The Anonymous Widower

Bombardier’s Plug-and-Play Train


The heart of any electric train is the electrical system that takes the electricity from the overhead wires or third rail and distributes it to the traction motors that actually power the train. If regenerative braking is fitted, then the same system also handles any electricity generated by braking.

So that is where I’ll start.

This article in Global Rail News from 2011, which is entitled Bombardier’s AVENTRA – A new era in train performance, gives some details of the Aventra’s electrical systems. This is said.

AVENTRA can run on both 25kV AC and 750V DC power – the high-efficiency transformers being another area where a heavier component was chosen because, in the long term, it’s cheaper to run. Pairs of cars will run off a common power bus with a converter on one car powering both. The other car can be fitted with power storage devices such as super-capacitors or Lithium-Iron batteries if required.

Bombardier have confirmed the wiring for onboard power storage to me.

So this could mean, that if the overhead wire or third rail can’t accept electricity generated by regenerative braking, then if batteries are fitted, these can store the energy for reuse, and there will be an energy saving. With a commuter train doing frequent stops, the braking energy at a stop, copntributes to getting the train moving again.

If there is no way to recycle or store the braking energy, it is passed through resistors on the roof of the train, and used to heat the atmosphere.

If you look at just-released pictures of the Class 345 train, the trains appear to have the pantograph on one or more of the intermediate cars, unlike some electric multiple units which have them on the driving cars.

I did find this snippet on the Internet which gives the formation of the trains.

When operating as nine-car trains, the Class 345 trains will have two Driving Motor Standard Opens (DMSO), two Pantograph Motor Standard Opens (PMSO), four Motor Standard Opens (MSO) and one Trailer Standard Open (TSO). They will be formed as DMSO+PMSO+MSO+MSO+TSO+MSO+MSO+PMSO+DMSO.

The snippet has a date of August 13th, 2016, so it’s very much up-to-date. It tells us the following.

  • All cars except one, have traction motors, which are responsible for both driving the train and providing a lot of the braking effort.
  • The pantograph car is motored, whereas on a Class 378 train it isn’t.
  • The only trailer car is in the middle of the train.
  • The train has two pantograph cars.
  • Would a pantograph car and one or more motor cars work together as was described in the Global Rail News article?

One of the big differences between the Aventra and the previous generation of Electrostar trains, is that many more cars are powered.

  • Distributing force along the train could be a very good way of applying greater total force to the track, to accelerate and brake the train faster.
  • Distributed power might be better in slippery rail conditions.
  • Splitting the power system between cars and using lighter-weight and better-designed FLEXX Eco bogies, may distribute the weight better along the train.
  • As there are more traction motors, does this mean they are smaller and possibly lighter and cost less.

I suspect that the distributed power approach has other advantages.

As the two pieces of information gleaned from the Internet are five years apart, I suspect that Bombardier have moved on from this concept of a pair of cars, one with the pantograph, third rail shoe and the converter and one with the energy storage.

I suspect that the electrical and motor systems of the Class 345 trains could be one of the following.

  • The whole train has a common power bus  and all motored axles are connected to it.
  • The train is effectively two half trains, each with their own power bus consisting of four cars in the following formation; DMSO+PMSO+MSO+MSO, with a trailer car without power in between.

These are my thoughts on the two approaches.

  • The second approach must have advantages in terms of reliability as there are two of everything.
  • The initial trains running from May 2017, will be seven cars, so will they be two three-car trains with a formation of DMSO+PMSO+MSO and a TSO in the middle? This would give a thorough test to all types of cars.
  • Going from seven to nine cars, just means adding an MSO to each half-train.
  • If necessary, Crossrail will lengthen trains to ten cars. Would they do this by adding another TSO?
  • The two pantographs must be at least a hundred metres apart, which could come in handy for jumping gaps in the overhead wires.
  • If the half-train approach is used, the two electrical buses would probably be connected together intelligently to share power.

So I wouldn’t be surprised to find, that the Class 345 trains are effectively two half trains working as one.

So how does a concept like this, fit with other train orders and lengths?

Class 710 Trains

The Class 710 trains for London Overground are four-car commuter trains, which will trundle around North-East London. I think they could have a formation of something like DMSO+PMSO+MSO+DMSO, which would fit the published information in the Global Rail News article of an electrical system based on at least two cars.

Incidentally, the five-car Class 378 trains with their three cars in the middle have two powered cars and a trailer car.

I said these trains will just trundle around London, but it would appear that all cars are powered, so I suspect they will accelerate away as fast as the track, passengers and the signals will allow.

