On track for net-zero railway: Hitachi’s Blues Train

In 1825 George Stephenson’s Locomotion took 450 people 25 miles from Darlington to Stockton at 15 miles per hour. The first public passenger steam train was born. Many would agree that the steam train was one of the most impactful exports of the industrial revolution, giving the world something that it never truly had before: speed.

Recently, another first-in-class train was unveiled by Hitachi at the InnoTrans transport fair in Berlin – The Blues Train. The Blues Train will be the first ever ‘tri-mode’ train to enter passenger service in Europe. If the steam train gave the world speed two centuries ago, what does The Blues Train give us now?

Getting Rail

While the industrial revolution changed the world in many ways for the better, it also gave humans the tools that would ultimately precipitate today’s climate crisis. In a bid to tackle the changes in the world’s climate, the UK has set a target to become carbon-neutral by 2050, in line with other countries’ similar commitments.

Transport is the single biggest contributor to UK’s CO2 emissions. However, in 2019, only 1.4% of these emissions were due to rail. Therefore, just by switching from more carbon-intensive modes of transport to rail, the carbon footprint of the transport sector can be dramatically reduced. Nevertheless, there is a drive for making rail transport an even cleaner alternative than it is currently. Indeed, the UK Government has set a goal to fully decarbonise its rail network by 2040.

Multiple reports1 agree that electrification of existing rail lines should be seen as the first choice in the hierarchy of options for achieving this goal. An electrified rail network can support electric trains throughout by supplying electric power to the trains via overhead lines or third rails, thus eliminating the need for diesel-only trains. A big efficiency advantage of electric trains is their ability to perform regenerative braking in which braking energy is returned to the power network. However, currently only about 38% of the UK’s 20,000-mile rail network is electrified. This is well below the levels of electrification in France, Germany and Spain (58.5%, 53.1% and 63.7% respectively), which could themselves be higher. The EU-27 average in 2019 was 56%. While the UK Government has launched a number of schemes to upgrade and electrify its rail network, this is a costly undertaking and progress has been slow.

Accordingly, there is ample space across the whole of Europe for developments in locomotive technology to contribute to achieving the parallel goals of decarbonising the railways and encouraging their use.

Moving away from diesel-only trains: bi-mode trains

In the early 2000s, France pioneered the use of a new type of train in Europe: the bi-mode train. Simply put, bi-mode trains are electric trains that have a self-propulsion capability. Bi-mode trains can run on both electrified and non-electrified routes by switching between electric and diesel power. When travelling along an electrified route, bi-mode trains receive power from an overhead line via a pantograph or from a third rail; while along a non-electrified route, the trains can self-propel using an on-board diesel power generator.

Bi-mode trains offer multiple advantages over diesel-only trains. For example, they enable through journeys beyond the electrified network that would otherwise require a change of trains, extra time for attaching or removing locomotives, or running diesel trains ‘under the wires’. Additionally, the bi-mode operation allows these trains to continue to run if the electrification system fails, or on diversionary routes, which can reduce congestion in the rail network.

Since the first bi-mode trains of 20 years ago, leading developers of train technology such as Hitachi Rail have significantly improved bi-mode technology. Hitachi Rail, one of the four main suppliers of trains in the UK currently manufacturing British Rail Classes 800 and 802 of the UK’s bi-mode rolling stock, have made innovations in the bi-mode space to reduce trains’ weight and complexity.

Specifically, Hitachi Rail have developed a bi-mode train in which a single power conversion device can be connected to both a single-phase AC power supply (i.e. an overhead line), and to a three-phase AC power supply (i.e. an on-board diesel power generator). Thus, the single power conversion device is used to convert AC power from either the overhead line or the diesel power generator to DC power. Some of the DC power is then used for powering auxiliary on-board apparatuses, such as air conditioners and lighting devices, while the rest is inverted into three-phase AC power to drive the train’s traction motors. This patent-protected technology provides improved switching between the two types of power sources.

Hitachi’s ongoing innovation, driven by the ambition to reduce carbon emissions for governments, cities and customers, has recently reached a new high with the unveiling of the tri-mode ‘Blues Train’.

From bi-mode to tri-mode

The Blues Train is similar to bi-mode trains in that it has the ability to operate seamlessly on electrified and non-electrified routes. As before, on electrified routes, the train uses pantographs to draw power from the overhead lines. However, when it moves to non-electrified lines, the train employs a combination of battery and diesel power.

This hybrid technology provides unparalleled flexibility to operate in the most suitable mode depending on various external conditions. For example, when the train is near a station, or in an urban area, without overhead lines it can be powered solely by the battery to eliminate emissions, including harmful NOx, and to reduce noise pollution. In contrast, on relatively long-distance, less sensitive, non-electrified routes (e.g. rural lines) the train can be powered using a mixture of contributions from the diesel power generator and the battery. The battery can recharge while the train is in operation by regenerative braking, or by drawing power from the overhead lines or the diesel power generator as appropriate.

The extra power offered by the on-board battery means the train’s acceleration and performance (with a top speed of 160km/h) is superior to existing diesel-only trains, offering reduced journey times. This comes with a more than 50% reduction in carbon emissions and fuel consumption.


The urgent need to tackle climate change and reduce pollution is driving innovation in transport technology. As a result, adaptability, is emerging as an important driving force in innovation, and the Blues Train embodies this well.

The tri-mode operation of the Blues Train allows for a smoother running service that meets the demanding targets around carbon intensity, pollution and increase in railway use. Here, battery power plays an important role as a facilitator technology in the shift to lower-carbon transport.



  1. RIA Electrification Cost Challenge Report; Rail Industry Decarbonisation Taskforce Report.


About the authors

This blog was co-authored by Darena Slavova and Fynn McLennan.

Fynn Author


Fynn McLennan

Fynn is a trainee patent attorney in the chemistry team. Fynn has a Master's (MChem) degree from the University of Oxford. During his undergraduate degree, he completed research projects modelling battery cathode materials and ion transport as well as ab initio modelling of quantum tunnelling processes. His thesis centred around simulating the ultrafast dynamics of photo-excited, conjugated polymers and developing novel ways of extracting information through experiment.

Email: Fynn.McLennan@mewburn.com