bus industry.

Probably the most difficult decision in the design is the train length, but why not make them all identical go-anywhere four carriage dual-voltage trains?

Incidentally, that go-anywhere capability will be enhanced when ERTMS becomes standard for all trains.

How Would BEMUs Affect Various Schemes?

The next few sections will look at various proposed schemes and how BEMUs might affect them.

The Felixstowe Branch

I’ve used the Felixstowe branch for over fifty years and the individual train capacity is now smaller than it was in the 1960s. But the frequency has improved and the service has got better since the Bacon Factory Chord was created.

It carries upwards of thirty freight trains each way every day and has long been mooted for electrification. Unless the complete route from
Felixstowe to Nuneaton and inside Felixstowe Port were also electrified, electrification of the branch line is probably a waste of time, as there would need to be a change of locomotive at some point.

I sometimes wonder if you want to have overhead wiring in a port or goods yard, with cranes lifting containers all the time.

I believe that the Class 88 locomotive is a better solution, as this would give electric haulage on electrified lines like the Great Eastern Main Line and diesel haulage on the branch and in the port.

Passengers on the line would like better and larger trains and this could be solved by a BEMU charging every time it returned to the Ipswich end of the branch.

Ipswich To Cambridge And Lowestoft

If you are going to run a BEMU from Ipswich to Felixstowe, then surely it would be a good idea to run the trains on the services from Ipswich to Cambridge and Lowestoft.

The gap between the overhead wires at Cambridge and Haughley Junction is less than thirty miles and would easily be jumped by a BEMU, charging itself at the two ends of the line.

Ipswich to Lowestoft is fifty miles which would certainly be too far for a BEMU going out and back on one filling of electricity at Ipswich. But as I believe a BEMU should be dual voltage, why not put in a shielded length of third-rail away from the platform side of the train in Lowestoft station. This picture shows the platform layout at Lowestoft with the current Norwich and Ipswich Class 156 trains in the platforms.

Two Class 156 At Lowestoft

Surely, Network Rail’s engineers can come up with a third-rail system in the station for charging BEMUs, that meets the most draconian Health and Safety regulations.

If BEMUs were to also run the Norwich to Lowestoft services, then you’d have electrified the passenger services to the United Kingdom’s most easterly town.

What would a picture of two Aventra BEMU profiles in Lowestoft station, do for the town?

Completing The East Anglian Electrification Of Passenger Services

If some means of range extending like a third-rail-based charger in some terminal stations, then there is no reason that all unelectrified lines in East Anglia could be run successfully by BEMUs. These would include.

  1. Cambridge and Ely to Norwich on the Breckland Line
  2. Norwich to Yarmouth on the Wherry Lines
  3. Norwich to Cromer and Sheringham on the Bittern Line
  4. Marks Tey to Sudbury on the Gainsborough Line

The BEMUs would also be an ideal train for the proposed re-opening of Bramley Line between Wisbech and March and the possible creation of the Norfolk Orbital Railway from Sheringham to Wymondham.

Completing The Electrification In East Sussex

East Sussex Council has produced a document called Shaping Rail In East Sussex, and also proposes the electrification of the Marshlink Line and improving and fully electrifying the Wealden Line and Oxted Line.

I believe that BEMUs could be the key to completing the electrification of this important commuter area and releasing sixteen Class 171 diesel multiple units for areas with no electrification at all.

As BEMUs would effectively be a one-for-one replacement for the Class 171 and no infrastructure work would be needed except for the track work at Lewes, as the new trains were delivered, a Class 171 could be released to go and replace a Pacer or Sprinter.

The Borders Railway

I suspect that various Scots and their politicians will be a bit miffed, that a beautiful new railway will be running second-hand trains. I suspect that something like Class 171 or Class 172 will be used, but wouldn’t it be nice if four-coach electric trains were to be used on the route.

As the route is not being electrified, but power is available at the Edinburgh end and the line is only sixty miles out and back, the line would be an ideal candidate for equipping with sexy new BEMUs.

The only problem is that the Scots have just signed a deal with Hitachi to deliver a whole stable of new AT200 electric trains.

However, it should be noted that Abellio Greater Anglia is one of the partners in the testing of the experimental Class 379 BEMU and that Abellio ScotRail is the new Scottish franchise holder.

Incidentally, Abellio’s parent; Nederlandse Spoorwegen still have sa few diesel multiple units, so perhaps they have other motives in being involved with the BEMU.

Glasgow Crossrail And The Airport Rail Link

Glasgow Crossrail is a proposal to improve rail services in Glasgow described like this in Wikipedia.