As the braking is regenerative and either returns the braking energy to the overhead wires or stores it on the train, the trains will stop quickly and will be very efficient, with rapid stops at all stations.

Obviously, I can’t get any figure for how much time, the Class 710 trains will save say between Hackney Downs and Chingford, but I can show some figures on the eleven intermediate station Crossrail route between Stratford and Shenfield.

This currently takes 36 minutes in a Class 315 train and after Crossrail opens this will be 32 minutes in a Class 345 train.

So it looks like the new trains could save twenty seconds a stop. Not much, but the Shenfield Metro is probably running to a good speed.

Abellio’s Five Car Trains

These five-car trains could be two of the driving cars (DMSO) with a three-car set in the middle, so the formation could be DMSO+PMSO+MSO+MSO+DMSO or DMSO+PMSO+MSO+TSO+DMSO, depending on how much oomph was required.

Like the Class 710 trains, they would have a lot of powered axles and this helps create a specification including.

  • 100 mph capability.
  • Fast acceleration and braking.
  • An exceptional 100-0-100 mph time leading to extremely rapid stops.

They truly are pocket rockets.

Abellio’s Ten Car Trains

These ten-car trains will be similar to the five-car ones with a formation of something like.


where XXSO is anything that the operator wanted, but would normally be a MSO or a TSO.

Interim Conclusions On Aventras

I think I can draw some very important conclusions from what I have said already.

  • The Aventra is very different to an Electrostar.
  • The concept of having a sub-train of two or possibly three cars as outlined in the article in Global Rail News seems to work well with all of the trains ordered so far.
  • The sub-train probably wouldn’t include a driving car, as this would mean that in shorter trains, two types of driving can would be needed.
  • The driving cars could be identical except for the passenger compartment and the number of doors.
  • The overall design concept is very flexible.
  • All trains have a high proportion of motor cars and hence powered bogies, which probably means quick acceleration and good braking.
  • Train length can be filled out using additional motor or trailer cars.
  • Total train power can be adjusted by choosing the right mix of motor and trailer cars.

I shall now look at various topics in detail.

Train and Car Length

We know very little about the lengths of the cars in the various different Aventras, except these snippets from Modern Railways in September 2016 and some other sources.

  • Class 345 trains will have cars around 23 metres with three doors on either side.
  • Class 710 trains will have cars around 20 metres with two doors on either side.
  • The five-car Abellio East Anglia trains will be 110 metres long.
  • The ten-car Abellio East Anglia trains will be 240 metres long.

I suspect that  different car lengths and number of doors can be easily handled by a well-thought-out manufacturing process.

Much of the differences between the various fleets will come down to the interior design and equipment specified by the operator.

In The Aventra Car Length Puzzle, I came to the following conclusions.

  • The Aventra design is very flexible.
  • Driving cars generally seem to be around twenty metres.
  • There is an appropriate number of equal length intermediate cars between the two driving cars.

In some ways, it’s almost like a mini-HST.

And just like the HST and Bombardier’s successful Class 378 train for the London Overground, capacity and length is changed by just adding or removing intermediate cars.

I also stated in the related article, that Abellio’s five- and ten-car Aventras for East Anglia, could use these two basic car lengths.

  • A 20 metre driving car.
  • A 25 metre intermediate car.

My lengths might be wrong, but surely to have just two car types of the same size, gives a degree of design and operational flexibility , that must help the operator to a large degree.

In addition, if all driving cars are roughly the same size between the various Aventras, this must ease manufacture and support of the trains.

Different Driving Cars

First Class seats are expensive on space and fittings to provide and aren’t needed on all services.

If you take the selection of Abellio routes in East Anglia, that will be run exclusively by Aventras, how many destinations will actually need First Class seats?

  • Clacton, Frinton and Walton
  • Southend
  • Bishops Stortford and Hertford East

So as trains like the Class 360 trains have First Class at one end of the formation, will we see at least two types of driving car?

  • One with an appropriate number of First Class seats.
  • One which is all Standard Class.

I suspect that from the bulkhead behind the driver forward, all driving cars will be more or less identical with a few differences due to operator, route and signalling, but on the passenger side, the layout will be adjusted to the route.

We could even see quick change interiors in the small section of the driving car behind the driver.

After all airliners have been configured in this way for many years, with movable screens to separate Business seats from the riff-raff.

So could we see various configurations of the driving cars?

  • First Class
  • Standard Class
  • Mixed First and Standard Class
  • Bicycle Racks
  • Heavy Luggage and Parcel Space
  • Toilets
  • Buffets and shops.

Obviously, the train operator, would make sure that their driving cars were right for the routes they served.

Flexible Train Lengths

Bombardier seem to have possibly used the experience they gained with the Class 378 trains on the London Overground, which have progressively been lengthened from three to four and five-cars since delivery five years ago, just by adding extra intermediate cars.

I suspect that appropriate driving and intermediate cars can be shuffled together in order, to create any length of train from four-cars upwards.

I showed earlier, how the Cl;ass 345 trains could be adjusted as time progresses, so Abellio might benefit from a similar flexibility.

Abellio have ordered both five- and ten-car trains for their East Anglian routes, so could we see trains put into alternative formations, if that suits the route and passenger demand better?

Incidentally, I travel regularly on Virgin’s Pendolinos to the North West and these Class 390 trains have changed in length over the years.

They are a good example of future-proofing a train design, so that formations can change as the routes and requirements evolve.

Nothing would seem to prevent the length of an operator’s fleet of Aventra trains from being changed.

The Aventra Marketplace

I have just found this article in Rail Engineer from February 2014, which is entitled An Exciting New Aventra.

Jon Shaw from Bombardier is quoted as saying this about the market for the Aventra.

We looked ahead for ten years and spoke to potential stakeholders and customers, including the Department for Transport, as well as Transport for London, and all of the operators and train leasing companies and passenger focus groups, and they told us what they thought was going to happen over the ten years ahead. Essentially, four styles of train will be needed. One will be the dedicated metro trains, running all day at high capacity. Then there will be slow-speed and medium speed commuter trains, as we have today. Lastly, there is what we see as a new market, which is high speed commuters – they can serve a commuter market, but when they go onto that main line, they’re going to hit 125 mile an hour and so they don’t delay the main intercity trains.

So it looks like the four current orders fit these markets.

Aventras and Onboard Energy Storage

The article in Rail Engineer also quotes Jon Shaw on onboard energy storage.

As part of these discussions, another need was identified. Aventra will be an electric train, but how would it serve stations set off the electrified network? Would a diesel version be needed as well?

So plans were made for an Aventra that could run away from the wires, using batteries or other forms of energy storage. “We call it an independently powered EMU, but it’s effectively an EMU that you could put the pantograph down and it will run on the energy storage to a point say 50 miles away. There it can recharge by putting the pantograph back up briefly in a terminus before it comes back.

I believe that once the concept of onboard energy storage is accepted, that Bombarduier’s engineers have found other ways to use it to the benefit of passengers, operators and Network Rail.

Aventras and Regenerative Braking

All Aventras have regenerative braking and of the various lines on which they will run, some will be able to handle the reverse currents.

However, other lines may not be able to handle regenerative braking.

If that is the case, then Aventras can be fitted with batteries or other forms of onboard energy storage to handle the braking.

There will obviously be a point where it is more affordable to handle regenerative braking on the train, rather than at the trackside.

Note that the energy generated from braking is easily calculated from the fomula for the kinetic energy in a moving object.

0.5 * (mass) * (velocity) * (velocity)

So stopping a train from 100 mph would release four times as much energy as from 50 mph. On starting again, a similar amount of energy would be need to be given to the train to regain line speed. If this is stored in the onboard storage of the train, then this must be able to hold the energy generated by one stop from the typical line speed.

It is not as onerous an application as actually driving the train for a few miles, as if more energy is needed to accelerate the train, the train will obtain it from the overhead wires or third rail.

The Full Aventra IPEMU

In the Rail |Engineer article Jon Shaw of Bombardier talked about a train with a fifty mile range on the onboard storage. He called it an independently powered EMU or IPEMU.

So what would a full Aventra IPEMU look like?

With sufficient onboard storage the four-car Class 710 train could be used as an IPEMU.  The storage would probably give a range similar to that of the Class 379 BEMU demonstration. This would mean the range is at least a one-way trip on the Mayflower Line, which is 11.3 miles or just under dozen miles.

This may not seem to be a very large range, but there are quite a few branch lines, where the out-and-back trip is less than or not much more than a dozen miles.

All connect or will in a couple of years to electrified main lines. Some even use a dedicated bay platform, which could be wired for charging.

The Mayflower Line is also a line, where the electrification has been simplified to save money.

Only one track is fully electrified and this restricts the services that electric trains can provide. However, if an Aventra IPEMU had a range of just a dozen miles, then with just some new track, possibly a set of points and no new electrification, services could be improved.