The proposed Crossrail initiative involves electrifying and reopening the City Union Line for regular passenger use in conjunction with new filler sections of track which will connect the North Clyde, Ayrshire, and Kilmarnock and East Kilbride suburban routes together, therefore allowing through running of services through the centre of Glasgow in a North-South axis.

It has been an on-and-off project over the years, as has the closely-related Glasgow Airport Rail Link.

Perhaps by selectively using BEMUs on the City Union Line, some of the major problems of rail transport in Scotland’s largest city can be alleviated, until the budget allows full electrification across the city.

Replacing Pacers Out Of Electrified Hubs

I asked in the title of this post if a new battery electric multiple unit (BEMU) could be a replacement for the truly-dreadful Pacers.

On some routes out of Liverpool, Manchester, Leeds and other electrified hubs, Pacers perform out and back services, which could probably be replaced by a BEMU.

As electrification progresses more and more, Pacers will find that they operate more of their routes partially under the wires. All of these routes will become candidates for BEMUs.

As the new trains will elsewhere displace some modern diesel multiple units, these could also probably chase a few Pacers to the scrapyard.

So in my view, new BEMUs may not always directly replace the Pacers, but they will certainly hasten their demise.

Should The Gospel Oak To Barking Line Be Electrified?

I know that freight is an important driver of electrification of the Gospel Oak to Barking Line, but how would the availability of a number of BEMUs affect how the work will proceed?

The Gospel Oak to Barking Line is being electrified at a cost of £115million. In addition eight new four carriage trains are being ordered for the line.

Electrification of the line is said to be difficult, as there are numerous bridges and viaducts.

But the line is also desperately short of capacity for passengers and desperately needs the new electric trains.

As the line is partly electrified, why not drop the full electrification for a few years and buy eight new BEMUs?

They would pick up power east of Woodgrange Park station and around South Tottenham, leaving only about twenty miles to run on the batteries.

If the batteries need a top up at Gospel Oak, why not put in a short length of overhead wire at the western end of the line. Or heresy of heresies, a short length of third rail!

As circumstances and funds allowed the rest of the line would be electrified.

All of the flexibility in the schedule would be down to the unique characteristics of the BEMU.

Some residents along the line might be annoyed by the continuing noise and smell of the diesel freight locomotives passing through if the line remains without full electrification, but passengers will get twice as many carriages as at present, in brand new electric trains. Passengers won’t care that they’re powered by batteries, so long as they are reliable, comfortable and punctual


Who’d have thought that such a rather unusual concept of a battery electric multiple unit would have so many possibilities?

I think I’ve seen the future and it just might work!




February 10, 2015 - Posted by | Transport/Travel | , , , , , , ,


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  3. […] only alternative to electrifying the Windermere branch is to use a battery-assisted electric train, like the one I rode in at Manningtree. But although that technology appears to be very successful, […]

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  5. […] rumoured to be capable of battery running, using technology I saw demonstrated and talked about in Is The Battery Electric Multiple Unit (BEMU) A Big Innovation In Train Design? Modern Railways says the […]

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  8. […] What surprises me, is that Bombardier haven’t created another demonstrator to prove the concept, just as they did at Manningtree. […]

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  10. […] To a passenger they would appear to be a normal four-car electric muliple unit. I described my ride in the prototype between Manningtree and Harwich in Is The Battery Electric Multiple Unit (BEMU) A Big Innovation In Train Design? […]

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  14. […] rode in public service in early 2015 is mentioned. I found this train impressive, as I reported in Is The Battery Electric Multiple Unit (BEMU) A Big Innovation In Train Design?. This was my […]

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  15. Very interesting. Especially the physics of extra weight producing lower rolling resistance.

    What about the historic Windermere to Oxenholme line, that links a World Heritage Lake District to Manchester Airport via an electrified main line?

    Only 20 miles round trip on non electrified lines.

    And an £18 Million electrification project promised and recently cancelled?

    How about an analysis of BEMU use for this case?

    Comment by G | June 20, 2018 | Reply

  16. […] The other was Bombardier’s Class 379 BEMU, that I wrote about in Is The Battery Electric Multiple Unit (BEMU) A Big Innovation In Train Design?. […]

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  20. […] The technology has been a long-term arriving, as I had my first ride in a battery-electric train in February 2015, which I wrote about in Is The Battery Electric Multiple Unit (BEMU) A Big Innovation In Train Design?. […]

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  21. […] Network Rail must have known that from before 2015, when they ran the Class 379 IPEMU trial on the Mayflower Line, which I wrote about in Is The Battery Electric Multiple Unit (BEMU) A Big Innovation In Train Design?. […]

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