Other lines in this sorry or a neglected state include.

How many other Hall Farm Curves are there, where a short chord or line connects or could connect two electrified lines?

But as I said earlier, a dozen miles is a bit limiting. In Abellio’s East Anglia routes, these are the out-and-back distances for some lines.

There might also to be less than 25 miles of line without electrification between Haughley Junction and Cambridge.

Looking at these distances, an Aventra IPEMU with a range of greater than 25 miles would be a lot more useful.

But Jon Shaw of Bombardier is quoted in the article in Rail Engineer  of saying this.

We call it an independently powered EMU, but it’s effectively an EMU that you could put the pantograph down and it will run on the energy storage to a point say 50 miles away. There it can recharge by putting the pantograph back up briefly in a terminus before it comes back.

So what is available to increase the range?

My original musings in this section started with a four-car Class 710 train. But supposing we started with a five-car Aventra similar than those that have been ordered by Abellio for East Anglia.

The train could have this formation.


If both MSO cars had onboard energy storage, it would be a pocket rocket with a minimum range of at least 24 (2×12) miles on batteries!


  1. Are two cars with onboard energy storage needed to get sufficient range from the Aventra IPEMU?
  2. Two cars with onboard energy storage are obviously better than one!
  3. It would appear that the definitive Aventra IPEMU is a five-car train.
  4. The 50 mile range quoted by Jon haw could be available through better and larger storage technology.

As a trained control engineer, I know that balancing and controlling all these energy sources and sophisticated traction motors in an efficient and reliable manner will be very much possible and very rewarding for the engineers.

Aventra Is A Smart Train

This article in Rail Magazine is entitled Rise Of The Smart Train

It describes how trains can report faults remotely and make them easier and quicker to service. There is particular mention of Bombardier and the Class 710 trains.

Who is generally responsible for the servicing of a new fleet of trains?

These days maintenance is usually bundled into the lease contract. So a good train manufacturer can make more profits by making maintenance of a train easier and faster.

The smartness is not just about maintaining tracks.

This is from another article in Rail Magazine.

The trains have overhead line monitoring as a standard feature, and track monitoring equipment is also standard. So the operators don’t need to come and ask us to include it – it’s part of the build now.” That can help Network Rail identify, and fix, any problems much quicker.

When will cars report potholes?

There is also this snippet from this article in the Derby Telegraph

The train is also fitted with a “driver assistance system”, which takes into account gradients and route conditions to minimise power consumption.
Trials of the system, using a Class 365, brought a 13% energy saving, Bombardier said.

That could mean a saving in energy costs for the operator or extra range if running on the onboard energy storage.

Aventras Can Be Woken Up By Remote Control

This is discussed in Do Bombardier Aventras Have Remote Wake-Up?.

Regenerative Braking, Onboard Energy Storage And Current Orders

Nothing has been said about how any of the Aventra orders for London and East Anglia will use their regenerative braking, or whether the trains will be fitted with onboard energy storage.


I will consider Crossrail and the Class 345 trains first.

  • The contract for the trains was signed in February 2014 after the article in Global Rail News was published in March 2011.
  • This page on the Crossrail web site, says that trains will return braking energy to the grid.
  • Only Class 345 trains will use the Crossrail tunnels.
  • The Western surface section would be served by a variety of trains.
  • The Shenfield branch would probably only be served by Aventras.
  • The Abbey Wood branch would only be served by Class 345 trains.
  • Trains with onboard energy storage would have a limited recovery capability to travel to the next station, in case of an overhead line power failure.
  • If the trains  were fitted with onboard energy storage, the Old Oak Common depot could have less overhead wires, with positive cost and safely implications.

I think it is also true to say that other advantages apply, if the Crossrails tunnels and trains have been designed as an integrated system.

But I can’t find anything about how regenerative braking will be handled on London’s new line.

I wouldn’t rule out that all Class 345 trains were fitted with some form of onboard energy storage.


These statements will apply to the Class 710 trains, which will run on the London Overground.

  • Some of the electrification on the lines on which the Class 710 trains will run probably needs refurbishment and updating to accept the current flows from regenerative braking.
  • Will the Gospel Oak to Barking Line be electrified for regenerative braking? I suspect yes, as some electric locomotives will have regenerative braking in the future.
  • An IPEMU-capability that handled regenerative braking and gave a range of a dozen miles could be easily fitted to a Class 710 train.
  • Two Class 710 trains with an IPEMU-capability could  run a four trains per hour (tph) service on the  Greenford Branch, if this branch became part of London Overground.
  • Two Class 710 trains with an IPEMU-capability could  run a 4 tph service on the  Romford to  Upminster  Line with the reinstatement of a passing loop.
  • Class 710 trains with an IPEMU-capability could use a Hall Farm Curve without electrification to run between Chingford and Walthamstow to Lea Bridge and Stratford.
  • The Class 710 trains will use extended depots at Willesden and Ilford, so being able to be stored and run on lines without electrification could be an advantage.
  • Currently some trains are stabled overnight at Chingford. Would remote wake-up be used?
  • There may be places, where electrification can be simplified, if all trains had an IPEMU-capability.

A possible advantage is that the short extension to Barking Riverside could be built without electrification, as the length is well within the range of a Class 710 train with an IPEMU-capability.

Logic suggests that all Class 710 trains will have some onboard energy storage.


When considering the five- and ten-car trains for Abellio’s East Anglian routes, I think they can be thought of as several separate fleets for different routes.

  • ten-car trains without onboard energy storage.
  • ten-car trains  with enough onboard energy storage to handle regenerative braking, remote wake-up and limited movement without power.
  • five-car trains without onboard energy storage.
  • five-car trains with enough onboard energy storage to handle regenerative braking, remote wake-up and limited movement without power.
  • five-car trains with enough onboard energy storage to handle a 25 mile trip using the onboard energy storage.

I very much believe that because of the regenerative braking, overnight stabling and other issues, that all trains will have at least one MSO car equipped with onboard energy storage.

So we are left with the following train types.

  • ten-car trains  with enough onboard energy storage to handle regenerative braking, remote wake-up and limited movement without power.
  • five-car trains with enough onboard energy storage to handle regenerative braking, remote wake-up and limited movement without power.
  • five-car trains with enough onboard energy storage to handle a 25 mile trip using the onboard energy storage.

This effectively means there is an efficient ten-car train with some onboard energy storage for the following routes.

  • London to Southend
  • London to Clacton
  • London to Colchester
  • London to Ipswich – If still required.

Would the ten-car trains need one set of onboard energy storage or two?

An efficient five-car train with some onboard energy storage could be used on less busy routes.

  • London to Braintree
  • Witham to Braintree. – Shuttle using energy storage.
  • London to Harwich
  • Manningtree to Harwich. – Shuttle using energy storage.
  • London to Walton
  • Thorpe-le-Soken to Walton. – Shuttle using energy storage.
  • Stratford to Bishops Stortford
  • London to Bishops Stortford.
  • London to Hertford East.

What is interesting is that for the Braintree, Harwich and Walton route, the same trains can be used as direct trains to London or a shuttle to the main line station. All these branches probably need a bit of work to accommodate a second train.

Does this mean that all stations on the branch can have a 2 tph service to the main line and a 1 tph service to London?

The following routes will  need a five-car train with enough onboard energy storage for a 25 mile range.

  • Crouch Valley Line
  • Gainsborough Line
  • Felixstowe Branch
  • Cambridge to Ipswich

All services could go to 2 tph if required.

So it would appear that all trains will have at least one set of onboard energy storage and some five-car trains will have two sets to do the longer routes without elerctrification.


I’m fairly certain that all Aventras will use onboard energy storage for the following reasons.

  • If the train is fitted with remote control wake-up, some onboard power is needed to get the train ready.
  • Onboard energy storage allows depots and stabling sidings to be without overhead wires to save costs and increase safety.
  • Onboard energy storage handles the regenerative braking of the train.
  • Onboard energy storage can be used to move a train to safety after overhead line or third rail failure.

Even a small amount of onboard energy storage can move the train a few miles or so.

But if this analysis shows one thing, it is how a philosophy based on a series of standard coaches are just connected  together to create such a variety of trains, for such different purposes.

From the three train fleets ordered so far we have.

  • A  nine-car people carrier for 1,500, that can be any length from seven to ten-cars.
  • A four-car suburban runabout, in two variants with different power and seating.
  • A ten-car fast long distance train, that can take large numbers of commuters to and from work.
  • A five-car version of the ten-car long distance train, for thinner routes.
  • A five-car fast long-distance train, that can also travel independently for perhaps twenty-five milsl.

The Aventra really is true plug and play.








September 2, 2016 - Posted by | Transport/Travel | , , , , ,


  1. […] In Bombardier’s Plug-and-Play Train, I showed that all Aventras will have a certain amount of onboard energy storage to handle regenerative braking and enable short movements using stored energy. […]

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